How to have both 32bit and 64bit float in C++

Question

I have a file spec (here: http://www.septentrio.com/secure/asterx1v_2_1/SBF%20Reference%20Guide.pdf) that has fields marked as both 32-bit and 64-bit floats (see page 8). How can I use both widths in my program? I am developing on Mac OSX right now but I will also deploy on a Linux machine.

More details:

I know I could tell the compiler the width, but how could I distinguish two different float widths? Maybe someone also has a suggestion for changing the way I parse, which is to reinterpret_cast(buffer+offset) and then use the values. These file sizes are huge (4GB) so I need performance.

Answer 1

This might seem obvious, nevertheless:

On Intel platform and many others float is 32-bit floating point value, and double is 64-bit floating point value. Try this approach. Most likely it will work.

To be absolutely sure check sizeof of your types at the start of your program or statically during compilation if your compiler allows this.

Once again, try the simple solution first.

Float and double arithmetic is both implemented on Intel and it is fast. In any case native arithmetic is the fastest of what you can get from the CPU.

IEEE 754 (http://en.wikipedia.org/wiki/IEEE_floating_point) defines not one floating point format, but several, like 4, 8, 16 bytes, etc. They all have different range and precision but they are all still IEEE values.