转自：http://blog.chinaunix.net/uid-24194439-id-90780.html
一些字符串函数的实现
http://www.cnblogs.com/JCSU/articles/1305401.html【参考】
这些函数实现最好参考linux内核源码，向大师学习！
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static char *str_cpy(char *dest, const char *src)
{
int i = 0;
while(*dest++ = *src++);
return dest;
}
char str_rev(char *s)
{
char *d = s + strlen(s) - 1;
char temp;
while(d > s)
{
temp = *d;
*d = *s;
*s = temp;
d--;
s++;
}
}
static int str_len(const char *s)
{
int len = 0;
while(*s++)
len++;
return len;
}
static char *str_cat(char *dest, const char *src)
{
char *const old = dest;
while(*dest)
dest++;
while(*dest++ = *src++);
return old;
}
/*static int str_cmp(const char *dst, const char *src)
{ int i = 0;
while(*(dst + i) == *(src + i))
{
if(*(src+i) == '\0')
return 0;
i++;
}
if(*dst > *src)
return 1;
else
return -1;
}*/
int str_cmp(const char * cs, const char * ct)
{
signed char __res;
while(1)
{
if((__res = *cs - *ct++) != 0 || !cs++)
break;
}
return __res;
}
int main(void)
{
char a[20]="hello";
char b[10];
char c[]="hellz";
str_cpy(b,a);
printf("str_cpy:b<-a:%s \n", b);
str_rev(a);
printf("str_rev:a=%s \n", a);
printf("str_cmp:%d \n",str_cmp(a, c));
str_len(b);
printf("str_len:b=%d \n", str_len(b));
printf("strcat:a+b:%s \n", str_cat(a,c));
return 0;
}
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一个简单的回文字符串检测
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#include <stdio.h>
#include <string.h>
static int str_hui(const char *src);
void main(void)
{
char src[]="abcdcba";
printf("%s %s\n", src, str_hui(src) ? "no" : "yes");
printf("%s\n", src);
}
static int str_hui(const char *src)
{
const char *end = src;//*end = src + strlen(src) - 1;定位结尾效果相同
while(*end != '\0')
++end;
--end;
while(end >= src)
{
if(*src++ != *end--)
{
return 1;
}
}
return 0;
}
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注意：1，如何定位到文件尾部 2，返回输出的技巧
