About

agnes is a NES emulation library written in C with an easy to use API, by Krzysztof Gabis. It consists of only 2 files (agnes.h and agnes.c).

Features

• Only 2 files (agnes.h and agnes.c).
• Easy to use.
• MIT licensed.
• Supports NROM, UxROM, MMC1 and MMC3 mappers.

API example

agnes_t *agnes = agnes_make();
agnes_load_ines_data(agnes, game_data, game_data_size);
while (true) {
    agnes_input_t input;
    get_input(&input);

    agnes_set_input(agnes, &input, NULL);

    agnes_next_frame(agnes);

    for (int y = 0; y < AGNES_SCREEN_HEIGHT; y++) {
        for (int x = 0; x < AGNES_SCREEN_WIDTH; x++) {
            agnes_color_t c = agnes_get_screen_pixel(agnes, x, y);
            display_pixel(x, y, c);
        }
    }
}
agnes_destroy(agnes);

Full and working examples can be found in examples directory.

Screenshots

Installation

Run:

$ npm i agnes.c

And then include agnes.h as follows:

// main.c
#include <agnes.h>

int main() { /* ... */ }

Finally, compile while adding the path node_modules/agnes.c to your compiler's include paths.

$ clang -I./node_modules/agnes.c main.c  # or, use gcc
$ gcc   -I./node_modules/agnes.c main.c

You may also use a simpler approach with the cpoach tool, which automatically adds the necessary include paths of all the installed dependencies for your project.

$ cpoach clang main.c  # or, use gcc
$ cpoach gcc   main.c

Testing

Run cd node_modules/agnes.c/tests && run_tests.sh ROM_DIRECTORY to compile and run tests.

Since I cannot add roms to this project they must be downloaded manually. Please look at contents of examples/recs.tar.gz for names of roms that are required to run tests. Emulator testing roms (such as nestest.nes or official_only.nes) can be obtained from here. If you want to update add a recording or update an existing one run recorder (located in tests dir).

TODO

• APU emulation.
• Optimizations.
• More mappers.
• Being able to access CPU and PPU state using API.

Splitting and joining

agnes.c can be split into separate files by running utils/split.py:

utils/split.py --input agnes.c --output-path src

It can be joined back into a single file with utils/join.py:

utils/join.py --template utils/agnes.c.templ --path src --output agnes.c

Contributing

I will always merge working bug fixes. However, if you want to add something new to the API, please create an "issue" on github for this first so we can discuss if it should end up in the library before you start implementing it.

Acknowledgements

NesDev Wiki

Other open-source NES emulators, that were extremely helpful as a reference:

• https://github.com/fogleman/nes
• https://github.com/AndreaOrru/LaiNES
• https://github.com/ulfalizer/nesalizer/blob/master/src/ppu.cpp
• https://github.com/daniel5151/ANESE

Also, many thanks to Mateusz Belicki for all his suggestions and help.

License

The MIT License (MIT)