C-language Linux kernel implementation of high and low level swap

Linux kernel is really profound, there are a lot of excellent algorithms, I have encountered in the work of the high-low level exchange problem, at that time for C language is not very skilled, think for a long period to write out. Recently, when looking at the kernel, I saw a kernel engineer implement this algorithm, as I thought before, then share it today.

In the development requirements, there are 32-bit, 16-bit, 8-bit high-low-level switching algorithms. So let's look at the code implementation in detail:

Also, pull the code out of the Linux kernel:

#include <stdio.h>//a 8-digit high-low 4-bit exchange static inline unsigned char bswap_8 (unsigned char v) {return ((V & 0xff) <&lt ; 4) |   (v >> 4); The parameters (V & 0xff) << 4 equal to the high position, v >> 4 bits equal to the low level}//The following two code analysis is identical/ /Convert a 16-bit high-low 8-bit to static inline unsigned short bswap_16 (unsigned short v) {return ((V & 0xff) << 8) | (v >> 8);} Swap a 32-bit high-low 16-bit for static inline unsigned int bswap_32 (unsigned int v) {return ((V & 0xff) << 24) | ((V & 0xff00) << 8) | ((V & 0xff0000) >> 8) | (v >> 24);} int main (void) {unsigned short v = 0x1000;p rintf ("1, \ n Original v:%d\n", V);p rintf ("16-digit high-low 8-bit converted v:%d (0x%x) =========>0x% X--->%d\n ", v,v, Bswap_16 (v), Bswap_16 (v)), unsigned char a = 0x0a;p rintf (" \n2, \ n Original a:%d\n ", a);p rintf (" 8-digit high-low 4-bit converted A :%d (0x%x) ==========>0x%x--->%d\n ", a,a, Bswap_8 (a), Bswap_8 (a)); unsigned int b = 0x00001111; printf ("\n3, \ n Original b:%d\n", b);p rintf ("32-digit 16-bit conversion b:%d (0x%x) ========>0x%x--->%d\N ", B,b, bswap_32 (b), bswap_32 (b)); return 0;} 

Operation Result:

From the running results, three interfaces have realized the exchange of data high and low level, and verified the success!

C-language Linux kernel implementation of high and low level swap