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Provide helpers to get I/O buffers in OnAudioBuffer handlers #56

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Provide helpers to get I/O buffers in OnAudioBuffer handlers #56

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e885e27
just expose the raw pointer for now, see if that helps
baadc0de Apr 28, 2022
2696998
request 2 output channes.. will that work?
baadc0de Apr 28, 2022
69e534e
fix typo
baadc0de Apr 28, 2022
7f03693
access to input & output buffers
baadc0de Apr 28, 2022
3c3ef1a
Merge pull request #1 from helgoboss/master
baadc0de Sep 6, 2022
c63b539
Merge pull request #2 from helgoboss/master
baadc0de Oct 4, 2022
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33 changes: 31 additions & 2 deletions main/medium/src/audio_hook_register.rs
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Original file line number Diff line number Diff line change
@@ -1,11 +1,12 @@
use crate::{decode_user_data, encode_user_data, Hz};
use reaper_low::raw::audio_hook_register_t;
use reaper_low::raw::{audio_hook_register_t, ReaSample};
use reaper_low::{firewall, raw};

use std::fmt;
use std::fmt::Debug;
use std::os::raw::c_int;
use std::ptr::{null_mut, NonNull};
use std::slice::{from_raw_parts_mut};

/// Consumers need to implement this trait in order to be called back in the real-time audio thread.
///
Expand Down Expand Up @@ -58,7 +59,35 @@ impl AudioHookRegister {

/// Returns the current number of output channels.
pub fn output_nch(&self) -> u32 {
unsafe { self.0.as_ref() }.input_nch as u32
unsafe { self.0.as_ref() }.output_nch as u32
}

/// Get access to the underlying samples of an output channel
pub fn output_channel_samples(&self, ch: usize, args: &OnAudioBufferArgs) -> Option<&mut [ReaSample]> {
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One goal of the medium-level API is to not change the naming too much. It would be more in line with the other code to have only one method get_buffer() and introduce a BufferKind enum to distinguish between input and output buffer (built analogously to e.g. enum RecordArmMode in misc_enums.rs).

Another goal is to use consistent data types. Therefore I would prefer u32 as channel type instead of usize (input_nch() and output_nch() both return u32 values).

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Got it, will change accordingly.

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Instead of passing the OnAudioBufferArgs parameter, I think it would make sense to make get_buffer() a method of the OnAudioBufferArgs struct itself - because it contains a reference to the AudioHookRegister and therefore has all information necessary to implement the method.

The final signature in OnAudioBufferArgs would look like this:

pub fn get_buffer(&self, kind: BufferKind, ch: u32) -> Option<&mut [ReaSample]>

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I'll try it this way and update the PR.

unsafe {
if let Some(get_buffer) = self.0.as_ref().GetBuffer {
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As far as I know, GetBuffer is supposed to always return Some in the context in which we access it (as parameter of OnAudioBuffer). Therefore it would be consequent to panic here with expect() instead of returning None. This makes sure that if REAPER really returns a null pointer one day, we become aware of that change in the contract and can handle that accordingly (e.g. by adjusting the signature). That's at least the approach I have pursued so far in reaper-rs.

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Sounds good, I'll change it.

let ptr = get_buffer(true, ch as i32);
if ptr != null_mut() {
return Some(from_raw_parts_mut(ptr, args.len as usize));
}
}
}

None
}

/// Get access to the underlying samples of an input channel
pub fn input_channel_samples(&self, ch: usize, args: &OnAudioBufferArgs) -> Option<&mut [ReaSample]> {
unsafe {
if let Some(get_buffer) = self.0.as_ref().GetBuffer {
let ptr = get_buffer(false, ch as i32);
if ptr != null_mut() {
return Some(from_raw_parts_mut(ptr, args.len as usize));
}
}
}

None
}
}

Expand Down