通过输入重定向读取二进制文件 c++ 的最佳方法

2022-01-07 00:00:00 stdin stream c++ cin

我试图在运行时读取一个大型二进制文件，认为输入重定向 (stdin)，并且 stdin 是强制性的.

I am trying to read a large binary file thought input redirection (stdin) at runtime, and stdin is mandatory. 

./a.out < input.bin

到目前为止我已经使用过 fgets.但是 fgets 会跳过空格和换行符.我想包括两者.我的 currentBuffersize 可以动态变化.

So far I have used fgets. But fgets skips blanks and newline. I want to include both. My currentBuffersize could dynamically vary.

FILE * inputFileStream = stdin; 
int currentPos = INIT_BUFFER_SIZE;
int currentBufferSize = 24; // opt
unsigned short int count = 0; // As Max number of packets 30,000/65,536
while (!feof(inputFileStream)) {
    char buf[INIT_BUFFER_SIZE]; // size of byte
    fgets(buf, sizeof(buf), inputFileStream);
    cout<<buf;
    cout<<endl;
}

提前致谢.

推荐答案

如果是我，我可能会做类似的事情:

If it were me I would probably do something similar to this:

const std::size_t INIT_BUFFER_SIZE = 1024;

int main()
{
    try
    {
        // on some systems you may need to reopen stdin in binary mode
        // this is supposed to be reasonably portable
        std::freopen(nullptr, "rb", stdin);

        if(std::ferror(stdin))
            throw std::runtime_error(std::strerror(errno));

        std::size_t len;
        std::array<char, INIT_BUFFER_SIZE> buf;

        // somewhere to store the data
        std::vector<char> input;

        // use std::fread and remember to only use as many bytes as are returned
        // according to len
        while((len = std::fread(buf.data(), sizeof(buf[0]), buf.size(), stdin)) > 0)
        {
            // whoopsie
            if(std::ferror(stdin) && !std::feof(stdin))
                throw std::runtime_error(std::strerror(errno));

            // use {buf.data(), buf.data() + len} here
            input.insert(input.end(), buf.data(), buf.data() + len); // append to vector
        }

        // use input vector here
    }
    catch(std::exception const& e)
    {
        std::cerr << e.what() << '
';
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}

请注意，您可能需要以二进制模式重新打开stdin，不确定它的可移植性如何，但各种文档表明跨系统的支持相当好.

Note you may need to re-open stdin in binary mode not sure how portable that is but various documentation suggests is reasonably well supported across systems.

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