string.c

#include "string.h"

// Calculate length of a string
size_t strlen(const char* str) {
    size_t len = 0;
    while (str[len] != '\0') {
        len++;
    }
    return len;
}

// Compare two strings
int strcmp(const char* str1, const char* str2) {
    while (*str1 && (*str1 == *str2)) {
        str1++;
        str2++;
    }
    return *(unsigned char*)str1 - *(unsigned char*)str2;
}

// Fill memory with a specific byte
void* memset(void* dest, int val, size_t len) {
    unsigned char* ptr = (unsigned char*)dest;
    while (len-- > 0) {
        *ptr++ = (unsigned char)val;
    }
    return dest;
}

// Helper to reverse a string (used in itoa)
void reverse(char* str, int length) {
    int start = 0;
    int end = length - 1;
    while (start < end) {
        char temp = str[start];
        str[start] = str[end];
        str[end] = temp;
        start++;
        end--;
    }
}

// Convert integer to ASCII string
void itoa(int num, char* str, int base) {
    int i = 0;
    int isNegative = 0;

    // Handle 0 explicitly, otherwise empty string is returned
    if (num == 0) {
        str[i++] = '0';
        str[i] = '\0';
        return;
    }

    // In standard itoa(), negative numbers are handled only with base 10.
    if (num < 0 && base == 10) {
        isNegative = 1;
        num = -num;
    }

    // Process individual digits
    while (num != 0) {
        int rem = num % base;
        str[i++] = (rem > 9) ? (rem - 10) + 'a' : rem + '0';
        num = num / base;
    }

    // If number is negative, append '-'
    if (isNegative) {
        str[i++] = '-';
    }

    str[i] = '\0'; // Append string terminator

    // Reverse the string
    reverse(str, i);
}