nt-lite/code/libc.c

// everyone needs a little libc
#include <stddef.h>
#include <stdint.h>

char* strcpy(char* dest, const char* src) {
    char* d = dest;
    while (*src) *d++ = *src++;
    *d = 0;
    return dest;
}

char* strncpy(char* dest, const char* src, size_t n) {
    size_t i;
    for (i = 0; i < n && src[i]; i++) dest[i] = src[i];
    for (; i < n; i++) dest[i] = 0;
    return dest;
}

int strcmp(const char* s1, const char* s2) {
    while (*s1 && *s1 == *s2) s1++, s2++;
    return (unsigned char)*s1 - (unsigned char)*s2;
}

int _stricmp(const char* s1, const char* s2) {
    // 0x20 (32) is the bit that differs between 'A' and 'a'
    while (*s1 && ((*s1 | 0x20) == (*s2 | 0x20))) {
        s1++, s2++;
    }
    return (unsigned char)(*s1 | 0x20) - (unsigned char)(*s2 | 0x20);
}

size_t strlen(const char* s) {
    size_t n = 0;
    while (*s++) n++;
    return n;
}

char* strchr(const char* s, int c) {
    while (*s) {
        if (*s == (char)c) return (char *)s;
        s++;
    }
    return NULL;
}

void* memmove(void* dest, const void* src, size_t n) {
    uint8_t* d = (uint8_t *)dest;
    const uint8_t* s = (const uint8_t *)src;
    if (d < s) {
        for (size_t i = 0; i < n; i++) d[i] = s[i];
    } else if (d > s) {
        for (size_t i = n; i > 0; i--) d[i - 1] = s[i - 1];
    }
    return dest;
}

int memcmp(const void* s1, const void* s2, size_t n) {
    const uint8_t* a = (const uint8_t *)s1;
    const uint8_t* b = (const uint8_t *)s2;
    for (size_t i = 0; i < n; i++) {
        if (a[i] != b[i]) return a[i] - b[i];
    }
    return 0;
}