Merge pull request #4 from Richard-Qin-001/dev/shell

Rebuilt the system's underlying structure; it is now stable enough to merge. 

The system now supports a read-only file system and has a simple shell implemented.

39 files changed, 3317 insertions, 106 deletions

diff --git a/include/common/fcntl.h b/include/common/fcntl.h
new file mode 100644
index 0000000..24d40fa
--- /dev/null
+++ b/include/common/fcntl.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#define O_RDONLY 0x000
+#define O_WRONLY 0x001
+#define O_RDWR 0x002
+#define O_CREATE 0x200
+#define O_TRUNC 0x400
+
+#define NOFILE 16
\ No newline at end of file
diff --git a/include/common/types.h b/include/common/types.h
index 7403a54..8924699 100644
--- a/include/common/types.h
+++ b/include/common/types.h
@@ -1,22 +1,27 @@
 #pragma once
 
-typedef unsigned char      uint8_t;
-typedef unsigned short     uint16_t;
-typedef unsigned int       uint32_t;
-typedef unsigned long long uint64_t;
+typedef unsigned char       uint8_t;
+typedef unsigned short      uint16_t;
+typedef unsigned int        uint32_t;
+typedef unsigned long long  uint64_t;
 
-typedef signed char        int8_t;
-typedef signed short       int16_t;
-typedef signed int         int32_t;
-typedef signed long long   int64_t;
+typedef signed char         int8_t;
+typedef signed short        int16_t;
+typedef signed int          int32_t;
+typedef signed long long    int64_t;
 
-typedef uint64_t           size_t;
-typedef uint64_t           uintptr_t;
-
-typedef uint64_t           uint64;
-typedef uint32_t           uint32;
-typedef uint8_t            uint8;
+typedef uint64_t            size_t;
+typedef uint64_t            uintptr_t;
 
+typedef uint64_t            uint64;
+typedef uint32_t            uint32;
+typedef uint16_t            uint16;
+typedef uint8_t             uint8;
 typedef unsigned int        uint;
 typedef unsigned short      ushort;
-typedef unsigned char       uchar;
\ No newline at end of file
+typedef unsigned char       uchar;
+
+typedef int64_t             int64;
+typedef int32_t             int32;
+typedef int16_t             int16;
+typedef int8_t              int8;
\ No newline at end of file
diff --git a/include/drivers/plic.h b/include/drivers/plic.h
new file mode 100644
index 0000000..11e8c8a
--- /dev/null
+++ b/include/drivers/plic.h
@@ -0,0 +1,17 @@
+#pragma once
+#include "common/types.h"
+
+namespace PLIC
+{
+    // Global initialization (executed only once by hart 0)
+    void init();
+
+    // Per-core initialization (executed when each CPU starts)
+    void inithart();
+
+    // Claim interrupt: Get the currently occurring interrupt number (IRQ)
+    int claim();
+
+    // End of interrupt: notify the PLIC that this IRQ has been handled
+    void complete(int irq);
+} // namespace PILC
diff --git a/include/drivers/uart.h b/include/drivers/uart.h
index 4d00d94..26c2394 100644
--- a/include/drivers/uart.h
+++ b/include/drivers/uart.h
@@ -1,9 +1,36 @@
 #pragma once
-typedef unsigned long long uint64_t;
+#include "common/types.h"
 
-namespace Drivers {
+#define UART0 0x10000000L
+#define RHR 0 // Receive Holding Register (read mode)
+#define THR 0 // Transmit Holding Register (write mode)
+#define IER 1 // Interrupt Enable Register
+#define FCR 2 // FIFO Control Register
+#define ISR 2 // Interrupt Status Register
+#define LCR 3 // Line Control Register
+#define LSR 5 // Line Status Register
+
+#define LSR_RX_READY 0x01 // input is waiting to be read from RHR
+#define LSR_TX_IDLE 0x20  // THR can accept another character to send
+
+#define UART_RX_BUF_SIZE 128
+
+// ANSI Escape Codes for Modern Terminal Colors
+#define ANSI_RESET "\033[0m"
+#define ANSI_RED "\033[31m"
+#define ANSI_GREEN "\033[32m"
+#define ANSI_YELLOW "\033[33m"
+#define ANSI_BLUE "\033[34m"
+#define ANSI_CLEAR "\033[2J\033[1;1H"
+
+namespace Drivers
+{
     void uart_init();
+    void uart_intr();
+    int console_read(uint64 target, int len);
+
     void uart_putc(char c);
-    void uart_puts(const char* s);
-    void print_hex(uint64_t val);
+    void uart_puts(const char *s);
+    void uart_put_int(int value);
+    void print_hex(uint64 value);
 }
\ No newline at end of file
diff --git a/include/drivers/virtio.h b/include/drivers/virtio.h
new file mode 100644
index 0000000..ea2c9a6
--- /dev/null
+++ b/include/drivers/virtio.h
@@ -0,0 +1,103 @@
+#pragma once
+#include "common/types.h"
+
+// VirtIO MMIO Base Address
+#define VIRTIO0 0x10001000
+
+// MMIO Registers (Modern / Version 2)
+#define VIRTIO_MMIO_MAGIC_VALUE 0x000
+#define VIRTIO_MMIO_VERSION 0x004
+#define VIRTIO_MMIO_DEVICE_ID 0x008
+#define VIRTIO_MMIO_VENDOR_ID 0x00c
+#define VIRTIO_MMIO_DEVICE_FEATURES 0x010
+#define VIRTIO_MMIO_DEVICE_FEATURES_SEL 0x014
+#define VIRTIO_MMIO_DRIVER_FEATURES 0x020
+#define VIRTIO_MMIO_DRIVER_FEATURES_SEL 0x024
+#define VIRTIO_MMIO_QUEUE_SEL 0x030
+#define VIRTIO_MMIO_QUEUE_NUM_MAX 0x034
+#define VIRTIO_MMIO_QUEUE_NUM 0x038
+#define VIRTIO_MMIO_QUEUE_READY 0x044
+#define VIRTIO_MMIO_QUEUE_NOTIFY 0x050
+#define VIRTIO_MMIO_INTERRUPT_STATUS 0x060
+#define VIRTIO_MMIO_INTERRUPT_ACK 0x064
+#define VIRTIO_MMIO_STATUS 0x070
+
+// 64-bit Queue Address Registers (Modern)
+#define VIRTIO_MMIO_QUEUE_DESC_LOW 0x080
+#define VIRTIO_MMIO_QUEUE_DESC_HIGH 0x084
+#define VIRTIO_MMIO_QUEUE_DRIVER_LOW 0x090
+#define VIRTIO_MMIO_QUEUE_DRIVER_HIGH 0x094
+#define VIRTIO_MMIO_QUEUE_DEVICE_LOW 0x0a0
+#define VIRTIO_MMIO_QUEUE_DEVICE_HIGH 0x0a4
+
+// Status Bits
+#define VIRTIO_CONFIG_S_ACKNOWLEDGE 1
+#define VIRTIO_CONFIG_S_DRIVER 2
+#define VIRTIO_CONFIG_S_DRIVER_OK 4
+#define VIRTIO_CONFIG_S_FEATURES_OK 8
+
+// Feature Bits
+#define VIRTIO_BLK_F_RO 5
+#define VIRTIO_BLK_F_SCSI 7
+#define VIRTIO_BLK_F_CONFIG_WCE 11
+#define VIRTIO_BLK_F_MQ 12
+#define VIRTIO_F_ANY_LAYOUT 27
+#define VIRTIO_RING_F_INDIRECT_DESC 28
+#define VIRTIO_RING_F_EVENT_IDX 29
+#define VIRTIO_F_VERSION_1 32
+
+// Descriptor Flags
+#define VRING_DESC_F_NEXT 1
+#define VRING_DESC_F_WRITE 2
+
+#define NUM_DESCS 8
+
+#define VIRTIO_BLK_T_IN 0
+#define VIRTIO_BLK_T_OUT 1
+
+// Device Configuration Layout (Offset 0x100)
+#define VIRTIO_MMIO_CONFIG 0x100
+
+namespace VirtIO
+{
+    struct VRingDesc
+    {
+        uint64 addr;
+        uint32 len;
+        uint16 flags;
+        uint16 next;
+    };
+
+    struct VRingAvail
+    {
+        uint16 flags;
+        uint16 idx;
+        uint16 ring[NUM_DESCS];
+    };
+
+    struct VRingUsedElem
+    {
+        uint32 id;
+        uint32 len;
+    };
+
+    struct VRingUsed
+    {
+        uint16 flags;
+        uint16 idx;
+        struct VRingUsedElem ring[NUM_DESCS];
+    };
+
+    struct __attribute__((packed)) BlockRequest
+    {
+        uint32 type; // 0=Read, 1=Write
+        uint32 reserved;
+        uint64 sector;
+    };
+
+    void init();
+    void intr();
+    void rw(int write, uint64 blockno, char *buf);
+    void test_rw();
+    void test_bio();
+}
\ No newline at end of file
diff --git a/include/fs/fat32.h b/include/fs/fat32.h
new file mode 100644
index 0000000..c794bd7
--- /dev/null
+++ b/include/fs/fat32.h
@@ -0,0 +1,111 @@
+#pragma once
+#include "fs/fs.h"
+#include "kernel/buf.h"
+
+// Disk Layout Structures (On-Disk)
+
+// FAT32 Boot Sector (BPB)
+struct FAT32_BPB
+{
+    uint8 jmpBoot[3];
+    char oemName[8];
+    uint16 bytesPerSector;
+    uint8 secPerClus;
+    uint16 reservedSecCnt;
+    uint8 numFATs;
+    uint16 rootEntCnt;
+    uint16 totSec16;
+    uint8 media;
+    uint16 FATSz16;
+    uint16 secPerTrk;
+    uint16 numHeads;
+    uint32 hiddSec;
+    uint32 totSec32;
+    uint32 FATSz32;
+    uint16 extFlags;
+    uint16 FSVer;
+    uint32 rootClus;
+    uint16 FSInfo;
+    uint16 bkBootSec;
+    uint8 reserved[12];
+    uint8 drvNum;
+    uint8 reserved1;
+    uint8 bootSig;
+    uint32 volID;
+    char volLab[11];
+    char filSysType[8];
+} __attribute__((packed));
+
+// FAT32 Directory Entry (32 bytes)
+struct FAT32_DirEnt
+{
+    char name[11]; // 8.3 filename
+    uint8 attr;    // File attributes
+    uint8 ntRes;
+    uint8 crtTimeTenth;
+    uint16 crtTime;
+    uint16 crtDate;
+    uint16 lstAccDate;
+    uint16 fstClusHI; // High 16 bits of first cluster
+    uint16 wrtTime;
+    uint16 wrtDate;
+    uint16 fstClusLO; // Low 16 bits of first cluster
+    uint32 fileSize;
+} __attribute__((packed));
+
+#define ATTR_READ_ONLY 0x01
+#define ATTR_HIDDEN 0x02
+#define ATTR_SYSTEM 0x04
+#define ATTR_VOLUME_ID 0x08
+#define ATTR_DIRECTORY 0x10
+#define ATTR_ARCHIVE 0x20
+#define ATTR_LONG_NAME 0x0F
+
+// In-Memory Classes
+
+class FAT32FileSystem;
+
+class FAT32Inode : public Inode
+{
+public:
+    FAT32FileSystem *fs;
+
+    // FAT32 Private Data
+    uint32 first_clus;  // The starting cluster number of the file
+    uint32 parent_clus; // Starting cluster number of the parent directory
+    uint32 dir_offset;  // The byte offset of this directory entry in the parent directory
+
+    FAT32Inode() : fs(nullptr), first_clus(0) {}
+    // Implement VFS Interface
+    void update() override;
+    int read(char *dst, uint32 off, uint32 n, int isUser) override;
+    int write(const char *src, uint32 off, uint32 n, int isUser) override;
+    Inode *lookup(const char *name) override;
+    Inode *create(const char *name, short type, short major, short minor) override;
+    void truncate() override;
+};
+
+class FAT32FileSystem : public FileSystem
+{
+public:
+    uint32 fat_start_sector;
+    uint32 data_start_sector;
+    uint32 root_cluster;
+    uint32 sectors_per_cluster;
+    uint32 bytes_per_cluster;
+
+    void init() override;
+    Inode* root() override;
+
+    // Helper functions
+    uint32 next_cluster(uint32 cluster); // Check the FAT table for the next cluster
+    uint32 alloc_cluster();              // Assign a new cluster
+    uint32 cluster_to_sector(uint32 cluster);
+
+    // directory entry parsing
+    void read_dir_ent(struct FAT32_DirEnt *de, char *filename);
+};
+
+extern FAT32FileSystem fat32_fs;
+
+void fat32_test();
\ No newline at end of file
diff --git a/include/fs/file.h b/include/fs/file.h
new file mode 100644
index 0000000..2f23176
--- /dev/null
+++ b/include/fs/file.h
@@ -0,0 +1,36 @@
+#pragma once
+#include "common/types.h"
+#include "fs/fs.h"
+
+enum FileType
+{
+    FD_NONE,
+    FD_INODE,
+    FD_DEVICE,
+    FD_PIPE
+};
+
+struct file
+{
+    enum FileType type;
+    int ref;
+    char readable;
+    char writable;
+
+    struct pipe *pipe; // pipeline pointer
+    Inode *ip;         // VFS Inode
+    uint32 off;        // Current Offset
+};
+
+namespace FileTable
+{
+    void init();
+    struct file *alloc();             // Allocate a free file handle
+    struct file *dup(struct file *f); // Duplicate handle (sys_dup)
+    void close(struct file *f);       // Close handle
+
+    int stat(struct file *f, uint64 addr);
+    int read(struct file *f, uint64 addr, int n);
+    int write(struct file *f, uint64 addr, int n);
+    int lseek(struct file *f, int offset, int whence);
+} // namespace FileTable
diff --git a/include/fs/fs.h b/include/fs/fs.h
new file mode 100644
index 0000000..f40bc0c
--- /dev/null
+++ b/include/fs/fs.h
@@ -0,0 +1,93 @@
+#pragma once
+#include "common/types.h"
+#include "kernel/spinlock.h"
+#include "fs/stat.h"
+
+class FileSystem;
+
+// VFS Inode (Abstract Base Class)
+
+class Inode
+{
+private:
+    ;
+public:
+    // VFS Common Fields
+    uint32 dev;  // Device number (VirtIO Block ID)
+    uint32 inum; // Inode number
+    int ref_cnt; // Memory reference count (number of struct file or processes referencing it)
+    int valid;   // Whether the data is valid (whether metadata has been read from disk)
+
+    Mutex lock; // Sleep lock: protects internal Inode data and atomicity of read/write operations
+
+    // Metadata Cache (for speeding up getattr)
+    short type;  // T_DIR, T_FILE, T_DEVICE
+    short major; // Major device number (only for T_DEVICE)
+    short minor; // Minor device number (only for T_DEVICE)
+    short nlink; // Number of hard links
+    uint32 size; // File size
+
+    Inode() : ref_cnt(0), valid(0)
+    {
+        lock.init("inode");
+    }
+    virtual ~Inode() {}
+
+    /* Core Operation Interface (Subclass Must Implement) */
+    // Update metadata
+    // Sync size, type, links, etc. from memory back to disk
+    virtual void update() = 0;
+    // Read content
+    // Read n bytes from the file at offset into dst
+    // Returns the actual number of bytes read, returns -1 on error
+    virtual int read(char *dst, uint32 off, uint32 n, int isUser) = 0;
+    // 3. Write content
+    // Write n bytes from src to the file at the given offset
+    // Need to handle file growth
+    virtual int write(const char *src, uint32 off, uint32 n, int isUser) = 0;
+    // Directory Lookup (only valid when type == T_DIR)
+    // Search for a file named 'name' in the current directory and return its Inode pointer (locked)
+    // Return nullptr if not found
+    virtual Inode *lookup(const char *name) = 0;
+    // Create file/directory (only effective when type == T_DIR)
+    // Create a new entry in the current directory
+    virtual Inode *create(const char *name, short type, short major, short minor) = 0;
+    // Get file status (populate the stat structure)
+    // Default implementation, subclasses can override to provide more detailed information
+    virtual void getattr(struct kstat *st);
+    // Truncate file (set size to 0, release all data blocks)
+    virtual void truncate() = 0;
+};
+
+// File System Abstraction (SuperBlock)
+class FileSystem
+{
+private:
+    ;
+public:
+    virtual void init() = 0;
+    virtual Inode* root() = 0;
+    virtual ~FileSystem() {};
+};
+
+// Inode Cache Interface (Global Function)
+namespace VFS
+{
+    void init();
+
+    // Decrease the reference count, and if it reaches 0, free the memory
+    void iput(Inode *ip);
+    // Increase reference count
+    Inode *idup(Inode *ip);
+    // lock and load data
+    void ilock(Inode *ip);
+    // unlock
+    void iunlock(Inode *ip);
+    void iunlockput(Inode *ip);
+    // Mount the root filesystem
+    void mount_root(Inode *root);
+    // Get system root node
+    Inode *get_root();
+    // Path Analysis
+    Inode *namei(const char *path);
+} // namespace VFS
diff --git a/include/fs/stat.h b/include/fs/stat.h
new file mode 100644
index 0000000..cdce05a
--- /dev/null
+++ b/include/fs/stat.h
@@ -0,0 +1,22 @@
+#pragma once
+#include "common/types.h"
+
+#define T_DIR 1    // Directory
+#define T_FILE 2   // File
+#define T_DEVICE 3 // Device
+
+struct kstat
+{
+    int dev;        // File System's disk device
+    uint32 ino;     // Inode number
+    short type;     //Type of file
+    short nlink;    // Number of links to file
+    uint64 size;    // Size of file in bytes
+
+    uint32 mode;  // Protection: rwx
+    uint32 uid;   // User ID
+    uint32 gid;   // Group ID
+    uint32 atime; // Access time
+    uint32 mtime; // Modified time
+    uint32 ctime; // Change time
+};
diff --git a/include/kernel/buf.h b/include/kernel/buf.h
new file mode 100644
index 0000000..099523d
--- /dev/null
+++ b/include/kernel/buf.h
@@ -0,0 +1,30 @@
+#pragma once
+#include "common/types.h"
+#include "kernel/spinlock.h"
+
+#define BSIZE 1024
+#define NBUF 30
+
+struct Buf
+{
+    int valid;        // Whether the data has been read from the disk (1=valid, 0=invalid)
+    int disk;         // Whether it has been held by the driver (dirty bit/write-back flag is usually extended here)
+    uint32 dev;       // Device Number
+    uint32 blockno;   // Block number
+    uint32 refcnt;    // Reference Counting
+    struct Buf *prev; // LRU linked list
+    struct Buf *next;
+    uchar data[BSIZE];
+
+    Mutex lock; // Sleep Lock
+};
+
+namespace BufferCache
+{
+    void init();
+    struct Buf *bread(uint32 dev, uint32 blockno);
+    void bwrite(struct Buf *b);
+    void brelse(struct Buf *b);
+    void bpin(struct Buf *b);
+    void bunpin(struct Buf *b);
+} // namespace BufferCache
diff --git a/include/kernel/cpu.h b/include/kernel/cpu.h
new file mode 100644
index 0000000..92890b6
--- /dev/null
+++ b/include/kernel/cpu.h
@@ -0,0 +1,19 @@
+#pragma once
+#include "common/types.h"
+#include "kernel/proc_def.h"
+
+struct RunQueue;
+
+struct cpu
+{
+    struct Proc *proc;
+    struct Context context;
+    int noff;
+    int intena;
+
+    struct RunQueue *runqueue;
+};
+
+
+extern struct cpu cpus[];
+struct cpu *mycpu();
\ No newline at end of file
diff --git a/include/kernel/elf.h b/include/kernel/elf.h
new file mode 100644
index 0000000..c216f1c
--- /dev/null
+++ b/include/kernel/elf.h
@@ -0,0 +1,46 @@
+#pragma once
+#include "common/types.h"
+
+#define ELF_MAGIC 0x464C457F // "\x7FELF" in little endian
+
+// ELF File Header
+struct elfhdr
+{
+    uint32 magic; // Must equal ELF_MAGIC
+    uint8 elf[12];
+    uint16 type;
+    uint16 machine;
+    uint32 version;
+    uint64 entry; // Program Entry Point (Virtual Address)
+    uint64 phoff; // File offset of the Program Header Table
+    uint64 shoff;
+    uint32 flags;
+    uint16 ehsize;
+    uint16 phentsize;
+    uint16 phnum; // Number of Program Headers
+    uint16 shentsize;
+    uint16 shnum;
+    uint16 shstrndx;
+};
+
+// Program Header
+// Describes how to load segments from a file into memory
+struct proghdr
+{
+    uint32 type;
+    uint32 flags;
+    uint64 off;   // Offset of the section in the file
+    uint64 vaddr; // Virtual address of the segment in memory
+    uint64 paddr;
+    uint64 filesz; // Size of the section in the file
+    uint64 memsz;  // The size of the segment in memory (memsz >= filesz)
+    uint64 align;
+};
+
+// Values for Proghdr type
+#define ELF_PROG_LOAD 1
+
+// Flag bits for Proghdr flags
+#define ELF_PROG_FLAG_EXEC 1
+#define ELF_PROG_FLAG_WRITE 2
+#define ELF_PROG_FLAG_READ 4
\ No newline at end of file
diff --git a/include/kernel/exec.h b/include/kernel/exec.h
new file mode 100644
index 0000000..964e3bb
--- /dev/null
+++ b/include/kernel/exec.h
@@ -0,0 +1,6 @@
+#pragma once
+
+namespace Exec
+{
+    int exec(char *path, char **argv);
+}
\ No newline at end of file
diff --git a/include/kernel/mm.h b/include/kernel/mm.h
index 07d675b..3b59edb 100644
--- a/include/kernel/mm.h
+++ b/include/kernel/mm.h
@@ -3,20 +3,25 @@
 
 namespace VM
 {
-    typedef uint64_t *pagetable_t;
-    typedef uint64_t pte_t;
+    extern uint64 *kernel_pagetable;
 
-    pte_t *walk(pagetable_t pagetable, uint64 va, int alloc);
-    int mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm);
-    void kvmmap(uint64 va, uint64 pa, uint64 sz, int perm);
     void kvminit();
     void kvminithart();
-    pagetable_t uvmcreate();
-    void uvminit(pagetable_t pagetable, uchar *src, uint sz);
-    void uvmunmap(pagetable_t pagetable, uint64 va, uint64 npages, int do_free);
-    void uvmfree(pagetable_t pagetable, uint64 sz);
-    int uvmcopy(pagetable_t oldpt, pagetable_t newpt, uint64 sz);
-    uint64 uvmalloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz);
-    uint64 uvmdealloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz);
-    int copyin(pagetable_t pagetable, char *dst, uint64 srcva, uint64 len);
+
+    uint64 *uvmcreate();
+    void uvminit(uint64 *pagetable, uchar *src, uint64 sz);
+    uint64 uvmalloc(uint64 *pagetable, uint64 oldsz, uint64 newsz, int xperm);
+    uint64 uvmdealloc(uint64 *pagetable, uint64 oldsz, uint64 newsz);
+    void uvmfree(uint64 *pagetable, uint64 sz);
+    int uvmcopy(uint64 *oldpt, uint64 *newpt, uint64 sz);
+    void uvmunmap(uint64 *pagetable, uint64 va, uint64 npages, int do_free);
+
+    int copyout(uint64 *pagetable, uint64 dstva, char *src, uint64 len);
+    int copyin(uint64 *pagetable, char *dst, uint64 srcva, uint64 len);
+    int copyinstr(uint64 *pagetable, char *dst, uint64 srcva, uint64 max);
+
+    int handle_cow_fault(uint64 *pagetable, uint64 va);
+    int mappages(uint64 *pagetable, uint64 va, uint64 size, uint64 pa, int perm);
+
+    uint64 walkaddr(uint64 *pagetable, uint64 va);
 }
\ No newline at end of file
diff --git a/include/kernel/pmm.h b/include/kernel/pmm.h
index 3328450..d31473f 100644
--- a/include/kernel/pmm.h
+++ b/include/kernel/pmm.h
@@ -1,13 +1,50 @@
 #pragma once
 #include "common/types.h"
+#include "kernel/spinlock.h"
 
-#define PHYSTOP (0x80000000 + 128 * 1024 * 1024)
-#define PGSIZE 4096
+// Physical Memory Layout Definition
+#define KERNBASE 0x80000000
+// Set the memory size to 128MB
+#define PHYSIZE (128 * 1024 * 1024)
+#define PHYSTOP (KERNBASE + PHYSIZE)
 
-namespace PMM{
+// Buddy System Max Order
+// Order 10 => 2^10 pages = 1024 * 4KB = 4MB contiguous block
+// Order 11 => 2^11 pages = 8MB
+#define MAX_ORDER 11
+
+// Page flag
+#define PG_used 0x01     // This page is occupied
+#define PG_reserved 0x02 // This page is reserved (kernel code/data, DTB, MemMap)
+
+// Physical Page Metadata Structure
+struct Page
+{
+    uint8 flags;       // Page Status (PG_used, PG_reserved)
+    uint8 order;       // If it is the first page of a free block, record the order of the current block
+    uint16 refcnt;     // Reference Counting
+    struct Page *next; // Free list pointer (points to the next free block of the same size)
+    struct Page *prev; // Doubly linked list (easy to remove)
+};
+
+namespace PMM
+{
+    // Initialize physical memory management
     void init();
 
-    void* alloc_page();
+    // Core Allocation Interface (Buddy System)
+    // order: 0 ~ MAX_ORDER-1
+    void *alloc_pages(int order);
+    void free_pages(void *pa, int order);
+
+    // Compatible with old interface (allocate single page with order=0 and automatically reset to zero)
+    void *alloc_page();
+    void free_page(void *pa);
+
+    // Helper function
+    struct Page *pa_to_page(uint64 pa);
+    uint64 page_to_pa(struct Page *page);
 
-    void free_page(void* pa);
+    // Debug information
+    void print_free_lists();
 }
\ No newline at end of file
diff --git a/include/kernel/proc.h b/include/kernel/proc.h
index b557267..cbf2902 100644
--- a/include/kernel/proc.h
+++ b/include/kernel/proc.h
@@ -1,56 +1,8 @@
 #pragma once
 #include "common/types.h"
-#include "kernel/trap.h"
+#include "kernel/proc_def.h"
 #include "kernel/spinlock.h"
 
-struct Context
-{
-    uint64 ra;
-    uint64 sp;
-
-    uint64 s0;
-    uint64 s1;
-    uint64 s2;
-    uint64 s3;
-    uint64 s4;
-    uint64 s5;
-    uint64 s6;
-    uint64 s7;
-    uint64 s8;
-    uint64 s9;
-    uint64 s10;
-    uint64 s11;
-};
-
-enum ProcState{
-    UNUSED,
-    USED,
-    SLEEPING,
-    RUNNABLE,
-    RUNNING,
-    ZOMBIE,
-};
-
-struct Proc
-{
-    struct Context context;
-    struct Trapframe *tf;
-
-    uint64 *pagetable;
-
-    enum ProcState state;
-    int pid;
-
-    void* kstack;
-    char name[16];
-    uint64 sz;
-
-    struct Proc *parent;
-    void *chan;
-    int xstate;
-};
-
-
 namespace ProcManager
 {
     void init();
@@ -62,8 +14,11 @@ namespace ProcManager
     void user_init();
     void exit(int status);
     int wait(uint64 addr);
-    void sleep(void *chan, struct spinlock *lk);
+
+    void sleep(void *chan, Spinlock *lk);
     void wakeup(void *chan);
+
+    int growproc(int n);
 }
 
 void forkret();
diff --git a/include/kernel/proc_def.h b/include/kernel/proc_def.h
new file mode 100644
index 0000000..5ce4c03
--- /dev/null
+++ b/include/kernel/proc_def.h
@@ -0,0 +1,69 @@
+#pragma once
+#include "common/types.h"
+#include "common/fcntl.h"
+
+struct cpu;
+struct Trapframe;
+class Inode;
+struct file;
+
+enum ProcState
+{
+    UNUSED,
+    USED,
+    SLEEPING,
+    RUNNABLE,
+    RUNNING,
+    ZOMBIE,
+};
+
+#define PRIO_MAX 0
+#define PRIO_MIN 3
+#define N_PRIO 4
+
+// Context structure
+struct Context
+{
+    uint64 ra;
+    uint64 sp;
+    uint64 s0;
+    uint64 s1;
+    uint64 s2;
+    uint64 s3;
+    uint64 s4;
+    uint64 s5;
+    uint64 s6;
+    uint64 s7;
+    uint64 s8;
+    uint64 s9;
+    uint64 s10;
+    uint64 s11;
+};
+
+struct Proc
+{
+    struct Context context;
+    struct Trapframe *tf;
+    uint64 *pagetable;
+    enum ProcState state;
+    int pid;
+    void *kstack;
+    char name[16];
+    uint64 sz;
+    struct Proc *parent;
+    void *chan;
+    int xstate;
+
+    Inode *cwd;
+    struct file *ofile[NOFILE];
+
+    struct Proc *next;
+    struct Proc *prev;
+
+    struct Proc *all_next;
+    struct Proc *all_prev;
+
+    int priority;
+    int ticks;
+    struct cpu *cpu;
+};
\ No newline at end of file
diff --git a/include/kernel/riscv.h b/include/kernel/riscv.h
index 4b3d323..0c586a9 100644
--- a/include/kernel/riscv.h
+++ b/include/kernel/riscv.h
@@ -79,6 +79,7 @@ w_sip(uint64 x)
 // Supervisor Interrupt Enable
 #define SIE_SEIE (1L << 9) // external
 #define SIE_STIE (1L << 5) // timer
+#define SIE_SSIE (1L << 1) // software
 static inline uint64
 r_sie()
 {
@@ -375,7 +376,8 @@ typedef uint64 *pagetable_t; // 512 PTEs
 #define PTE_X (1L << 3)
 #define PTE_U (1L << 4) // user can access
 
-
+// COW Flag (PTE bit 8)
+#define PTE_COW (1L << 8)
 
 #if defined(LAB_MMAP) || defined(LAB_PGTBL) || defined(LAB_COW)
 #define PTE_LEAF(pte) (((pte) & PTE_R) | ((pte) & PTE_W) | ((pte) & PTE_X))
diff --git a/include/kernel/runqueue.h b/include/kernel/runqueue.h
new file mode 100644
index 0000000..ea6e4cc
--- /dev/null
+++ b/include/kernel/runqueue.h
@@ -0,0 +1,16 @@
+#pragma once
+#include "kernel/spinlock.h"
+#include "kernel/proc_def.h"
+
+struct RunQueue
+{
+    Spinlock lock;
+    struct Proc *heads[N_PRIO];
+    struct Proc *tails[N_PRIO];
+    uint64 count;
+
+    void init(const char *name);
+    void enqueue(struct Proc *p);
+    struct Proc *dequeue();
+    struct Proc *steal();
+};
\ No newline at end of file
diff --git a/include/kernel/slab.h b/include/kernel/slab.h
new file mode 100644
index 0000000..650f8a9
--- /dev/null
+++ b/include/kernel/slab.h
@@ -0,0 +1,10 @@
+#pragma once
+#include "common/types.h"
+
+namespace Slab
+{
+    void init();
+
+    void *kmalloc(uint64 size);
+    void kfree(void *ptr);
+}
\ No newline at end of file
diff --git a/include/kernel/spinlock.h b/include/kernel/spinlock.h
index aec4b6a..3102e68 100644
--- a/include/kernel/spinlock.h
+++ b/include/kernel/spinlock.h
@@ -1,20 +1,48 @@
 #pragma once
 #include "common/types.h"
 
-struct spinlock
+struct cpu;
+
+// Spinlock
+// Features: Non-interruptible, busy-wait loop, extremely short hold time.
+// Scenario: Protecting core data such as scheduler, interrupt handling, PMM, etc.
+class Spinlock
 {
-    uint locked;
+public:
+    volatile uint32 locked;     // Whether it is locked (0: unlocked, 1: locked)
+    const char *name;      // Lock Name (for debugging)
+    struct cpu *cpu; // The CPU holding the lock
+
+    // Constructor
+    Spinlock() : locked(0), name("uninit"), cpu(nullptr) {}
+
+    // Initialize lock name
+    void init(const char *name);
+
+    // Acquire lock
+    void acquire();
 
-    char *name;
-    int cpu_id;
+    // Release lock
+    void release();
+
+    // Check if the current CPU holds the lock
+    bool holding();
 };
 
-namespace Spinlock
+// Mutex
+// Features: Allows interruption, allows sleeping (yield CPU), can hold for a long time.
+// Scenarios: File system IO, device driver waiting, long-term buffering operations.
+class Mutex
 {
-    void init(struct spinlock *lk, char *name);
-    void acquire(struct spinlock *lk);
-    void release(struct spinlock *lk);
-    int holding(struct spinlock *lk);
-    void push_off();
-    void pop_off();
-}
\ No newline at end of file
+public:
+    uint32 locked;    // Whether it is locked
+    const char *name; // Lock Name
+    int pid;          // PID of the process holding the lock (for debugging)
+
+    Spinlock lk; // Internal spin lock, protects the state of the Mutex itself
+
+    void init(const char *name);
+    void acquire();
+    void release();
+    bool holding();
+};
\ No newline at end of file
diff --git a/include/kernel/sync.h b/include/kernel/sync.h
new file mode 100644
index 0000000..83d88c8
--- /dev/null
+++ b/include/kernel/sync.h
@@ -0,0 +1,38 @@
+#pragma once
+#include "common/types.h"
+#include "kernel/spinlock.h"
+#include "kernel/proc_def.h"
+
+
+struct WaitQueue
+{
+    Spinlock lock;
+    struct Proc *head;
+    struct Proc *tail;
+
+    void init(const char *name);
+    void sleep();
+    void wakeup();
+    void wakeup_all();
+};
+
+struct Semaphore
+{
+    int value;
+    WaitQueue wq;
+    Spinlock lock;
+
+    void init(int val, const char *name);
+    void wait();
+    void post();
+};
+
+struct CondVar
+{
+    WaitQueue wq;
+
+    void init(const char *name);
+    void wait(Spinlock *mutex_lock);
+    void signal();
+    void broadcast();
+};
\ No newline at end of file
diff --git a/include/kernel/syscall.h b/include/kernel/syscall.h
index 222f2f4..c0c9082 100644
--- a/include/kernel/syscall.h
+++ b/include/kernel/syscall.h
@@ -22,6 +22,8 @@
 #define SYS_link    20
 #define SYS_mkdir   21
 #define SYS_close   22
+#define SYS_disk_test 23
+#define SYS_lseek   24
 
 #ifndef __ASSEMBLER__
 void syscall();
diff --git a/include/kernel/trap.h b/include/kernel/trap.h
index 79bb037..35b225c 100644
--- a/include/kernel/trap.h
+++ b/include/kernel/trap.h
@@ -45,7 +45,6 @@ struct Trapframe
 namespace Trap
 {
     void init();
-    extern "C" void kernelvec();
-    extern "C" void kerneltrap(struct Trapframe *tf);
-}
-extern "C" void usertrap();
\ No newline at end of file
+    void inithart();
+    int devintr();
+}
\ No newline at end of file
diff --git a/include/lib/string.h b/include/lib/string.h
index aa87489..309bf02 100644
--- a/include/lib/string.h
+++ b/include/lib/string.h
@@ -10,4 +10,5 @@ void *memcpy(void *dst, const void *src, uint n);
 
 void strcpy(char *dst, const char *src);
 int strlen(const char *s);
-int strcmp(const char *s1, const char *s2);
\ No newline at end of file
+int strcmp(const char *s1, const char *s2);
+int strcasecmp(const char *s1, const char *s2);
\ No newline at end of file
diff --git a/include/ulib/assert.h b/include/ulib/assert.h
new file mode 100644
index 0000000..a083aff
--- /dev/null
+++ b/include/ulib/assert.h
@@ -0,0 +1,20 @@
+#ifndef _ASSERT_H
+#define _ASSERT_H
+
+#ifdef NDEBUG
+#define assert(ignore) ((void)0)
+#else
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+    void __assert_fail(const char *expr, const char *file, int line, const char *func);
+#ifdef __cplusplus
+}
+#endif
+
+#define assert(expr) \
+    ((expr) ? (void)0 : __assert_fail(#expr, __FILE__, __LINE__, __func__))
+#endif
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/cstdlib b/include/ulib/cstdlib
new file mode 100644
index 0000000..69b9bb6
--- /dev/null
+++ b/include/ulib/cstdlib
@@ -0,0 +1,52 @@
+#ifndef _CPP_CSTDLIB
+#define _CPP_CSTDLIB
+
+#include "stdlib.h"
+
+namespace std
+{
+    using :: malloc;
+    using :: free;
+    using :: calloc;
+    using :: realloc;
+
+    using :: exit;
+    using :: abort;
+    using :: atexit;
+    using :: getenv;
+    using :: system;
+
+    using :: atoi;
+    using :: atol;
+    using :: atoll;
+    using :: atof;
+
+    using :: strtol;
+    using :: strtoul;
+    using :: strtoll;
+    using :: strtoull;
+
+    using :: strtod;
+    using :: strtof;
+
+    using :: bsearch;
+    using :: qsort;
+
+    using :: abs;
+    using :: labs;
+    using :: llabs;
+    using :: div;
+    using :: ldiv;
+    using :: lldiv;
+
+    using :: rand;
+    using :: srand;
+
+    using :: mblen;
+    using :: mbtowc;
+    using :: wctomb;
+    using :: mbstowcs;
+    using :: wcstombs;
+}
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/cstring b/include/ulib/cstring
new file mode 100644
index 0000000..bb8ab44
--- /dev/null
+++ b/include/ulib/cstring
@@ -0,0 +1,32 @@
+#ifndef _CPP_CSTRING
+#define _CPP_CSTRING
+
+#include "string.h"
+
+namespace std
+{
+    using::memchr;
+    using::memcmp;
+    using::memcpy;
+    using::memmove;
+    using::memset;
+    using::strcat;
+    using::strchr;
+    using::strcmp;
+    using::strcpy;
+    using::strcspn;
+    using::strdup;
+    using::strerror;
+    using::strlcat;
+    using::strlcpy;
+    using::strlen;
+    using::strncat;
+    using::strncmp;
+    using::strpbrk;
+    using::strrchr;
+    using::strspn;
+    using::strstr;
+    using::strtok;
+} // namespace std
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/ctypes.h b/include/ulib/ctypes.h
new file mode 100644
index 0000000..3e0bc22
--- /dev/null
+++ b/include/ulib/ctypes.h
@@ -0,0 +1,26 @@
+#ifndef _CTYPE_H
+#define _CTYPE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    static inline int isdigit(int c) { return c >= '0' && c <= '9'; }
+    static inline int islower(int c) { return c >= 'a' && c <= 'z'; }
+    static inline int isupper(int c) { return c >= 'A' && c <= 'Z'; }
+    static inline int isalpha(int c) { return islower(c) || isupper(c); }
+    static inline int isalnum(int c) { return isalpha(c) || isdigit(c); }
+    static inline int isspace(int c) { return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r'; }
+    static inline int isprint(int c) { return c >= 32 && c <= 126; }
+    static inline int iscntrl(int c) { return c < 32 || c == 127; }
+    static inline int isxdigit(int c) { return isdigit(c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'); }
+
+    static inline int tolower(int c) { return isupper(c) ? c + 32 : c; }
+    static inline int toupper(int c) { return islower(c) ? c - 32 : c; }
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/cxx.cc b/include/ulib/cxx.cc
new file mode 100644
index 0000000..d24de1e
--- /dev/null
+++ b/include/ulib/cxx.cc
@@ -0,0 +1,32 @@
+#include "ulib/stdlib.h"
+
+
+void *operator new(unsigned long n)
+{
+    return malloc(n);
+}
+
+void *operator new[](unsigned long n)
+{
+    return malloc(n);
+}
+
+void operator delete(void *p)
+{
+    free(p);
+}
+
+void operator delete[](void *p)
+{
+    free(p);
+}
+
+void operator delete(void *p, unsigned long)
+{
+    free(p);
+}
+
+void operator delete[](void *p, unsigned long)
+{
+    free(p);
+}
\ No newline at end of file
diff --git a/include/ulib/errno.h b/include/ulib/errno.h
new file mode 100644
index 0000000..03ff8fd
--- /dev/null
+++ b/include/ulib/errno.h
@@ -0,0 +1,31 @@
+#ifndef _ERRNO_H
+#define _ERRNO_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+extern int errno;
+
+// Linux/ASM-Generic
+#define EPERM 1   /* Operation not permitted */
+#define ENOENT 2  /* No such file or directory */
+#define ESRCH 3   /* No such process */
+#define EINTR 4   /* Interrupted system call */
+#define EIO 5     /* I/O error */
+#define ENXIO 6   /* No such device or address */
+#define E2BIG 7   /* Argument list too long */
+#define ENOEXEC 8 /* Exec format error */
+#define EBADF 9   /* Bad file number */
+#define ECHILD 10 /* No child processes */
+#define EAGAIN 11 /* Try again */
+#define ENOMEM 12 /* Out of memory */
+#define EACCES 13 /* Permission denied */
+#define EFAULT 14 /* Bad address */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/iostream b/include/ulib/iostream
new file mode 100644
index 0000000..83ed74c
--- /dev/null
+++ b/include/ulib/iostream
@@ -0,0 +1,110 @@
+#ifndef _IOSTREAM
+#define _IOSTREAM
+
+#include "stdio.h"
+
+namespace std
+{
+    class ostream
+    {
+    private:
+        FILE* _stream;
+    public:
+        ostream(FILE* f) : _stream(f) {}
+
+        ostream& operator<<(const char* str)
+        {
+            fprintf(_stream, "%s", str);
+            return *this;
+        }
+
+        ostream& operator<<(int n)
+        {
+            fprintf(_stream, "%d", n);
+            return *this;
+        }
+
+        ostream &operator<<(long n)
+        {
+            fprintf(_stream, "%ld", n);
+            return *this;
+        }
+
+        ostream &operator<<(long long n)
+        {
+            fprintf(_stream, "%lld", n);
+            return *this;
+        }
+
+        ostream &operator<<(double f)
+        {
+            fprintf(_stream, "%f", f);
+            return *this;
+        }
+
+        ostream &operator<<(char c)
+        {
+            fputc(c, _stream);
+            return *this;
+        }
+
+        ostream &operator<<(void *p)
+        {
+            fprintf(_stream, "%p", p);
+            return *this;
+        }
+
+        ostream &operator<<(ostream &(*func)(ostream &))
+        {
+            return func(*this);
+        }
+
+        ostream &flush()
+        {
+            fflush(_stream);
+            return *this;
+        }
+    };
+
+    class istream{
+    private:
+        FILE* _stream;
+    public:
+        istream(FILE *f) : _stream(f) {}
+
+        istream& operator>>(int n)
+        {
+            fscanf(_stream, "%d", n);
+            return *this;
+        }
+
+        istream &operator>>(double &f)
+        {
+            fscanf(_stream, "%lf", &f);
+            return *this;
+        }
+
+        istream &operator>>(char *str)
+        {
+            fscanf(_stream, "%s", str);
+            return *this;
+        }
+
+        istream &operator>>(char &c)
+        {
+            char tmp[2];
+            fscanf(_stream, " %c", tmp);
+            c = tmp[0];
+            return *this;
+        }
+    };
+
+    inline ostream &endl(ostream &os)
+    {
+        os << '\n';
+        os.flush();
+        return os;
+    }
+}
+
+#endif
\ No newline at end of file
diff --git a/include/ulib/limits.h b/include/ulib/limits.h
new file mode 100644
index 0000000..030ffbb
--- /dev/null
+++ b/include/ulib/limits.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#define CHAR_BIT 8
+#define SCHAR_MIN (-128)
+#define SCHAR_MAX 127
+#define UCHAR_MAX 255
+
+#define SHRT_MIN (-32768)
+#define SHRT_MAX 32767
+#define USHRT_MAX 65535
+
+#define INT_MIN (-2147483648)
+#define INT_MAX 2147483647
+#define UINT_MAX 4294967295U
+
+#define LONG_MAX 9223372036854775807L
+#define LONG_MIN (-LONG_MAX - 1L)
+#define ULONG_MAX 18446744073709551615UL
+
+#define LLONG_MAX 9223372036854775807LL
+#define LLONG_MIN (-LLONG_MAX - 1LL)
+#define ULLONG_MAX 18446744073709551615ULL
\ No newline at end of file
diff --git a/include/ulib/stb_sprintf.h b/include/ulib/stb_sprintf.h
new file mode 100644
index 0000000..00dc123
--- /dev/null
+++ b/include/ulib/stb_sprintf.h
@@ -0,0 +1,1916 @@
+// stb_sprintf - v1.10 - public domain snprintf() implementation
+// originally by Jeff Roberts / RAD Game Tools, 2015/10/20
+// http://github.com/nothings/stb
+//
+// allowed types:  sc uidBboXx p AaGgEef n
+// lengths      :  hh h ll j z t I64 I32 I
+//
+// Contributors:
+//    Fabian "ryg" Giesen (reformatting)
+//    github:aganm (attribute format)
+//
+// Contributors (bugfixes):
+//    github:d26435
+//    github:trex78
+//    github:account-login
+//    Jari Komppa (SI suffixes)
+//    Rohit Nirmal
+//    Marcin Wojdyr
+//    Leonard Ritter
+//    Stefano Zanotti
+//    Adam Allison
+//    Arvid Gerstmann
+//    Markus Kolb
+//
+// LICENSE:
+//
+//   See end of file for license information.
+
+#ifndef STB_SPRINTF_H_INCLUDE
+#define STB_SPRINTF_H_INCLUDE
+
+/*
+Single file sprintf replacement.
+
+Originally written by Jeff Roberts at RAD Game Tools - 2015/10/20.
+Hereby placed in public domain.
+
+This is a full sprintf replacement that supports everything that
+the C runtime sprintfs support, including float/double, 64-bit integers,
+hex floats, field parameters (%*.*d stuff), length reads backs, etc.
+
+Why would you need this if sprintf already exists?  Well, first off,
+it's *much* faster (see below). It's also much smaller than the CRT
+versions code-space-wise. We've also added some simple improvements
+that are super handy (commas in thousands, callbacks at buffer full,
+for example). Finally, the format strings for MSVC and GCC differ
+for 64-bit integers (among other small things), so this lets you use
+the same format strings in cross platform code.
+
+It uses the standard single file trick of being both the header file
+and the source itself. If you just include it normally, you just get
+the header file function definitions. To get the code, you include
+it from a C or C++ file and define STB_SPRINTF_IMPLEMENTATION first.
+
+It only uses va_args macros from the C runtime to do it's work. It
+does cast doubles to S64s and shifts and divides U64s, which does
+drag in CRT code on most platforms.
+
+It compiles to roughly 8K with float support, and 4K without.
+As a comparison, when using MSVC static libs, calling sprintf drags
+in 16K.
+
+API:
+====
+int stbsp_sprintf( char * buf, char const * fmt, ... )
+int stbsp_snprintf( char * buf, int count, char const * fmt, ... )
+  Convert an arg list into a buffer.  stbsp_snprintf always returns
+  a zero-terminated string (unlike regular snprintf).
+
+int stbsp_vsprintf( char * buf, char const * fmt, va_list va )
+int stbsp_vsnprintf( char * buf, int count, char const * fmt, va_list va )
+  Convert a va_list arg list into a buffer.  stbsp_vsnprintf always returns
+  a zero-terminated string (unlike regular snprintf).
+
+int stbsp_vsprintfcb( STBSP_SPRINTFCB * callback, void * user, char * buf, char const * fmt, va_list va )
+    typedef char * STBSP_SPRINTFCB( char const * buf, void * user, int len );
+  Convert into a buffer, calling back every STB_SPRINTF_MIN chars.
+  Your callback can then copy the chars out, print them or whatever.
+  This function is actually the workhorse for everything else.
+  The buffer you pass in must hold at least STB_SPRINTF_MIN characters.
+    // you return the next buffer to use or 0 to stop converting
+
+void stbsp_set_separators( char comma, char period )
+  Set the comma and period characters to use.
+
+FLOATS/DOUBLES:
+===============
+This code uses a internal float->ascii conversion method that uses
+doubles with error correction (double-doubles, for ~105 bits of
+precision).  This conversion is round-trip perfect - that is, an atof
+of the values output here will give you the bit-exact double back.
+
+One difference is that our insignificant digits will be different than
+with MSVC or GCC (but they don't match each other either).  We also
+don't attempt to find the minimum length matching float (pre-MSVC15
+doesn't either).
+
+If you don't need float or doubles at all, define STB_SPRINTF_NOFLOAT
+and you'll save 4K of code space.
+
+64-BIT INTS:
+============
+This library also supports 64-bit integers and you can use MSVC style or
+GCC style indicators (%I64d or %lld).  It supports the C99 specifiers
+for size_t and ptr_diff_t (%jd %zd) as well.
+
+EXTRAS:
+=======
+Like some GCCs, for integers and floats, you can use a ' (single quote)
+specifier and commas will be inserted on the thousands: "%'d" on 12345
+would print 12,345.
+
+For integers and floats, you can use a "$" specifier and the number
+will be converted to float and then divided to get kilo, mega, giga or
+tera and then printed, so "%$d" 1000 is "1.0 k", "%$.2d" 2536000 is
+"2.53 M", etc. For byte values, use two $:s, like "%$$d" to turn
+2536000 to "2.42 Mi". If you prefer JEDEC suffixes to SI ones, use three
+$:s: "%$$$d" -> "2.42 M". To remove the space between the number and the
+suffix, add "_" specifier: "%_$d" -> "2.53M".
+
+In addition to octal and hexadecimal conversions, you can print
+integers in binary: "%b" for 256 would print 100.
+
+PERFORMANCE vs MSVC 2008 32-/64-bit (GCC is even slower than MSVC):
+===================================================================
+"%d" across all 32-bit ints (4.8x/4.0x faster than 32-/64-bit MSVC)
+"%24d" across all 32-bit ints (4.5x/4.2x faster)
+"%x" across all 32-bit ints (4.5x/3.8x faster)
+"%08x" across all 32-bit ints (4.3x/3.8x faster)
+"%f" across e-10 to e+10 floats (7.3x/6.0x faster)
+"%e" across e-10 to e+10 floats (8.1x/6.0x faster)
+"%g" across e-10 to e+10 floats (10.0x/7.1x faster)
+"%f" for values near e-300 (7.9x/6.5x faster)
+"%f" for values near e+300 (10.0x/9.1x faster)
+"%e" for values near e-300 (10.1x/7.0x faster)
+"%e" for values near e+300 (9.2x/6.0x faster)
+"%.320f" for values near e-300 (12.6x/11.2x faster)
+"%a" for random values (8.6x/4.3x faster)
+"%I64d" for 64-bits with 32-bit values (4.8x/3.4x faster)
+"%I64d" for 64-bits > 32-bit values (4.9x/5.5x faster)
+"%s%s%s" for 64 char strings (7.1x/7.3x faster)
+"...512 char string..." ( 35.0x/32.5x faster!)
+*/
+
+#if defined(__clang__)
+ #if defined(__has_feature) && defined(__has_attribute)
+  #if __has_feature(address_sanitizer)
+   #if __has_attribute(__no_sanitize__)
+    #define STBSP__ASAN __attribute__((__no_sanitize__("address")))
+   #elif __has_attribute(__no_sanitize_address__)
+    #define STBSP__ASAN __attribute__((__no_sanitize_address__))
+   #elif __has_attribute(__no_address_safety_analysis__)
+    #define STBSP__ASAN __attribute__((__no_address_safety_analysis__))
+   #endif
+  #endif
+ #endif
+#elif defined(__GNUC__) && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))
+ #if defined(__SANITIZE_ADDRESS__) && __SANITIZE_ADDRESS__
+  #define STBSP__ASAN __attribute__((__no_sanitize_address__))
+ #endif
+#endif
+
+#ifndef STBSP__ASAN
+#define STBSP__ASAN
+#endif
+
+#ifdef STB_SPRINTF_STATIC
+#define STBSP__PUBLICDEC static
+#define STBSP__PUBLICDEF static STBSP__ASAN
+#else
+#ifdef __cplusplus
+#define STBSP__PUBLICDEC extern "C"
+#define STBSP__PUBLICDEF extern "C" STBSP__ASAN
+#else
+#define STBSP__PUBLICDEC extern
+#define STBSP__PUBLICDEF STBSP__ASAN
+#endif
+#endif
+
+#if defined(__has_attribute)
+ #if __has_attribute(format)
+   #define STBSP__ATTRIBUTE_FORMAT(fmt,va) __attribute__((format(printf,fmt,va)))
+ #endif
+#endif
+
+#ifndef STBSP__ATTRIBUTE_FORMAT
+#define STBSP__ATTRIBUTE_FORMAT(fmt,va)
+#endif
+
+#ifdef _MSC_VER
+#define STBSP__NOTUSED(v)  (void)(v)
+#else
+#define STBSP__NOTUSED(v)  (void)sizeof(v)
+#endif
+
+#include <stdarg.h> // for va_arg(), va_list()
+#include <stddef.h> // size_t, ptrdiff_t
+
+#ifndef stbsp__uintptr
+#if defined(__riscv) && (__riscv_xlen == 64)
+#define stbsp__uintptr unsigned long long
+#elif defined(__ppc64__) || defined(__powerpc64__) || defined(__aarch64__) || defined(_M_X64) || defined(__x86_64__) || defined(__x86_64) || defined(__s390x__)
+#define stbsp__uintptr unsigned long long
+#else
+#define stbsp__uintptr unsigned int
+#endif
+#endif
+
+#ifndef STB_SPRINTF_MIN
+#define STB_SPRINTF_MIN 512 // how many characters per callback
+#endif
+typedef char *STBSP_SPRINTFCB(const char *buf, void *user, int len);
+
+#ifndef STB_SPRINTF_DECORATE
+#define STB_SPRINTF_DECORATE(name) stbsp_##name // define this before including if you want to change the names
+#endif
+
+STBSP__PUBLICDEC int STB_SPRINTF_DECORATE(vsprintf)(char *buf, char const *fmt, va_list va);
+STBSP__PUBLICDEC int STB_SPRINTF_DECORATE(vsnprintf)(char *buf, int count, char const *fmt, va_list va);
+STBSP__PUBLICDEC int STB_SPRINTF_DECORATE(sprintf)(char *buf, char const *fmt, ...) STBSP__ATTRIBUTE_FORMAT(2,3);
+STBSP__PUBLICDEC int STB_SPRINTF_DECORATE(snprintf)(char *buf, int count, char const *fmt, ...) STBSP__ATTRIBUTE_FORMAT(3,4);
+
+STBSP__PUBLICDEC int STB_SPRINTF_DECORATE(vsprintfcb)(STBSP_SPRINTFCB *callback, void *user, char *buf, char const *fmt, va_list va);
+STBSP__PUBLICDEC void STB_SPRINTF_DECORATE(set_separators)(char comma, char period);
+
+#endif // STB_SPRINTF_H_INCLUDE
+
+#ifdef STB_SPRINTF_IMPLEMENTATION
+
+#define stbsp__uint32 unsigned int
+#define stbsp__int32 signed int
+
+#ifdef _MSC_VER
+#define stbsp__uint64 unsigned __int64
+#define stbsp__int64 signed __int64
+#else
+#define stbsp__uint64 unsigned long long
+#define stbsp__int64 signed long long
+#endif
+#define stbsp__uint16 unsigned short
+
+#ifndef stbsp__uintptr
+#if defined(__ppc64__) || defined(__powerpc64__) || defined(__aarch64__) || defined(_M_X64) || defined(__x86_64__) || defined(__x86_64) || defined(__s390x__)
+#define stbsp__uintptr stbsp__uint64
+#else
+#define stbsp__uintptr stbsp__uint32
+#endif
+#endif
+
+#ifndef STB_SPRINTF_MSVC_MODE // used for MSVC2013 and earlier (MSVC2015 matches GCC)
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define STB_SPRINTF_MSVC_MODE
+#endif
+#endif
+
+#ifdef STB_SPRINTF_NOUNALIGNED // define this before inclusion to force stbsp_sprintf to always use aligned accesses
+#define STBSP__UNALIGNED(code)
+#else
+#define STBSP__UNALIGNED(code) code
+#endif
+
+#ifndef STB_SPRINTF_NOFLOAT
+// internal float utility functions
+static stbsp__int32 stbsp__real_to_str(char const **start, stbsp__uint32 *len, char *out, stbsp__int32 *decimal_pos, double value, stbsp__uint32 frac_digits);
+static stbsp__int32 stbsp__real_to_parts(stbsp__int64 *bits, stbsp__int32 *expo, double value);
+#define STBSP__SPECIAL 0x7000
+#endif
+
+static char stbsp__period = '.';
+static char stbsp__comma = ',';
+static struct
+{
+   short temp; // force next field to be 2-byte aligned
+   char pair[201];
+} stbsp__digitpair =
+{
+  0,
+   "00010203040506070809101112131415161718192021222324"
+   "25262728293031323334353637383940414243444546474849"
+   "50515253545556575859606162636465666768697071727374"
+   "75767778798081828384858687888990919293949596979899"
+};
+
+STBSP__PUBLICDEF void STB_SPRINTF_DECORATE(set_separators)(char pcomma, char pperiod)
+{
+   stbsp__period = pperiod;
+   stbsp__comma = pcomma;
+}
+
+#define STBSP__LEFTJUST 1
+#define STBSP__LEADINGPLUS 2
+#define STBSP__LEADINGSPACE 4
+#define STBSP__LEADING_0X 8
+#define STBSP__LEADINGZERO 16
+#define STBSP__INTMAX 32
+#define STBSP__TRIPLET_COMMA 64
+#define STBSP__NEGATIVE 128
+#define STBSP__METRIC_SUFFIX 256
+#define STBSP__HALFWIDTH 512
+#define STBSP__METRIC_NOSPACE 1024
+#define STBSP__METRIC_1024 2048
+#define STBSP__METRIC_JEDEC 4096
+
+static void stbsp__lead_sign(stbsp__uint32 fl, char *sign)
+{
+   sign[0] = 0;
+   if (fl & STBSP__NEGATIVE) {
+      sign[0] = 1;
+      sign[1] = '-';
+   } else if (fl & STBSP__LEADINGSPACE) {
+      sign[0] = 1;
+      sign[1] = ' ';
+   } else if (fl & STBSP__LEADINGPLUS) {
+      sign[0] = 1;
+      sign[1] = '+';
+   }
+}
+
+static STBSP__ASAN stbsp__uint32 stbsp__strlen_limited(char const *s, stbsp__uint32 limit)
+{
+   char const * sn = s;
+
+   // get up to 4-byte alignment
+   for (;;) {
+      if (((stbsp__uintptr)sn & 3) == 0)
+         break;
+
+      if (!limit || *sn == 0)
+         return (stbsp__uint32)(sn - s);
+
+      ++sn;
+      --limit;
+   }
+
+   // scan over 4 bytes at a time to find terminating 0
+   // this will intentionally scan up to 3 bytes past the end of buffers,
+   // but becase it works 4B aligned, it will never cross page boundaries
+   // (hence the STBSP__ASAN markup; the over-read here is intentional
+   // and harmless)
+   while (limit >= 4) {
+      stbsp__uint32 v = *(stbsp__uint32 *)sn;
+      // bit hack to find if there's a 0 byte in there
+      if ((v - 0x01010101) & (~v) & 0x80808080UL)
+         break;
+
+      sn += 4;
+      limit -= 4;
+   }
+
+   // handle the last few characters to find actual size
+   while (limit && *sn) {
+      ++sn;
+      --limit;
+   }
+
+   return (stbsp__uint32)(sn - s);
+}
+
+STBSP__PUBLICDEF int STB_SPRINTF_DECORATE(vsprintfcb)(STBSP_SPRINTFCB *callback, void *user, char *buf, char const *fmt, va_list va)
+{
+   static char hex[] = "0123456789abcdefxp";
+   static char hexu[] = "0123456789ABCDEFXP";
+   char *bf;
+   char const *f;
+   int tlen = 0;
+
+   bf = buf;
+   f = fmt;
+   for (;;) {
+      stbsp__int32 fw, pr, tz;
+      stbsp__uint32 fl;
+
+      // macros for the callback buffer stuff
+      #define stbsp__chk_cb_bufL(bytes)                        \
+         {                                                     \
+            int len = (int)(bf - buf);                         \
+            if ((len + (bytes)) >= STB_SPRINTF_MIN) {          \
+               tlen += len;                                    \
+               if (0 == (bf = buf = callback(buf, user, len))) \
+                  goto done;                                   \
+            }                                                  \
+         }
+      #define stbsp__chk_cb_buf(bytes)    \
+         {                                \
+            if (callback) {               \
+               stbsp__chk_cb_bufL(bytes); \
+            }                             \
+         }
+      #define stbsp__flush_cb()                      \
+         {                                           \
+            stbsp__chk_cb_bufL(STB_SPRINTF_MIN - 1); \
+         } // flush if there is even one byte in the buffer
+      #define stbsp__cb_buf_clamp(cl, v)                \
+         cl = v;                                        \
+         if (callback) {                                \
+            int lg = STB_SPRINTF_MIN - (int)(bf - buf); \
+            if (cl > lg)                                \
+               cl = lg;                                 \
+         }
+
+      // fast copy everything up to the next % (or end of string)
+      for (;;) {
+         while (((stbsp__uintptr)f) & 3) {
+         schk1:
+            if (f[0] == '%')
+               goto scandd;
+         schk2:
+            if (f[0] == 0)
+               goto endfmt;
+            stbsp__chk_cb_buf(1);
+            *bf++ = f[0];
+            ++f;
+         }
+         for (;;) {
+            // Check if the next 4 bytes contain %(0x25) or end of string.
+            // Using the 'hasless' trick:
+            // https://graphics.stanford.edu/~seander/bithacks.html#HasLessInWord
+            stbsp__uint32 v, c;
+            v = *(stbsp__uint32 *)f;
+            c = (~v) & 0x80808080;
+            if (((v ^ 0x25252525) - 0x01010101) & c)
+               goto schk1;
+            if ((v - 0x01010101) & c)
+               goto schk2;
+            if (callback)
+               if ((STB_SPRINTF_MIN - (int)(bf - buf)) < 4)
+                  goto schk1;
+            #ifdef STB_SPRINTF_NOUNALIGNED
+                if(((stbsp__uintptr)bf) & 3) {
+                    bf[0] = f[0];
+                    bf[1] = f[1];
+                    bf[2] = f[2];
+                    bf[3] = f[3];
+                } else
+            #endif
+            {
+                *(stbsp__uint32 *)bf = v;
+            }
+            bf += 4;
+            f += 4;
+         }
+      }
+   scandd:
+
+      ++f;
+
+      // ok, we have a percent, read the modifiers first
+      fw = 0;
+      pr = -1;
+      fl = 0;
+      tz = 0;
+
+      // flags
+      for (;;) {
+         switch (f[0]) {
+         // if we have left justify
+         case '-':
+            fl |= STBSP__LEFTJUST;
+            ++f;
+            continue;
+         // if we have leading plus
+         case '+':
+            fl |= STBSP__LEADINGPLUS;
+            ++f;
+            continue;
+         // if we have leading space
+         case ' ':
+            fl |= STBSP__LEADINGSPACE;
+            ++f;
+            continue;
+         // if we have leading 0x
+         case '#':
+            fl |= STBSP__LEADING_0X;
+            ++f;
+            continue;
+         // if we have thousand commas
+         case '\'':
+            fl |= STBSP__TRIPLET_COMMA;
+            ++f;
+            continue;
+         // if we have kilo marker (none->kilo->kibi->jedec)
+         case '$':
+            if (fl & STBSP__METRIC_SUFFIX) {
+               if (fl & STBSP__METRIC_1024) {
+                  fl |= STBSP__METRIC_JEDEC;
+               } else {
+                  fl |= STBSP__METRIC_1024;
+               }
+            } else {
+               fl |= STBSP__METRIC_SUFFIX;
+            }
+            ++f;
+            continue;
+         // if we don't want space between metric suffix and number
+         case '_':
+            fl |= STBSP__METRIC_NOSPACE;
+            ++f;
+            continue;
+         // if we have leading zero
+         case '0':
+            fl |= STBSP__LEADINGZERO;
+            ++f;
+            goto flags_done;
+         default: goto flags_done;
+         }
+      }
+   flags_done:
+
+      // get the field width
+      if (f[0] == '*') {
+         fw = va_arg(va, stbsp__uint32);
+         ++f;
+      } else {
+         while ((f[0] >= '0') && (f[0] <= '9')) {
+            fw = fw * 10 + f[0] - '0';
+            f++;
+         }
+      }
+      // get the precision
+      if (f[0] == '.') {
+         ++f;
+         if (f[0] == '*') {
+            pr = va_arg(va, stbsp__uint32);
+            ++f;
+         } else {
+            pr = 0;
+            while ((f[0] >= '0') && (f[0] <= '9')) {
+               pr = pr * 10 + f[0] - '0';
+               f++;
+            }
+         }
+      }
+
+      // handle integer size overrides
+      switch (f[0]) {
+      // are we halfwidth?
+      case 'h':
+         fl |= STBSP__HALFWIDTH;
+         ++f;
+         if (f[0] == 'h')
+            ++f;  // QUARTERWIDTH
+         break;
+      // are we 64-bit (unix style)
+      case 'l':
+         fl |= ((sizeof(long) == 8) ? STBSP__INTMAX : 0);
+         ++f;
+         if (f[0] == 'l') {
+            fl |= STBSP__INTMAX;
+            ++f;
+         }
+         break;
+      // are we 64-bit on intmax? (c99)
+      case 'j':
+         fl |= (sizeof(size_t) == 8) ? STBSP__INTMAX : 0;
+         ++f;
+         break;
+      // are we 64-bit on size_t or ptrdiff_t? (c99)
+      case 'z':
+         fl |= (sizeof(ptrdiff_t) == 8) ? STBSP__INTMAX : 0;
+         ++f;
+         break;
+      case 't':
+         fl |= (sizeof(ptrdiff_t) == 8) ? STBSP__INTMAX : 0;
+         ++f;
+         break;
+      // are we 64-bit (msft style)
+      case 'I':
+         if ((f[1] == '6') && (f[2] == '4')) {
+            fl |= STBSP__INTMAX;
+            f += 3;
+         } else if ((f[1] == '3') && (f[2] == '2')) {
+            f += 3;
+         } else {
+            fl |= ((sizeof(void *) == 8) ? STBSP__INTMAX : 0);
+            ++f;
+         }
+         break;
+      default: break;
+      }
+
+      // handle each replacement
+      switch (f[0]) {
+         #define STBSP__NUMSZ 512 // big enough for e308 (with commas) or e-307
+         char num[STBSP__NUMSZ];
+         char lead[8];
+         char tail[8];
+         char *s;
+         char const *h;
+         stbsp__uint32 l, n, cs;
+         stbsp__uint64 n64;
+#ifndef STB_SPRINTF_NOFLOAT
+         double fv;
+#endif
+         stbsp__int32 dp;
+         char const *sn;
+
+      case 's':
+         // get the string
+         s = va_arg(va, char *);
+         if (s == 0)
+            s = (char *)"null";
+         // get the length, limited to desired precision
+         // always limit to ~0u chars since our counts are 32b
+         l = stbsp__strlen_limited(s, (pr >= 0) ? pr : ~0u);
+         lead[0] = 0;
+         tail[0] = 0;
+         pr = 0;
+         dp = 0;
+         cs = 0;
+         // copy the string in
+         goto scopy;
+
+      case 'c': // char
+         // get the character
+         s = num + STBSP__NUMSZ - 1;
+         *s = (char)va_arg(va, int);
+         l = 1;
+         lead[0] = 0;
+         tail[0] = 0;
+         pr = 0;
+         dp = 0;
+         cs = 0;
+         goto scopy;
+
+      case 'n': // weird write-bytes specifier
+      {
+         int *d = va_arg(va, int *);
+         *d = tlen + (int)(bf - buf);
+      } break;
+
+#ifdef STB_SPRINTF_NOFLOAT
+      case 'A':              // float
+      case 'a':              // hex float
+      case 'G':              // float
+      case 'g':              // float
+      case 'E':              // float
+      case 'e':              // float
+      case 'f':              // float
+         va_arg(va, double); // eat it
+         s = (char *)"No float";
+         l = 8;
+         lead[0] = 0;
+         tail[0] = 0;
+         pr = 0;
+         cs = 0;
+         STBSP__NOTUSED(dp);
+         goto scopy;
+#else
+      case 'A': // hex float
+      case 'a': // hex float
+         h = (f[0] == 'A') ? hexu : hex;
+         fv = va_arg(va, double);
+         if (pr == -1)
+            pr = 6; // default is 6
+         // read the double into a string
+         if (stbsp__real_to_parts((stbsp__int64 *)&n64, &dp, fv))
+            fl |= STBSP__NEGATIVE;
+
+         s = num + 64;
+
+         stbsp__lead_sign(fl, lead);
+
+         if (dp == -1023)
+            dp = (n64) ? -1022 : 0;
+         else
+            n64 |= (((stbsp__uint64)1) << 52);
+         n64 <<= (64 - 56);
+         if (pr < 15)
+            n64 += ((((stbsp__uint64)8) << 56) >> (pr * 4));
+// add leading chars
+
+#ifdef STB_SPRINTF_MSVC_MODE
+         *s++ = '0';
+         *s++ = 'x';
+#else
+         lead[1 + lead[0]] = '0';
+         lead[2 + lead[0]] = 'x';
+         lead[0] += 2;
+#endif
+         *s++ = h[(n64 >> 60) & 15];
+         n64 <<= 4;
+         if (pr)
+            *s++ = stbsp__period;
+         sn = s;
+
+         // print the bits
+         n = pr;
+         if (n > 13)
+            n = 13;
+         if (pr > (stbsp__int32)n)
+            tz = pr - n;
+         pr = 0;
+         while (n--) {
+            *s++ = h[(n64 >> 60) & 15];
+            n64 <<= 4;
+         }
+
+         // print the expo
+         tail[1] = h[17];
+         if (dp < 0) {
+            tail[2] = '-';
+            dp = -dp;
+         } else
+            tail[2] = '+';
+         n = (dp >= 1000) ? 6 : ((dp >= 100) ? 5 : ((dp >= 10) ? 4 : 3));
+         tail[0] = (char)n;
+         for (;;) {
+            tail[n] = '0' + dp % 10;
+            if (n <= 3)
+               break;
+            --n;
+            dp /= 10;
+         }
+
+         dp = (int)(s - sn);
+         l = (int)(s - (num + 64));
+         s = num + 64;
+         cs = 1 + (3 << 24);
+         goto scopy;
+
+      case 'G': // float
+      case 'g': // float
+         h = (f[0] == 'G') ? hexu : hex;
+         fv = va_arg(va, double);
+         if (pr == -1)
+            pr = 6;
+         else if (pr == 0)
+            pr = 1; // default is 6
+         // read the double into a string
+         if (stbsp__real_to_str(&sn, &l, num, &dp, fv, (pr - 1) | 0x80000000))
+            fl |= STBSP__NEGATIVE;
+
+         // clamp the precision and delete extra zeros after clamp
+         n = pr;
+         if (l > (stbsp__uint32)pr)
+            l = pr;
+         while ((l > 1) && (pr) && (sn[l - 1] == '0')) {
+            --pr;
+            --l;
+         }
+
+         // should we use %e
+         if ((dp <= -4) || (dp > (stbsp__int32)n)) {
+            if (pr > (stbsp__int32)l)
+               pr = l - 1;
+            else if (pr)
+               --pr; // when using %e, there is one digit before the decimal
+            goto doexpfromg;
+         }
+         // this is the insane action to get the pr to match %g semantics for %f
+         if (dp > 0) {
+            pr = (dp < (stbsp__int32)l) ? l - dp : 0;
+         } else {
+            pr = -dp + ((pr > (stbsp__int32)l) ? (stbsp__int32) l : pr);
+         }
+         goto dofloatfromg;
+
+      case 'E': // float
+      case 'e': // float
+         h = (f[0] == 'E') ? hexu : hex;
+         fv = va_arg(va, double);
+         if (pr == -1)
+            pr = 6; // default is 6
+         // read the double into a string
+         if (stbsp__real_to_str(&sn, &l, num, &dp, fv, pr | 0x80000000))
+            fl |= STBSP__NEGATIVE;
+      doexpfromg:
+         tail[0] = 0;
+         stbsp__lead_sign(fl, lead);
+         if (dp == STBSP__SPECIAL) {
+            s = (char *)sn;
+            cs = 0;
+            pr = 0;
+            goto scopy;
+         }
+         s = num + 64;
+         // handle leading chars
+         *s++ = sn[0];
+
+         if (pr)
+            *s++ = stbsp__period;
+
+         // handle after decimal
+         if ((l - 1) > (stbsp__uint32)pr)
+            l = pr + 1;
+         for (n = 1; n < l; n++)
+            *s++ = sn[n];
+         // trailing zeros
+         tz = pr - (l - 1);
+         pr = 0;
+         // dump expo
+         tail[1] = h[0xe];
+         dp -= 1;
+         if (dp < 0) {
+            tail[2] = '-';
+            dp = -dp;
+         } else
+            tail[2] = '+';
+#ifdef STB_SPRINTF_MSVC_MODE
+         n = 5;
+#else
+         n = (dp >= 100) ? 5 : 4;
+#endif
+         tail[0] = (char)n;
+         for (;;) {
+            tail[n] = '0' + dp % 10;
+            if (n <= 3)
+               break;
+            --n;
+            dp /= 10;
+         }
+         cs = 1 + (3 << 24); // how many tens
+         goto flt_lead;
+
+      case 'f': // float
+         fv = va_arg(va, double);
+      doafloat:
+         // do kilos
+         if (fl & STBSP__METRIC_SUFFIX) {
+            double divisor;
+            divisor = 1000.0f;
+            if (fl & STBSP__METRIC_1024)
+               divisor = 1024.0;
+            while (fl < 0x4000000) {
+               if ((fv < divisor) && (fv > -divisor))
+                  break;
+               fv /= divisor;
+               fl += 0x1000000;
+            }
+         }
+         if (pr == -1)
+            pr = 6; // default is 6
+         // read the double into a string
+         if (stbsp__real_to_str(&sn, &l, num, &dp, fv, pr))
+            fl |= STBSP__NEGATIVE;
+      dofloatfromg:
+         tail[0] = 0;
+         stbsp__lead_sign(fl, lead);
+         if (dp == STBSP__SPECIAL) {
+            s = (char *)sn;
+            cs = 0;
+            pr = 0;
+            goto scopy;
+         }
+         s = num + 64;
+
+         // handle the three decimal varieties
+         if (dp <= 0) {
+            stbsp__int32 i;
+            // handle 0.000*000xxxx
+            *s++ = '0';
+            if (pr)
+               *s++ = stbsp__period;
+            n = -dp;
+            if ((stbsp__int32)n > pr)
+               n = pr;
+            i = n;
+            while (i) {
+               if ((((stbsp__uintptr)s) & 3) == 0)
+                  break;
+               *s++ = '0';
+               --i;
+            }
+            while (i >= 4) {
+               *(stbsp__uint32 *)s = 0x30303030;
+               s += 4;
+               i -= 4;
+            }
+            while (i) {
+               *s++ = '0';
+               --i;
+            }
+            if ((stbsp__int32)(l + n) > pr)
+               l = pr - n;
+            i = l;
+            while (i) {
+               *s++ = *sn++;
+               --i;
+            }
+            tz = pr - (n + l);
+            cs = 1 + (3 << 24); // how many tens did we write (for commas below)
+         } else {
+            cs = (fl & STBSP__TRIPLET_COMMA) ? ((600 - (stbsp__uint32)dp) % 3) : 0;
+            if ((stbsp__uint32)dp >= l) {
+               // handle xxxx000*000.0
+               n = 0;
+               for (;;) {
+                  if ((fl & STBSP__TRIPLET_COMMA) && (++cs == 4)) {
+                     cs = 0;
+                     *s++ = stbsp__comma;
+                  } else {
+                     *s++ = sn[n];
+                     ++n;
+                     if (n >= l)
+                        break;
+                  }
+               }
+               if (n < (stbsp__uint32)dp) {
+                  n = dp - n;
+                  if ((fl & STBSP__TRIPLET_COMMA) == 0) {
+                     while (n) {
+                        if ((((stbsp__uintptr)s) & 3) == 0)
+                           break;
+                        *s++ = '0';
+                        --n;
+                     }
+                     while (n >= 4) {
+                        *(stbsp__uint32 *)s = 0x30303030;
+                        s += 4;
+                        n -= 4;
+                     }
+                  }
+                  while (n) {
+                     if ((fl & STBSP__TRIPLET_COMMA) && (++cs == 4)) {
+                        cs = 0;
+                        *s++ = stbsp__comma;
+                     } else {
+                        *s++ = '0';
+                        --n;
+                     }
+                  }
+               }
+               cs = (int)(s - (num + 64)) + (3 << 24); // cs is how many tens
+               if (pr) {
+                  *s++ = stbsp__period;
+                  tz = pr;
+               }
+            } else {
+               // handle xxxxx.xxxx000*000
+               n = 0;
+               for (;;) {
+                  if ((fl & STBSP__TRIPLET_COMMA) && (++cs == 4)) {
+                     cs = 0;
+                     *s++ = stbsp__comma;
+                  } else {
+                     *s++ = sn[n];
+                     ++n;
+                     if (n >= (stbsp__uint32)dp)
+                        break;
+                  }
+               }
+               cs = (int)(s - (num + 64)) + (3 << 24); // cs is how many tens
+               if (pr)
+                  *s++ = stbsp__period;
+               if ((l - dp) > (stbsp__uint32)pr)
+                  l = pr + dp;
+               while (n < l) {
+                  *s++ = sn[n];
+                  ++n;
+               }
+               tz = pr - (l - dp);
+            }
+         }
+         pr = 0;
+
+         // handle k,m,g,t
+         if (fl & STBSP__METRIC_SUFFIX) {
+            char idx;
+            idx = 1;
+            if (fl & STBSP__METRIC_NOSPACE)
+               idx = 0;
+            tail[0] = idx;
+            tail[1] = ' ';
+            {
+               if (fl >> 24) { // SI kilo is 'k', JEDEC and SI kibits are 'K'.
+                  if (fl & STBSP__METRIC_1024)
+                     tail[idx + 1] = "_KMGT"[fl >> 24];
+                  else
+                     tail[idx + 1] = "_kMGT"[fl >> 24];
+                  idx++;
+                  // If printing kibits and not in jedec, add the 'i'.
+                  if (fl & STBSP__METRIC_1024 && !(fl & STBSP__METRIC_JEDEC)) {
+                     tail[idx + 1] = 'i';
+                     idx++;
+                  }
+                  tail[0] = idx;
+               }
+            }
+         };
+
+      flt_lead:
+         // get the length that we copied
+         l = (stbsp__uint32)(s - (num + 64));
+         s = num + 64;
+         goto scopy;
+#endif
+
+      case 'B': // upper binary
+      case 'b': // lower binary
+         h = (f[0] == 'B') ? hexu : hex;
+         lead[0] = 0;
+         if (fl & STBSP__LEADING_0X) {
+            lead[0] = 2;
+            lead[1] = '0';
+            lead[2] = h[0xb];
+         }
+         l = (8 << 4) | (1 << 8);
+         goto radixnum;
+
+      case 'o': // octal
+         h = hexu;
+         lead[0] = 0;
+         if (fl & STBSP__LEADING_0X) {
+            lead[0] = 1;
+            lead[1] = '0';
+         }
+         l = (3 << 4) | (3 << 8);
+         goto radixnum;
+
+      case 'p': // pointer
+         fl |= (sizeof(void *) == 8) ? STBSP__INTMAX : 0;
+         pr = sizeof(void *) * 2;
+         fl &= ~STBSP__LEADINGZERO; // 'p' only prints the pointer with zeros
+                                    // fall through - to X
+
+      case 'X': // upper hex
+      case 'x': // lower hex
+         h = (f[0] == 'X') ? hexu : hex;
+         l = (4 << 4) | (4 << 8);
+         lead[0] = 0;
+         if (fl & STBSP__LEADING_0X) {
+            lead[0] = 2;
+            lead[1] = '0';
+            lead[2] = h[16];
+         }
+      radixnum:
+         // get the number
+         if (fl & STBSP__INTMAX)
+            n64 = va_arg(va, stbsp__uint64);
+         else
+            n64 = va_arg(va, stbsp__uint32);
+
+         s = num + STBSP__NUMSZ;
+         dp = 0;
+         // clear tail, and clear leading if value is zero
+         tail[0] = 0;
+         if (n64 == 0) {
+            lead[0] = 0;
+            if (pr == 0) {
+               l = 0;
+               cs = 0;
+               goto scopy;
+            }
+         }
+         // convert to string
+         for (;;) {
+            *--s = h[n64 & ((1 << (l >> 8)) - 1)];
+            n64 >>= (l >> 8);
+            if (!((n64) || ((stbsp__int32)((num + STBSP__NUMSZ) - s) < pr)))
+               break;
+            if (fl & STBSP__TRIPLET_COMMA) {
+               ++l;
+               if ((l & 15) == ((l >> 4) & 15)) {
+                  l &= ~15;
+                  *--s = stbsp__comma;
+               }
+            }
+         };
+         // get the tens and the comma pos
+         cs = (stbsp__uint32)((num + STBSP__NUMSZ) - s) + ((((l >> 4) & 15)) << 24);
+         // get the length that we copied
+         l = (stbsp__uint32)((num + STBSP__NUMSZ) - s);
+         // copy it
+         goto scopy;
+
+      case 'u': // unsigned
+      case 'i':
+      case 'd': // integer
+         // get the integer and abs it
+         if (fl & STBSP__INTMAX) {
+            stbsp__int64 i64 = va_arg(va, stbsp__int64);
+            n64 = (stbsp__uint64)i64;
+            if ((f[0] != 'u') && (i64 < 0)) {
+               n64 = (stbsp__uint64)-i64;
+               fl |= STBSP__NEGATIVE;
+            }
+         } else {
+            stbsp__int32 i = va_arg(va, stbsp__int32);
+            n64 = (stbsp__uint32)i;
+            if ((f[0] != 'u') && (i < 0)) {
+               n64 = (stbsp__uint32)-i;
+               fl |= STBSP__NEGATIVE;
+            }
+         }
+
+#ifndef STB_SPRINTF_NOFLOAT
+         if (fl & STBSP__METRIC_SUFFIX) {
+            if (n64 < 1024)
+               pr = 0;
+            else if (pr == -1)
+               pr = 1;
+            fv = (double)(stbsp__int64)n64;
+            goto doafloat;
+         }
+#endif
+
+         // convert to string
+         s = num + STBSP__NUMSZ;
+         l = 0;
+
+         for (;;) {
+            // do in 32-bit chunks (avoid lots of 64-bit divides even with constant denominators)
+            char *o = s - 8;
+            if (n64 >= 100000000) {
+               n = (stbsp__uint32)(n64 % 100000000);
+               n64 /= 100000000;
+            } else {
+               n = (stbsp__uint32)n64;
+               n64 = 0;
+            }
+            if ((fl & STBSP__TRIPLET_COMMA) == 0) {
+               do {
+                  s -= 2;
+                  *(stbsp__uint16 *)s = *(stbsp__uint16 *)&stbsp__digitpair.pair[(n % 100) * 2];
+                  n /= 100;
+               } while (n);
+            }
+            while (n) {
+               if ((fl & STBSP__TRIPLET_COMMA) && (l++ == 3)) {
+                  l = 0;
+                  *--s = stbsp__comma;
+                  --o;
+               } else {
+                  *--s = (char)(n % 10) + '0';
+                  n /= 10;
+               }
+            }
+            if (n64 == 0) {
+               if ((s[0] == '0') && (s != (num + STBSP__NUMSZ)))
+                  ++s;
+               break;
+            }
+            while (s != o)
+               if ((fl & STBSP__TRIPLET_COMMA) && (l++ == 3)) {
+                  l = 0;
+                  *--s = stbsp__comma;
+                  --o;
+               } else {
+                  *--s = '0';
+               }
+         }
+
+         tail[0] = 0;
+         stbsp__lead_sign(fl, lead);
+
+         // get the length that we copied
+         l = (stbsp__uint32)((num + STBSP__NUMSZ) - s);
+         if (l == 0) {
+            *--s = '0';
+            l = 1;
+         }
+         cs = l + (3 << 24);
+         if (pr < 0)
+            pr = 0;
+
+      scopy:
+         // get fw=leading/trailing space, pr=leading zeros
+         if (pr < (stbsp__int32)l)
+            pr = l;
+         n = pr + lead[0] + tail[0] + tz;
+         if (fw < (stbsp__int32)n)
+            fw = n;
+         fw -= n;
+         pr -= l;
+
+         // handle right justify and leading zeros
+         if ((fl & STBSP__LEFTJUST) == 0) {
+            if (fl & STBSP__LEADINGZERO) // if leading zeros, everything is in pr
+            {
+               pr = (fw > pr) ? fw : pr;
+               fw = 0;
+            } else {
+               fl &= ~STBSP__TRIPLET_COMMA; // if no leading zeros, then no commas
+            }
+         }
+
+         // copy the spaces and/or zeros
+         if (fw + pr) {
+            stbsp__int32 i;
+            stbsp__uint32 c;
+
+            // copy leading spaces (or when doing %8.4d stuff)
+            if ((fl & STBSP__LEFTJUST) == 0)
+               while (fw > 0) {
+                  stbsp__cb_buf_clamp(i, fw);
+                  fw -= i;
+                  while (i) {
+                     if ((((stbsp__uintptr)bf) & 3) == 0)
+                        break;
+                     *bf++ = ' ';
+                     --i;
+                  }
+                  while (i >= 4) {
+                     *(stbsp__uint32 *)bf = 0x20202020;
+                     bf += 4;
+                     i -= 4;
+                  }
+                  while (i) {
+                     *bf++ = ' ';
+                     --i;
+                  }
+                  stbsp__chk_cb_buf(1);
+               }
+
+            // copy leader
+            sn = lead + 1;
+            while (lead[0]) {
+               stbsp__cb_buf_clamp(i, lead[0]);
+               lead[0] -= (char)i;
+               while (i) {
+                  *bf++ = *sn++;
+                  --i;
+               }
+               stbsp__chk_cb_buf(1);
+            }
+
+            // copy leading zeros
+            c = cs >> 24;
+            cs &= 0xffffff;
+            cs = (fl & STBSP__TRIPLET_COMMA) ? ((stbsp__uint32)(c - ((pr + cs) % (c + 1)))) : 0;
+            while (pr > 0) {
+               stbsp__cb_buf_clamp(i, pr);
+               pr -= i;
+               if ((fl & STBSP__TRIPLET_COMMA) == 0) {
+                  while (i) {
+                     if ((((stbsp__uintptr)bf) & 3) == 0)
+                        break;
+                     *bf++ = '0';
+                     --i;
+                  }
+                  while (i >= 4) {
+                     *(stbsp__uint32 *)bf = 0x30303030;
+                     bf += 4;
+                     i -= 4;
+                  }
+               }
+               while (i) {
+                  if ((fl & STBSP__TRIPLET_COMMA) && (cs++ == c)) {
+                     cs = 0;
+                     *bf++ = stbsp__comma;
+                  } else
+                     *bf++ = '0';
+                  --i;
+               }
+               stbsp__chk_cb_buf(1);
+            }
+         }
+
+         // copy leader if there is still one
+         sn = lead + 1;
+         while (lead[0]) {
+            stbsp__int32 i;
+            stbsp__cb_buf_clamp(i, lead[0]);
+            lead[0] -= (char)i;
+            while (i) {
+               *bf++ = *sn++;
+               --i;
+            }
+            stbsp__chk_cb_buf(1);
+         }
+
+         // copy the string
+         n = l;
+         while (n) {
+            stbsp__int32 i;
+            stbsp__cb_buf_clamp(i, n);
+            n -= i;
+            STBSP__UNALIGNED(while (i >= 4) {
+               *(stbsp__uint32 volatile *)bf = *(stbsp__uint32 volatile *)s;
+               bf += 4;
+               s += 4;
+               i -= 4;
+            })
+            while (i) {
+               *bf++ = *s++;
+               --i;
+            }
+            stbsp__chk_cb_buf(1);
+         }
+
+         // copy trailing zeros
+         while (tz) {
+            stbsp__int32 i;
+            stbsp__cb_buf_clamp(i, tz);
+            tz -= i;
+            while (i) {
+               if ((((stbsp__uintptr)bf) & 3) == 0)
+                  break;
+               *bf++ = '0';
+               --i;
+            }
+            while (i >= 4) {
+               *(stbsp__uint32 *)bf = 0x30303030;
+               bf += 4;
+               i -= 4;
+            }
+            while (i) {
+               *bf++ = '0';
+               --i;
+            }
+            stbsp__chk_cb_buf(1);
+         }
+
+         // copy tail if there is one
+         sn = tail + 1;
+         while (tail[0]) {
+            stbsp__int32 i;
+            stbsp__cb_buf_clamp(i, tail[0]);
+            tail[0] -= (char)i;
+            while (i) {
+               *bf++ = *sn++;
+               --i;
+            }
+            stbsp__chk_cb_buf(1);
+         }
+
+         // handle the left justify
+         if (fl & STBSP__LEFTJUST)
+            if (fw > 0) {
+               while (fw) {
+                  stbsp__int32 i;
+                  stbsp__cb_buf_clamp(i, fw);
+                  fw -= i;
+                  while (i) {
+                     if ((((stbsp__uintptr)bf) & 3) == 0)
+                        break;
+                     *bf++ = ' ';
+                     --i;
+                  }
+                  while (i >= 4) {
+                     *(stbsp__uint32 *)bf = 0x20202020;
+                     bf += 4;
+                     i -= 4;
+                  }
+                  while (i--)
+                     *bf++ = ' ';
+                  stbsp__chk_cb_buf(1);
+               }
+            }
+         break;
+
+      default: // unknown, just copy code
+         s = num + STBSP__NUMSZ - 1;
+         *s = f[0];
+         l = 1;
+         fw = fl = 0;
+         lead[0] = 0;
+         tail[0] = 0;
+         pr = 0;
+         dp = 0;
+         cs = 0;
+         goto scopy;
+      }
+      ++f;
+   }
+endfmt:
+
+   if (!callback)
+      *bf = 0;
+   else
+      stbsp__flush_cb();
+
+done:
+   return tlen + (int)(bf - buf);
+}
+
+// cleanup
+#undef STBSP__LEFTJUST
+#undef STBSP__LEADINGPLUS
+#undef STBSP__LEADINGSPACE
+#undef STBSP__LEADING_0X
+#undef STBSP__LEADINGZERO
+#undef STBSP__INTMAX
+#undef STBSP__TRIPLET_COMMA
+#undef STBSP__NEGATIVE
+#undef STBSP__METRIC_SUFFIX
+#undef STBSP__NUMSZ
+#undef stbsp__chk_cb_bufL
+#undef stbsp__chk_cb_buf
+#undef stbsp__flush_cb
+#undef stbsp__cb_buf_clamp
+
+// ============================================================================
+//   wrapper functions
+
+STBSP__PUBLICDEF int STB_SPRINTF_DECORATE(sprintf)(char *buf, char const *fmt, ...)
+{
+   int result;
+   va_list va;
+   va_start(va, fmt);
+   result = STB_SPRINTF_DECORATE(vsprintfcb)(0, 0, buf, fmt, va);
+   va_end(va);
+   return result;
+}
+
+typedef struct stbsp__context {
+   char *buf;
+   int count;
+   int length;
+   char tmp[STB_SPRINTF_MIN];
+} stbsp__context;
+
+static char *stbsp__clamp_callback(const char *buf, void *user, int len)
+{
+   stbsp__context *c = (stbsp__context *)user;
+   c->length += len;
+
+   if (len > c->count)
+      len = c->count;
+
+   if (len) {
+      if (buf != c->buf) {
+         const char *s, *se;
+         char *d;
+         d = c->buf;
+         s = buf;
+         se = buf + len;
+         do {
+            *d++ = *s++;
+         } while (s < se);
+      }
+      c->buf += len;
+      c->count -= len;
+   }
+
+   if (c->count <= 0)
+      return c->tmp;
+   return (c->count >= STB_SPRINTF_MIN) ? c->buf : c->tmp; // go direct into buffer if you can
+}
+
+static char * stbsp__count_clamp_callback( const char * buf, void * user, int len )
+{
+   stbsp__context * c = (stbsp__context*)user;
+   (void) sizeof(buf);
+
+   c->length += len;
+   return c->tmp; // go direct into buffer if you can
+}
+
+STBSP__PUBLICDEF int STB_SPRINTF_DECORATE( vsnprintf )( char * buf, int count, char const * fmt, va_list va )
+{
+   stbsp__context c;
+
+   if ( (count == 0) && !buf )
+   {
+      c.length = 0;
+
+      STB_SPRINTF_DECORATE( vsprintfcb )( stbsp__count_clamp_callback, &c, c.tmp, fmt, va );
+   }
+   else
+   {
+      int l;
+
+      c.buf = buf;
+      c.count = count;
+      c.length = 0;
+
+      STB_SPRINTF_DECORATE( vsprintfcb )( stbsp__clamp_callback, &c, stbsp__clamp_callback(0,&c,0), fmt, va );
+
+      // zero-terminate
+      l = (int)( c.buf - buf );
+      if ( l >= count ) // should never be greater, only equal (or less) than count
+         l = count - 1;
+      buf[l] = 0;
+   }
+
+   return c.length;
+}
+
+STBSP__PUBLICDEF int STB_SPRINTF_DECORATE(snprintf)(char *buf, int count, char const *fmt, ...)
+{
+   int result;
+   va_list va;
+   va_start(va, fmt);
+
+   result = STB_SPRINTF_DECORATE(vsnprintf)(buf, count, fmt, va);
+   va_end(va);
+
+   return result;
+}
+
+STBSP__PUBLICDEF int STB_SPRINTF_DECORATE(vsprintf)(char *buf, char const *fmt, va_list va)
+{
+   return STB_SPRINTF_DECORATE(vsprintfcb)(0, 0, buf, fmt, va);
+}
+
+// =======================================================================
+//   low level float utility functions
+
+#ifndef STB_SPRINTF_NOFLOAT
+
+// copies d to bits w/ strict aliasing (this compiles to nothing on /Ox)
+#define STBSP__COPYFP(dest, src)                   \
+   {                                               \
+      int cn;                                      \
+      for (cn = 0; cn < 8; cn++)                   \
+         ((char *)&dest)[cn] = ((char *)&src)[cn]; \
+   }
+
+// get float info
+static stbsp__int32 stbsp__real_to_parts(stbsp__int64 *bits, stbsp__int32 *expo, double value)
+{
+   double d;
+   stbsp__int64 b = 0;
+
+   // load value and round at the frac_digits
+   d = value;
+
+   STBSP__COPYFP(b, d);
+
+   *bits = b & ((((stbsp__uint64)1) << 52) - 1);
+   *expo = (stbsp__int32)(((b >> 52) & 2047) - 1023);
+
+   return (stbsp__int32)((stbsp__uint64) b >> 63);
+}
+
+static double const stbsp__bot[23] = {
+   1e+000, 1e+001, 1e+002, 1e+003, 1e+004, 1e+005, 1e+006, 1e+007, 1e+008, 1e+009, 1e+010, 1e+011,
+   1e+012, 1e+013, 1e+014, 1e+015, 1e+016, 1e+017, 1e+018, 1e+019, 1e+020, 1e+021, 1e+022
+};
+static double const stbsp__negbot[22] = {
+   1e-001, 1e-002, 1e-003, 1e-004, 1e-005, 1e-006, 1e-007, 1e-008, 1e-009, 1e-010, 1e-011,
+   1e-012, 1e-013, 1e-014, 1e-015, 1e-016, 1e-017, 1e-018, 1e-019, 1e-020, 1e-021, 1e-022
+};
+static double const stbsp__negboterr[22] = {
+   -5.551115123125783e-018,  -2.0816681711721684e-019, -2.0816681711721686e-020, -4.7921736023859299e-021, -8.1803053914031305e-022, 4.5251888174113741e-023,
+   4.5251888174113739e-024,  -2.0922560830128471e-025, -6.2281591457779853e-026, -3.6432197315497743e-027, 6.0503030718060191e-028,  2.0113352370744385e-029,
+   -3.0373745563400371e-030, 1.1806906454401013e-032,  -7.7705399876661076e-032, 2.0902213275965398e-033,  -7.1542424054621921e-034, -7.1542424054621926e-035,
+   2.4754073164739869e-036,  5.4846728545790429e-037,  9.2462547772103625e-038,  -4.8596774326570872e-039
+};
+static double const stbsp__top[13] = {
+   1e+023, 1e+046, 1e+069, 1e+092, 1e+115, 1e+138, 1e+161, 1e+184, 1e+207, 1e+230, 1e+253, 1e+276, 1e+299
+};
+static double const stbsp__negtop[13] = {
+   1e-023, 1e-046, 1e-069, 1e-092, 1e-115, 1e-138, 1e-161, 1e-184, 1e-207, 1e-230, 1e-253, 1e-276, 1e-299
+};
+static double const stbsp__toperr[13] = {
+   8388608,
+   6.8601809640529717e+028,
+   -7.253143638152921e+052,
+   -4.3377296974619174e+075,
+   -1.5559416129466825e+098,
+   -3.2841562489204913e+121,
+   -3.7745893248228135e+144,
+   -1.7356668416969134e+167,
+   -3.8893577551088374e+190,
+   -9.9566444326005119e+213,
+   6.3641293062232429e+236,
+   -5.2069140800249813e+259,
+   -5.2504760255204387e+282
+};
+static double const stbsp__negtoperr[13] = {
+   3.9565301985100693e-040,  -2.299904345391321e-063,  3.6506201437945798e-086,  1.1875228833981544e-109,
+   -5.0644902316928607e-132, -6.7156837247865426e-155, -2.812077463003139e-178,  -5.7778912386589953e-201,
+   7.4997100559334532e-224,  -4.6439668915134491e-247, -6.3691100762962136e-270, -9.436808465446358e-293,
+   8.0970921678014997e-317
+};
+
+#if defined(_MSC_VER) && (_MSC_VER <= 1200)
+static stbsp__uint64 const stbsp__powten[20] = {
+   1,
+   10,
+   100,
+   1000,
+   10000,
+   100000,
+   1000000,
+   10000000,
+   100000000,
+   1000000000,
+   10000000000,
+   100000000000,
+   1000000000000,
+   10000000000000,
+   100000000000000,
+   1000000000000000,
+   10000000000000000,
+   100000000000000000,
+   1000000000000000000,
+   10000000000000000000U
+};
+#define stbsp__tento19th ((stbsp__uint64)1000000000000000000)
+#else
+static stbsp__uint64 const stbsp__powten[20] = {
+   1,
+   10,
+   100,
+   1000,
+   10000,
+   100000,
+   1000000,
+   10000000,
+   100000000,
+   1000000000,
+   10000000000ULL,
+   100000000000ULL,
+   1000000000000ULL,
+   10000000000000ULL,
+   100000000000000ULL,
+   1000000000000000ULL,
+   10000000000000000ULL,
+   100000000000000000ULL,
+   1000000000000000000ULL,
+   10000000000000000000ULL
+};
+#define stbsp__tento19th (1000000000000000000ULL)
+#endif
+
+#define stbsp__ddmulthi(oh, ol, xh, yh)                            \
+   {                                                               \
+      double ahi = 0, alo, bhi = 0, blo;                           \
+      stbsp__int64 bt;                                             \
+      oh = xh * yh;                                                \
+      STBSP__COPYFP(bt, xh);                                       \
+      bt &= ((~(stbsp__uint64)0) << 27);                           \
+      STBSP__COPYFP(ahi, bt);                                      \
+      alo = xh - ahi;                                              \
+      STBSP__COPYFP(bt, yh);                                       \
+      bt &= ((~(stbsp__uint64)0) << 27);                           \
+      STBSP__COPYFP(bhi, bt);                                      \
+      blo = yh - bhi;                                              \
+      ol = ((ahi * bhi - oh) + ahi * blo + alo * bhi) + alo * blo; \
+   }
+
+#define stbsp__ddtoS64(ob, xh, xl)          \
+   {                                        \
+      double ahi = 0, alo, vh, t;           \
+      ob = (stbsp__int64)xh;                \
+      vh = (double)ob;                      \
+      ahi = (xh - vh);                      \
+      t = (ahi - xh);                       \
+      alo = (xh - (ahi - t)) - (vh + t);    \
+      ob += (stbsp__int64)(ahi + alo + xl); \
+   }
+
+#define stbsp__ddrenorm(oh, ol) \
+   {                            \
+      double s;                 \
+      s = oh + ol;              \
+      ol = ol - (s - oh);       \
+      oh = s;                   \
+   }
+
+#define stbsp__ddmultlo(oh, ol, xh, xl, yh, yl) ol = ol + (xh * yl + xl * yh);
+
+#define stbsp__ddmultlos(oh, ol, xh, yl) ol = ol + (xh * yl);
+
+static void stbsp__raise_to_power10(double *ohi, double *olo, double d, stbsp__int32 power) // power can be -323 to +350
+{
+   double ph, pl;
+   if ((power >= 0) && (power <= 22)) {
+      stbsp__ddmulthi(ph, pl, d, stbsp__bot[power]);
+   } else {
+      stbsp__int32 e, et, eb;
+      double p2h, p2l;
+
+      e = power;
+      if (power < 0)
+         e = -e;
+      et = (e * 0x2c9) >> 14; /* %23 */
+      if (et > 13)
+         et = 13;
+      eb = e - (et * 23);
+
+      ph = d;
+      pl = 0.0;
+      if (power < 0) {
+         if (eb) {
+            --eb;
+            stbsp__ddmulthi(ph, pl, d, stbsp__negbot[eb]);
+            stbsp__ddmultlos(ph, pl, d, stbsp__negboterr[eb]);
+         }
+         if (et) {
+            stbsp__ddrenorm(ph, pl);
+            --et;
+            stbsp__ddmulthi(p2h, p2l, ph, stbsp__negtop[et]);
+            stbsp__ddmultlo(p2h, p2l, ph, pl, stbsp__negtop[et], stbsp__negtoperr[et]);
+            ph = p2h;
+            pl = p2l;
+         }
+      } else {
+         if (eb) {
+            e = eb;
+            if (eb > 22)
+               eb = 22;
+            e -= eb;
+            stbsp__ddmulthi(ph, pl, d, stbsp__bot[eb]);
+            if (e) {
+               stbsp__ddrenorm(ph, pl);
+               stbsp__ddmulthi(p2h, p2l, ph, stbsp__bot[e]);
+               stbsp__ddmultlos(p2h, p2l, stbsp__bot[e], pl);
+               ph = p2h;
+               pl = p2l;
+            }
+         }
+         if (et) {
+            stbsp__ddrenorm(ph, pl);
+            --et;
+            stbsp__ddmulthi(p2h, p2l, ph, stbsp__top[et]);
+            stbsp__ddmultlo(p2h, p2l, ph, pl, stbsp__top[et], stbsp__toperr[et]);
+            ph = p2h;
+            pl = p2l;
+         }
+      }
+   }
+   stbsp__ddrenorm(ph, pl);
+   *ohi = ph;
+   *olo = pl;
+}
+
+// given a float value, returns the significant bits in bits, and the position of the
+//   decimal point in decimal_pos.  +/-INF and NAN are specified by special values
+//   returned in the decimal_pos parameter.
+// frac_digits is absolute normally, but if you want from first significant digits (got %g and %e), or in 0x80000000
+static stbsp__int32 stbsp__real_to_str(char const **start, stbsp__uint32 *len, char *out, stbsp__int32 *decimal_pos, double value, stbsp__uint32 frac_digits)
+{
+   double d;
+   stbsp__int64 bits = 0;
+   stbsp__int32 expo, e, ng, tens;
+
+   d = value;
+   STBSP__COPYFP(bits, d);
+   expo = (stbsp__int32)((bits >> 52) & 2047);
+   ng = (stbsp__int32)((stbsp__uint64) bits >> 63);
+   if (ng)
+      d = -d;
+
+   if (expo == 2047) // is nan or inf?
+   {
+      *start = (bits & ((((stbsp__uint64)1) << 52) - 1)) ? "NaN" : "Inf";
+      *decimal_pos = STBSP__SPECIAL;
+      *len = 3;
+      return ng;
+   }
+
+   if (expo == 0) // is zero or denormal
+   {
+      if (((stbsp__uint64) bits << 1) == 0) // do zero
+      {
+         *decimal_pos = 1;
+         *start = out;
+         out[0] = '0';
+         *len = 1;
+         return ng;
+      }
+      // find the right expo for denormals
+      {
+         stbsp__int64 v = ((stbsp__uint64)1) << 51;
+         while ((bits & v) == 0) {
+            --expo;
+            v >>= 1;
+         }
+      }
+   }
+
+   // find the decimal exponent as well as the decimal bits of the value
+   {
+      double ph, pl;
+
+      // log10 estimate - very specifically tweaked to hit or undershoot by no more than 1 of log10 of all expos 1..2046
+      tens = expo - 1023;
+      tens = (tens < 0) ? ((tens * 617) / 2048) : (((tens * 1233) / 4096) + 1);
+
+      // move the significant bits into position and stick them into an int
+      stbsp__raise_to_power10(&ph, &pl, d, 18 - tens);
+
+      // get full as much precision from double-double as possible
+      stbsp__ddtoS64(bits, ph, pl);
+
+      // check if we undershot
+      if (((stbsp__uint64)bits) >= stbsp__tento19th)
+         ++tens;
+   }
+
+   // now do the rounding in integer land
+   frac_digits = (frac_digits & 0x80000000) ? ((frac_digits & 0x7ffffff) + 1) : (tens + frac_digits);
+   if ((frac_digits < 24)) {
+      stbsp__uint32 dg = 1;
+      if ((stbsp__uint64)bits >= stbsp__powten[9])
+         dg = 10;
+      while ((stbsp__uint64)bits >= stbsp__powten[dg]) {
+         ++dg;
+         if (dg == 20)
+            goto noround;
+      }
+      if (frac_digits < dg) {
+         stbsp__uint64 r;
+         // add 0.5 at the right position and round
+         e = dg - frac_digits;
+         if ((stbsp__uint32)e >= 24)
+            goto noround;
+         r = stbsp__powten[e];
+         bits = bits + (r / 2);
+         if ((stbsp__uint64)bits >= stbsp__powten[dg])
+            ++tens;
+         bits /= r;
+      }
+   noround:;
+   }
+
+   // kill long trailing runs of zeros
+   if (bits) {
+      stbsp__uint32 n;
+      for (;;) {
+         if (bits <= 0xffffffff)
+            break;
+         if (bits % 1000)
+            goto donez;
+         bits /= 1000;
+      }
+      n = (stbsp__uint32)bits;
+      while ((n % 1000) == 0)
+         n /= 1000;
+      bits = n;
+   donez:;
+   }
+
+   // convert to string
+   out += 64;
+   e = 0;
+   for (;;) {
+      stbsp__uint32 n;
+      char *o = out - 8;
+      // do the conversion in chunks of U32s (avoid most 64-bit divides, worth it, constant denomiators be damned)
+      if (bits >= 100000000) {
+         n = (stbsp__uint32)(bits % 100000000);
+         bits /= 100000000;
+      } else {
+         n = (stbsp__uint32)bits;
+         bits = 0;
+      }
+      while (n) {
+         out -= 2;
+         *(stbsp__uint16 *)out = *(stbsp__uint16 *)&stbsp__digitpair.pair[(n % 100) * 2];
+         n /= 100;
+         e += 2;
+      }
+      if (bits == 0) {
+         if ((e) && (out[0] == '0')) {
+            ++out;
+            --e;
+         }
+         break;
+      }
+      while (out != o) {
+         *--out = '0';
+         ++e;
+      }
+   }
+
+   *decimal_pos = tens;
+   *start = out;
+   *len = e;
+   return ng;
+}
+
+#undef stbsp__ddmulthi
+#undef stbsp__ddrenorm
+#undef stbsp__ddmultlo
+#undef stbsp__ddmultlos
+#undef STBSP__SPECIAL
+#undef STBSP__COPYFP
+
+#endif // STB_SPRINTF_NOFLOAT
+
+// clean up
+#undef stbsp__uint16
+#undef stbsp__uint32
+#undef stbsp__int32
+#undef stbsp__uint64
+#undef stbsp__int64
+#undef STBSP__UNALIGNED
+
+#endif // STB_SPRINTF_IMPLEMENTATION
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/
diff --git a/include/ulib/stdio.h b/include/ulib/stdio.h
new file mode 100644
index 0000000..2e19b87
--- /dev/null
+++ b/include/ulib/stdio.h
@@ -0,0 +1,97 @@
+/* Standard I/O Library for Lume OS */
+
+#ifndef _STDIO_H
+#define _STDIO_H
+
+#include <stdarg.h>
+#include "ulib/types.h"
+
+#ifdef __cplusplus
+extern "C"  {
+#endif
+
+/*Type Definition (Adjusted According to Architecture)*/
+#ifndef NULL
+#define NULL ((void *)0)
+#endif
+
+/*Macro definition*/
+#define EOF (-1)
+
+#define SEEK_SET 0
+#define SEEK_CUR 1
+#define SEEK_END 2
+
+#define BUFSIZ 1024
+
+
+/* FILE structure */
+typedef struct
+{
+    int fd;
+    int flags;
+    int error;
+    int eof;
+
+    char buffer[BUFSIZ];
+
+    int buf_write_pos;
+
+    int buf_read_pos;
+    int buf_read_cnt;
+
+    int buf_mode;
+} FILE;
+
+/* standard stream object */
+extern FILE *stdin;
+extern FILE *stdout;
+extern FILE *stderr;
+
+/* Function Declaration */
+
+/* File Operations */
+FILE *fopen(const char *filename, const char *mode);
+int fclose(FILE *stream);
+int fflush(FILE *stream); // Not implement
+
+/* Formatted input and output */
+int printf(const char *format, ...);
+int scanf(const char *format, ...);
+int sprintf(char *str, const char *format, ...);
+int snprintf(char *str, uint64 size, const char *format, ...);
+int vsnprintf(char *str, uint64 size, const char *format, va_list ap);
+int sscanf(const char *str, const char *format, ...);
+
+int fprintf(FILE *stream, const char *format, ...);
+int fscanf(FILE *stream, const char *format, ...);
+
+/* Character/String Read and Write */
+int fputc(int c, FILE *stream);
+int fputs(const char *s, FILE *stream);
+int fgetc(FILE *stream);
+char *fgets(char *str, int n, FILE *stream);
+int ungetc(int c, FILE *stream);
+
+/* Common Macros/Wrapper Functions */
+#define getchar() fgetc(stdin)
+#define putchar(c) fputc((c), stdout)
+
+/* Binary read and write */
+uint64 fread(void *ptr, uint64 size, uint64 nmemb, FILE *stream);
+uint64 fwrite(const void *ptr, uint64 size, uint64 nmemb, FILE *stream);
+
+/* File location */
+int fseek(FILE *stream, long offset, int whence);
+long ftell(FILE *stream);
+void rewind(FILE *stream);
+
+/* Status Inquiry */
+int feof(FILE *stream);
+int ferror(FILE *stream);
+void clearerr(FILE *stream);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* _STDIO_H */
\ No newline at end of file
diff --git a/include/ulib/stdlib.h b/include/ulib/stdlib.h
new file mode 100644
index 0000000..7dc325e
--- /dev/null
+++ b/include/ulib/stdlib.h
@@ -0,0 +1,95 @@
+#ifndef _STDLIB_H
+#define _STDLIB_H
+
+#include "ulib/types.h"
+#include "ulib/limits.h"
+#include "ulib/errno.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#ifndef NULL
+#define NULL ((void *)0)
+#endif
+
+#define ERANGE 34 /* Math result not representable */
+#define ENOMEM 12 /* Out of memory */
+
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+#define RAND_MAX 32767
+#define MB_CUR_MAX 1
+
+typedef struct
+{
+    int quot;
+    int rem;
+} div_t;
+typedef struct
+{
+    long quot;
+    long rem;
+} ldiv_t;
+typedef struct
+{
+    long long quot;
+    long long rem;
+} lldiv_t;
+
+typedef int (*__compar_fn_t)(const void *, const void *);
+
+/* Memory Management */
+void *malloc(size_t size);
+void free(void *ptr);
+void *calloc(size_t nmemb, size_t size);
+void *realloc(void *ptr, size_t size);
+
+/* Process Control */
+int exit(int status);
+void abort(void);
+int atexit(void (*function)(void));
+char *getenv(const char *name);
+int system(const char *command);
+
+/* String Conversion */
+int atoi(const char *nptr);
+long atol(const char *nptr);
+long long atoll(const char *nptr);
+double atof(const char *nptr);
+
+long strtol(const char *nptr, char **endptr, int base);
+unsigned long strtoul(const char *nptr, char **endptr, int base);
+long long strtoll(const char *nptr, char **endptr, int base);
+unsigned long long strtoull(const char *nptr, char **endptr, int base);
+
+double strtod(const char *nptr, char **endptr);
+float strtof(const char *nptr, char **endptr);
+
+/* Search & Sort*/
+void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
+void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
+
+/* Math & Mics */
+int abs(int j);
+long labs(long j);
+long long llabs(long long j);
+div_t div(int numer, int denom);
+ldiv_t ldiv(long numer, long denom);
+lldiv_t lldiv(long long numer, long long denom);
+
+int rand(void);
+void srand(unsigned int seed);
+
+int mblen(const char *s, size_t n);
+int mbtowc(wchar_t *pwc, const char *s, size_t n);
+int wctomb(char *s, wchar_t wchar);
+size_t mbstowcs(wchar_t *dest, const char *src, size_t n);
+size_t wcstombs(char *dest, const wchar_t *src, size_t n);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _STDLIB_H */
\ No newline at end of file
diff --git a/include/ulib/string.h b/include/ulib/string.h
new file mode 100644
index 0000000..6e87157
--- /dev/null
+++ b/include/ulib/string.h
@@ -0,0 +1,70 @@
+#ifndef _STRING_H
+#define _STRING_H
+
+#include "ulib/types.h"
+#include "ulib/errno.h"
+
+#ifndef _SIZE_T
+#define _SIZE_T
+typedef unsigned long long size_t;
+#endif
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Memory Manipulation*/
+    void *memcpy(void *dest, const void *src, size_t n);
+
+    void *memmove(void *dest, const void *src, size_t n);
+
+    void *memset(void *dest, int c, size_t n);
+
+    int memcmp(const void *s1, const void *s2, size_t n);
+
+    void *memchr(const void *s, int c, size_t n);
+
+    /* String Manipulation */
+
+    size_t strlen(const char *s);
+
+    char *strcpy(char *dest, const char *src);
+
+    char *strncpy(char *dest, const char *src, size_t n);
+
+    char *strcat(char *dest, const char *src);
+
+    char *strncat(char *dest, const char *src, size_t n);
+
+    int strcmp(const char *s1, const char *s2);
+
+    int strncmp(const char *s1, const char *s2, size_t n);
+
+    char *strchr(const char *s, int c);
+
+    char *strrchr(const char *s, int c);
+
+    char *strstr(const char *haystack, const char *needle);
+
+    char *strdup(const char *s);
+
+    size_t strlcpy(char *dest, const char *src, size_t size);
+
+    size_t strlcat(char *dest, const char *src, size_t size);
+
+    size_t strspn(const char *s, const char *accept);
+
+    size_t strcspn(const char *s, const char *reject);
+
+    char *strpbrk(const char *s, const char *accept);
+
+    char *strtok(char *str, const char *delim);
+
+    char *strerror(int errnum);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _STRING_H */
\ No newline at end of file
diff --git a/include/ulib/types.h b/include/ulib/types.h
new file mode 100644
index 0000000..2f15bf1
--- /dev/null
+++ b/include/ulib/types.h
@@ -0,0 +1,21 @@
+#ifndef _ULIB_TYPES_H
+#define _ULIB_TYPES_H
+
+#include "common/types.h"
+
+#ifndef _ULIB_ALIASES
+#define _ULIB_ALIASES
+typedef unsigned int uint;
+typedef unsigned short ushort;
+typedef unsigned char uchar;
+#endif
+
+#ifndef NULL
+#define NULL ((void *)0)
+#endif
+
+#ifndef __cplusplus
+typedef int wchar_t;
+#endif
+
+#endif
\ No newline at end of file
diff --git a/include/user/user.h b/include/user/user.h
index 7ab4923..7624a21 100644
--- a/include/user/user.h
+++ b/include/user/user.h
@@ -24,6 +24,7 @@ extern "C" {
     int sleep(int ticks);
     int uptime();
 
-    
+    // Debug
     void putc(char c);
+    int disk_test();
 }
\ No newline at end of file