趁着没发霉重写库函数之strstr

#include <stdio.h>
int strlen(char * str)
{
char * pstr = str;

unsigned int len = 0;

if(!str)

{
printf("Param error!\n");
return 0;
}
while(*pstr++!='\0')
len ++;
return len;
}
int strstr(char * src,char *s_dest)
{
int src_len = 0,dest_len = 0,i,j,index = 0;
char * psrc = src,* pdest= s_dest;
if(!src || ! s_dest)
{
printf("Param error!\n");
return -1;
}
dest_len = strlen(s_dest);
src_len = strlen(src);
while(*psrc && *pdest)
{
if(*psrc == *pdest)
{
psrc ++;
pdest ++;
if(!index)
index = psrc-src;
}
else
{
psrc ++;
pdest = s_dest;
index = 0;
}
}
if(dest_len == (pdest- s_dest))
return index;
else
return -1;
}