Question

#include <fstream> 
#include <vector>
#include <iostream>

int main()
{
    bool bWriteConsole = true;
    std::streambuf *buf;
    std::ofstream outfile;

    if (bWriteConsole)
        buf = std::cout.rdbuf();
    else
    {
        outfile.open("./hello.bin", std::ofstream::binary | std::ofstream::out);
        buf = outfile.rdbuf();
    }

    std::ostream outstream(buf);
    std::vector<char> m_tableBuffer;
    double dValue = 1.2345;
    const void* dBytes = &dValue;
    std::copy(static_cast<const char *>(dBytes), static_cast<const char *>(dBytes) + sizeof(double), std::back_inserter(m_tableBuffer));

    outstream.write((char*)m_tableBuffer.data(), m_tableBuffer.size());

    if (!bWriteConsole)
        outfile.close();
    else
        std::cout << std::flush;

    return 0;
}

我需要向现有应用程序中添加一个函数，以便它可以将二进制流输出到stdout而不是文件。原型如上所示。

问题>此实现是否存在任何问题？有没有考虑RAII的优雅解决方案？

谢谢

==根据来自luk32的评论进行了更新

void function2()
{
    bool bWriteConsole = true;
    std::ofstream outfile;

    if (!bWriteConsole)
        outfile.open("./hello.bin", std::ofstream::binary | std::ofstream::out);

    std::vector<char> m_tableBuffer;
    double dValue = 1.2345;
    const void* dBytes = &dValue;
    std::copy(static_cast<const char *>(dBytes), static_cast<const char *>(dBytes) + sizeof(double), std::back_inserter(m_tableBuffer));

    if (!bWriteConsole)
    {
        outfile.write((char*)m_tableBuffer.data(), m_tableBuffer.size());
        outfile.close();
    }
    else
    {
        std::cout.write((char*)m_tableBuffer.data(), m_tableBuffer.size());
        std::cout.flush();
    }
}

Answer 1

我的版本更类似于此：

#include <iostream>
#include <fstream>

void function2(bool bWriteConsole)
{
    std::ofstream outfile;

    if (!bWriteConsole)
        outfile.open("./hello.bin", std::ofstream::binary | std::ofstream::out);

    double dValue = 1.2345;

    // writing out
    std::ostream& out = bWriteConsole ? std::cout : outfile;
    out.write(reinterpret_cast<char*>(&dValue), sizeof dValue);
    out.flush();
}

编写代码为2行，如果您确实要刷新，则为3行。 outfile.close()也将刷新，因此与您的方法相比，无条件刷新不会有任何危害。当outfile超出范围时，文件将关闭，因此不必写入文件，除非您真的想在进行进一步处理之前手动关闭文件。在这里是多余的（RAII的优点在这里发挥了作用。）

Aaand可能重构写作：

template<typename T>
void dump(T val, std::ostream& out ) {
    out.write(reinterpret_cast<char*>(&val), sizeof val);
    out.flush();
}

void function2(bool bWriteConsole)
{
    std::ofstream outfile;

    if (!bWriteConsole)
        outfile.open("./hello.bin", std::ofstream::binary | std::ofstream::out);

    double dValue = 1.2345;
    dump(dValue, bWriteConsole ? std::cout : outfile);
    // writing out
}

将二进制流写入文件或标准输出的良好实践

1 个答案: