C++實現PyMysql的基本功能

用C++實現一個Thmysql類，實現Python標準庫PyMysql的基本功能，並提供與PyMysql相似的API，並用pybind11將Thmysql封裝爲Python庫。

PyMysql	Thmysql(C++)	Thmysql(Python)
connect	connect	connect
cursor	——	——
execute	execute	execute
fetchone	fetchone	fetchone
fetchall	fetchall	fetchall
close	close	close

一.開發環境

• Windows64位操做系統；
• mysql 5.5.28 for Win64(x86);
• pycharm 2019.1.1。

二.PyMysql數據庫查詢

#文件名：python_test.py
import pymysql
# 鏈接database
conn = pymysql.connect(host="localhost",user="root",password="123456",
                       database="test",charset="utf8")

# 獲得一個能夠執行SQL語句的光標對象
cursor = conn.cursor() # 執行完畢返回的結果集默認以元組顯示
# 執行SQL語句
cursor.execute("use information_schema")

cursor.execute("select version();")
first_line = cursor.fetchone()
print(first_line)

cursor.execute("select * from character_sets;")
res = cursor.fetchall()
print(res)
# 關閉光標對象
cursor.close()
# 關閉數據庫鏈接
conn.close()

三.開發步驟

1. 將mysql安裝目錄下的include和lib文件夾拷到project目錄中；
2. 將lib文件夾中的libmysql.dll文件拷到system32路徑下；
3. 定義MysqlInfo結構體，實現C++版的Thmysql類；
4. 編寫封裝函數；
5. 經過setuptools將C++代碼編譯爲Python庫。

四.代碼實現

// 文件名：thmysql.h
#include <Windows.h>
#include "mysql.h"
#include <iostream>
#include <string>
#include <vector>

#pragma comment(lib, "lib/libmysql.lib")
using namespace std;

typedef struct MysqlInfo{
    string m_host;
    string m_user;
    string m_passwd;
    string m_db;
    unsigned int m_port;
    string m_unix_socket;
    unsigned long m_client_flag;

    MysqlInfo(){}
    MysqlInfo(string host, string user, string passwd, string db, unsigned int port,
                 string unix_socket, unsigned long client_flag){
        m_host = host;
        m_user = user;
        m_passwd = passwd;
        m_db = db;
        m_port = port;
        m_unix_socket = unix_socket;
        m_client_flag = client_flag;
    }
}MysqlInfo;

class Thmysql{
    public:
        Thmysql();
        void connect(MysqlInfo&);
        void execute(string);
        vector<vector<string>> fetchall();
        vector<string> fetchone();
        void close();
    private:
        MYSQL mysql;
        MYSQL_RES * mysql_res;
        MYSQL_FIELD * mysql_field;
        MYSQL_ROW mysql_row;
        int columns;
        vector<vector<string>> mysql_data;
        vector<string> first_line;
};

// 文件名：thmysql.cpp
#include <iostream>
#include "thmysql.h"

Thmysql::Thmysql(){
    if(mysql_library_init(0, NULL, NULL) != 0){
        cout << "MySQL library initialization failed" << endl;
    }
    if(mysql_init(&mysql) == NULL){
        cout << "Connection handle initialization failed" << endl;
    }
}

void Thmysql::connect(MysqlInfo& msInfo){
    string host = msInfo.m_host;
    string user = msInfo.m_user;
    string passwd = msInfo.m_passwd;
    string db = msInfo.m_db;
    unsigned int port = msInfo.m_port;
    string unix_socket = msInfo.m_unix_socket;
    unsigned long client_flag = msInfo.m_client_flag;

    if(mysql_real_connect(&mysql, host.c_str(), user.c_str(), passwd.c_str(), db.c_str(),
       port, unix_socket.c_str(), client_flag) == NULL){
        cout << "Unable to connect to MySQL" << endl;
    }
}

void Thmysql::execute(string sqlcmd){
    mysql_query(&mysql, sqlcmd.c_str());

    if(mysql_errno(&mysql) != 0){
        cout << "error: " << mysql_error(&mysql) << endl;
    }
}

vector<vector<string>> Thmysql::fetchall(){
    // 獲取 sql 指令的執行結果
    mysql_res = mysql_use_result(&mysql);
    // 獲取查詢到的結果的列數
    columns = mysql_num_fields(mysql_res);
    // 獲取全部的列名
    mysql_field = mysql_fetch_fields(mysql_res);
    mysql_data.clear();
    while(mysql_row = mysql_fetch_row(mysql_res)){
        vector<string> row_data;
        for(int i = 0; i < columns; i++){
            if(mysql_row[i] == nullptr){
                row_data.push_back("None");
            }else{
                row_data.push_back(mysql_row[i]);
            }
        }
        mysql_data.push_back(row_data);
    }
    // 沒有mysql_free_result會形成內存泄漏：Commands out of sync; you can't run this command now
    mysql_free_result(mysql_res);
    return mysql_data;
}

vector<string> Thmysql::fetchone(){
    // 獲取 sql 指令的執行結果
    mysql_res = mysql_use_result(&mysql);
    // 獲取查詢到的結果的列數
    columns = mysql_num_fields(mysql_res);
    // 獲取全部的列名
    mysql_field = mysql_fetch_fields(mysql_res);
    first_line.clear();
    mysql_row = mysql_fetch_row(mysql_res);
    for(int i = 0; i < columns; i++){
        if(mysql_row[i] == nullptr){
            first_line.push_back("None");
        }else{
            first_line.push_back(mysql_row[i]);
        }
    }
    mysql_free_result(mysql_res);
    return first_line;
}

void Thmysql::close(){
    mysql_close(&mysql);
    mysql_library_end();
}

// 文件名：thmysql_wrapper.cpp
#include "pybind11/pybind11.h"
#include "pybind11/stl.h"
#include "thmysql.h"

namespace py = pybind11;

PYBIND11_MODULE(thmysql, m){
    m.doc() = "C++操做Mysql";
    py::class_<MysqlInfo>(m, "MysqlInfo")
        .def(py::init())
        .def(py::init<string, string, string, string, unsigned int, string, unsigned long>(),
             py::arg("host"), py::arg("user"), py::arg("passwd"), py::arg("db"),py::arg("port"),
             py::arg("unix_socket") = "NULL", py::arg("client_flag")=0)
        .def_readwrite("host", &MysqlInfo::m_host)
        .def_readwrite("user", &MysqlInfo::m_user)
        .def_readwrite("passwd", &MysqlInfo::m_passwd)
        .def_readwrite("db", &MysqlInfo::m_db)
        .def_readwrite("port", &MysqlInfo::m_port)
        .def_readwrite("unix_socket", &MysqlInfo::m_unix_socket)
        .def_readwrite("client_flag", &MysqlInfo::m_client_flag);

    py::class_<Thmysql>(m, "Thmysql")
        .def(py::init())
        .def("connect", &Thmysql::connect)
        .def("execute", &Thmysql::execute, py::arg("sql_cmd"))
        .def("fetchall", &Thmysql::fetchall)
        .def("fetchone", &Thmysql::fetchone)
        .def("close", &Thmysql::close);
}

#文件名：setup.py
from setuptools import setup, Extension

functions_module = Extension(
    name='thmysql',
    sources=['thmysql.cpp', 'thmysql_wrapper.cpp'],
    include_dirs=[r'D:\software\pybind11-master\include',
                  r'D:\software\Anaconda\include',
                  r'D:\project\thmysql\include'],
)

setup(ext_modules=[functions_module])

五.Thmysql數據庫查詢

#文件名：test.py
from thmysql import Thmysql, MysqlInfo

info = MysqlInfo("localhost", "root", "123456", "", 3306)
conn = Thmysql()
# 鏈接database
conn.connect(info)
# 執行SQL語句
conn.execute("use information_schema")

conn.execute("select version();")
first_line = conn.fetchone()
print(first_line)

conn.execute("select * from character_sets;")
res = conn.fetchall()
print(res)
# 關閉數據庫鏈接
conn.close()