复制代码 代码如下:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

//memcpy：按字节复制
原型：extern void* memcpy(void *dest,void *src,unsigned int count)
//功能：由src所指内存区域复制count个字节到dest所指的内存区域；
//同strcpy
void *memcpy_su(void *dest, void *src, unsigned int count)
{

assert ((dest!=NULL)&&(src!=NULL));
char* bdest = (char*)dest;
char* bsrc = (char*) src;
while(count-->0)
*bdest++ = *bsrc++;
return dest;
}

//strcpy：复制字符串，遇到'\0'就结束
//原型：extern char *strcpy(char *dest,char *src)
//功能：把src所指由'\0'结束的字符串复制到dest所指的数组中；
//说明：src和dest所指内存区域是不可以重叠的且dest必须有足够的空间来容纳字符串。返回dest指针。
char *strcpy_su(char *dest,char *src)
{
assert((dest!=NULL)&&(src!=NULL));
char *address = dest;
while((*dest++=*src++)!='\0')
continue;
return dest;
}
//memset：设置buffer所指的内存区域的前count个字节，用字符c来代替
//原型：extern void *memset(void *buffer,int c,int count);
void *memset_su(void *buffer, int c, int count)
{
assert ((buffer!=NULL));
char* buffer2 = (char*)buffer;
while(count-->0)
*buffer2++ = c;
return buffer;
}

void main()
{
char str1[100]="abchjhgjghjgjgh";
char str2[50]="efghdfkdjf";

strcpy(str1, str2);
printf("%s\n",str1);


char a[3];
memset(a, 'a', sizeof(a)-1);
memset(&a[2], '\0',1);
printf("%s\n",a);


memcpy(str1, str2, strlen(str2));
printf("%s\n",str1);

}