string函数的一些实现

 /*************************************************************************
     > File Name: test.cpp
  ************************************************************************/
 #include"stdlib.h"
 #include"stdio.h"
 #include"string.h"

 char *mystrcat(char *dest,const char *src)
 {
     char* temp = dest;
     while(*dest != '\0')
     {
         dest++;
     }

     while((*dest++ = *src++) != '\0');

     return temp;
 }
 char *mystrncat(char *dest,const char *src,size_t n)
 {

     char* temp = dest;
     while(*dest != '\0')
     {
         dest++;
     }

     while(n--> && (*dest++ = *src++) != '\0');

     return temp;
 }

 void* mymemset(void *s, int c, size_t n )
 {
     unsigned char uc = c;
     unsigned char *su = (unsigned char*)s;
     while(n-->)
     {
         *su = uc;
         su++;
     }
 }

 int mystrlen(const char* str)
 {
     return *str?(mystrlen(++str)+):;
     /*
     const char* eos = str;
     while(*eos++);
     return (eos-str-1);
     */
 }

 void* mymemcpy(void*dst, const void* src,size_t size)
 {

     if(src==NULL || dst==NULL) return NULL;
     void* ret = dst;
     while(size--)
     {
         *(char*)dst = *(char*)src;
         dst = (char*)dst + ;
         src = (char*)src + ;
     }
     return ret;
 }

 void* mymemmove(void*dst, const void* src,size_t size)
 {
     if(src==NULL || dst==NULL) return NULL;
     char* psrc;
     char* pdst;
     //存在覆盖，自后向前进行拷贝
     if((src<dst) && (char*)src+size > (char*)dst)
     {
         psrc = (char*)src + size-;
         pdst = (char*)dst + size-;
         while(size--)
             *pdst-- = *psrc--;
     }
     else
     {
         psrc = (char*)src;
         pdst = (char*)dst;
         while(size--)
         {
             *pdst++ = *psrc++;
         }
     }
 }

 int mymemcmp(const void * ptr1, const void * ptr2, size_t num)
 {
     if(ptr1==NULL || ptr2==NULL || num<) return ;

     char* pch1 = (char*)ptr1;
     char* pch2 = (char*)ptr2;

     while(num-- && *pch1++ == *pch2++);
     return (pch1-pch2)<<;
 }

 int mystrcmp ( const char * str1, const char * str2 )
 {
     if(str1==NULL || str2 ==NULL) return ;

     while(*str1 == *str2)
     {
         str1++;
         str2++;
     }

     return (*str1-*str2);
 }

 int mystrncmp( const char * str1, const char * str2, size_t num )
 {

     if(str1==NULL || str2 ==NULL) return ;

     while(num-- && *str1 == *str2)
     {
         str1++;
         str2++;
     }

     return (*str1-*str2);
 }

 int main()
 {
     char ch1[] = "hello";
     char ch2[] = "herld";
  //   printf("strcat : %s\n", mystrncat(ch1,ch2,2));

     printf("%d\n",mystrcmp(ch2,ch1));

     printf("%d\n",mystrncmp(ch2,ch1,));

     return ;
 }