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Snappy使用

Snappy是谷歌开源的压缩和解压的开发包，目标在于实现高速的压缩而不是最大的压缩

项目地址：GitHub - google/snappy：快速压缩器/解压缩器

Cmake版本升级

该项目需要比较新的cmake，CMake 3.16.3 or higher is required，所以回出现如下错误，更新cmake就可以

CMake Error at third_party/benchmark/CMakeLists.txt:1 (cmake_minimum_required):CMake 3.16.3 or higher is required.  You are running version 3.10.2

查看当前版本

cmake -version

删除安装的Cmake（最好直接删除路径下的Cmake，免得卸载Cmake出现多个库的问题）

搜索cmake路径which cmake
切换到cmake路径cd /usr/bin/
删除cmakesudo rm cmake

下载高版本cmake：Index of /files/v3.18 (cmake.org)

解压安装包
tar xf  cmake-3.18.3.tar.gz安装cmake
cd cmake-3.18.3
sudo apt-get install libssl-dev build-essential 
./configure
make
sudo make install

将编译的cmake复制到原始删除cmake的路径下

sudo cp bin/Cmake /usr/bin/

Snappy编译

1、克隆代码库

git clone https://github.com/google/snappy.git

2、编译代码库

git submodule update --init
mkdir build
cd build && cmake ../ && make

调用

C++ 程序使用Snappy，需要包含对应的链接库，

请包含来自 您的调用文件，并链接到已编译的库、头文件，最简单的方法

压缩：snappy::Compress(input.data(), input.size(), &output);

解压：snappy::Uncompress(input.data(), input.size(), &output);

示例，将Snappy编译好的libsnappy.a，snappy.h，snappy-stubs-public.h三个文件放在同一路径下

新建test.cpp测试程序，如下

#include <iostream>
#include "snappy.h"
#include <string.h>using namespace std;int main()
{string input = "this is the demo for Snappy\n";//repeat three timesfor(int i=0; i<3; i++){input += input;}cout << "origin：" << input.size() << endl;cout << input << endl;cout << "#########################################\n\n" << endl;string Compress_output = "";snappy::Compress(input.data(), input.size(), &Compress_output);	cout << "compress：" << Compress_output.size() << endl;cout << Compress_output << endl;cout << "#########################################\n\n" << endl;string UnCompress_output = "";snappy::Uncompress(Compress_output.data(), Compress_output.size(), &UnCompress_output);cout << "uncompress：" << UnCompress_output.size() << endl;cout << UnCompress_output << endl;return 1;
}

编译执行

g++ test.cpp libsnappy.a -std=gnu++11 -o test
./test

压缩前224个字节，压缩后42个字节