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string.c
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string.c
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#include "string.h"
int strcmp(const char* str1, const char* str2)
{
int result = 0;
while (!(result = *str1 - *str2) && *str1)
{
str1++;
str2++;
}
return result;
}
int strncmp(const char* str1, const char* str2, size_t count)
{
int result = 0;
while (*str1 && *str2 && !(result = *str1 - *str2) && count)
{
str1++;
str2++;
count--;
}
return result;
}
size_t strlen(const char* str)
{
size_t length = 0;
while (*str != '\0')
{
length++;
str++;
}
return length;
}
char* strncpy (char * dst, const char * src, size_t count)
{
for(size_t i = 0; i < count && src[i]; i++)
{
dst[i] = src[i];
}
return dst;
}
//http://clc-wiki.net/wiki/C_standard_library:string.h:strncat
char* strncat(char* dst, const char* src, size_t count)
{
char *ret = dst;
while (*dst)
dst++;
while (count--)
if (!(*dst++ = *src++))
return ret;
*dst = 0;
return ret;
}
//https://articles.leetcode.com/implement-strstr-to-find-substring-in/
char* strstr(const char *str, const char *target)
{
if (!*target) return (char*)str;
char *p1 = (char*)str, *p2 = (char*)target;
char *p1Adv = (char*)str;
while (*++p2)
p1Adv++;
while (*p1Adv) {
char *p1Begin = p1;
p2 = (char*)target;
while (*p1 && *p2 && *p1 == *p2) {
p1++;
p2++;
}
if (!*p2)
return p1Begin;
p1 = p1Begin + 1;
p1Adv++;
}
return NULL;
}
void* memcpy(void* dst, const void* src, size_t count)
{
for(size_t i = 0; i < count; i++)
{
((uint8_t*)dst)[i] = ((uint8_t*)src)[i];
}
return dst;
}
//why is mine wrong?
/*
void* memmove(void* dst, const void* src, size_t count)
{
if((uintptr_t)dst < (uintptr_t)src)
{
//copy forward
for (size_t i = 0; i < count; i++)
{
((uint8_t*)dst)[i] = ((uint8_t*)src)[i];
}
}
else
{
//copy backwards
for (count -= 1; count >= 0; count--)
{
((uint8_t*)dst)[count] = ((uint8_t*)src)[count];
}
}
return dst;
}
*/
void *memmove(void *dest, void const *src, size_t n)
{
register char *dp = dest;
register char const *sp = src;
if(dp < sp) {
while(n-- > 0)
*dp++ = *sp++;
} else {
dp += n;
sp += n;
while(n-- > 0)
*--dp = *--sp;
}
return dest;
}
void* memset(void* dst, uint8_t val, size_t size)
{
for(size_t i = 0; i < size; i++)
{
((uint8_t*)dst)[i] = val;
}
return dst;
}
int memcmp(const void* dst, const void* src, size_t count)
{
for(size_t i = 0; i < count; i++)
{
if(((uint8_t*)dst)[i] == ((uint8_t*)src)[i])
{
return ((uint8_t*)dst)[i] - ((uint8_t*)src)[i];
}
}
return 0;
}