string.c

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/*
 * Copyright (c) 2006-2018 Ali Mashtizadeh
 * All rights reserved.
 */
 
#include <stddef.h>
#include <stdint.h>
#include <string.h>
 
char *
strchr(const char *s, int c)
{
    int i;
    for (i = 0; ; i++)
    {
        if (s[i] == c)
            return (char *)s + i;
        if (s[i] == '\0')
            return NULL;
    }
}
 
char *
strcpy(char *to, const char *from)
{
    char *save = to;
 
    for (; (*to = *from); ++from, ++to);
 
    return save;
}
 
char *
strncpy(char *to, const char *from, size_t length)
{
    char *save = to;
 
    for (; (*to = *from) != '\0' && length > 0; ++from, ++to, length--);
 
    *to = '\0';
 
    return save;
}
 
char *
strcat(char *s, const char *append)
{
    char *save = s;
 
    for (; *s; ++s);
    while ((*s++ = *append++));
 
    return save;
}
 
 
char *
strncat(char *dst, const char *src, size_t n)
{
    if (n != 0) {
        char *d = dst;
        const char *s = src;
 
        while (*d != 0)
            d++;
 
        do {
            if ((*d = *s++) == 0)
                break;
 
            d++;
        } while (--n != 0);
 
        *d = 0;
    }
 
    return dst;
}
 
int
strcmp(const char *s1, const char *s2)
{
    while (*s1 == *s2++)
        if (*s1++ == 0)
            return 0;
 
    return (*(const uint8_t *)s1 - *(const uint8_t *)(s2 - 1));
}
 
int
strncmp(const char *s1, const char *s2, size_t len)
{
    if (len == 0)
        return 0;
 
    while (*s1 == *s2) {
        if (*s1 == 0)
            return 0;
 
        s1++;
        s2++;
 
        len--;
        if (len == 0)
            return 0;
    }
 
    return (*(const uint8_t *)s1 - *(const uint8_t *)s2);
}
 
size_t
strlen(const char *str)
{
    const char *s;
 
    for (s = str; *s; ++s);
 
    return (s - str);
}
 
char *
strtok_r(char *str, const char *delim, char **last)
{
    char *rval;
 
    if (str == NULL)
        str = *last;
 
    // Skip deliminaters in the front
    while ((str[0] != '\0') && strchr(delim, str[0])) {
        str++;
    }
 
    // We've reached the end of the string
    if (str[0] == '\0')
        return NULL;
 
    // Return first non-delim until the next
    rval = str;
 
    // Skip deliminaters in the front
    while ((str[0] != '\0') && !strchr(delim, str[0])) {
        str++;
    }
 
    if (str[0] != '\0') {
        str[0] = '\0';
        str++;
    }
    *last = str;
 
    return rval;
}
 
char *
strtok(char *str, const char *delim)
{
    static char *last;
 
    return strtok_r(str, delim, &last);
}
 
void *
memset(void *dst, int c, size_t length)
{
    uint8_t *p = (uint8_t *)dst;
 
    while (length-- != 0) {
        *p = c;
        p += 1;
    };
 
    return dst;
}
 
void *
memcpy(void *dst, const void *src, size_t length)
{
    uint8_t *d = (uint8_t *)dst;
    const uint8_t *s = (const uint8_t *)src;
 
    while (length-- != 0) {
        *d = *s;
        d += 1;
        s += 1;
    };
 
    return dst;
}
 
int
memcmp(const void *b1, const void *b2, size_t length)
{
    int i;
    const char *c1 = (const char *)b1;
    const char *c2 = (const char *)b2;
 
    for (i = 0; i < length; i++)
    {
        if (*c1 != *c2)
            return *c2 - *c1;
        c1++;
        c2++;
    }
 
    return 0;
}