Reading binary float from file

[boxfish]

Hi,
I'm trying to write code in C++ that loads .3ds files. .3ds files use floats in binary for vertex coordinates, but I don't know how to read them. I googled stuff for a bit, until it seemed like reinterpret_cast was the way to do it, but this code

float readFloat(ifstream& file) {
    char bytes[sizeof(float)];
    for (int i = 0; i < sizeof(float); i++)
        bytes[i] = file.get();
    return reinterpret_cast<float>(bytes);
}

gives me this error:
invalid reinterpret_cast from type `char*' to type `float'
Do any of you know how to read a float from a file? I will appreciate any help you can give me.

[gpraghuram]

After getting the data try to use atof to get the float value.

Raghu

[JosAH]

Make that last line:

return *reinterpret_cast<float*>(bytes);
 

kind regards,

Jos

[weaknessforcats]

Errr...
Why can't you just:

float readFloat(ifstream& file) {
    float bytes;
    file >> bytes;
    return bytes;
}
 

[newb16]

Errr...
Why can't you just:

Because it assumes it's ascii string like 1.23e4, not 4 bytes of ieee754

[Laharl]

Which "it" do you mean? The file format or the C++? The C++ most certainly assumes it's 4 bytes of IEEE754.

[boxfish]

Hi,
Thanks for all your replies. This works. Yay.

float readFloat(ifstream& file) {
    char bytes[sizeof(float)];
    for (int i = 0; i < sizeof(float); i++)
        bytes[i] = file.get();
    float* floatPtr = reinterpret_cast<float*>(bytes);
    return *floatPtr;
}

Well, it compiles anyway. Should load .3ds files when I get my program doing that. Thanks Jos. And hopefully when I post this message I will be upgraded to a member. Hooray.

[JosAH]

Hi,
Thanks for all your replies. This works. Yay.

float readFloat(ifstream& file) {
    char bytes[sizeof(float)];
    for (int i = 0; i < sizeof(float); i++)
        bytes[i] = file.get();
    float* floatPtr = reinterpret_cast<float*>(bytes);
    return *floatPtr;
}

Well, it compiles anyway. Should load .3ds files when I get my program doing that. Thanks Jos. And hopefully when I post this message I will be upgraded to a member. Hooray.

Also have a look at the istream::read function to get rid of that silly loop ;-)

kind regards,

Jos

[boxfish]

Alright, the loop's gone.