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

//memcpy：按字節(jié)復制
原型：extern void* memcpy(void *dest,void *src,unsigned int count)
//功能：由src所指內(nèi)存區(qū)域復制count個字節(jié)到dest所指的內(nèi)存區(qū)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：復制字符串，遇到'\0'就結(jié)束
//原型：extern char *strcpy(char *dest,char *src)
//功能：把src所指由'\0'結(jié)束的字符串復制到dest所指的數(shù)組中；
//說明：src和dest所指內(nèi)存區(qū)域是不可以重疊的且dest必須有足夠的空間來容納字符串。返回dest指針。
char *strcpy_su(char *dest,char *src)
{
       assert((dest!=NULL)&&(src!=NULL));
       char *address = dest;
       while((*dest++=*src++)!='\0')
              continue;
       return dest;
}
//memset：設(shè)置buffer所指的內(nèi)存區(qū)域的前count個字節(jié)，用字符c來代替
//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);

}