ifstream无故失败

ifstream fails without any reason?

本文关键字：失败 ifstream      更新时间：2023-10-16

我有一个三维球体的列表，当我保存列表时，我循环通过：

void Facade::Save(std::ostream& fs)
{
    fs<<x<<" "<<y<<" "<<z<<" "<<r<<" "; //save fields
    fs<<color[0]<<" "<<color[1]<<" "<<color[2]<<std::endl;
}

当我恢复列表时，我使用：

    void Facade::Load(std::ifstream& fs, BallList* blist)
    {
        GLfloat c[3];
        fs>>x>>y>>z>>r;
        //fails there, why
        fs>>c[0]>>c[1]>>c[2];
        .....   
    }

我不知道出了什么问题，但在读取最后一行时，无法读取最后一个球体的颜色分量，读取最后一次球体的半径后流失败。我检查了球体列表文件：

7.05008 8.99167 -7.16849 2.31024 1 0 0
3.85784 -3.93902 -1.46886 0.640751 1 0 0
9.33226 3.66375 -6.93533 2.25451 1 0 0
6.43361 1.64098 -6.17298 0.855785 1 0 0
6.34388 -0.494705 -6.88894 1.50784 1 0 0

这看起来不错。有人能告诉我为什么会发生这种事吗？这是ifstream的一个bug吗？顺便说一下，我正在使用Unicode。

回路附在下面：

void BallList::Load(std::istream& fs)
{
    Clear();
    Facade ball1;
    while(!fs.fail() && !fs.eof())
    {
        ball1.Load(fs, this);
        Add(ball1);
    }
    /*
    balls.pop_back(); //this is a work around, get rid of the last one
    originalballs.pop_back();
    */
}
void BallList::Save(std::ostream& fs)
{
    vector<Facade>::iterator itero = this->originalballs.begin();
    while (itero != this->originalballs.end())
    {
        itero->Save(fs);
        itero++;
    }
    /*
    //work around the ifstream problem: the color of the last sphere cannot be read
    //add a dummy item as the last
    itero = this->originalballs.begin();
    if(itero != this->originalballs.end())
    {
        itero->Save(fs);
    }
    */
}

我预计在正确读取5个球（球体）后会失败。

循环的设计使得尝试读取第6个球将失败，但仍调用Add（）！！你应该重新定义一下你的代码：

std::ifstream& Facade::Load(std::ifstream& fs, BallList* blist)
{
    GLfloat c[3];
    fs>>x>>y>>z>>r;        // This will fail if there is no input.
                           // Once all 5 balls have been read
                           // There is only a new line character on the stream.
                           // Thus the above line will fail and the fail bit is now set.
    fs>>c[0]>>c[1]>>c[2];
    return fs;  // returned so it can be tested in loop.
}
void BallList::Load(std::istream& fs)
{
    Clear();
    Facade ball1;
    while(ball1.Load(fs, this))  // Only enter loop if the load worked
    {                            // Load worked if the stream is in a good state.
        // Only call Add() if Load() worked.
        Add(ball1);
    }
}

PS。留白是你的朋友。就我个人而言，我认为这更容易阅读：

    fs >> x >> y >> z >> r;
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