从文件中读取4个十六进制值并转换为float

Question

So I have been creating a file format in java but know I need to read in that binary file in from a C++ application.

The binary file just contains a huge number of floating point numbers represented by 4 hex values.

Sample Data in hex: FF B6 DD 99 8D FF 39 61 0C 62 FF 42 , FF B6 DD 99 is a float, 8D FF 39 61 is a float and so on...

How do i read in the file 4 hex values at a time and convert into a float?

    std::fstream fRead;
    fRead.open("path");

    if (fRead.fail())
    {
        fRead.close();
    } 
    else 
    {
        char packetPart[3];

        while (true) 
        {
            fRead.read(packetPart, 4);
            //std::cout << std::hex << std::setw(2) << std::setfill('0') << int(packetPart[0]) << std::endl;
            //I was trying to display the hex value but it didn't work.
        }
    }

    fRead.close();

Answer 1

Try this:

ifstream inp_file("path", ios::binary);
//...
float my_float = 0.0f;
inp_file.read((char *) &my_float, sizeof(my_float));

This will only work if your platform has the same floating point implementation as the Java implementation.

By the way, in your code:

char packetPart[3];

while (true) 
{
    fRead.read(packetPart, 4);

You are reading 4 characters into a 3 character capacity array. You should ask yourself, "where does the 4 character go?".