收集的资料:
https://gitee.com/zhengnianli/EmbedSummary
lz4
在我们嵌入式开发中,通信中有些数据量较大的数据可以压缩之后再进行传输。
压缩算法有很多,常用的有如下几种:
- lz4压缩算法
- zstd压缩算法
- xz压缩算法
- gzip压缩算法
本次来介绍压缩界的速度之王——lz4压缩库。一些数据如:
lz4源码下载链接:
http://security.ubuntu.com/ubuntu/pool/main/l/lz4/
lz4的使用
首先,从上面的链接中下载源码进行编译:
然后在源码根目录创建一个文件夹lz4_x86_lib:
编译lz4:
makemake install PREFIX=$(pwd)/lz4_x86_lib
得到:
lz4库交叉编译可参照:https://blog.csdn.net/nh5431313/article/details/106387168
lz4库有几套压缩、解压接口,我们使用最简单的接口:
int LZ4_compress_default(const char* source, char* dest, int sourceSize, int maxDestSize);int LZ4_decompress_safe (const char* source, char* dest, int compressedSize, int maxDecompressedSize);
测试例子:
把字符串"12345678901234567890123456789012345678901234567890"进行lz4压缩,再解压,再把解压之后的内容打印出来。
编写测试代码:
// 微信公众号:嵌入式大杂烩#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/time.h>#include <time.h>#include "lz4.h"long long get_sys_time_us(void){ long long time_us = 0; struct timeval sys_current_time; gettimeofday(&sys_current_time, NULL); time_us = (long long)sys_current_time.tv_sec*1000000 + sys_current_time.tv_usec; return time_us;}int main(int arc, char *argv[]){ // 压缩 char *src0 = "12345678901234567890123456789012345678901234567890"; char dst0[64] = {0}; int src0_size = strlen(src0) + 1; int max_dst0_size = sizeof(dst0); int dst0_compress_size = 0; printf("before compress = %s, bytes = %d\n", src0, src0_size); if (src0_size < max_dst0_size) { long long compress_start_time = get_sys_time_us(); dst0_compress_size = LZ4_compress_default(src0, dst0, src0_size, max_dst0_size); long long compress_end_time = get_sys_time_us(); printf("after compress = %s\n", dst0); printf("compress_time = %lld us\n", compress_end_time - compress_start_time); } else { printf("compress error! src0_size >= max_dst0_size\n"); } // 解压 char src1[64] = {0}; char dst1[64] = {0}; int compressed_size = dst0_compress_size; int max_decompressed_size = sizeof(dst1); int dst1_decompress_size = 0; if (dst0_compress_size < max_decompressed_size) { memcpy(src1, dst0, dst0_compress_size); printf("before decompress = %s\n", src1); } else { printf("dst0_compress_size >= max_decompressed_size\n"); } if (compressed_size < max_decompressed_size) { long long decompress_start_time = get_sys_time_us(); dst1_decompress_size = LZ4_decompress_safe(src1, dst1, compressed_size, max_decompressed_size); long long decompress_end_time = get_sys_time_us(); printf("after decompress = %s, bytes = %d\n", dst1, dst1_decompress_size); printf("decompress_time = %lld us\n", decompress_end_time - decompress_start_time); } else { printf("decompress error! compressed_size >= max_decompressed_size\n"); } return 0;}
编译运行:
gcc -o lz4_test lz4_test.c -Llz4_x86_lib/lib -Ilz4_x86_lib/include -llz4./lz4_test
更多实例可参照源码路径下的examples。
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