string.c

#include "string.h"

size_t strlen(const char* str) {
    size_t len = 0;
    while (str[len]) len++;
    return len;
}

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

char* strtok(char* str, const char* delim) {
    static char* last;
    if (str) last = str;
    if (!last) return NULL;

    while (*last && *last == *delim) last++;
    if (!*last) return NULL;

    char* token = last;
    while (*last && *last != *delim) last++;
    if (*last) {
        *last = '\0';
        last++;
    } else {
        last = NULL;
    }
    return token;
}

// Custom strcpy implementation
char* strcpy(char* dest, const char* src) {
    char* d = dest;
    while ((*d++ = *src++) != '\0');
    return dest;
}

char* strcat(char *dest, const char *src) {
    char *original_dest = dest;

    // Find the end of the destination string
    while (*dest != '\0') {
        dest++;
    }

    // Append the source string to the end of the destination string
    while (*src != '\0') {
        *dest = *src;
        dest++;
        src++;
    }

    // Add the null terminator to the end of the concatenated string
    *dest = '\0';

    // Return a pointer to the beginning of the destination string
    return original_dest;
}