网络字节序(Big Endian)

网络字节序(Big Endian)

test.c
-------------------------------------
01 #include <stdio.h>
02 #include <arpa/inet.h>
03
04 int main()
05 {
06     unsigned short name = 0x123;
07     unsigned char * p = (unsigned char *)&name;
08     printf("p[0] = 0x%x\n", p[0]);
09     printf("p[1] = 0x%x\n", p[1]);
10
11     printf("htons(0x%x) = 0x%x\n", name, htons(name));
12
13     name = htons(name);
14     p = (unsigned char *)&name;
15     printf("p[0] = 0x%x\n", p[0]);
16     printf("p[1] = 0x%x\n", p[1]);
17
18     return 0;
19 }


# gcc test.c
# ./a.out
p[0] = 0x23
p[1] = 0x1
htons(0x123) = 0x2301
p[0] = 0x1
p[1] = 0x23


网络字节序(Big Endian)

起始地址
|------|------|
| 0x01 | 0x23 |
|------|------|

X86体系结构(Little Endian)

起始地址
|------|------|
| 0x23 | 0x01 |
|------|------|

注: 字节序 not 位序



test.c
-------------------------------------
 01 #include <stdio.h>
02 #include <arpa/inet.h>
03
04 int main()
05 {
06     unsigned int name = 0x01234567;
07     unsigned char * p = (unsigned char *)&name;
08     printf("p[0] = 0x%x\n", p[0]);
09     printf("p[1] = 0x%x\n", p[1]);
10     printf("p[2] = 0x%x\n", p[2]);
11     printf("p[3] = 0x%x\n", p[3]);
12
13     printf("htols(0x%x) = 0x%x\n", name, htonl(name));
14
15     name = htonl(name);
16     p = (unsigned char *)&name;
17     printf("p[0] = 0x%x\n", p[0]);
18     printf("p[1] = 0x%x\n", p[1]);
19     printf("p[2] = 0x%x\n", p[2]);
20     printf("p[3] = 0x%x\n", p[3]);
21
22     return 0;
23 }


# gcc test.c
# ./a.out
p[0] = 0x67
p[1] = 0x45
p[2] = 0x23
p[3] = 0x1
htols(0x1234567) = 0x67452301
p[0] = 0x1
p[1] = 0x23
p[2] = 0x45
p[3] = 0x67


网络字节序(Big Endian)

起始地址
|------|------|------|------|
| 0x01 | 0x23 | 0x45 | 0x67 |
|------|------|------|------|

X86体系结构(Little Endian)

起始地址
|------|------|------|------|
| 0x67 | 0x45 | 0x23 | 0x01 |
|------|------|------|------|

#C And Clib

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