15.【cocos2d-x 源码分析】:localStorage的详细分析

对应源码位置：cocos2d-x-3.3\cocos\storage\local-storage\localStorage

localStorage 的接口

cocos2d-x提供了简单的本地数据存储的功能，其主要是由对sqlite的封装来实现。

//初始化 数据库 void CC_DLL localStorageInit( const std::string& fullpath = ""); //释放数据库 void CC_DLL localStorageFree(); //存一个key-value void CC_DLL localStorageSetItem( const std::string& key, const std::string& value); //根据key获取value std::string CC_DLL localStorageGetItem( const std::string& key ); //删除 key对应的 项 void CC_DLL localStorageRemoveItem( const std::string& key );

localStorage 的接口的实现

//是否初始化的标志 static int _initialized = 0; static sqlite3 *_db; //查询 static sqlite3_stmt *_stmt_select; //删除 static sqlite3_stmt *_stmt_remove; //更新 static sqlite3_stmt *_stmt_update; //static表明 别处不能用 static void localStorageCreateTable() { //创建 data表 两个属性 key为主键 const char *sql_createtable = "CREATE TABLE IF NOT EXISTS data(key TEXT PRIMARY KEY,value TEXT);"; sqlite3_stmt *stmt; int ok=sqlite3_prepare_v2(_db, sql_createtable, -1, &stmt, nullptr); ok |= sqlite3_step(stmt); ok |= sqlite3_finalize(stmt); if( ok != SQLITE_OK && ok != SQLITE_DONE) printf("Error in CREATE TABLE\n"); } void localStorageInit( const std::string& fullpath/* = "" */) { //如果没有初始化 if( ! _initialized ) { int ret = 0; //未给路径 则创建内存数据库 if (fullpath.empty()) ret = sqlite3_open(":memory:",&_db); else ret = sqlite3_open(fullpath.c_str(), &_db); //建表 localStorageCreateTable(); //先准备语句 // SELECT const char *sql_select = "SELECT value FROM data WHERE key=?;"; ret |= sqlite3_prepare_v2(_db, sql_select, -1, &_stmt_select, nullptr); // REPLACE const char *sql_update = "REPLACE INTO data (key, value) VALUES (?,?);"; ret |= sqlite3_prepare_v2(_db, sql_update, -1, &_stmt_update, nullptr); // DELETE const char *sql_remove = "DELETE FROM data WHERE key=?;"; ret |= sqlite3_prepare_v2(_db, sql_remove, -1, &_stmt_remove, nullptr); if( ret != SQLITE_OK ) { printf("Error initializing DB\n"); // report error } _initialized = 1; } } void localStorageFree() { //已经初始化了 就都关闭了 if( _initialized ) { sqlite3_finalize(_stmt_select); sqlite3_finalize(_stmt_remove); sqlite3_finalize(_stmt_update); //关闭数据库 sqlite3_close(_db); _initialized = 0; } } /** sets an item in the LS */ void localStorageSetItem( const std::string& key, const std::string& value) { //一定要确保已经初始化了 assert( _initialized ); //配置 查询 int ok = sqlite3_bind_text(_stmt_update, 1, key.c_str(), -1, SQLITE_TRANSIENT); ok |= sqlite3_bind_text(_stmt_update, 2, value.c_str(), -1, SQLITE_TRANSIENT); ok |= sqlite3_step(_stmt_update); ok |= sqlite3_reset(_stmt_update); if( ok != SQLITE_OK && ok != SQLITE_DONE) printf("Error in localStorage.setItem()\n"); } //select std::string localStorageGetItem( const std::string& key ) { assert( _initialized ); std::string ret; int ok = sqlite3_reset(_stmt_select); ok |= sqlite3_bind_text(_stmt_select, 1, key.c_str(), -1, SQLITE_TRANSIENT); ok |= sqlite3_step(_stmt_select); const unsigned char *text = sqlite3_column_text(_stmt_select, 0); if (text) ret = (const char*)text; if( ok != SQLITE_OK && ok != SQLITE_DONE && ok != SQLITE_ROW) printf("Error in localStorage.getItem()\n"); return ret; } //删除对应项 void localStorageRemoveItem( const std::string& key ) { assert( _initialized ); int ok = sqlite3_bind_text(_stmt_remove, 1, key.c_str(), -1, SQLITE_TRANSIENT); ok |= sqlite3_step(_stmt_remove); ok |= sqlite3_reset(_stmt_remove); if( ok != SQLITE_OK && ok != SQLITE_DONE) printf("Error in localStorage.removeItem()\n"); }

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下一篇分析 HttpClient 的实现。