說明
big endian和little endian表示如何存放多字節(jié)數(shù)據(jù)。前者低位字節(jié)排放在內(nèi)存的高端，后者相反。將unsigned long數(shù)據(jù)強(qiáng)制轉(zhuǎn)換成unsigned char*數(shù)據(jù)，則它們在兩種模式下的對應(yīng)關(guān)系如下：
big endian：
ul = (uc[0]<< 24) + (uc[1]<<16) + (uc[2]<<8) + uc[3];
little endian:
ul = (uc[3]<<24) + (uc[2]<<16) + (uc[1]<<8) + uc[0];
實(shí)驗(yàn)代碼
/** * @file little_big_endian.cpp * @brief 測試大小端字節(jié)序 * @copyright public domain */#include <iostream>static bool is_little_endian() {union {long l;char cs[4];} t;t.l = 1;return t.cs[0] == 1;}int main() {unsigned long ul = 0x12345678;unsigned char* uc = (unsigned char*)&ul;if (is_little_endian()) {bool r = (uc[0] + (uc[1]<<8) + (uc[2]<<16) + (uc[3]<<24)) == ul;std::cout << "little: (uc[0] + (uc[1]<<8) + (uc[2]<<16) + (uc[3]<<24)) == ul is " << (r ? "true" : "false") << std::endl;} else {bool r = (uc[3] + (uc[2]<<8) + (uc[1]<<16) + (uc[0]<<24)) == ul;std::cout << "little: (uc[3] + (uc[2]<<8) + (uc[1]<<16) + (uc[0]<<24)) == ul is " << (r ? "true" : "false") << std::endl;}return 0;}
運(yùn)行及結(jié)果
$ g++ little_big_endian.cpp
$ ./a.out
little: (uc[0] + (uc[1]<<8) + (uc[2]<<16) + (uc[3]<<24)) == ul is true
常見問題
字節(jié)序的問題容易出現(xiàn)在不同電腦交互數(shù)據(jù)的時(shí)候，因此當(dāng)數(shù)據(jù)輸出時(shí)——保存成文件或在網(wǎng)絡(luò)上傳輸——就應(yīng)該考慮字節(jié)序。