自编字符操作函数

#ifndef __STRING__H__
#define __STRING__H__

#include
#include

char *strcpy_(char *dest,char *src);

int strcmp_(char *s1,char *s2);

int strlen_(char *s);

char *strcat_(char *dest,char *src);

char *strchr_(char *s,char c);

char *strstr_(char *haystack,char *needle);

#endif

 

 

 

#include"string_.h"
char *strcpy_(char *dest,char *src)
{
 char *ptr =dest;
 while(*dest++=*src++);
 return ptr;
}

int strcmp_(char *s1,char *s2)
{
 while(*s1 && *s2 && *s1 == *s2&&s1++&&s2++);
 if(!*s1 && !*s2)
 return 0;
 return *s1 > *s2 ?1:-1; 
}

int strlen_(char *s)
{
 int i;
 for(i=0;*s++ != '\0';i++);
 return i ; 
}

char *strcat_(char *dest,char *src)
{ 
 char *ptr=dest;
 while(*dest && dest++);
 while(*dest++=*src++);
 return ptr; 
}

char *strchr_(char *s,char c)
{
 while(*s&&*s!=c&&s++);
 if(*s)
 return s;
 return NULL;
}

char *strstr_(char *haystack,char *needle)
{
 char *ptr=NULL;
 char *need=needle;
 while(*haystack!=0)
 { 
  if(*haystack == *needle)
  {
   ptr=haystack;
   while(*haystack&&*needle&&*haystack==*needle&&haystack++&&needle++);
    if(!*needle)
    return ptr;
    else if(!*haystack)
     return NULL;
    else
     needle = need;
  }
  haystack++;
  
 }
 return NULL;
}

 

 

 

 

#include
#include
#include
#include "string_.h"

int main()
{
  char *str="abcd";
  char s1[50] ="aidfvafdcvp";
  char s2[50]="afd";
 char *m;
 m = (char*)malloc(50);
 printf("strcpy : s1=%s,\t复制后: %s\n",s1,strcpy(m,s1));
 printf("strcpy_: s1=%s,\t复制后: %s\n\n\n",s1,strcpy_(m,s1));

 printf("strlen : s1:%s,\t长度: %d\n",s1,strlen(s1));
 printf("strlen_: s1:%s,\t长度: %d\n\n\n",s1,strlen_(s1));

 printf("strcat : s1=%s,\t s2=%s\t",s1,s2);
 printf(" 返回值: %s\n",strcat(s1,s2));
 printf("******************  再次连接s2＝“afd”  ******************\n");
 printf("strcat_: s1=%s,\t s2=%s\t",s1,s2);
 printf(" 返回值: %s\n\n\n",strcat_(s1,s2));

 printf("strchr : 在s1中查找‘d’\t s1=%s\t 返回值:%s\n",s1,strchr(s1,'d'));
 printf("strchr_: 在s1中查找‘d’\t s1=%s\t 返回值:%s\n\n\n",s1,strchr_(s1,'d'));

 printf("strcmp: %s\t %s\t 返回值: %d\n",s1,s2,strcmp(s1,s2));
 printf("strcmp_:%s\t %s\t 返回值: %d\n\n\n",s1,s2,strcmp_(s1,s2));

 printf("strstr : s1=%s\ts2=%s\t 返回值:%s\n",s1,s2,strstr(s1,s2));
 printf("strstr_: s1=%s\ts2=%s\t 返回值:%s\n",s1,s2,strstr_(s1,s2));
 return 0; 
}