sscanf虽然是个不错的函数,它可以很简单的将字符串转成特定的格式,比如转成整数、浮点数等等。但是如果使用不慎,会带来很大的麻烦。
今天笔者在使用sscanf时,就遇到了一个诡异的问题。
代码的书写如下:
//begin added by liuzhiyong 20160504
int HexToBin(char *src,char *bin,int length)
{
int i = 0;
int j = 0;
printf("HexToBin src = %s length = %d\n",src,length);
unsigned char temp;
char buf[3]={0};
for (i = 0;i < length; i+=2)
{
strncpy(buf,src+i,2);
buf[2] = 0;
sscanf(buf,"%x",&temp);
bin[j] = temp;
j++;
printf("i = %d j = %d buf = %s temp = %d\n",i,j,buf,temp);
}
return 1;
}
//end 20160504
貌似没问题,但在实际调用的时候,陷入了死循环,经打印i的值始终为0.
通过分析,"%x"这个格式转化出来的值的类型是int,而且它会把后面的变量当成int来处理,而int的值在内存中为4个字节。而temp只是一个字节,sscanf将i的值也顺带赋值了,赋值为0.
了解到问题的根源后,将代码修改为:
扫描二维码关注公众号,回复:
12447655 查看本文章
//begin added by liuzhiyong 20160504
int HexToBin(char *src,char *bin,int length)
{
int i = 0;
int j = 0;
printf("HexToBin src = %s length = %d\n",src,length);
int temp;
char buf[3]={0};
for (i = 0;i < length; i+=2)
{
strncpy(buf,src+i,2);
buf[2] = 0;
sscanf(buf,"%x",&temp);
bin[j] = (unsigned char)temp;
j++;
printf("i = %d j = %d buf = %s temp = %d\n",i,j,buf,temp);
}
return 1;
}
//end 20160504
问题得以解决。