C reading (from stdin) stops at 0x1a character

Question

currently I'm implementing the Burrows-Wheeler transform (and inverse transform) for raw data (like jpg etc.). When testing on normal data like textfiles no problems occur. But when it comes to reading jpg files e.g. it stops reading at character 0x1a aka substitute character. I've been searching through the internet for solutions which doesn't take OS dependend code but without results... I was thinking to read in stdin in binary mode but that isn't quite easy I guess. Is there any simple method to solve this problem?

code:

buffer = (unsigned char*) calloc(block_size+1,sizeof(unsigned char));
length = fread((unsigned char*) buffer, 1, block_size, stdin);
if(length == 0){
    // file is empty
}else{
    b_length = length;
    while(length == b_length){
        buffer[block_size] = '\0';
        encodeBlock(buffer,length);
        length = fread((unsigned char*) buffer, 1, block_size, stdin);      
    }
    if(length != 0){            
        buffer[length] = '\0';
        encodeBlock(buffer,length);
    }
}
free(buffer);

Answer 1

As you've noticed, you're reading from stdin in ASCII mode and it is hitting the SUB character (substitute, aka CTRL+Z, aka DOS End-of-File).

You have to change the mode to binary with setmode while on Windows:

#if defined(WIN32)
#include <io.h>
#include <fcntl.h>
#endif /* defined(WIN32) */

/* ... */

#if defined(WIN32)
_setmode(_fileno(stdin), _O_BINARY);
#endif /* defined(WIN32) */

On platforms other than Windows you don't run into this distinction in modes.

Answer 2

You cannot do this without an OS dependency. The C language specification says (7.19.3)

At program startup, three text streams are predefined...

stdin is a text stream. Depending on your OS, there may be ways to change the mode of an existing stream or access the low-level stream data, but you claim that you do not want any OS-specific code.