Add libretro frontend with support for RetroArch

This feature includes:

Support for building for android using the NDK

Generate .info metadata file at compile time in order to make it less confusing for usage

Improve speed of the joypad handling in general by pulling only when necessary
previously it pulled every constant number of frames, now it pulls once every frame

cycle_frame will return on vblank event to achieve a more accurate emulation

Cargo.toml

@@ -3,10 +3,11 @@ members = [
     "sdl",
     "core",
     "rpi",
-    "common"
+    "common", 
+    "libretro"
 ]
 
 [workspace.package]
 version = "4.0.0"
 authors = ["alloncm <alloncm@gmail.com>"]
-rust-version = "1.70"   # cause of once cell
+rust-version = "1.73"   # cause of cargo-ndk used to build for android platform

Makefile.toml

@@ -2,7 +2,7 @@
 default_to_workspace = false
 
 [tasks.all]
-dependencies = ["test", "sdl", "rpios", "rpibm"]
+dependencies = ["test", "sdl", "rpios", "rpibm", "libretro"]
 
 [tasks.test]
 command = "cargo"
@@ -57,4 +57,14 @@ install_crate = {rustup_component_name = "llvm-tools-preview"}
 [tasks.install_rust_src]
 toolchain = "nightly"
 command = "rustup"
-args = ["component", "add", "rust-src"]
+args = ["component", "add", "rust-src"]
+
+[tasks.libretro]
+command = "cargo"
+args = ["build", "--release", "--package", "magenboy_libretro"]
+dependencies = ["libretro_android"]
+
+[tasks.libretro_android]
+install_crate = {crate_name = "cargo-ndk", binary = "cargo", test_arg = "ndk"}
+command = "cargo"
+args = ["ndk", "--target=aarch64-linux-android", "build", "--release", "--package", "magenboy_libretro"]

README.md

@@ -79,6 +79,10 @@ rustup component add llvm-tools-preview
 
 3. Builds the image
 
+### Libretro
+
+See - [LibretroDocs](docs/Libretro.md)
+
 ## Running
 
 ### Desktop

sdl/src/audio/audio_resampler.rs → common/src/audio/audio_resampler.rs

@@ -6,14 +6,12 @@ pub trait AudioResampler{
 }
 
 pub trait ResampledAudioDevice<AR:AudioResampler> : AudioDevice{
-    const VOLUME:Sample = 10 as Sample;
-
     fn push_buffer(&mut self, buffer:&[StereoSample; BUFFER_SIZE]){
         let resample = self.get_resampler().resample(buffer);
         for sample in resample{
             let(buffer, index) = self.get_audio_buffer();
-            buffer[*index] = sample.left_sample * Self::VOLUME;
-            buffer[*index + 1] = sample.left_sample * Self::VOLUME;
+            buffer[*index] = sample.left_sample;
+            buffer[*index + 1] = sample.right_sample;
             *index += 2;
             if *index == BUFFER_SIZE{
                 *index = 0;

sdl/src/audio/manual_audio_resampler.rs → common/src/audio/manual_audio_resampler.rs

@@ -1,4 +1,4 @@
-use magenboy_core::apu::audio_device::{BUFFER_SIZE, DEFAULT_SAPMPLE, Sample, StereoSample};
+use magenboy_core::apu::audio_device::{BUFFER_SIZE, StereoSample};
 use super::audio_resampler::AudioResampler;
 
 
@@ -12,15 +12,6 @@ pub struct ManualAudioResampler{
     skip_to_use:u32,
 }
 
-impl ManualAudioResampler{
-    fn interpolate_sample(samples:&[StereoSample])->StereoSample{
-        let interpulated_left_sample = samples.iter().fold(DEFAULT_SAPMPLE, |acc, x| acc + x.left_sample) / samples.len() as Sample;
-        let interpulated_right_sample = samples.iter().fold(DEFAULT_SAPMPLE, |acc, x| acc + x.right_sample) / samples.len() as Sample;
-
-        return StereoSample{left_sample: interpulated_left_sample, right_sample: interpulated_right_sample};
-    }
-}
-
 impl AudioResampler for ManualAudioResampler{
     fn new(original_frequency:u32, target_frequency:u32)->Self{
         // Calling round in order to get the nearest integer and resample as precise as possible
@@ -59,7 +50,7 @@ impl AudioResampler for ManualAudioResampler{
             self.sampling_counter += 1;
 
             if self.sampling_counter == self.skip_to_use {
-                let interpolated_sample = Self::interpolate_sample(&self.sampling_buffer);
+                let interpolated_sample = StereoSample::interpolate(&self.sampling_buffer);
                 self.sampling_counter = 0;
                 self.sampling_buffer.clear();
 

common/src/lib.rs

@@ -4,6 +4,12 @@ cfg_if::cfg_if!{ if #[cfg(feature = "std")] {
     pub mod mbc_handler;
     pub mod mpmc_gfx_device;
     pub mod logging;
+    pub mod audio{
+        mod audio_resampler;
+        mod manual_audio_resampler;
+        pub use audio_resampler::*;
+        pub use manual_audio_resampler::*;
+    }
 }}
 
 pub mod menu;

common/src/mbc_handler.rs

@@ -20,7 +20,7 @@ fn try_get_save_data(name:&String)->Option<Vec<u8>>{
     }
 }
 
-pub fn release_mbc<'a>(program_name:&String, mbc: &'a dyn Mbc){
+pub fn release_mbc<'a>(program_name:&String, mbc: &'a mut dyn Mbc){
     if mbc.has_battery(){
         while fs::write(format!("{}{}", program_name, ".sav"), mbc.get_ram()).is_err() {}       
         info!("saved succesfully");

common/src/scale.c

@@ -40,7 +40,7 @@ extern void scale_buffer(const uint16_t* input_buffer, int input_buffer_width, i
             const uint16_t pixel = ((uint16_t)blue) | (((uint16_t)green) << 5) | (((uint16_t)red) << 11);
 
             output_buffer[output_offset_counter * 2] = (uint8_t)(pixel >> 8);
-            output_buffer[(output_offset_counter * 2) + 1] = (uint8_t)(pixel && 0xFF);
+            output_buffer[(output_offset_counter * 2) + 1] = (uint8_t)(pixel & 0xFF);
             output_offset_counter++;
         }
     }

core/src/apu/apu_registers_updater.rs

@@ -10,7 +10,7 @@ use super::{
     square_sample_producer::SquareSampleProducer, 
     volume_envelop::VolumeEnvlope, 
     wave_sample_producer::WaveSampleProducer,
-    sound_utils::NUMBER_OF_CHANNELS
+    NUMBER_OF_CHANNELS
 };
 
 

core/src/apu/audio_device.rs

@@ -1,8 +1,13 @@
+use super::NUMBER_OF_CHANNELS;
+
 pub type Sample = i16;
 pub const DEFAULT_SAPMPLE:Sample = 0 as Sample;
+const MAX_MASTER_VOLUME:Sample = 8;
+pub const SAMPLE_MAX: Sample = Sample::MAX / (MAX_MASTER_VOLUME * NUMBER_OF_CHANNELS as Sample);
 
-pub const BUFFER_SIZE:usize = 2048;
+pub const BUFFER_SIZE:usize = 0x2000;
 
+#[derive(Clone, Copy)]
 #[repr(C, packed)]
 pub struct StereoSample{
     pub left_sample:Sample,
@@ -13,11 +18,12 @@ impl StereoSample{
     pub const fn const_defualt()->Self{
         Self{left_sample:DEFAULT_SAPMPLE, right_sample:DEFAULT_SAPMPLE}
     }
-}
 
-impl Clone for StereoSample{
-    fn clone(&self) -> Self {
-        Self{left_sample:self.left_sample,right_sample:self.right_sample}
+    pub fn interpolate(samples:&[StereoSample])->StereoSample{
+        let left_sample = (samples.iter().fold(0, |acc, x| acc + x.left_sample as i64) / samples.len() as i64) as Sample;
+        let right_sample = (samples.iter().fold(0, |acc, x| acc + x.right_sample as i64) / samples.len() as i64) as Sample;
+
+        return StereoSample{left_sample, right_sample};
     }
 }
 

core/src/apu/channel.rs

@@ -1,6 +1,4 @@
-use super::audio_device::{DEFAULT_SAPMPLE, Sample};
-use super::sample_producer::SampleProducer;
-use super::timer::Timer;
+use super::{audio_device::{Sample, DEFAULT_SAPMPLE, SAMPLE_MAX}, sample_producer::*, timer::Timer};
 
 pub struct Channel<Procuder: SampleProducer>{
     pub enabled:bool,
@@ -50,20 +48,24 @@ impl<Procuder: SampleProducer> Channel<Procuder>{
 
     pub fn get_audio_sample(&mut self)->Sample{
         if self.enabled{
-
-            let sample = if self.timer.cycle(){
+            if self.timer.cycle(){
                 self.timer.update_cycles_to_tick(self.sample_producer.get_updated_frequency_ticks(self.frequency));
-                self.sample_producer.produce() as Sample
+                let digital_sample = self.sample_producer.produce();
+                self.last_sample = Self::convert_digital_to_analog(digital_sample);
             }
-            else{
-                self.last_sample
-            };
-
-            self.last_sample = sample;
-
-            return self.last_sample;
         }
+        else{
+            self.last_sample = DEFAULT_SAPMPLE;
+        }
+
+        return self.last_sample;
+    }
+
+    fn convert_digital_to_analog(digital_sample:u8)->Sample{
+        const RATIO:Sample = SAMPLE_MAX / MAX_DIGITAL_SAMPLE as Sample;
 
-        return DEFAULT_SAPMPLE;
+        // Expandibg the sample to the full range of the Sample type while still 
+        // allowing furhter calculations without overflowing
+        return (digital_sample as Sample - (MAX_DIGITAL_SAMPLE as Sample / 2)) * RATIO;
     }
 }

core/src/apu/gb_apu.rs

@@ -7,7 +7,7 @@ use super::{
     sound_terminal::SoundTerminal,
     square_sample_producer::SquareSampleProducer, 
     wave_sample_producer::WaveSampleProducer,
-    sound_utils::NUMBER_OF_CHANNELS
+    NUMBER_OF_CHANNELS
 };
 
 pub struct GbApu<Device: AudioDevice>{

core/src/apu/mod.rs

@@ -11,8 +11,8 @@ pub mod freq_sweep;
 pub mod volume_envelop;
 pub mod noise_sample_producer;
 
-mod sound_utils;
 mod apu_registers_updater;
 
 pub use apu_registers_updater::*;
 
+pub(self) const NUMBER_OF_CHANNELS:usize = 4;

core/src/apu/sample_producer.rs

@@ -1,4 +1,8 @@
+/// Max value for digital sample according to the Pandocs
+pub const MAX_DIGITAL_SAMPLE:u8 = 0xF;
+
 pub trait SampleProducer{
+    /// Produces a digital sample in range of 0 to 0xF 
     fn produce(&mut self)->u8;
     fn get_updated_frequency_ticks(&self, freq:u16)->u16;
     fn reset(&mut self);

core/src/apu/sound_terminal.rs

@@ -1,4 +1,4 @@
-use super::{audio_device::{DEFAULT_SAPMPLE, Sample}, sound_utils::NUMBER_OF_CHANNELS};
+use super::{audio_device::{DEFAULT_SAPMPLE, Sample}, NUMBER_OF_CHANNELS};
 
 type ChannelMask = u16;
 

core/src/apu/square_sample_producer.rs

@@ -1,6 +1,11 @@
-use super::{sample_producer::SampleProducer, sound_utils::DUTY_TABLE};
-use super::freq_sweep::FreqSweep;
-use super::volume_envelop::VolumeEnvlope;
+use super::{freq_sweep::FreqSweep, sample_producer::SampleProducer, volume_envelop::VolumeEnvlope};
+
+const DUTY_TABLE:[[u8; 8]; 4] = [
+    [0,0,0,0,0,0,0,1],
+    [1,0,0,0,0,0,0,1],
+    [1,0,0,0,0,1,1,1],
+    [0,1,1,1,1,1,1,0],
+];
 
 pub struct SquareSampleProducer{
     pub wave_duty:u8,

core/src/keypad/joypad_handler.rs

@@ -3,8 +3,7 @@ use super::{joypad_provider::JoypadProvider, joypad::Joypad, button::Button};
 
 
 pub struct JoypadHandler<JP:JoypadProvider>{
-    pub register:u8,
-
+    register:u8,
     joypad:Joypad,
     joypad_provider:JP,
 }
@@ -20,7 +19,9 @@ impl<JP:JoypadProvider> JoypadHandler<JP>{
 
     pub fn poll_joypad_state(&mut self){
         self.joypad_provider.provide(&mut self.joypad);
+    }
 
+    pub fn get_register(&mut self) -> u8{
         let buttons = (self.register & BIT_5_MASK) == 0;
         let directions = (self.register & BIT_4_MASK) == 0;
 
@@ -36,8 +37,10 @@ impl<JP:JoypadProvider> JoypadHandler<JP>{
             flip_bit_u8(&mut self.register, 2, !self.joypad.buttons[Button::Up as usize]);
             flip_bit_u8(&mut self.register, 3, !self.joypad.buttons[Button::Down as usize]);
         }
-    }
 
+        return self.register;
+    }
+
     pub fn set_register(&mut self, value:u8){
         self.register &= 0b1100_1111;   // Reset bit 4 & 5
         self.register |= value & 0b0011_0000;   // Seting the bits

core/src/machine/gameboy.rs

@@ -53,9 +53,9 @@ impl<'a, JP:JoypadProvider, AD:AudioDevice, GFX:GfxDevice> GameBoy<'a, JP, AD, G
     }
 
     pub fn cycle_frame(&mut self){
-        while self.mmu.m_cycle_counter < CYCLES_PER_FRAME{
-            self.mmu.poll_joypad_state();
-
+        self.mmu.poll_joypad_state();
+
+        while !self.mmu.consume_vblank_event(){
             //CPU
             let mut cpu_cycles_passed = 1;
             if !self.cpu.halt && !self.mmu.dma_block_cpu(){
@@ -72,8 +72,6 @@ impl<'a, JP:JoypadProvider, AD:AudioDevice, GFX:GfxDevice> GameBoy<'a, JP, AD, G
                 self.mmu.cycle(interrupt_cycles);
             }
         }
-
-        self.mmu.m_cycle_counter = 0;
     }
 
     fn execute_opcode(&mut self)->u8{

core/src/mmu/carts/mbc1.rs

@@ -12,7 +12,7 @@ pub struct Mbc1<'a>{
 }
 
 impl<'a> Mbc for Mbc1<'a>{
-    fn get_ram(&self) ->&[u8] {
+    fn get_ram(&mut self) ->&mut [u8] {
         self.ram
     }
 

core/src/mmu/carts/mbc3.rs

@@ -16,7 +16,7 @@ pub struct Mbc3<'a>{
 
 impl<'a> Mbc for Mbc3<'a>{
 
-    fn get_ram(&self) ->&[u8] {
+    fn get_ram(&mut self) ->&mut [u8] {
         self.ram
     }
 

core/src/mmu/carts/mbc5.rs

@@ -12,8 +12,8 @@ pub struct Mbc5<'a>{
 }
 
 impl<'a> Mbc for Mbc5<'a> {
-    fn get_ram(&self)->&[u8] {
-        &self.ram
+    fn get_ram(&mut self)->&mut [u8] {
+        self.ram
     }
 
     fn has_battery(&self)->bool {