之前写过一篇“如何判断机器的CPU是大端还是小端？http://www.orangespeech.com/?p=89”的blog, 现在更新一下开源代码中的简洁实现：

int IsLittleEndian() {
int check = 1;
  return (*reinterpret_cast<char*>(&check) != 0);
}

C的实现如下：

 #define BIG_ENDIAN      0
 #define LITTLE_ENDIAN   1

  int little_endian(void)
  {
      short int w = 0x0001;
      char *byte = (char *) &w;
      return(byte[0] ? LITTLE_ENDIAN : BIG_ENDIAN);
  }

顺带给出字节交换的代码，同样厉害！

#define SWAP8(a) { \
  int t = ((char*)&a)[0]; ((char*)&a)[0]=((char*)&a)[7]; ((char*)&a)[7]=t;\
      t = ((char*)&a)[1]; ((char*)&a)[1]=((char*)&a)[6]; ((char*)&a)[6]=t;\
      t = ((char*)&a)[2]; ((char*)&a)[2]=((char*)&a)[5]; ((char*)&a)[5]=t;\
      t = ((char*)&a)[3]; ((char*)&a)[3]=((char*)&a)[4]; ((char*)&a)[4]=t;}
#define SWAP4(a) { \
  int t = ((char*)&a)[0]; ((char*)&a)[0]=((char*)&a)[3]; ((char*)&a)[3]=t;\
      t = ((char*)&a)[1]; ((char*)&a)[1]=((char*)&a)[2]; ((char*)&a)[2]=t;}
#define SWAP2(a) { \
  int t = ((char*)&a)[0]; ((char*)&a)[0]=((char*)&a)[1]; ((char*)&a)[1]=t;}