6字节的数组和4字节的数据比较

只看该作者 · 2010-1-28 22:02

本帖最后由 jerkoh 于 2010-1-28 22:06 编辑

一个应用如下
unsigned char buf1[6];
unsigned char buf2[4];

如当buf1[6]={0x00,0x00,0x77,0x88,0x99,0xaa};
buf2[4]={0x77,0x88,0x99,0xaa};

如何快速的比较 buf1[5] buf1[4] buf1[3] buf1[2] 组合的ULONG buf1[1] buf1[0] 的值不计算在内

和buf2[3] buf2[2] buf2[1] buf2[0] 组合的ULONG 是否相等

只看该作者 · 2010-1-28 22:22

本帖最后由 jerkoh 于 2010-1-28 22:55 编辑

#include <string.h>
unsigned char buf1[6]={0x00,0x00,0x77,0x88,0x99,0xaa};
unsigned char buf2[4]={0x77,0x88,0x99,0xaa};
void main()
{
while(1)
{
   /*
      if(memcmp(buf1+2,buf2,sizeof(buf2))==0)
      {
         for(;;);             //12Mhz A time 0.00009  //库函数最慢
      }
      else
      {
         for(;;);
      }
      */
      if((buf1[5]==buf2[3])&&\
               (buf1[4]==buf2[2])&&\
               (buf1[3]==buf2[1])&&\
               (buf1[2]==buf2[0]))
      {
         for(;;);    //B 12Mhz  time 0.000012  最笨方法最快

      }
      else
      {
         for(;;);
      }

}

#include <string.h>
unsigned char buf1[6]={0x00,0x00,0x77,0x88,0x99,0xaa};
//unsigned char buf2[4]={0x77,0x88,0x99,0xaa};
union
{
  unsigned char buf2[4];
  unsigned long ul_buf;
}ul2char;
typedef struct
{
  unsigned char STH;
  unsigned char STL;
  unsigned long ul_data;
}ULdata;
void main()
{
ULdata xdata *ptr;
while(1)
{
  ul2char.ul_buf=0x778899aal;
  ptr=(ULdata xdata *)(buf1);
  if(ul2char.ul_buf==ptr->ul_data)
  {
for(;;); //C 12mhz 0.000064          //xdata 改idata 0.000053 复杂操作  速度中等
  }
}

除了上面方法有没其他？时间用的更少的来PK下