The agnes from kgabis

agnes's Introduction

About

agnes is a NES emulation library written in C with an easy to use API. 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:

git clone https://github.com/kgabis/agnes.git

and copy agnes.h and agnes.c to you source code tree.

Testing

Run run_tests.sh ROM_DIRECTORY (in tests 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:

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

License

The MIT License (MIT)

agnes's People

Contributors

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agnes's Issues

Why doesn't this include audio?

I know it's hard to make this library, but I'm just wondering why audio was never implemented

Non mirrored CHR banks causes out of bounds memory access

I created a ROM that can crash the emulator or allow it to access out of bounds memory.

The ROM essentially writes a value from 0 to 255 to the MMC3 CHR banks registers, then increments this value every frame.

If the ROM has just one bank, the expected behavior is for that one bank to be mirrored.

I fixed it in the tool I included agnes in with modulus at the mapper level, but this breaks CHR RAM and doesn't properly respect powers of two for mirroring.

	int modValue = mapper->agnes->gamepack.chr_rom_banks_count*8;
    switch (mapper->chr_mode) {
        case 0: { // R0_1, R0_2, R1_1, R1_2, R2, R3, R4, R5
            mapper->chr_bank_offsets[0] = ((mapper->regs[0]%modValue) & 0xfe) * 1024;
			//similar modulus for all other lines

A real fix would probably be to allocate memory to the next power of two at load (for weird CHR bank values like 3 rather than 4), then AND instead of %

I've attached the ROM (It is homebrew, not commercial):
anim.zip

kgabis / agnes Goto Github PK