neser 0.1.0

NESER - NES Emulator in Rust - is a NES emulator written in Rust. It aims to be a high-quality, hardware-accurate emulator that is also easy to use and extend. It supports a wide range of NES games and features, including various mappers, audio processing, and input handling. NESER is designed to be modular and extensible, allowing developers to easily add new features or support for additional hardware. It can be run using one of two frontends: a native desktop application using SDL2, or a web application using WebAssembly. The desktop application provides a high-performance, feature-rich experience with support for various input devices and display options, while the web application allows users to play NES games directly in their browsers without needing to install any software in a BYOR manner (Bring Your Own Roms).
Documentation 
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use crate::sdl_frontend::sdl_audio::{AudioConsumer, AudioStats};
use crate::sdl_frontend::sdl_audio_resampler::SdlAudioResampler;
use ringbuf::traits::Consumer;
use sdl2::audio::AudioCallback;
use std::sync::{
    Arc,
    atomic::{AtomicU32, AtomicUsize, Ordering},
};

/// SDL2 audio callback implementation
pub(crate) struct SdlAudioCallbackImpl {
    pub(crate) sample_consumer: AudioConsumer,
    pub(crate) volume: Arc<AtomicU32>,
    pub(crate) stats: Arc<AudioStats>,
    pub(crate) fill_level: Arc<AtomicUsize>,
    pub(crate) resampler: SdlAudioResampler,
}

impl AudioCallback for SdlAudioCallbackImpl {
    type Channel = f32;

    fn callback(&mut self, out: &mut [f32]) {
        // Load current volume
        let volume = f32::from_bits(self.volume.load(Ordering::Relaxed));
        let fill_level = self.fill_level.load(Ordering::Relaxed);
        self.resampler.update_rate(fill_level);

        for sample in out.iter_mut() {
            let raw_sample = self.resampler.render_next(&mut || {
                let sample = self.sample_consumer.try_pop();
                if sample.is_some() {
                    self.fill_level.fetch_sub(1, Ordering::Relaxed);
                }
                sample
            });

            match raw_sample {
                Some(raw_sample) => {
                    self.stats.received_samples.fetch_add(1, Ordering::Relaxed);
                    // NES APU mix() outputs 0.0-1.177, where 0.0 represents silence
                    // SDL2 f32 format expects -1.0 to +1.0 where 0.0 is silence
                    // The NES output needs to be scaled to use the full SDL2 range
                    // and shifted so NES silence (0.0) maps to SDL2 silence (0.0)
                    //
                    // Strategy: Map NES 0.0-1.177 to SDL2 0.0-1.0
                    const NES_APU_MAX: f32 = 1.177;
                    let normalized = raw_sample / NES_APU_MAX;
                    let final_sample = normalized * volume;

                    // Safety clamp to prevent any unexpected clipping
                    *sample = final_sample.clamp(-1.0, 1.0);
                }
                None => {
                    self.stats.underrun_samples.fetch_add(1, Ordering::Relaxed);
                    // Buffer underrun - output silence
                    *sample = 0.0;
                }
            }
        }
    }
}