i am going to read a TDMS file in matlab using Mexfunction in C language in a 64 bit windows machine, but i will develop the app in 32 bit windows machine. i know in there is a difference between 32 bit machine and 64 bits with the size of variables. i used a lot of fread(.. sizeof(type)..). is it going to be a problem when it is running in 64 bit machine? if so, how can i make it portable to 64 bits mahince?
thanks
Yes, there could potentially be an issue depending on what you do. For instance, if you rely on pointer size being 4 bytes or 8 bytes, this will be an issue. However, if you are doing something benign than maybe not. I think we'd have to see the specific code to be able to tell you. In short, there should be a straightforward way to go about this without caring about whether or not you are in a 64-bit or 32-bit architecture.
ISO C99 provides the header <stdint.h>, which defines, amongst others, types of the form intN_t and uintN_t, where N is the width of the corresponding integer or unsigned integer type. If an implementation provides integer types of width 8, 16, 32 or 64, it should provide the corresponding typedefs.
The more general problem is that you will have to know what the size of the variables were on the machine that WROTE the file, not the machine that is reading them. In other words, you can say sizeof(int) and get say 8 on some crazy 64 bit system, but if the file was saved on a normal 32 bit machine, sizeof(int) may be 4 (or even 2, according to ansi c, I think). The sizeof command will tell you the size of an int, or whatever, on your local machine at the time of compile. But it can't tell you anything about the machine that saved the file.
Your best bet is to see if the TDMS standard (I'm not familiar with it) defines variable sizes. If so, you should use those, rather than sizeof.
A poor second alternative is to have a test sequence at the beginning of the file and dynamically adjust your variable sizes until you can read the test sequence correctly.