#include "string.h"

void memcpy(void *dst, const void *src, size_t size) {
    for (size_t i = 0; i < size; i++) {
        ((char *)dst)[i] = ((const char *)src)[i];
    }
}

void kmemmove(char *dst, char *src, size_t size) {
    if (dst == src)
        return;
    if (dst > src && dst < src + size) { //   s d
        // copy right-to-left
        for (; size != 0; size--) {
            dst[size - 1] = src[size - 1];
        }
    } else {
        // copy left-to-right
        for (size_t i = 0; i < size; ++i) {
            dst[i] = src[i];
        }
    }
}

int strncmp(const char *s1, const char *s2, size_t size) {
    while (size && *s1 && *s2 && *s1 == *s2) {
        size--;
        s1++;
        s2++;
    }
    if (!size) {
        return 0;
    }
    return (unsigned char)(*s1) - (unsigned char)(*s2);
}

bool cstr_equal(const char *s1, const char *s2) {
    while (*s1 && *s2 && *s1 == *s2) {
        s1++;
        s2++;
    }
    return *s1 == 0 && *s2 == 0;
}

bool cstr_starts_with(const char *A, const char *B) {
    while (*A && *B) {
        if (*A != *B)
            return false;
        A++;
        B++;
    }
    return *B == 0;
}