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.

6 files changed, 1969 insertions, 0 deletions

diff --git a/src/ulib/assert.c b/src/ulib/assert.c
new file mode 100644
index 0000000..ca2da84
--- /dev/null
+++ b/src/ulib/assert.c
@@ -0,0 +1,8 @@
+#include "stdio.h"
+#include "stdlib.h"
+
+void __assert_fail(const char *expr, const char *file, int line, const char *func)
+{
+    fprintf(stderr, "Assertion failed: %s (%s: %s: %d)\n", expr, file, func, line);
+    abort();
+}
\ No newline at end of file
diff --git a/src/ulib/cxx.cc b/src/ulib/cxx.cc
new file mode 100644
index 0000000..6c892ab
--- /dev/null
+++ b/src/ulib/cxx.cc
@@ -0,0 +1,31 @@
+#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/src/ulib/iostream.cpp b/src/ulib/iostream.cpp
new file mode 100644
index 0000000..d5394f9
--- /dev/null
+++ b/src/ulib/iostream.cpp
@@ -0,0 +1,8 @@
+#include "ulib/iostream"
+
+namespace std
+{
+    istream cin(stdin);
+    ostream cout(stdout);
+    ostream cerr(stderr);
+} // namespace std
diff --git a/src/ulib/stdio.c b/src/ulib/stdio.c
new file mode 100644
index 0000000..f8e7a9a
--- /dev/null
+++ b/src/ulib/stdio.c
@@ -0,0 +1,1052 @@
+#include "ulib/stdio.h"
+#include "ulib/string.h"
+#include "ulib/stdlib.h"
+
+/* Include STB Sprintf Implementation */
+#define STB_SPRINTF_IMPLEMENTATION
+#include "ulib/stb_sprintf.h"
+
+const int STDIN_FD = 0;
+const int STDOUT_FD = 1;
+const int STDERR_FD = 2;
+
+
+
+extern int open(const char *path, int flags);
+extern int close(int fd);
+extern int read(int fd, void *buf, uint64 count);
+extern int write(int fd, const void *buf, uint64 count);
+extern int lseek(int fd, int offset, int whence);
+
+static int isspace(int c)
+{
+    return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r';
+}
+
+/*  Core Formatting Implementation  */
+
+static int _ul_to_str_invert(char *buf, uint64 val, int base, int uppercase)
+{
+    int i = 0;
+    const char *digits = uppercase ? "0123456789ABCDEF" : "0123456789abcdef";
+    if (val == 0)
+    {
+        buf[i++] = '0';
+        return i;
+    }
+    while (val != 0)
+    {
+        buf[i++] = digits[val % base];
+        val /= base;
+    }
+    return i;
+}
+
+typedef struct
+{
+    char *buf;
+    uint64 limit;
+    uint64 written;
+    FILE *stream;
+} _OutContext;
+
+static void _out_char(_OutContext *ctx, char c)
+{
+    if (ctx->stream)
+    {
+        fputc(c, ctx->stream);
+        ctx->written++;
+    }
+    else
+    {
+        if (ctx->limit > 0 && ctx->written < ctx->limit - 1)
+        {
+            ctx->buf[ctx->written] = c;
+        }
+        ctx->written++;
+    }
+}
+
+static int _vprintf_core(_OutContext *ctx, const char *format, va_list ap)
+{
+    const char *p = format;
+    char num_buf[32];
+
+    while (*p)
+    {
+        if (*p != '%')
+        {
+            _out_char(ctx, *p++);
+            continue;
+        }
+        p++;
+
+        int flag_left = 0, flag_zero = 0, flag_plus = 0, flag_space = 0, flag_hash = 0;
+        while (1)
+        {
+            if (*p == '-')
+                flag_left = 1;
+            else if (*p == '0')
+                flag_zero = 1;
+            else if (*p == '+')
+                flag_plus = 1;
+            else if (*p == ' ')
+                flag_space = 1;
+            else if (*p == '#')
+                flag_hash = 1;
+            else
+                break;
+            p++;
+        }
+
+        int width = 0;
+        if (*p == '*')
+        {
+            width = va_arg(ap, int);
+            if (width < 0)
+            {
+                flag_left = 1;
+                width = -width;
+            }
+            p++;
+        }
+        else
+        {
+            while (*p >= '0' && *p <= '9')
+            {
+                width = width * 10 + (*p - '0');
+                p++;
+            }
+        }
+
+        int precision = -1;
+        if (*p == '.')
+        {
+            p++;
+            if (*p == '*')
+            {
+                precision = va_arg(ap, int);
+                p++;
+            }
+            else
+            {
+                precision = 0;
+                while (*p >= '0' && *p <= '9')
+                {
+                    precision = precision * 10 + (*p - '0');
+                    p++;
+                }
+            }
+        }
+
+        int len_mod = 0;
+        if (*p == 'l')
+        {
+            len_mod = 1;
+            p++;
+            if (*p == 'l')
+            {
+                len_mod = 2;
+                p++;
+            }
+        }
+        else if (*p == 'z')
+        {
+            len_mod = 2;
+            p++;
+        }
+
+        char spec = *p++;
+        if (!spec)
+            break;
+
+        if (spec == 'd' || spec == 'i' || spec == 'u' || spec == 'x' || spec == 'X' || spec == 'p')
+        {
+            uint64 val;
+            int is_signed = (spec == 'd' || spec == 'i');
+            int base = (spec == 'x' || spec == 'X' || spec == 'p') ? 16 : 10;
+
+            if (spec == 'p')
+                val = (uint64)va_arg(ap, void *);
+            else if (len_mod == 2)
+                val = is_signed ? (uint64)va_arg(ap, int64) : va_arg(ap, uint64);
+            else if (len_mod == 1)
+                val = is_signed ? (uint64)va_arg(ap, long) : (uint64)va_arg(ap, unsigned long);
+            else
+                val = is_signed ? (uint64)((int64)va_arg(ap, int)) : (uint64)va_arg(ap, uint32);
+
+            char sign_char = 0;
+            if (is_signed)
+            {
+                int64 sval = (int64)val;
+                if (sval < 0)
+                {
+                    sign_char = '-';
+                    val = (uint64)(-sval);
+                }
+                else if (flag_plus)
+                    sign_char = '+';
+                else if (flag_space)
+                    sign_char = ' ';
+            }
+
+            int digit_len = _ul_to_str_invert(num_buf, val, base, (spec == 'X'));
+            if (precision >= 0)
+                flag_zero = 0;
+            int prec_zeros = (precision > digit_len) ? precision - digit_len : 0;
+            if (precision == 0 && val == 0)
+                digit_len = 0;
+
+            int prefix_len = sign_char ? 1 : 0;
+            char *prefix_str = NULL;
+            if (spec == 'p' || (flag_hash && val != 0 && (spec == 'x' || spec == 'X')))
+            {
+                prefix_str = (spec == 'X') ? "0X" : "0x";
+                prefix_len += 2;
+            }
+
+            int padding = (width > prefix_len + prec_zeros + digit_len) ? width - (prefix_len + prec_zeros + digit_len) : 0;
+
+            if (!flag_left && !flag_zero)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+            if (sign_char)
+                _out_char(ctx, sign_char);
+            if (prefix_str)
+            {
+                _out_char(ctx, prefix_str[0]);
+                _out_char(ctx, prefix_str[1]);
+            }
+            int total_zeros = prec_zeros + ((flag_zero && !flag_left) ? padding : 0);
+            for (int i = 0; i < total_zeros; i++)
+                _out_char(ctx, '0');
+            for (int i = digit_len - 1; i >= 0; i--)
+                _out_char(ctx, num_buf[i]);
+            if (flag_left)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+        }
+        else if (spec == 'f' || spec == 'F' || spec == 'e' || spec == 'E' || spec == 'g' || spec == 'G')
+        {
+            char fmt_tmp[32];
+            int f_idx = 0;
+            fmt_tmp[f_idx++] = '%';
+            if (flag_left)
+                fmt_tmp[f_idx++] = '-';
+            if (flag_zero)
+                fmt_tmp[f_idx++] = '0';
+            if (flag_plus)
+                fmt_tmp[f_idx++] = '+';
+            if (flag_space)
+                fmt_tmp[f_idx++] = ' ';
+            if (flag_hash)
+                fmt_tmp[f_idx++] = '#';
+            if (width > 0)
+                f_idx += sprintf(&fmt_tmp[f_idx], "%d", width);
+            if (precision >= 0)
+                f_idx += sprintf(&fmt_tmp[f_idx], ".%d", precision);
+            fmt_tmp[f_idx++] = spec;
+            fmt_tmp[f_idx] = '\0';
+            double f_val = va_arg(ap, double);
+            char f_buf[128];
+            stbsp_snprintf(f_buf, sizeof(f_buf), fmt_tmp, f_val);
+            for (int i = 0; f_buf[i] != '\0'; i++)
+                _out_char(ctx, f_buf[i]);
+        }
+        else if (spec == 's')
+        {
+            const char *s = va_arg(ap, char *);
+            if (!s)
+                s = "(null)";
+            int len = 0;
+            const char *tmp = s;
+            while (*tmp && (precision < 0 || len < precision))
+            {
+                tmp++;
+                len++;
+            }
+            int padding = (width > len) ? width - len : 0;
+            if (!flag_left)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+            for (int i = 0; i < len; i++)
+                _out_char(ctx, s[i]);
+            if (flag_left)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+        }
+        else if (spec == 'c')
+        {
+            char c = (char)va_arg(ap, int);
+            int padding = (width > 1) ? width - 1 : 0;
+            if (!flag_left)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+            _out_char(ctx, c);
+            if (flag_left)
+                for (int i = 0; i < padding; i++)
+                    _out_char(ctx, ' ');
+        }
+        else
+        {
+            _out_char(ctx, '%');
+            if (spec != '%')
+                _out_char(ctx, spec);
+        }
+    }
+    return (int)ctx->written;
+}
+
+int vsnprintf(char *str, uint64 size, const char *format, va_list ap)
+{
+    _OutContext ctx;
+    ctx.buf = str;
+    ctx.limit = size;
+    ctx.written = 0;
+    ctx.stream = NULL;
+    _vprintf_core(&ctx, format, ap);
+    if (size > 0)
+    {
+        if (ctx.written < size)
+            str[ctx.written] = '\0';
+        else
+            str[size - 1] = '\0';
+    }
+    return (int)ctx.written;
+}
+int snprintf(char *str, uint64 size, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    int ret = vsnprintf(str, size, format, ap);
+    va_end(ap);
+    return ret;
+}
+int sprintf(char *str, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    int ret = vsnprintf(str, (uint64)-1, format, ap);
+    va_end(ap);
+    return ret;
+}
+int printf(const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    _OutContext ctx;
+    ctx.buf = NULL;
+    ctx.limit = 0;
+    ctx.written = 0;
+    ctx.stream = stdout;
+    _vprintf_core(&ctx, format, ap);
+    va_end(ap);
+    return (int)ctx.written;
+}
+
+/*  Core Function Implementation  */
+
+typedef struct
+{
+    const char *buf;
+    int fd;
+    uint64 pos;
+    int ungotten;
+} _InContext;
+
+static int _in_char(_InContext *ctx)
+{
+    if (ctx->ungotten >= 0)
+    {
+        int c = ctx->ungotten;
+        ctx->ungotten = -1;
+        return c;
+    }
+    if (ctx->fd == -1)
+    {
+        if (ctx->buf[ctx->pos] == '\0')
+            return -1;
+        return (unsigned char)ctx->buf[ctx->pos++];
+    }
+    char c;
+    if (read(ctx->fd, &c, 1) == 1)
+        return (unsigned char)c;
+    return -1;
+}
+
+static void _unget_char(_InContext *ctx, int c)
+{
+    if (c != -1)
+        ctx->ungotten = c;
+}
+static void _skip_space(_InContext *ctx)
+{
+    int c;
+    while ((c = _in_char(ctx)) != -1)
+    {
+        if (!isspace(c))
+        {
+            _unget_char(ctx, c);
+            break;
+        }
+    }
+}
+
+static double _simple_strtod(const char *str, char **endptr)
+{
+    double val = 0.0;
+    int sign = 1;
+    if (*str == '-')
+    {
+        sign = -1;
+        str++;
+    }
+    else if (*str == '+')
+        str++;
+    while (*str >= '0' && *str <= '9')
+    {
+        val = val * 10.0 + (*str - '0');
+        str++;
+    }
+    if (*str == '.')
+    {
+        str++;
+        double div = 10.0;
+        while (*str >= '0' && *str <= '9')
+        {
+            val += (*str - '0') / div;
+            div *= 10.0;
+            str++;
+        }
+    }
+    if (*str == 'e' || *str == 'E')
+    {
+        str++;
+        int esign = 1;
+        if (*str == '-')
+        {
+            esign = -1;
+            str++;
+        }
+        else if (*str == '+')
+            str++;
+        int eval = 0;
+        while (*str >= '0' && *str <= '9')
+        {
+            eval = eval * 10 + (*str - '0');
+            str++;
+        }
+        double p = 1.0;
+        while (eval--)
+            p *= 10.0;
+        if (esign == 1)
+            val *= p;
+        else
+            val /= p;
+    }
+    if (endptr)
+        *endptr = (char *)str;
+    return sign * val;
+}
+
+static int _vscanf_core(_InContext *ctx, const char *format, va_list ap)
+{
+    int assigned = 0;
+    const char *p = format;
+    while (*p)
+    {
+        if (isspace(*p))
+        {
+            _skip_space(ctx);
+            while (isspace(*p))
+                p++;
+            continue;
+        }
+        if (*p != '%')
+        {
+            _skip_space(ctx);
+            int c = _in_char(ctx);
+            if (c != *p)
+            {
+                _unget_char(ctx, c);
+                return assigned;
+            }
+            p++;
+            continue;
+        }
+        p++;
+        int suppress = 0;
+        if (*p == '*')
+        {
+            suppress = 1;
+            p++;
+        }
+        int width = -1;
+        while (*p >= '0' && *p <= '9')
+        {
+            if (width == -1)
+                width = 0;
+            width = width * 10 + (*p - '0');
+            p++;
+        }
+        int len_mod = 0;
+        if (*p == 'l')
+        {
+            len_mod = 1;
+            p++;
+            if (*p == 'l')
+            {
+                len_mod = 2;
+                p++;
+            }
+        }
+        else if (*p == 'h')
+        {
+            p++;
+            if (*p == 'h')
+                p++;
+        }
+        char spec = *p++;
+        if (!spec)
+            break;
+
+        if (spec == 'd' || spec == 'i' || spec == 'u' || spec == 'x')
+        {
+            _skip_space(ctx);
+            char num_buf[64];
+            int i = 0, c = _in_char(ctx);
+            if (c == '-' || c == '+')
+            {
+                num_buf[i++] = (char)c;
+                c = _in_char(ctx);
+            }
+            int base = (spec == 'x') ? 16 : (spec == 'i' ? 0 : 10);
+            while (c != -1 && i < 63)
+            {
+                int digit = (c >= '0' && c <= '9');
+                int hex = (base == 16 || base == 0) && ((c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'));
+                int x = (c == 'x' || c == 'X');
+                if (base == 0 && i == 1 && num_buf[0] == '0' && x)
+                    base = 16;
+                if (width > 0 && i >= width)
+                    break;
+                if (digit || hex || x)
+                {
+                    num_buf[i++] = (char)c;
+                    c = _in_char(ctx);
+                }
+                else
+                    break;
+            }
+            num_buf[i] = '\0';
+            _unget_char(ctx, c);
+            if (i == 0)
+                return assigned;
+            if (!suppress)
+            {
+                int64 val = strtoll(num_buf, NULL, base);
+                if (len_mod == 2)
+                    *va_arg(ap, int64 *) = val;
+                else if (len_mod == 1)
+                    *va_arg(ap, long *) = (long)val;
+                else
+                    *va_arg(ap, int *) = (int)val;
+                assigned++;
+            }
+        }
+        else if (spec == 'f' || spec == 'F' || spec == 'e' || spec == 'E' || spec == 'g' || spec == 'G')
+        {
+            _skip_space(ctx);
+            char num_buf[64];
+            int i = 0, c = _in_char(ctx);
+            if (c == '-' || c == '+')
+            {
+                num_buf[i++] = (char)c;
+                c = _in_char(ctx);
+            }
+            while (c != -1 && i < 63)
+            {
+                if ((c >= '0' && c <= '9') || c == '.' || c == 'e' || c == 'E' || c == '+' || c == '-')
+                {
+                    num_buf[i++] = (char)c;
+                    c = _in_char(ctx);
+                }
+                else
+                    break;
+            }
+            num_buf[i] = '\0';
+            _unget_char(ctx, c);
+            if (i == 0)
+                return assigned;
+            if (!suppress)
+            {
+                double val = _simple_strtod(num_buf, NULL);
+                if (len_mod == 1)
+                    *va_arg(ap, double *) = val;
+                else
+                    *va_arg(ap, float *) = (float)val;
+                assigned++;
+            }
+        }
+        else if (spec == 's')
+        {
+            _skip_space(ctx);
+            char *buf = suppress ? NULL : va_arg(ap, char *);
+            int i = 0, c = _in_char(ctx);
+            while (c != -1 && !isspace(c))
+            {
+                if (width > 0 && i >= width)
+                    break;
+                if (!suppress)
+                    buf[i] = (char)c;
+                i++;
+                c = _in_char(ctx);
+            }
+            if (!suppress)
+                buf[i] = '\0';
+            _unget_char(ctx, c);
+            if (i > 0 && !suppress)
+                assigned++;
+        }
+        else if (spec == 'c')
+        {
+            int count = (width > 0) ? width : 1;
+            char *buf = suppress ? NULL : va_arg(ap, char *);
+            for (int i = 0; i < count; i++)
+            {
+                int c = _in_char(ctx);
+                if (c == -1)
+                    return assigned;
+                if (!suppress)
+                    buf[i] = (char)c;
+            }
+            if (!suppress)
+                assigned++;
+        }
+    }
+    return assigned;
+}
+
+int sscanf(const char *str, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    _InContext ctx;
+    ctx.buf = str;
+    ctx.fd = -1;
+    ctx.pos = 0;
+    ctx.ungotten = -1;
+    int ret = _vscanf_core(&ctx, format, ap);
+    va_end(ap);
+    return ret;
+}
+int scanf(const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    _InContext ctx;
+    ctx.buf = NULL;
+    ctx.fd = STDIN_FD;
+    ctx.pos = 0;
+    ctx.ungotten = -1;
+    int ret = _vscanf_core(&ctx, format, ap);
+    va_end(ap);
+    return ret;
+}
+
+/*  FILE Stream Implementation  */
+
+#define O_RDONLY 00
+#define O_WRONLY 01
+#define O_RDWR 02
+#define O_CREAT 0100
+#define O_TRUNC 01000
+#define O_APPEND 02000
+
+
+static FILE _stdin = {.fd = 0,  .buf_mode = 1};
+static FILE _stdout = {.fd = 1, .buf_mode = 1};
+static FILE _stderr = {.fd = 2, .buf_mode = 2};
+
+FILE *stdin = &_stdin;
+FILE *stdout = &_stdout;
+FILE *stderr = &_stderr;
+
+FILE *fopen(const char *filename, const char *mode)
+{
+    int flags = 0;
+    if (strcmp(mode, "r") == 0)
+        flags = O_RDONLY;
+    else if (strcmp(mode, "w") == 0)
+        flags = O_WRONLY | O_CREAT | O_TRUNC;
+    else if (strcmp(mode, "a") == 0)
+        flags = O_WRONLY | O_CREAT | O_APPEND;
+    else if (strcmp(mode, "r+") == 0)
+        flags = O_RDWR;
+    else
+        return NULL;
+
+    int64 fd = open(filename, flags);
+    if (fd < 0)
+        return NULL;
+
+    FILE *f = (FILE *)malloc(sizeof(FILE));
+    if (!f)
+    {
+        close(fd);
+        return NULL;
+    }
+
+    memset(f, 0, sizeof(FILE));
+    f->fd = (int)fd;
+    f->flags = flags;
+
+    if (fd == 1)
+        f->buf_mode = 1;
+    else if (fd == 2)
+        f->buf_mode = 2;
+    else
+        f->buf_mode = 0;
+    return f;
+}
+
+int fclose(FILE *stream)
+{
+    if (!stream)
+        return -1;
+    fflush(stream);
+    if (stream != stdin && stream != stdout && stream != stderr)
+    {
+        close(stream->fd);
+        free(stream);
+    }
+    return 0;
+}
+
+int fflush(FILE *stream)
+{
+    if (!stream)
+        return EOF;
+
+    if (stream->buf_write_pos > 0)
+    {
+        int64 ret = write(stream->fd, stream->buffer, stream->buf_write_pos);
+        if (ret < stream->buf_write_pos)
+        {
+            stream->error = 1;
+            stream->buf_write_pos = 0;
+            return EOF;
+        }
+        stream->buf_write_pos = 0;
+    }
+    return 0;
+}
+
+int fprintf(FILE *stream, const char *format, ...)
+{
+    if (!stream)
+        return -1;
+    va_list ap;
+    va_start(ap, format);
+    _OutContext ctx;
+    ctx.buf = NULL;
+    ctx.limit = 0;
+    ctx.written = 0;
+    ctx.stream  = stream;
+    _vprintf_core(&ctx, format, ap);
+    va_end(ap);
+    return (int)ctx.written;
+}
+
+int fscanf(FILE *stream, const char *format, ...)
+{
+    if (!stream)
+        return -1;
+    va_list ap;
+    va_start(ap, format);
+    _InContext ctx;
+    ctx.buf = NULL;
+    ctx.fd = stream->fd;
+    ctx.pos = 0;
+    ctx.ungotten = -1;
+    int ret = _vscanf_core(&ctx, format, ap);
+    va_end(ap);
+    return ret;
+}
+
+int fputc(int c, FILE *stream)
+{
+    if (!stream)
+        return EOF;
+    if (stream->buf_mode == 2)
+    {
+        char ch = (char)c;
+        if (write(stream->fd, &ch, 1) != 1)
+        {
+            stream->error = 1;
+            return EOF;
+        }
+        return c;
+    }
+
+    stream->buffer[stream->buf_write_pos++] = (char)c;
+
+    if (stream->buf_write_pos >= BUFSIZ)
+    {
+        fflush(stream);
+    }
+    else if (stream->buf_mode == 1 && c == '\n')
+    {
+        fflush(stream);
+    }
+
+    return c;
+}
+
+int fputs(const char *s, FILE *stream)
+{
+    if (!stream)
+        return -1;
+    while (*s)
+    {
+        if (fputc(*s++, stream) == EOF)
+            return EOF;
+    }
+    return 0;
+}
+
+int fgetc(FILE *stream)
+{
+    if (!stream)
+        return EOF;
+
+    if (stream->buf_write_pos > 0)
+    {
+        fflush(stream);
+    }
+
+    if (stream->buf_read_pos < stream->buf_read_cnt)
+    {
+        return (unsigned char)stream->buffer[stream->buf_read_pos++];
+    }
+
+    int64 ret = read(stream->fd, stream->buffer, BUFSIZ);
+    if (ret <= 0)
+    {
+        if (ret == 0)
+            stream->eof = 1;
+        else
+            stream->error = 1;
+        return EOF;
+    }
+
+    stream->buf_read_cnt = (int)ret;
+    stream->buf_read_pos = 0;
+    return (unsigned char)stream->buffer[stream->buf_read_pos++];
+}
+
+char *fgets(char *str, int n, FILE *stream)
+{
+    if (!stream || n <= 0)
+        return NULL;
+    int i = 0, c;
+    while (i < n - 1)
+    {
+        c = fgetc(stream);
+        if (c == -1)
+        {
+            if (i == 0)
+                return NULL;
+            break;
+        }
+        str[i++] = (char)c;
+        if (c == '\n')
+            break;
+    }
+    str[i] = '\0';
+    return str;
+}
+
+uint64 fread(void *ptr, uint64 size, uint64 nmemb, FILE *stream)
+{
+    if (!stream || size == 0 || nmemb == 0)
+        return 0;
+
+    uint64 total_bytes = size * nmemb;
+    uint64 bytes_read = 0;
+    char *dst = (char *)ptr;
+
+    if (stream->buf_write_pos > 0)
+        fflush(stream);
+
+    while (bytes_read < total_bytes)
+    {
+        if (stream->buf_read_pos < stream->buf_read_cnt)
+        {
+            uint64 available = stream->buf_read_cnt - stream->buf_read_pos;
+            uint64 remaining = total_bytes - bytes_read;
+            uint64 to_copy = (available < remaining) ? available : remaining;
+
+            memcpy(dst + bytes_read, stream->buffer + stream->buf_read_pos, to_copy);
+
+            stream->buf_read_pos += to_copy;
+            bytes_read += to_copy;
+        }
+        else
+        {
+            uint64 remaining = total_bytes - bytes_read;
+
+            if (remaining >= BUFSIZ)
+            {
+                int64 ret = read(stream->fd, dst + bytes_read, remaining);
+                if (ret <= 0)
+                {
+                    if (ret == 0)
+                        stream->eof = 1;
+                    else
+                        stream->error = 1;
+                    return bytes_read / size;
+                }
+                bytes_read += ret;
+            }
+            else
+            {
+                stream->buf_read_pos = 0;
+                stream->buf_read_cnt = 0;
+                int64 ret = read(stream->fd, stream->buffer, BUFSIZ);
+
+                if (ret <= 0)
+                {
+                    if (ret == 0)
+                        stream->eof = 1;
+                    else
+                        stream->error = 1;
+                    return bytes_read / size;
+                }
+                stream->buf_read_cnt = (int)ret;
+            }
+        }
+    }
+    return bytes_read / size;
+}
+
+uint64 fwrite(const void *ptr, uint64 size, uint64 nmemb, FILE *stream)
+{
+    if (!stream || !ptr || size == 0 || nmemb == 0)
+        return 0;
+    uint64 total_bytes = size * nmemb;
+    const char *src = (const char *)ptr;
+    uint64 bytes_written = 0;
+
+    if (stream->buf_mode == 2)
+    {
+        while (bytes_written < total_bytes)
+        {
+            int64 ret = write(stream->fd, src + bytes_written, total_bytes - bytes_written);
+            if (ret <= 0)
+            {
+                stream->error = 1;
+                break;
+            }
+            bytes_written += ret;
+        }
+        return bytes_written / size;
+    }
+
+    while (bytes_written < total_bytes)
+    {
+        uint64 space_left = BUFSIZ - stream->buf_write_pos;
+        uint64 remaining = total_bytes - bytes_written;
+
+        if (remaining <= space_left)
+        {
+            memcpy(stream->buffer + stream->buf_write_pos, src + bytes_written, remaining);
+            stream->buf_write_pos += remaining;
+            bytes_written += remaining;
+            if (stream->buf_write_pos == BUFSIZ)
+                fflush(stream);
+        }
+        else
+        {
+            memcpy(stream->buffer + stream->buf_write_pos, src + bytes_written, space_left);
+            stream->buf_write_pos += space_left;
+            bytes_written += space_left;
+            fflush(stream);
+        }
+    }
+
+    return bytes_written / size;
+}
+
+int fseek(FILE *stream, long offset, int whence)
+{
+    if (!stream)
+        return -1;
+
+    if (stream->buf_write_pos > 0)
+    {
+        fflush(stream);
+    }
+    stream->buf_read_pos = 0;
+    stream->buf_read_cnt = 0;
+    stream->eof = 0;
+
+    if (lseek(stream->fd, offset, whence) < 0)
+    {
+        stream->error = 1;
+        return -1;
+    }
+    return 0;
+}
+long ftell(FILE *stream)
+{
+    if (!stream)
+        return -1L;
+    int64 ret = lseek(stream->fd, 0, SEEK_CUR);
+    if (ret < 0)
+    {
+        stream->error = 1;
+        return -1L;
+    }
+    return (long)ret;
+}
+void rewind(FILE *stream)
+{
+    if (stream)
+    {
+        fseek(stream, 0, SEEK_SET);
+        stream->error = 0;
+    }
+}
+
+int feof(FILE *stream)
+{
+    return (stream) ? stream->eof : 1;
+}
+int ferror(FILE *stream)
+{
+     return (stream) ? stream->error : 1;
+}
+void clearerr(FILE *stream)
+{
+    if (stream)
+    {
+        stream->error = 0;
+        stream->eof = 0;
+    }
+}
+
+int ungetc(int c, FILE *stream)
+{
+    if (!stream || c == EOF)
+        return EOF;
+
+    if (stream->buf_read_pos > 0)
+    {
+        stream->buf_read_pos--;
+        stream->buffer[stream->buf_read_pos] = (char)c;
+        stream->eof = 0;
+        return c;
+    }
+    return EOF;
+}
\ No newline at end of file
diff --git a/src/ulib/stdlib.c b/src/ulib/stdlib.c
new file mode 100644
index 0000000..89d5a08
--- /dev/null
+++ b/src/ulib/stdlib.c
@@ -0,0 +1,539 @@
+#include "ulib/stdlib.h"
+#include "ulib/string.h"
+#include "ulib/ctypes.h"
+
+extern int sys_exit(int status);
+extern void *sbrk(long increment);
+
+#undef errno
+int errno = 0;
+
+#define ATEXIT_MAX 32
+static void (*__atexit_funcs[ATEXIT_MAX])(void);
+static int __atexit_func_count = 0;
+
+int atexit(void (*function)(void))
+{
+    if (__atexit_func_count >= ATEXIT_MAX)
+        return -1;
+    __atexit_funcs[__atexit_func_count++] = function;
+    return 0;
+}
+
+int exit(int status)
+{
+    while (__atexit_func_count > 0)
+    {
+        (__atexit_funcs[--__atexit_func_count])();
+    }
+    sys_exit(status);
+
+    while (1)
+        ;
+    return 0;
+}
+
+void abort(void)
+{
+    exit(127);
+}
+
+char *getenv(const char *name)
+{
+    /* None  */
+    return NULL;
+}
+
+int system(const char *command)
+{
+    /* None */
+    return -1;
+}
+
+/* Memory Management */
+#define ALIGNMENT 16
+#define ALIGN(size) (((size) + (ALIGNMENT - 1)) & ~(ALIGNMENT - 1))
+
+typedef struct header
+{
+    size_t size;
+    struct header *next;
+} header_t;
+
+static header_t base;
+static header_t *freep = NULL;
+
+
+#define LOCK()
+#define UNLOCK()
+
+void free(void *ptr)
+{
+    header_t *bp, *p;
+
+    if (!ptr)
+        return;
+
+
+    bp = (header_t *)ptr - 1;
+
+    LOCK();
+
+
+    for (p = freep; !(bp > p && bp < p->next); p = p->next)
+    {
+        if (p >= p->next && (bp > p || bp < p->next))
+            break;
+    }
+
+    if ((char *)bp + bp->size == (char *)p->next)
+    {
+        bp->size += p->next->size;
+        bp->next = p->next->next;
+    }
+    else
+    {
+        bp->next = p->next;
+    }
+
+    if ((char *)p + p->size == (char *)bp)
+    {
+        p->size += bp->size;
+        p->next = bp->next;
+    }
+    else
+    {
+        p->next = bp;
+    }
+
+    freep = p;
+    UNLOCK();
+}
+
+static header_t *morecore(size_t nu)
+{
+    char *cp;
+    header_t *up;
+
+    if (nu < 4096)
+        nu = 4096;
+
+    nu = ALIGN(nu);
+
+    cp = (char *)sbrk(nu);
+    if (cp == (void *)-1)
+        return NULL;
+
+    up = (header_t *)cp;
+    up->size = nu;
+
+    free((void *)(up + 1));
+    return freep;
+}
+
+void *malloc(size_t size)
+{
+    header_t *p, *prevp;
+
+    if (size == 0)
+        return NULL;
+
+    size = ALIGN(size + sizeof(header_t));
+
+    LOCK();
+
+    if ((prevp = freep) == NULL)
+    {
+        base.next = freep = prevp = &base;
+        base.size = 0;
+    }
+
+    for (p = prevp->next;; prevp = p, p = p->next)
+    {
+        if (p->size >= size)
+        {
+            if (p->size == size)
+            {
+                prevp->next = p->next;
+            }
+            else
+            {
+                p->size -= size;
+
+                p = (header_t *)((char *)p + p->size);
+
+                p->size = size;
+            }
+            freep = prevp;
+            UNLOCK();
+            return (void *)(p + 1);
+        }
+
+        if (p == freep)
+        {
+            if ((p = morecore(size)) == NULL)
+            {
+                UNLOCK();
+                errno = ENOMEM;
+                return NULL;
+            }
+        }
+    }
+}
+
+void *calloc(size_t nmemb, size_t size)
+{
+    size_t total;
+    if (__builtin_mul_overflow(nmemb, size, &total))
+    {
+        errno = ENOMEM;
+        return NULL;
+    }
+    void *p = malloc(total);
+    if (p)
+        memset(p, 0, total);
+    return p;
+}
+
+void *realloc(void *ptr, size_t size)
+{
+    if (!ptr)
+        return malloc(size);
+    if (size == 0)
+    {
+        free(ptr);
+        return NULL;
+    }
+
+    header_t *bp = (header_t *)ptr - 1;
+    size_t new_size = ALIGN(size + sizeof(header_t));
+
+    if (bp->size >= new_size)
+        return ptr;
+
+    void *new_ptr = malloc(size);
+    if (!new_ptr)
+        return NULL;
+
+    memcpy(new_ptr, ptr, bp->size - sizeof(header_t));
+    free(ptr);
+    return new_ptr;
+}
+
+/* String Conversion*/
+
+unsigned long long strtoull(const char *nptr, char **endptr, int base)
+{
+    const char *s = nptr;
+    unsigned long long acc;
+    unsigned long long cutoff;
+    int c;
+    int neg = 0, any, cutlim;
+
+    if (base < 0 || base == 1 || base > 36)
+    {
+        if (endptr)
+            *endptr = (char *)nptr;
+        errno = 0; /* EINVAL */
+        return 0;
+    }
+
+    do
+    {
+        c = *s++;
+    } while (isspace(c));
+
+    if (c == '-')
+    {
+        neg = 1;
+        c = *s++;
+    }
+    else if (c == '+')
+    {
+        c = *s++;
+    }
+
+    if ((base == 0 || base == 16) && c == '0' && (*s == 'x' || *s == 'X'))
+    {
+        c = s[1];
+        s += 2;
+        base = 16;
+    }
+    if (base == 0)
+        base = (c == '0' ? 8 : 10);
+
+    cutoff = ULLONG_MAX / (unsigned long long)base;
+    cutlim = ULLONG_MAX % (unsigned long long)base;
+
+    for (acc = 0, any = 0;; c = *s++)
+    {
+        if (isdigit(c))
+            c -= '0';
+        else if (isalpha(c))
+            c -= isupper(c) ? 'A' - 10 : 'a' - 10;
+        else
+            break;
+
+        if (c >= base)
+            break;
+
+        if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
+            any = -1;
+        else
+        {
+            any = 1;
+            acc *= base;
+            acc += c;
+        }
+    }
+
+    if (any < 0)
+    {
+        acc = ULLONG_MAX;
+        errno = ERANGE;
+    }
+    else if (neg)
+        acc = -acc;
+
+    if (endptr != 0)
+        *endptr = (char *)(any ? s - 1 : nptr);
+
+    return acc;
+}
+
+long long strtoll(const char *nptr, char **endptr, int base)
+{
+    const char *s = nptr;
+    unsigned long long acc;
+    int c, neg = 0;
+
+    do
+    {
+        c = *s++;
+    } while (isspace(c));
+    if (c == '-')
+        neg = 1;
+
+    acc = strtoull(nptr, endptr, base);
+
+    if (errno == ERANGE && acc == ULLONG_MAX)
+        return neg ? LLONG_MIN : LLONG_MAX;
+
+    if (!neg && acc > (unsigned long long)LLONG_MAX)
+    {
+        errno = ERANGE;
+        return LLONG_MAX;
+    }
+    if (neg && acc > (unsigned long long)LLONG_MAX + 1)
+    {
+        errno = ERANGE;
+        return LLONG_MIN;
+    }
+
+    return neg ? -(long long)acc : (long long)acc;
+}
+
+unsigned long strtoul(const char *nptr, char **endptr, int base)
+{
+    unsigned long long ret = strtoull(nptr, endptr, base);
+    if (ret > ULONG_MAX)
+    {
+        errno = ERANGE;
+        return ULONG_MAX;
+    }
+    return (unsigned long)ret;
+}
+
+long strtol(const char *nptr, char **endptr, int base)
+{
+    long long ret = strtoll(nptr, endptr, base);
+    if (ret > LONG_MAX)
+    {
+        errno = ERANGE;
+        return LONG_MAX;
+    }
+    if (ret < LONG_MIN)
+    {
+        errno = ERANGE;
+        return LONG_MIN;
+    }
+    return (long)ret;
+}
+
+int atoi(const char *nptr) { return (int)strtol(nptr, NULL, 10); }
+long atol(const char *nptr) { return strtol(nptr, NULL, 10); }
+long long atoll(const char *nptr) { return strtoll(nptr, NULL, 10); }
+
+double strtod(const char *nptr, char **endptr)
+{
+    double val = 0.0;
+    int sign = 1;
+    const char *s = nptr;
+
+    while (isspace(*s))
+        s++;
+    if (*s == '-')
+    {
+        sign = -1;
+        s++;
+    }
+    else if (*s == '+')
+        s++;
+
+    while (isdigit(*s))
+    {
+        val = val * 10.0 + (*s - '0');
+        s++;
+    }
+    if (*s == '.')
+    {
+        double factor = 1.0;
+        s++;
+        while (isdigit(*s))
+        {
+            factor *= 0.1;
+            val += (*s - '0') * factor;
+            s++;
+        }
+    }
+
+    if (endptr)
+        *endptr = (char *)s;
+    return val * sign;
+}
+
+double atof(const char *nptr) { return strtod(nptr, NULL); }
+float strtof(const char *nptr, char **endptr) { return (float)strtod(nptr, endptr); }
+
+/* Sort & Search */
+
+static void swap_bytes(char *a, char *b, size_t size)
+{
+    char temp;
+    while (size--)
+    {
+        temp = *a;
+        *a++ = *b;
+        *b++ = temp;
+    }
+}
+
+void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *))
+{
+    if (nmemb < 2 || size == 0)
+        return;
+
+    char *base_ptr = (char *)base;
+    char *pivot = base_ptr + (nmemb - 1) * size;
+    char *i = base_ptr;
+    char *j = base_ptr;
+
+    /* Partition */
+    for (; j < pivot; j += size)
+    {
+        if (compar(j, pivot) < 0)
+        {
+            if (i != j)
+                swap_bytes(i, j, size);
+            i += size;
+        }
+    }
+    swap_bytes(i, pivot, size);
+
+    /* Recurse */
+    size_t left_count = (i - base_ptr) / size;
+    qsort(base, left_count, size, compar);
+    qsort(i + size, nmemb - left_count - 1, size, compar);
+}
+
+void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *))
+{
+    size_t l = 0, u = nmemb;
+    while (l < u)
+    {
+        size_t idx = (l + u) / 2;
+        const void *p = (void *)((const char *)base + (idx * size));
+        int cmp = compar(key, p);
+        if (cmp < 0)
+            u = idx;
+        else if (cmp > 0)
+            l = idx + 1;
+        else
+            return (void *)p;
+    }
+    return NULL;
+}
+
+/* Math & Mics */
+
+int abs(int j) { return (j < 0) ? -j : j; }
+long labs(long j) { return (j < 0) ? -j : j; }
+long long llabs(long long j) { return (j < 0) ? -j : j; }
+
+div_t div(int numer, int denom)
+{
+    div_t res = {numer / denom, numer % denom};
+    return res;
+}
+ldiv_t ldiv(long numer, long denom)
+{
+    ldiv_t res = {numer / denom, numer % denom};
+    return res;
+}
+lldiv_t lldiv(long long numer, long long denom)
+{
+    lldiv_t res = {numer / denom, numer % denom};
+    return res;
+}
+
+static unsigned long next = 1;
+int rand(void)
+{
+    next = next * 1103515245 + 12345;
+    return (unsigned int)(next / 65536) % 32768;
+}
+void srand(unsigned int seed) { next = seed; }
+
+/* Stub */
+int mblen(const char *s, size_t n) { return (s && *s && n) ? 1 : 0; }
+int mbtowc(wchar_t *pwc, const char *s, size_t n)
+{
+    if (!s)
+        return 0;
+    if (n == 0)
+        return -1;
+    if (pwc)
+        *pwc = (wchar_t)*s;
+    return (*s != 0);
+}
+int wctomb(char *s, wchar_t wchar)
+{
+    if (!s)
+        return 0;
+    *s = (char)wchar;
+    return 1;
+}
+size_t mbstowcs(wchar_t *dest, const char *src, size_t n)
+{
+    size_t i = 0;
+    while (src[i] && i < n)
+    {
+        dest[i] = (wchar_t)src[i];
+        i++;
+    }
+    if (i < n)
+        dest[i] = 0;
+    return i;
+}
+size_t wcstombs(char *dest, const wchar_t *src, size_t n)
+{
+    size_t i = 0;
+    while (src[i] && i < n)
+    {
+        dest[i] = (char)src[i];
+        i++;
+    }
+    if (i < n)
+        dest[i] = 0;
+    return i;
+}
\ No newline at end of file
diff --git a/src/ulib/string.c b/src/ulib/string.c
new file mode 100644
index 0000000..5fc1cbd
--- /dev/null
+++ b/src/ulib/string.c
@@ -0,0 +1,331 @@
+#include "ulib/string.h"
+#include "ulib/stdlib.h"
+
+
+/* Memory Manipulation Functions  */
+
+void *memset(void *dst, int c, size_t n)
+{
+    char *cdst = (char *)dst;
+    for (size_t i = 0; i < n; i++)
+        cdst[i] = (char)c;
+    return dst;
+}
+
+void *memmove(void *vdst, const void *vsrc, size_t n)
+{
+    char *dst = (char *)vdst;
+    const char *src = (const char *)vsrc;
+    if (dst == src)
+        return vdst;
+
+    if (src > dst)
+    {
+        while (n--)
+            *dst++ = *src++;
+    }
+    else
+    {
+        dst += n;
+        src += n;
+        while (n-- > 0)
+            *--dst = *--src;
+    }
+    return vdst;
+}
+
+void *memcpy(void *vdst, const void *vsrc, size_t n)
+{
+    return memmove(vdst, vsrc, n);
+}
+
+int memcmp(const void *s1, const void *s2, size_t n)
+{
+    const unsigned char *p1 = (const unsigned char *)s1;
+    const unsigned char *p2 = (const unsigned char *)s2;
+    while (n--)
+    {
+        if (*p1 != *p2)
+            return *p1 - *p2;
+        p1++;
+        p2++;
+    }
+    return 0;
+}
+
+void *memchr(const void *s, int c, size_t n)
+{
+    const unsigned char *p = (const unsigned char *)s;
+    while (n--)
+    {
+        if (*p == (unsigned char)c)
+            return (void *)p;
+        p++;
+    }
+    return NULL;
+}
+
+/* String Manipulation Functions  */
+
+size_t strlen(const char *s)
+{
+    const char *p = s;
+    while (*p)
+        p++;
+    return (size_t)(p - s);
+}
+
+char *strcpy(char *dst, const char *src)
+{
+    char *os = dst;
+    while ((*dst++ = *src++) != 0)
+        ;
+    return os;
+}
+
+char *strncpy(char *dst, const char *src, size_t n)
+{
+    char *os = dst;
+    size_t i;
+
+    for (i = 0; i < n && src[i] != '\0'; i++)
+        dst[i] = src[i];
+
+    for (; i < n; i++)
+        dst[i] = '\0';
+
+    return os;
+}
+
+char *strcat(char *dst, const char *src)
+{
+    char *os = dst;
+    while (*dst)
+        dst++;
+    while ((*dst++ = *src++) != 0)
+        ;
+    return os;
+}
+
+char *strncat(char *dst, const char *src, size_t n)
+{
+    char *os = dst;
+    size_t dest_len = strlen(dst);
+    size_t i;
+
+    dst += dest_len;
+
+    for (i = 0; i < n && src[i] != '\0'; i++)
+        dst[i] = src[i];
+
+    dst[i] = '\0';
+
+    return os;
+}
+
+int strcmp(const char *p, const char *q)
+{
+    while (*p && *p == *q)
+    {
+        p++;
+        q++;
+    }
+    return (int)((unsigned char)*p - (unsigned char)*q);
+}
+
+int strncmp(const char *s1, const char *s2, size_t n)
+{
+    if (n == 0)
+        return 0;
+
+    while (n-- > 0 && *s1 && *s1 == *s2)
+    {
+        if (n == 0 || *s1 == '\0')
+            break;
+        s1++;
+        s2++;
+    }
+    return (int)((unsigned char)*s1 - (unsigned char)*s2);
+}
+
+char *strchr(const char *s, int c)
+{
+    while (*s != (char)c)
+    {
+        if (!*s++)
+            return NULL;
+    }
+    return (char *)s;
+}
+
+char *strrchr(const char *s, int c)
+{
+    const char *last = NULL;
+    do
+    {
+        if (*s == (char)c)
+            last = s;
+    } while (*s++);
+
+    return (char *)last;
+}
+
+
+char *strstr(const char *haystack, const char *needle)
+{
+    size_t n_len = strlen(needle);
+    if (n_len == 0)
+        return (char *)haystack;
+
+    for (; *haystack; haystack++)
+    {
+        if (*haystack != *needle)
+            continue;
+
+        if (strncmp(haystack, needle, n_len) == 0)
+            return (char *)haystack;
+    }
+    return NULL;
+}
+
+char *strdup(const char *s)
+{
+    size_t len = strlen(s) + 1;
+    char *new_str = (char *)malloc(len);
+    if (new_str == NULL)
+        return NULL;
+
+    return (char *)memcpy(new_str, s, len);
+}
+
+size_t strlcpy(char *dst, const char *src, size_t size)
+{
+    size_t src_len = strlen(src);
+
+    if (size > 0)
+    {
+        size_t copy_len = (src_len >= size) ? size - 1 : src_len;
+        memcpy(dst, src, copy_len);
+        dst[copy_len] = '\0';
+    }
+
+    return src_len;
+}
+
+size_t strlcat(char *dst, const char *src, size_t size)
+{
+    size_t dst_len = 0;
+    size_t src_len = strlen(src);
+
+    while (dst_len < size && dst[dst_len] != '\0')
+        dst_len++;
+
+    if (dst_len == size)
+        return size + src_len;
+
+    size_t space_left = size - dst_len;
+    size_t copy_len = (src_len >= space_left) ? space_left - 1 : src_len;
+
+    memcpy(dst + dst_len, src, copy_len);
+    dst[dst_len + copy_len] = '\0';
+
+    return dst_len + src_len;
+}
+
+
+size_t strspn(const char *s, const char *accept)
+{
+    const char *p = s;
+    const char *a;
+
+    while (*p)
+    {
+        for (a = accept; *a; a++)
+        {
+            if (*p == *a)
+                break;
+        }
+        if (*a == '\0')
+            return (size_t)(p - s);
+        p++;
+    }
+    return (size_t)(p - s);
+}
+
+size_t strcspn(const char *s, const char *reject)
+{
+    const char *p = s;
+    const char *r;
+
+    while (*p)
+    {
+        for (r = reject; *r; r++)
+        {
+            if (*p == *r)
+                return (size_t)(p - s);
+        }
+        p++;
+    }
+    return (size_t)(p - s);
+}
+
+char *strpbrk(const char *s, const char *accept)
+{
+    const char *a;
+    while (*s)
+    {
+        for (a = accept; *a; a++)
+        {
+            if (*s == *a)
+                return (char *)s;
+        }
+        s++;
+    }
+    return NULL;
+}
+
+char *strtok(char *str, const char *delim)
+{
+    static char *olds;
+    char *token;
+
+    if (str == NULL)
+        str = olds;
+
+    str += strspn(str, delim);
+    if (*str == '\0')
+    {
+        olds = str;
+        return NULL;
+    }
+
+    token = str;
+    str = strpbrk(token, delim);
+
+    if (str == NULL)
+    {
+        olds = strchr(token, '\0');
+    }
+    else
+    {
+        *str = '\0';
+        olds = str + 1;
+    }
+
+    return token;
+}
+
+char *strerror(int errnum)
+{
+    
+    switch (errnum)
+    {
+    case 0:
+        return "Success";
+    // case EINVAL: return "Invalid argument";
+    case ENOMEM: return "Out of memory";
+    
+    default:
+        return "Unknown error";
+    }
+}
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