mkcres

mkcres is a Python tool for generating and maintaining C/C++ resource files that can be embedded in a program. mkcres comes with a python command line tool and also a header and source for easy access to the embedded resources within the program.

Basically mkcres takes a JSON configuration file and turns it into a bunch of C source files that can be compiled together with your project and included in your build process. It also supports partial updates of the generated C files since mkcres only updates files if the modification date of a file changes. A single file can appear in the resources multiple times under a different name but will be compiled in only once.

Table of Contents

• Usage
  • Configuration
  • Command line options
  • Usage in your C code
    • Get a resource
    • Loop through all resources
  • Integrate with CMake
    • Drawbacks with CMake
  • Integrate within a Makefile
• Dependencies
• License

Usage

mkcres should work with Python versions 2 and 3, but will require at least version 2.7 since the argparse is used.

Configuration

The configuration is done in a JSON file. The file has to contain the CRES value, which is an array of prefix configurations. A prefix configuration can contain the prefix and an array of files. A resource can be later found and referenced via prefix + filename or prefix + alias if the alias for a resource file is set. If prefix is not set, it will be automatically an empty string.

Here is an example JSON configuration file:

{ 
  "CRES": [
    {
      "prefix": "icons/",
      "files": [
        { "name": "img/app32x32.png" },
        { "name": "x.png", "alias": "img/exit.png" }
      ]
    }, 
    {
      "prefix": "other_stuff/",
      "files": [
        { "name": "encryption_key_v1.pub", "alias": "key.pub" },
        { "name": "lookup.sqlite" }
      ]
    }
  ]
}

Command line options

• TODO: Describe command line usage and arguments

Usage in your C code

To use the resources compiled with your executable code include the mkcres C-header cresource.h.

#include "cresource.h"

Also have a look at the examples in the example directory.

Get a resource

Use the function get_cresource to get a resource file:

/** Get a resource with the given filename. Returns a null ptr if the resource
* was not found. */
cresource_t* get_cresource(const char* filename);

If the resource exists, the function will return a pointer to a cresource_t struct, null otherwise. This is how cresource_t is defined:

typedef const struct {
const char *name;
const unsigned long size;
const unsigned char *data;
} cresource_t;

Loop through all resources

TODO

Integrate with CMake

For easy use within CMake files the function mkcres_add_library(name config_file mkcres_dir) of the helper script mkcres.cmake can be used. Lets have a look at a simple example:

# Assuming you have all the mkcres files in a subdirectory called 'mkcres'
# (mkcres.cmake mkcres.py cresource.c cresource.h)

include(mkcres/mkcres.cmake)
mkcres_add_library(myresources resources.json "./mkcres")

add_executable(example main.c)
target_link_libraries(example myresources)

Using the mkcres_add_library function will automatically add additional make targets to your project:

• mkcres-update: will update the C resource files form all targets added with mkcres_add_library
• mkcres-force-rewrite: will rewrite all the C resource files completely from all targets added with mkcres_add_library

For a full example have a look at the CMake example in the examples directory.

Drawbacks with CMake

run make mkcres-update before running make when changing the JSON resource configuration so that resources files are added or removed - otherwise the first make call will result in an error. Here is why:

Once a CMake build is configured and if the JSON configuration is changed, so that resources files are added or removed the first make call will result in either a linker or a CMake error. This is because CMake needs the full list of source files for a target (executable or library) at configuration time. In the background mkcres.py creates another CMake file that will be included from mkcres.cmake. This file contains the list of C-resource files to be compiled.

A make step will update the generated include file for CMake but this is at a point where CMake already has included the file to change and will only be detected from CMake with the next make run. Unfortunately there is no way around this.

Integrate within a Makefile

mkcres can be integrated with basically everywhere where Python is available. For an integration into your Makefiles have a look at the Makefile example in the examples directory.

Dependencies

mkcres needs Python version 2.7 or higher since it uses the argparse library.

License

See LICENSE.