async并发识别二维码

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• 前言
• 总结

在测试运算中有所需要，在此记录下C++实现基础的并发；

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;
std::mutex m_lock;
std::chrono::high_resolution_clock::time_point a1;
std::chrono::high_resolution_clock::time_point a2;
int inital = 0;
typedef void(*callback)();

void statical_count()
{
    m_lock.lock();
    a2 = std::chrono::high_resolution_clock::now();
    inital++;
    if(inital == 1000)
    {
        float total_cost = std::chrono::duration(a2 - a1).count();
        cout << setprecision(3) << total_cost << "ms" << endl;
    }
    m_lock.unlock();
}


int deal_bar_code(QString name, callback vv)
{
    zbar::ImageScanner scanner;
    scanner.set_config(zbar::zbar_symbol_type_e::ZBAR_QRCODE, zbar::ZBAR_CFG_ENABLE, 1);
    QImage image(name);
    image = image.convertToFormat(QImage::Format_Grayscale8, Qt::AutoColor);
    int width = image.width();
    int height = image.height();
    uchar *raw = (uchar *)image.bits();
    zbar::Image imageZbar(width, height, "Y800", raw, width * height);
    scanner.scan(imageZbar); //扫描条码
    zbar::Image::SymbolIterator symbol = imageZbar.symbol_begin();
    if (imageZbar.symbol_begin() == imageZbar.symbol_end())
    {
        qDebug() << name << endl;
        return 0;
    }
    QString m_data = QString::fromStdString(symbol->get_data());
    return m_data.toInt();
}
int main(int argc, char *argv[])
{
    vector val_list;
    QDir dir("C://Users//aqiang//Desktop//test_zbar//templist");
    QStringList datafilter;
    datafilter << "*.png";
    QFileInfoList infolist = dir.entryInfoList(datafilter, QDir::Files);
    for(int i = 0; i < 100;i ++)
    {
        for(int j = 0; j < infolist.size(); j++)
        {
            val_list.push_back(infolist.at(j).absoluteFilePath());
        }
    }

    vector> res;
    a1 = std::chrono::high_resolution_clock::now();
    for_each(val_list.begin(), val_list.end(), [&](QString &nane){res.push_back(std::async(std::launch::async, deal_bar_code, nane, statical_count));});
    system("pause");
    return 0;
}

充分发挥CPU的算力， 使用async，实现并发识别二维码，大幅提高了运算效率；
提示：async函数中，务必将第一个参数置为 std::launch::async, 使用默认参数， 将会退化为同步运算，而达不到异步效果。