From d8eaa13f2efc1eeca4e5f230d5a2d535aaf27338 Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Fri, 2 Jan 2026 00:47:16 +0800
Subject: dev(file-system): establish VFS and Read-only FAT32 File System

---
 src/fs/file.cc | 140 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 src/fs/file.cc

(limited to 'src/fs/file.cc')

diff --git a/src/fs/file.cc b/src/fs/file.cc
new file mode 100644
index 0000000..48af49e
--- /dev/null
+++ b/src/fs/file.cc
@@ -0,0 +1,140 @@
+#include "fs/file.h"
+#include "kernel/spinlock.h"
+#include "kernel/mm.h"
+#include "drivers/uart.h"
+#include "kernel/proc.h"
+
+#define NFILE 100
+
+namespace FileTable
+{
+    struct
+    {
+        Spinlock lock;
+        struct file files[NFILE];
+    } ftable;
+
+    void init()
+    {
+        ftable.lock.init("file_table");
+    }
+
+    struct file *alloc()
+    {
+        struct file *f;
+        ftable.lock.acquire();
+        for (f = ftable.files; f < ftable.files + NFILE; f++)
+        {
+            if (f->ref == 0)
+            {
+                f->ref = 1;
+                ftable.lock.release();
+                return f;
+            }
+        }
+        ftable.lock.release();
+        return nullptr;
+    }
+
+    struct file *dup(struct file *f)
+    {
+        ftable.lock.acquire();
+        if (f->ref < 1)
+        {
+            Drivers::uart_puts("panic: file dup\n");
+            while (1)
+                ;
+        }
+        f->ref++;
+        ftable.lock.release();
+        return f;
+    }
+
+    void close(struct file *f)
+    {
+        struct file ff;
+
+        ftable.lock.acquire();
+        if(f->ref < 1)
+        {
+            Drivers::uart_puts("panic: file close\n");
+            while (1)
+                ;
+        }
+        f->ref--;
+        if (f->ref > 0)
+        {
+            ftable.lock.release();
+            return;
+        }
+
+        ff = *f;
+        f->ref = 0;
+        f->type = FD_NONE;
+        ftable.lock.release();
+        if (ff.type == FD_INODE)
+        {
+            // Release the corresponding Inode
+            VFS::iput(ff.ip);
+        }
+        else if (ff.type == FD_PIPE)
+        {
+            // pipeclose(ff.pipe, ff.writable);
+        }
+    }
+
+    int read(struct file *f, uint64 addr, int n)
+    {
+        if (f->readable == 0)
+            return -1;
+        if (f->type == FD_INODE)
+        {
+            VFS::ilock(f->ip);
+            int r = f->ip->read((char*)addr, f->off, n, 1);
+            if(r > 0)
+            {
+                f->off += r;
+            }
+            VFS::iunlock(f->ip);
+            return r;
+        }
+        return -1;
+    }
+    
+    int write(struct file *f, uint64 addr, int n)
+    {
+        if (f->writable == 0)
+            return -1;
+        if (f->type == FD_INODE)
+        {
+            VFS::ilock(f->ip);
+            int r = f->ip->write((char *)addr, f->off, n, 1);
+            if (r > 0)
+            {
+                f->off += r;
+            }
+            VFS::iunlock(f->ip);
+            return r;
+        }
+        // else if (f->type == FD_PIPE) ...
+
+        return -1;
+    }
+
+    int stat(struct file *f, uint64 addr)
+    {
+        if (f->type == FD_INODE)
+        {
+            struct kstat st;
+            VFS::ilock(f->ip);
+            f->ip->getattr(&st);
+            VFS::iunlock(f->ip);
+
+            struct Proc *p = myproc();
+            if (VM::copyout(p->pagetable, addr, (char *)&st, sizeof(st)) < 0)
+                return -1;
+            return 0;
+        }
+        return -1;
+    }
+} // namespace FileTable
-- 
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