小编kim*_*say的帖子

我使用C++ 14的shared_timed_mutex编写了一个读写器问题的实现.在我看来,下面的代码应该导致Writer饿死,因为太多的读者线程一直在数据库上工作(在这个例子中是一个简单的数组):作者没有机会获得锁.

mutex cout_mtx;                 // controls access to standard output
shared_timed_mutex db_mtx;      // controls access to data_base

int data_base[] = { 0, 0, 0, 0, 0, 0 };

const static int NR_THREADS_READ = 10; 
const static int NR_THREADS_WRITE = 1;
const static int SLEEP_MIN = 10;
const static int SLEEP_MAX = 20;

void read_database(int thread_nr) {
    shared_lock<shared_timed_mutex> lck(db_mtx, defer_lock); // create a lock based on db_mtx but don't try to acquire the mutex yet
    while (true) {
        // generate new …

我现在正在进入Java图形,我正在阅读Andrew Davison撰写的Java中的Killer游戏编程.他编写了一个简单的窗口应用程序,它使用Image类进行离屏渲染,然后将图像复制到组件.我觉得令人困惑的是,人们可以创建图像然后获取图形上下文:

dbg = dbImage.getGraphics();

我发现它令人困惑,因为那时我们只使用dbg Graphics对象来绘制东西但后来我们在paintComponent方法中使用dbImage来显示我们绘制到dbg Object的所有东西:

g.drawImage(dbImage, 0, 0, null);

那么dbImage如何"知道"它包含我们绘制到dbg Graphics对象上的所有图形内容？

这是整个代码:

public class GamePanel extends JPanel implements Runnable{

    private static final int PWIDTH = 500;
    private static final int PHEIGHT = 400;

    private Thread animator;

    private volatile boolean running = false;

    private volatile boolean gameOver = false;

    private Graphics dbg;
    private Image dbImage = null;

    private Counter counter;

    public GamePanel(){
        setBackground(Color.white);
        setPreferredSize(new Dimension(PWIDTH, PHEIGHT));

        // create game components eg. counter.
        counter = new Counter(10);
        counter.start();
    } …

好的,这已经被覆盖了,例如:静态数组类变量"多重定义"C++

但我在这里遗漏了一些细节.

我有以下课程:Foo.cpp

#include <iostream>
#include "Model.h"

    int main(int argc, char** argv){
        std::cout << "hello" << std::endl;
        return 0;
    }

Model.h

#ifndef MODEL_H
#define MODEL_H

#include <string>
#include "md2Loader.h"

class Model{
    public:
    Model();
    Model(const std::string& model_file);

    private:
    md2_header_t header;
    modelData_t model;
};

#endif

Model.cpp

#include "Model.h"
#include "md2Loader.h"

Model::Model(){}

Model::Model(const std::string& model_file){
    model = md2Loader::load_model(model_file);
}

和md2Loader.h

#ifndef MD2LOADER_H
#define MD2LOADER_H

struct modelData_t{
    int numVertices;
    int numTextures;
    // etc
};

struct md2_header_t {
    std::string version;
};

class md2Loader{
public: …