How do you embed resource files in C?

Question

The only way I know how to do this is to convert the file into a C source file with a single byte/char array containing the contents of the resource file in hex.

Is there a better or easier way to do this?

Answer 1

Here's a nice trick I use with a gcc-arm cross compiler; including a file through an assembly language file. In this example it's the contents of the file public_key.pem I'm including.

pubkey.s

 .section ".rodata"
 .globl pubkey
 .type pubkey, STT_OBJECT
pubkey:
 .incbin "public_key.pem"
 .byte 0
 .size pubkey, .-pubkey

corresponding pubkey.h

#ifndef PUBKEY_H
#define PUBKEY_H
/*
 * This is a binary blob, the public key in PEM format,
 * brought in by pubkey.s
 */
extern const char pubkey[];

#endif // PUBKEY_H

Now the C sources can include pubkey.h , compile the pubkey.s with gcc and link it into your application, and there you go. sizeof(pubkey) also works.

Answer 2

The way you've described is the best/easiest/most portable. Just write a quick tool (or find an existing one) to generate the C files for you. And make sure you make correct use of the const (and possibly static ) keywords when you do it or your program will waste large amounts of memory.

Answer 3

I needed something like this a while ago and I created a tool for this. It's a python tool called mkcres ( https://github.com/jahnf/mkcres ) and I put it on github.

• Although documentation is lacking a little, there are examples on how to integrate it into a build process with CMake or plain make files.
• Takes a.json file as resource file generation configuration
• It can detect changes on resource files and automatically regenerate the corresponding C files if necessary.
• Downside: You'll need python (2 or 3)
• Upside: Not compiler specific, should work with every C/C++ compiler.