指针杂项演示：
同一个函数分两次调用，执行不同的功能：
1，基本操作，被调函数分配内存
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int getcontentlen(char *filename,char **buf,int *len)
{
char *tmp = (char*)malloc(100);
if(tmp == NULL) return -1;
strcpy(tmp,"Hello!");
*len = strlen(tmp);
*buf = tmp;
return 0;
}
int main()
{
int ret = 0;
char *filename = "myfile.txt";
char *buf = NULL;
int len = 0;
ret = getcontentlen(filename,&buf,&len);
if(ret != 0){return ret;}
printf("%s \n",buf);
printf("%d \n",len);
if(buf != NULL) free(buf);
return 0;
}
编译运行：
chunli@Linux:~/high$ gcc -g -o run main.c && ./run
Hello!
6
chunli@Linux:~/high$#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int getcontentlen(char *filename,char *buf,int *len)
{
if(buf == NULL)
{
*len = 10;
return 0;
}
else
{
strncpy(buf,"Goog morning!",10);
}
return 0;
}
int main()
{
int ret = 0;
char *filename = "myfile.txt";
int len = 0;
ret = getcontentlen(filename,NULL,&len);
char *buf = (char *)malloc(100);
ret = getcontentlen(filename,buf,&len);
printf("%s \n",buf);
return 0;
}
编译：
chunli@Linux:~/high$ gcc -g -o run main.c && ./run
Goog morni
chunli@Linux:~/high$本文出自 “魂斗罗” 博客，请务必保留此出处http://990487026.blog.51cto.com/10133282/1792292
C提高 6 指针杂项 API函数封装，sockets封装 ，内存泄漏检测，日志库
原文：http://990487026.blog.51cto.com/10133282/1792292