leveldb 键值数据库

#git clone --recurse-submodules https://github.com/google/leveldb.git
拉取子模块 及第三方库

#mkdir -p build && cd build
#cmake -DCMAKE_BUILD_TYPE=Releas .. && make

测试demo

#include <assert.h>
#include <string.h>
#include <leveldb/db.h>
#include <iostream>
//isSync 1:写入时直接写入磁盘，0:写入时在内存delete db 才会写入磁盘
void writevalue(leveldb::DB *db,std::string keyname,std::string value,bool isSync){
    leveldb::Options options;
    leveldb::WriteOptions write_options;
    write_options.sync = isSync;
    leveldb::Status status=db->Put(write_options, keyname,value);
     if(status.ok())
        std::cout<<"write key "<<keyname<<" ok\n";
     else
        std::cout<<"write key "<<keyname<<" failed "<<status.ToString()<<"\n";
}

void deleltevalue(leveldb::DB *db,std::string keyname){

     leveldb::Options options;
     leveldb::Status status=db->Delete(leveldb::WriteOptions(), keyname);
     if(status.ok())
        std::cout<<"delete key "<<keyname<<" ok\n";
     else
        std::cout<<"delete key "<<keyname<<" failed "<<status.ToString()<<"\n";
}



void readValue(leveldb::DB *db,std::string keyname){
     std::string keyvalue;
     leveldb::Options options;
     leveldb::Status status=db->Get(leveldb::ReadOptions(), keyname,&keyvalue);
     if(status.ok())
        std::cout<<"get key "<<keyname<<" value:"<<keyvalue<<"\n";
     else
        std::cout<<"get key "<<keyname<<" failed "<<status.ToString()<<"\n";
}




int main(){
    leveldb::DB* db;
    leveldb::Options options;
    options.create_if_missing = true;
    leveldb::Status status = leveldb::DB::Open(options,"./testdb3", &db);
    assert(status.ok());
    writevalue(db,"keyname1","keyvalue1",true);
    readValue(db,"keyname1");
    deleltevalue(db,"keyname1");
    readValue(db,"keyname1");

    writevalue(db,"keyname2","keyvalue2",true);
    writevalue(db,"keyname3","keyvalue3",true);
    writevalue(db,"keyname4","keyvalue4",true);


    leveldb::Iterator *it = db->NewIterator(leveldb::ReadOptions());
    //正序打印内容
    for (it->SeekToFirst(); it->Valid(); it->Next()) {
        std::cout << it->key().ToString() << ":" << it->value().ToString() << std::endl;
    }

    //反序打印内容
    for (it->SeekToLast(); it->Valid(); it->Prev()) {
        std::cout << it->key().ToString() << ":" << it->value().ToString() << std::endl;
    }



    delete db;
    return 0;
}

打印

write key keyname1 ok
get key keyname1 value:keyvalue1
delete key keyname1 ok
get key keyname1 failed NotFound: 
write key keyname2 ok
write key keyname3 ok
write key keyname4 ok
keyname2:keyvalue2
keyname3:keyvalue3
keyname4:keyvalue4
keyname4:keyvalue4
keyname3:keyvalue3
keyname2:keyvalue2

参考

【存储引擎】LevelDB 编译使用_level db cmake-CSDN博客