String.[ch]: memset, memcpy, memmove, memcmph and strlen, strnlen

lib/string.c

@@ -1,3 +1,5 @@
+#include <string.h>
+
 char *itoa(int value, char *str, int base) {
     char        *p = str;
     char        *p1, *p2;
@@ -37,3 +39,61 @@ char *itoa(int value, char *str, int base) {
 
     return str;
 }
+
+void *memset(void *dst, int c, size_t length) {
+    u8      *ptr = (u8 *)dst;
+    const u8 value = (u8)c;
+
+    while (length--) *(ptr++) = value;
+
+    return dst;
+}
+
+void *memcpy(void *dst, const void *src, size_t len) {
+    u8       *d = (u8 *)dst;
+    const u8 *s = (const u8 *)src;
+    for (size_t i = 0; i < len; i++) {
+        d[i] = s[i];
+    }
+    return dst;
+}
+
+void *memmove(void *dst, const void *src, size_t len) {
+    u8       *d = (u8 *)dst;
+    const u8 *s = (const u8 *)src;
+    if (d < s) {
+        for (size_t i = 0; i < len; i++) {
+            d[i] = s[i];
+        }
+    } else if (d > s) {
+        for (size_t i = len; i > 0; i--) {
+            d[i - 1] = s[i - 1];
+        }
+    }
+    return dst;
+}
+
+int memcmp(const void *s1, const void *s2, size_t len) {
+    const u8 *a = (const u8 *)s1;
+    const u8 *b = (const u8 *)s2;
+    for (size_t i = 0; i < len; i++) {
+        if (a[i] != b[i]) {
+            return (int)a[i] - (int)b[i];
+        }
+    }
+    return 0;
+}
+
+size_t strlen(const char *s) {
+    const char *p = s;
+    while (*p) ++p;
+    return (size_t)(p - s);
+}
+
+size_t strnlen(const char *s, size_t maxlen) {
+    size_t len = 0;
+    while (len < maxlen && s[len] != '\0') {
+        len++;
+    }
+    return len;
+}

lib/string.h

@@ -1,7 +1,40 @@
 #ifndef KERNEL_STRING_H
 #define KERNEL_STRING_H
 
+#include <types.h>
+
 /** Integer to ascii */
 char *itoa(int value, char *str, int base);
 
+/** Fill memory with constant byte */
+void *memset(void *dst, int c, size_t len);
+
+/** Copy `len` bytes from `src` to `dst`. Undefined if regions overlap. */
+void *memcpy(void *dst, const void *src, size_t len);
+
+/** Copy `len` bytes from `src` to `dst`, safe for overlapping regions. */
+void *memmove(void *dst, const void *src, size_t len);
+
+/** Compare `len` bytes of `s1` and `s2`.
+ *  Returns 0 if equal, <0 if s1 < s2, >0 if s1 > s2. */
+int memcmp(const void *s1, const void *s2, size_t len);
+
+/** Returns the length of a null-terminated string */
+size_t strlen(const char *s);
+
+/** Return length of string `s`, up to a max of `maxlen` bytes */
+size_t strnlen(const char *s, size_t maxlen);
+
+// TODO: These:
+/*
+int    strcmp(const char *s1, const char *s2);
+int    strncmp(const char *s1, const char *s2, size_t n);
+
+char  *strcpy(char *dst, const char *src);
+char  *strncpy(char *dst, const char *src, size_t n);
+
+char  *strchr(const char *s, int c);
+char  *strrchr(const char *s, int c);
+*/
+
 #endif