Thread: Is it possible to create in-memory streams in C?

Hey all!

I need to create a FILE* input stream in plain C, which reads from a memory buffer (char*) as if it were from standard input. I want be able to create
such a stream and read it with fgetc(), fscanf(), fread() or what ever stream based input function in the standard C library. Something similar to the StrStream class in C++ or the StringReader class in Java, but I want a plain C solution. It must be transparent to the user if the file pointer takes data from a file, socket, pipe or memory buffer!

It have to work in UNIX! I'm not interested in a
Win32 exclusive solution.

Is it possible at all? But in fact Java and C++ implements it so I think there must be a workaround. Otherwise there wouldn't be any StrStreams and StringReaders!

If you must use the FILE struct then you will have to initialize it yourself instead of using a prewritten function such as fopen. Check your compiler's includes to see what the members of FILE are and what they do.

M> No! The FILE struct is not the problem per se!
If I only could get a file descriptor coupled
to the memory location I could link it to a
FILE using fdopen().

Why not just use sscanf and sprintf for this?

M> That simply don't work. I can't use sscanf()
to feed a stream into the stomach of lex and
yacc for one sake.


Generic functions are difficult to get right, you would be better off just accepting a mode as the argument and then performing the correct operation according to the mode. Such as taking a -s flag for reading from strings and -f flag for reading from files.

M> There should darn well be a way to accomplish
such "generic" functions as you call'em. How
else would Java's StringReaders be
implemented? Maybe I have to look at the source of some compiler to solve the problem?

Regards Mats