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Cleanup unsafety using bytemuck

pull/83/head
Andrea Ciliberti 2 years ago
parent
commit
8a890392a3
  1. 1
      ctru-rs/Cargo.toml
  2. 13
      ctru-rs/examples/audio-filters.rs

1
ctru-rs/Cargo.toml

@ -30,6 +30,7 @@ futures = "0.3" @@ -30,6 +30,7 @@ futures = "0.3"
time = "0.3.7"
tokio = { version = "1.16", features = ["rt", "time", "sync", "macros"] }
cfg-if = "1.0.0"
bytemuck = "1.12.3"
[features]
default = ["romfs", "big-stack"]

13
ctru-rs/examples/audio-filters.rs

@ -17,21 +17,20 @@ const AUDIO_WAVE_LENGTH: usize = SAMPLES_PER_BUF * BYTES_PER_SAMPLE; @@ -17,21 +17,20 @@ const AUDIO_WAVE_LENGTH: usize = SAMPLES_PER_BUF * BYTES_PER_SAMPLE;
// Note Frequencies
const NOTEFREQ: [f32; 7] = [220., 440., 880., 1760., 3520., 7040., 14080.];
// audioBuffer is Stereo PCM16
// The audio format is Stereo PCM16
// As such, a sample is made up of 2 "Mono" samples (2 * i16 = u32), one for each channel (left and right)
fn fill_buffer(audio_data: &mut [u8], frequency: f32) {
let formatted_data = audio_data.chunks_exact_mut(4);
let formatted_data = bytemuck::cast_slice_mut::<_, [i16; 2]>(audio_data);
for (i, chunk) in formatted_data.enumerate() {
for (i, chunk) in formatted_data.iter_mut().enumerate() {
// This is a simple sine wave, with a frequency of `frequency` Hz, and an amplitude 30% of maximum.
let sample: f32 = (frequency * (i as f32 / SAMPLE_RATE as f32) * 2. * PI).sin();
let amplitude = 0.3 * i16::MAX as f32;
// This operation is safe, since we are writing to a slice of exactly 32 bits
let chunk_ptr: &mut [i16; 2] = unsafe { &mut *(chunk.as_mut_ptr() as *mut [i16; 2]) };
let result = (sample * amplitude) as i16;
// Stereo samples are interleaved: left and right channels.
chunk_ptr[0] = (sample * amplitude) as i16;
chunk_ptr[1] = (sample * amplitude) as i16;
*chunk = [result, result];
}
}

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