5 ms·

Smolnes: A NES emulator in less than 5000 significant bytes of C++

142 points by jpegqs 4y ago

userbinator 4y ago
IOCCC entry? Tiny emulators seem to appear there semi-regularly, e.g. this one was memorable years ago: https://news.ycombinator.com/item?id=18198374 https://news.ycombinator.com/item?id=18198374
- binji 4y ago
  This was brought up for the last one of these I made, but the code here is c++ so wouldn't be allowed. I don't use a lot of c++ features, but it might be hard to keep the code size small without them.
amilios 4y ago
Sometimes I think I'm good at programming, then I find something like this and I'm put back in my place.
mixmix 4y ago
If you want to understand how a NES emulator works, I highly recommend javidx9’s videos: https://youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ_4IgteYf https://youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ... I personally got more joy watching that series than out of HBO shows.
guenthert 4y ago
Well, 5000 bytes of C++ plus the SDL library.
- NobodyNada 4y ago
  The emulator receives keyboard input from SDL and generates a framebuffer which it passes back to SDL. SDL is only used to handle the grunt work of reading keyboard input and displaying the framebuffer in a window, which is not the interesting part of writing a NES emulator. It's also not a necessary part of an emulator -- it's actually easier to write an emulator that reads controller inputs from a TAS movie file and writes its output to a video file. Making it interactive is just more fun.
- Waterluvian 4y ago
  SDL isn’t the emulator. It’s the hardware.
- lifthrasiir 4y ago
  Even IOCCC allows SDL (for example, 2005/jetro [1] is the only entry that used SDL_Audio as far as I know), so it is not that significant. [1] https://github.com/ioccc-src/winner/blob/master/2005/jetro/jetro.c https://github.com/ioccc-src/winner/blob/master/2005/jetro/j...
- djmips 4y ago
  I guess I agree with the other comments here. The SDL is an abstraction that allows this emulator to be a bit portable. You could target this to some microcontroller with a framebuffer in hardware and then SDL disappears, you write directly to the framebuffer and read the inputs directly from some GPIO.
minraws 4y ago
you got me, though using SDL doesn't seem quite as fair if you use that title :P nice work though. I have been writing a compile-eval NES emulator in multiple languages, C++, Rust and such, it was a lot of fun. Still haven't managed to get it working with Rust, I still have hope.
- msla 4y ago
  > you got me, though using SDL doesn't seem quite as fair if you use that title :P The program would still be sitting on top of an OS, unless it was a booter, at which point it would be sitting on top of device firmware, which sits on top of specialized hardware. SDL is about as generic a library as it gets when it comes to game development. Compare all of the companies that get credit for making their own first-person shooters, when all they had to rely on was a first-person shooter engine and a bunch of licensed assets. Scrabbling in the very dirt and clay, they are.
molticrystal 4y ago
Those who enjoy this might also enjoy "Creating a NES emulator in C++11" [0] [1] [2] while not short in bytes of code(space) there is a nice video series short in minutes(time). Bisqwit takes you on a 30 minute tool assisted coding journey of making an NES emulator and also provides a 15 minute followup Q&A video explaining different aspects. [0] https://www.youtube.com/watch?v=y71lli8MS8s https://www.youtube.com/watch?v=y71lli8MS8s [1] http://youtu.be/XZWw745wPXY http://youtu.be/XZWw745wPXY [2] http://youtu.be/QIUVSD3yqqE http://youtu.be/QIUVSD3yqqE
- erwan577 4y ago
  Bisqwit's nesemu1 source is 940 lines at https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nesemu1/nesemu1.cc https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nese... It also uses SDL. NES emulation is a great low level programming project and the tradition will probably continue for some time.
- stavros 4y ago
  To save you a click, the video is someone speed-typing the source code to an emulator, with no commentary or explanation. You'd probably be better off reading the final result yourself.
  - molticrystal 4y ago
    > with no commentary or explanation. Enable subtitles/closed captioning to see additional commentary provided by him about what is happening. >the video is someone speed-typing the source code They are not actually typing it at all, from the faq https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nesemu1/FAQ.txt https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nese... Q) Is the video sped up? Or, is that your real typing speed? A) No, it's not sped up. But the input is pre-choreographed. The computer implements the choreography, as well as designs a part of it. It is a TAS, except I'm not speedrunning; I'm just aiming for 15 minutes and to utilize it in the most entertaining manner. My typing speed is not the focus of that video; it is not even being presented except in a small part of the 2/2 video. The focus is in the source code. He actually wrote his own editor that he uses in the video and I believe that assists with the choreography.
mythz 4y ago
A great resource for learning how to write an NES emulator is the Jakt NES monster video series [1] which covers writing the entire emulator where JT shows how to map specs of each instruction to code. The source code uses Jakt's modern syntax making it very readable [2]. [1] https://www.youtube.com/playlist?list=PLP2yfE2-FXdQBRpnZbcObTe33-eSeSRYl https://www.youtube.com/playlist?list=PLP2yfE2-FXdQBRpnZbcOb... [2] https://github.com/jntrnr/jaktnesmonster https://github.com/jntrnr/jaktnesmonster
a_t48 4y ago
I did something similar, but couldn’t figure out a clever enough way of resampling the audio from “native” rate down to something that Windows was happy with. What was your strategy?
- binji 4y ago
  I didn't handle audio for this emulator. But you can see how I handle resampling in my more fully-featured NES emulator here: https://github.com/binji/binjnes/blob/ca6977469168069a165176e6ac4c5778a06c8b59/src/emulator.c#L873 https://github.com/binji/binjnes/blob/ca6977469168069a165176... I'm not sure it's the right technique, but it seems to work pretty well!
binji 4y ago
Hi all, author here! Happy to answer any questions y'all have
pvitz 4y ago
While reading the code I stumbled upon "case 1 ... 10:” or similar and asked myself how I could have missed this range feature for so many years. It turns out that this is a GCC extension and indeed not part of the language. A list of the C extensions (and C++ extensions) can be found here: https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/C-Extensions.html#C-Extensions https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/C-Extensions.ht...
- binji 4y ago
  That's true, I should have mentioned that I use this extension. It is supported by clang as well, however.
lioeters 4y ago
Big fan of this author's work. They have a Gameboy emulator written in C, which can be compiled to WASM and run in the browser. https://github.com/binji/binjgb https://github.com/binji/binjgb I learned a lot from the code. Also I love this project with a bunch of demos in hand-written WebAssembly Text (WAT) format, which is like low-level Lisp that works only with raw memory, numbers, and minimal syntax. https://github.com/binji/raw-wasm https://github.com/binji/raw-wasm Then I discovered the same author is quite active in the WebAssembly ecosystem, including specs and tooling. Fascinating stuff! https://github.com/WebAssembly/spec https://github.com/WebAssembly/spec https://github.com/WebAssembly/wabt https://github.com/WebAssembly/wabt
- binji 4y ago
  Thanks! I don't work much on WebAssembly anymore, but I'm super excited to see all the progress being made.
mid-kid 4y ago
This is the same person who made pokegb, a similarly tiny Game Boy emulator: https://github.com/binji/pokegb https://github.com/binji/pokegb

142 points by jpegqs 4y ago

IOCCC entry? Tiny emulators seem to appear there semi-regularly, e.g. this one was memorable years ago: https://news.ycombinator.com/item?id=18198374 https://news.ycombinator.com/item?id=18198374

binji 4y ago
This was brought up for the last one of these I made, but the code here is c++ so wouldn't be allowed. I don't use a lot of c++ features, but it might be hard to keep the code size small without them.

amilios 4y ago

Sometimes I think I'm good at programming, then I find something like this and I'm put back in my place.

mixmix 4y ago

If you want to understand how a NES emulator works, I highly recommend javidx9’s videos: https://youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ_4IgteYf https://youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ... I personally got more joy watching that series than out of HBO shows.

guenthert 4y ago

Well, 5000 bytes of C++ plus the SDL library.

NobodyNada 4y ago
The emulator receives keyboard input from SDL and generates a framebuffer which it passes back to SDL. SDL is only used to handle the grunt work of reading keyboard input and displaying the framebuffer in a window, which is not the interesting part of writing a NES emulator. It's also not a necessary part of an emulator -- it's actually easier to write an emulator that reads controller inputs from a TAS movie file and writes its output to a video file. Making it interactive is just more fun.
Waterluvian 4y ago
SDL isn’t the emulator. It’s the hardware.
lifthrasiir 4y ago
Even IOCCC allows SDL (for example, 2005/jetro [1] is the only entry that used SDL_Audio as far as I know), so it is not that significant. [1] https://github.com/ioccc-src/winner/blob/master/2005/jetro/jetro.c https://github.com/ioccc-src/winner/blob/master/2005/jetro/j...
djmips 4y ago
I guess I agree with the other comments here. The SDL is an abstraction that allows this emulator to be a bit portable. You could target this to some microcontroller with a framebuffer in hardware and then SDL disappears, you write directly to the framebuffer and read the inputs directly from some GPIO.

minraws 4y ago

you got me, though using SDL doesn't seem quite as fair if you use that title :P nice work though. I have been writing a compile-eval NES emulator in multiple languages, C++, Rust and such, it was a lot of fun. Still haven't managed to get it working with Rust, I still have hope.

msla 4y ago
> you got me, though using SDL doesn't seem quite as fair if you use that title :P The program would still be sitting on top of an OS, unless it was a booter, at which point it would be sitting on top of device firmware, which sits on top of specialized hardware. SDL is about as generic a library as it gets when it comes to game development. Compare all of the companies that get credit for making their own first-person shooters, when all they had to rely on was a first-person shooter engine and a bunch of licensed assets. Scrabbling in the very dirt and clay, they are.

molticrystal 4y ago

Those who enjoy this might also enjoy "Creating a NES emulator in C++11" [0] [1] [2] while not short in bytes of code(space) there is a nice video series short in minutes(time). Bisqwit takes you on a 30 minute tool assisted coding journey of making an NES emulator and also provides a 15 minute followup Q&A video explaining different aspects. [0] https://www.youtube.com/watch?v=y71lli8MS8s https://www.youtube.com/watch?v=y71lli8MS8s [1] http://youtu.be/XZWw745wPXY http://youtu.be/XZWw745wPXY [2] http://youtu.be/QIUVSD3yqqE http://youtu.be/QIUVSD3yqqE

erwan577 4y ago
Bisqwit's nesemu1 source is 940 lines at https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nesemu1/nesemu1.cc https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nese... It also uses SDL. NES emulation is a great low level programming project and the tradition will probably continue for some time.
stavros 4y ago
To save you a click, the video is someone speed-typing the source code to an emulator, with no commentary or explanation. You'd probably be better off reading the final result yourself.
- molticrystal 4y ago
  > with no commentary or explanation. Enable subtitles/closed captioning to see additional commentary provided by him about what is happening. >the video is someone speed-typing the source code They are not actually typing it at all, from the faq https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nesemu1/FAQ.txt https://bisqwit.iki.fi/jutut/kuvat/programming_examples/nese... Q) Is the video sped up? Or, is that your real typing speed? A) No, it's not sped up. But the input is pre-choreographed. The computer implements the choreography, as well as designs a part of it. It is a TAS, except I'm not speedrunning; I'm just aiming for 15 minutes and to utilize it in the most entertaining manner. My typing speed is not the focus of that video; it is not even being presented except in a small part of the 2/2 video. The focus is in the source code. He actually wrote his own editor that he uses in the video and I believe that assists with the choreography.

mythz 4y ago

A great resource for learning how to write an NES emulator is the Jakt NES monster video series [1] which covers writing the entire emulator where JT shows how to map specs of each instruction to code. The source code uses Jakt's modern syntax making it very readable [2]. [1] https://www.youtube.com/playlist?list=PLP2yfE2-FXdQBRpnZbcObTe33-eSeSRYl https://www.youtube.com/playlist?list=PLP2yfE2-FXdQBRpnZbcOb... [2] https://github.com/jntrnr/jaktnesmonster https://github.com/jntrnr/jaktnesmonster

a_t48 4y ago

I did something similar, but couldn’t figure out a clever enough way of resampling the audio from “native” rate down to something that Windows was happy with. What was your strategy?

binji 4y ago
I didn't handle audio for this emulator. But you can see how I handle resampling in my more fully-featured NES emulator here: https://github.com/binji/binjnes/blob/ca6977469168069a165176e6ac4c5778a06c8b59/src/emulator.c#L873 https://github.com/binji/binjnes/blob/ca6977469168069a165176... I'm not sure it's the right technique, but it seems to work pretty well!

binji 4y ago

Hi all, author here! Happy to answer any questions y'all have

pvitz 4y ago

While reading the code I stumbled upon "case 1 ... 10:” or similar and asked myself how I could have missed this range feature for so many years. It turns out that this is a GCC extension and indeed not part of the language. A list of the C extensions (and C++ extensions) can be found here: https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/C-Extensions.html#C-Extensions https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/C-Extensions.ht...

binji 4y ago
That's true, I should have mentioned that I use this extension. It is supported by clang as well, however.

lioeters 4y ago

Big fan of this author's work. They have a Gameboy emulator written in C, which can be compiled to WASM and run in the browser. https://github.com/binji/binjgb https://github.com/binji/binjgb I learned a lot from the code. Also I love this project with a bunch of demos in hand-written WebAssembly Text (WAT) format, which is like low-level Lisp that works only with raw memory, numbers, and minimal syntax. https://github.com/binji/raw-wasm https://github.com/binji/raw-wasm Then I discovered the same author is quite active in the WebAssembly ecosystem, including specs and tooling. Fascinating stuff! https://github.com/WebAssembly/spec https://github.com/WebAssembly/spec https://github.com/WebAssembly/wabt https://github.com/WebAssembly/wabt

binji 4y ago
Thanks! I don't work much on WebAssembly anymore, but I'm super excited to see all the progress being made.

mid-kid 4y ago

This is the same person who made pokegb, a similarly tiny Game Boy emulator: https://github.com/binji/pokegb https://github.com/binji/pokegb