模仿：memove&strstr&strcmp&memcpy

最新推荐文章于 2024-04-18 18:25:34 发布

原创最新推荐文章于 2024-04-18 18:25:34 发布 · 129 阅读

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在这里插入代码片

#include<stdio.h>
#include<assert.h>
#include<string.h>
#include<stdlib.h>

void* Memcpy(void* dest, const void* src, size_t num)
{
assert(dest != NULL && src != NULL);
void* ret = dest;
for (size_t i = 0; i < num; i++)
{
(char*)dest = (char)src;
dest = (char*)dest + 1;
src = (char*)src + 1;
}
return ret;
}
void* Memmove(void* dest, const void* src, size_t num)
{
assert(dest != NULL && src != NULL);
char* cdest = (char*) dest;
char* csrc = (char*)src;
if (csrc < cdest && cdest < csrc + num)
{
char* pdest = cdest + num - 1;
char* psrc = csrc + num - 1;
for (size_t i = 0; i < num; i++)
{
*pdest = psrc;
pdest–;
psrc–;
}
}
else
{
Memcpy(dest, src, num);
}
return dest;
}
int main()
{
char str1[] = “hello simple world”;
char str2[] = “beatuful”;
void ret = Memmove(str1, str2, 8);
printf("%p\n", ret);
return 0;
}

void* Memcpy(void* dest, const void* src, size_t num)
{
assert(dest != NULL && src != NULL);
void* ret = dest;
for (size_t i = 0; i < num; i++)
{
(char*)dest = (char)src;
dest = (char*)dest + 1;
src = (char*)src + 1;
}
return ret;
}
int main()
{
int arr[] = { 1,2,3,4,5,6,7,8 };
int* p = arr + 2;
Memcpy(p, arr, 8);
for (int i = 0; i < 4; i++)
{
printf("%d ", arr[i]);
return 0;
}

const char* Strstr(const char* str1, const char* str2)
{
assert(str1 != NULL && str2 != NULL);
if (str2 == ‘\0’)
{
return NULL;
}
const char black = str1;
while (black != ‘\0’)
{
const char red = black;
const char* sub = str2;
while (*red != ‘\0’ && *sub != ‘\0’ && (*red == *sub))
{
red++;
sub++;
}
if (*sub == ‘\0’)
{
return black;
}
if (red == ‘\0’)
{
return NULL;
}
black++;
}
return NULL;
}
int main(）
{
char str1[] = “hello world”;
char str2[] = “world”;
char ret = Strstr(str1, str2);
printf("%p\n", ret);
return0；
}

int Strcmp(const char* str1, const char* str2)
{
assert str1 != NULL && str2 != NULL);
while (*str1 != ‘\0’ && *str2 != ‘\0’)
{
if (*str1 < *str2)
{
return -1;
}
else if (*str1 > * str2)
{
return 1;
}
else
{
str1++;
str2++;
}
}
if (*str1 < *str2)
{
return -1;
}
else if (*str1 > * str2)
{
return 1;
}
else
{
return 0;
}
}
int main（）
{
char str1[] = “hehe”;
char str2[] = “haha”;
int ret = Strcmp(str1, str2);
if (ret < 0)
{
printf(“str1 < str2 \n”);
}
if (ret > 0)
{
printf(“str1 > str2 \n”);
}
else
{
printf(“str1 == str2 \n”);
}
return 0；
}