Split monolithic libc.c into logical modules

This commit consolidates modular source files of libc for better
maintainability:
- lib/string.c: String manipulation functions
- lib/memory.c: Memory operations (memcpy, memset, etc.)
- lib/ctype.c: Character classification and conversion utilities
- lib/random.c: xorshift32 PRNG implementation
- lib/stdio.c: Standard I/O and printf formatting routines

Author: jserv

Makefile

@@ -21,7 +21,7 @@ KERNEL_OBJS := timer.o mqueue.o pipe.o semaphore.o mutex.o error.o syscall.o tas
 KERNEL_OBJS := $(addprefix $(BUILD_KERNEL_DIR)/,$(KERNEL_OBJS))
 deps += $(KERNEL_OBJS:%.o=%.o.d)
 
-LIB_OBJS := stdio.o libc.o malloc.o queue.o
+LIB_OBJS := ctype.o malloc.o memory.o random.o stdio.o string.o queue.o
 LIB_OBJS := $(addprefix $(BUILD_LIB_DIR)/,$(LIB_OBJS))
 deps += $(LIB_OBJS:%.o=%.o.d)
 

include/lib/libc.h

@@ -76,9 +76,6 @@ char *strpbrk(const char *s1, const char *s2);
 char *strsep(char **pp, const char *delim);
 char *strtok(char *s, const char *delim);
 char *strtok_r(char *s, const char *delim, char **holder);
-int32_t strtol(const char *s, char **end, int32_t base);
-int32_t atoi(const char *s);
-void itoa(int32_t i, char *s, int32_t base); /* Integer to ASCII conversion */
 
 /* Memory manipulation functions */
 void *memcpy(void *dst, const void *src, uint32_t n);
@@ -87,6 +84,11 @@ int32_t memcmp(const void *cs, const void *ct, uint32_t n);
 void *memset(void *s, int32_t c, uint32_t n);
 int32_t abs(int32_t n); /* Absolute value */
 
+/* Character classification and conversion functions */
+int32_t strtol(const char *s, char **end, int32_t base);
+int32_t atoi(const char *s);
+void itoa(int32_t i, char *s, int32_t base); /* Integer to ASCII conversion */
+
 /* Random number generation */
 
 #ifndef RAND_MAX

lib/ctype.c

@@ -0,0 +1,176 @@
+/* libc: string-to-number conversion functions. */
+
+#include <lib/libc.h>
+
+/* Base-10 string conversion without division or multiplication */
+static char *__str_base10(uint32_t value, char *buffer, int *length)
+{
+    if (value == 0) {
+        buffer[0] = '0';
+        *length = 1;
+        return buffer;
+    }
+    int pos = 0;
+
+    while (value > 0) {
+        uint32_t q, r, t;
+
+        q = (value >> 1) + (value >> 2);
+        q += (q >> 4);
+        q += (q >> 8);
+        q += (q >> 16);
+        q >>= 3;
+        r = value - (((q << 2) + q) << 1);
+        t = ((r + 6) >> 4);
+        q += t;
+        r -= (((t << 2) + t) << 1);
+
+        buffer[pos++] = '0' + r;
+        value = q;
+    }
+    *length = pos;
+
+    return buffer;
+}
+
+/* Handle signed integers */
+static char *__str_base10_signed(int32_t value, char *buffer, int *length)
+{
+    if (value < 0) {
+        buffer[0] = '-';
+        __str_base10((uint32_t) (-value), buffer + 1, length);
+        (*length)++;
+        return buffer;
+    }
+    return __str_base10((uint32_t) value, buffer, length);
+}
+
+/* Converts string @s to an integer. */
+int32_t strtol(const char *s, char **end, int32_t base)
+{
+    int32_t i;
+    uint32_t ch, value = 0, neg = 0;
+
+    /* Handle optional sign. */
+    if (s[0] == '-') {
+        neg = 1;
+        ++s;
+    }
+
+    /* Handle common base prefixes (0x for hex). */
+    if (s[0] == '0' && s[1] == 'x') {
+        base = 16;
+        s += 2;
+    }
+
+    /* Convert digits based on the specified base. */
+    for (i = 0; i <= 8; ++i) {
+        ch = *s++;
+        if ('0' <= ch && ch <= '9')
+            ch -= '0';
+        else if ('A' <= ch && ch <= 'Z')
+            ch = ch - 'A' + 10;
+        else if ('a' <= ch && ch <= 'z')
+            ch = ch - 'a' + 10;
+        else
+            break;
+        value = value * base + ch;
+    }
+
+    if (end)
+        *end = (char *) s - 1;
+    if (neg)
+        value = -(int32_t) value;
+
+    return value;
+}
+
+/* Converts string @s to an integer. */
+int32_t atoi(const char *s)
+{
+    int32_t n, f;
+
+    n = 0;
+    f = 0; /* Flag for sign. */
+
+    /* Skip leading whitespace and handle optional sign. */
+    for (;; s++) {
+        switch (*s) {
+        case ' ':
+        case '\t':
+        case '\n':
+        case '\r':
+            continue; /* Skip whitespace. */
+        case '-':
+            f++; /* Set negative flag. */
+            __attribute__((fallthrough));
+        case '+':
+            s++; /* Skip '+' sign. */
+        }
+        break;
+    }
+
+    /* Convert digits to integer. */
+    while (*s >= '0' && *s <= '9')
+        n = n * 10 + *s++ - '0';
+
+    return (f ? -n : n);
+}
+
+/* Converts integer @i to an ASCII string @s in the given @base. */
+void itoa(int32_t i, char *s, int32_t base)
+{
+    char c;
+    char *p = s;
+    char *q = s;
+    uint32_t h;
+    int32_t len;
+
+    if (base == 16) { /* Hexadecimal conversion */
+        h = (uint32_t) i;
+        do {
+            *q++ = '0' + (h % base);
+        } while (h /= base); /* Continue until number becomes 0. */
+
+        if ((i >= 0) && (i < 16)) /* Special case for small positive numbers */
+            *q++ = '0';
+
+        /* Reverse the string (digits are collected in reverse order). */
+        for (*q = 0; p <= --q; p++) {
+            /* Convert digit character if needed (e.g., 'a'-'f'). */
+            (*p > '9') ? (c = *p + 39) : (c = *p); /* ASCII 'a' is '0'+39 */
+            /* Swap characters. */
+            (*q > '9') ? (*p = *q + 39) : (*p = *q);
+            *q = c;
+        }
+    } else if (base == 10) { /* Decimal conversion */
+        __str_base10_signed(i, s, &len);
+
+        /* Reverse the string. */
+        q = s + len;
+        for (*q = 0; p <= --q; p++) {
+            c = *p;
+            *p = *q;
+            *q = c;
+        }
+    } else { /* Other bases */
+        if (i >= 0) {
+            do {
+                *q++ = '0' + (i % base);
+            } while (i /= base);
+        } else {
+            *q++ = '-';
+            p++;
+            do {
+                *q++ = '0' - (i % base);
+            } while (i /= base);
+        }
+
+        /* Reverse the string. */
+        for (*q = 0; p <= --q; p++) {
+            c = *p;
+            *p = *q;
+            *q = c;
+        }
+    }
+}