网络/存储字节序中有大、小端的概念，简而言之就是内存地址由高到低与数据由高位到低位的对应关系.
PS:哪个是大端，哪个是小端我也经常搞混.
简单的测试程序一枚.(Updated/linux 3.16)
1 #include <cstdio>
2 #include <string>
3 using namespace std;
4 #define THIS_PLATFORM __BYTE_ORDER == __LITTLE_ENDIAN
5
6 int main()
7 {
8
9 const char* ptr = "test";
10 printf("const var 's addr %p\n", ptr);
11 unsigned int y = 0x12345678;
12 string x = "1234567890";
13 #define FORstr(i,var) for(string::iterator i=var.begin(); i != var.end(); i++)
14
15 #define FORint(i,var) for(char* i = (char*)&(var); i < (char*)(&(var) + 1); i++)
16 //printf("%d\n", sizeof(x.data()));
17 printf("the string obj's addr is %p\n", &x);
18
19 FORstr(i, x){
20 printf("%p %c\n", i, *i);
21 }
22
23 printf("----\n");
24 for(int i = 0; i < x.size(); i++){
25 printf("%p %c\n", &x[i], x[i]);
26 }
27
28
29 printf("-------\n");
30 printf("THIS PLATFORM is %s.\n", THIS_PLATFORM == true ? "little_end" : "big_end");
31 FORint(i, y){
32 printf("%p %x\n", i, *i);
33 }
34
35 return 0;
36 }
Output -
const var 's addr 0x400d48
the string obj's addr is 0x7fff448287e0
0x7f5028 1
0x7f5029 2
0x7f502a 3
0x7f502b 4
0x7f502c 5
0x7f502d 6
0x7f502e 7
0x7f502f 8
0x7f5030 9
0x7f5031 0
----
0x7f5028 1
0x7f5029 2
0x7f502a 3
0x7f502b 4
0x7f502c 5
0x7f502d 6
0x7f502e 7
0x7f502f 8
0x7f5030 9
0x7f5031 0
-------
THIS PLATFORM is little_end.
0x7fff448287d8 78
0x7fff448287d9 56
0x7fff448287da 34
0x7fff448287db 12
Update--------------------
来个判断大小端的代码吧？
1 #include "common.h"
2 #include <string.h>
3
4 bool isLittlendian()
5 {
6 unsigned int x = 1;
7 string s = "";
8 s.resize(sizeof(x));
9 memcpy(&s[0], &x, sizeof(x));
10 return s[0] == 1;
11 }
12
13 int main()
14 {
15 printf("this platform is %s\n", isLittlendian()? "littlendian" : "bigendian" );
16 return 0;
17 }
