What is the purpose of using memory stream in the C standard library?

Question

In the C standard library, what is the purpose of using a memory stream (as created for an array via fmemopen())? How is it compared to manipulating the array directly?

Answer 1

This is very similar to using the std::stringstream in C++, which allows you to write to a string (including '\0' characters) and then use the string the way you'd like.

The idea is that we have many functions at our disposal, such as fprintf(), which can be used to write data to a stream in a formatted way. All those functions can be used with a memory based file without any need for further changes anywhere else than the fopen() to fmemopen().

So if you want to create a string which requires many fprintf(), using that function to generate the string in memory is extremely useful. The snprintf() could also be used if you just need one quick conversion.

Similarly, you can of course use fread() and fwrite() and the like. If you need to create a file which requires a lot of seeking and it's not that big that it can easily fit in memory, then it's going to go a lot faster. Once done, you can save the results to disk.