max / audiofiles

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1	//! Trim operation: extract a frame range from sample data.
2
3	use crate::error::CoreError;
4
5	/// Trim samples to the given frame range (inclusive start, exclusive end).
6	///
7	/// Operates on interleaved sample data. `start_frame` and `end_frame` are in
8	/// frame units (not sample units), so channel count is accounted for.
9	pub fn apply_trim(
10	samples: &mut Vec<f32>,
11	channels: u16,
12	start_frame: usize,
13	end_frame: usize,
14	) -> Result<(), CoreError> {
15	let ch = channels as usize;
16	if ch == 0 {
17	return Err(CoreError::Internal("trim: channels must be > 0".to_string()));
18	}
19	let total_frames = samples.len() / ch;
20
21	if start_frame >= end_frame {
22	return Err(CoreError::Internal(
23	"trim: start_frame must be less than end_frame".to_string(),
24	));
25	}
26	if end_frame > total_frames {
27	return Err(CoreError::Internal(format!(
28	"trim: end_frame ({end_frame}) exceeds total frames ({total_frames})"
29	)));
30	}
31
32	let start_sample = start_frame * ch;
33	let end_sample = end_frame * ch;
34	samples.drain(end_sample..);
35	samples.drain(..start_sample);
36	Ok(())
37	}
38
39	#[cfg(test)]
40	mod tests {
41	use super::*;
42
43	#[test]
44	fn trim_mono() {
45	let mut samples = vec![0.1, 0.2, 0.3, 0.4, 0.5];
46	apply_trim(&mut samples, 1, 1, 4).unwrap();
47	assert_eq!(samples, vec![0.2, 0.3, 0.4]);
48	}
49
50	#[test]
51	fn trim_stereo() {
52	// 4 frames of stereo: [L0,R0, L1,R1, L2,R2, L3,R3]
53	let mut samples = vec![0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8];
54	apply_trim(&mut samples, 2, 1, 3).unwrap();
55	// Should keep frames 1 and 2: [L1,R1, L2,R2]
56	assert_eq!(samples, vec![0.3, 0.4, 0.5, 0.6]);
57	}
58
59	#[test]
60	fn trim_full_range_is_noop() {
61	let mut samples = vec![0.1, 0.2, 0.3];
62	apply_trim(&mut samples, 1, 0, 3).unwrap();
63	assert_eq!(samples, vec![0.1, 0.2, 0.3]);
64	}
65
66	#[test]
67	fn trim_invalid_range() {
68	let mut samples = vec![0.1, 0.2, 0.3];
69	assert!(apply_trim(&mut samples, 1, 2, 1).is_err());
70	}
71
72	#[test]
73	fn trim_out_of_bounds() {
74	let mut samples = vec![0.1, 0.2, 0.3];
75	assert!(apply_trim(&mut samples, 1, 0, 10).is_err());
76	}
77
78	#[test]
79	fn trim_single_frame() {
80	let mut samples = vec![0.1, 0.2, 0.3, 0.4, 0.5];
81	apply_trim(&mut samples, 1, 2, 3).unwrap();
82	assert_eq!(samples, vec![0.3]);
83	}
84	}
85