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Valentin KleinandClaude Opus 5.5
59820ecafb
Limits::max_alloc budgets the decoded pixel buffer, but the PNM decoder collected one u32 per sample first (4x an 8-bit image, plus a u16 copy for 16-bit) and PFM built a Vec<f32> beside the output bytes. Samples are now rescaled and written straight into the native-endian output buffer (reserved fallibly), so the only header-sized allocation is the one Limits::check already charged. Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
37 lines
1.7 KiB
Rust
37 lines
1.7 KiB
Rust
//! #2938: `Limits::max_alloc` budgets the decoded pixel buffer, so the PNM decoder must not build a
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//! wider scratch copy (it used to collect one `u32` per sample, four times an 8-bit image) next to it.
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//!
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//! This file holds a single test so it runs in its own process: it reads the process's peak RSS
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//! (`VmHWM`, Linux only) and nothing else may allocate meanwhile.
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#[cfg(target_os = "linux")]
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fn peak_rss_bytes() -> Option<u64> {
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let status = std::fs::read_to_string("/proc/self/status").ok()?;
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let line = status.lines().find(|l| l.starts_with("VmHWM:"))?;
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let kib: u64 = line.trim_start_matches("VmHWM:").trim().trim_end_matches("kB").trim().parse().ok()?;
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Some(kib * 1024)
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}
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#[cfg(target_os = "linux")]
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#[test]
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fn pnm_decode_peak_memory_stays_near_the_output_size() {
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use photocraft_codecs::*;
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const SIDE: u32 = 4096; // 16 MiB of 8-bit gray output
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let out_bytes = (SIDE * SIDE) as u64;
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let mut file = format!("P5\n{SIDE} {SIDE}\n255\n").into_bytes();
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file.extend((0..out_bytes).map(|i| (i % 251) as u8));
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// Writing 5 resets the peak RSS to the current RSS; skip where the kernel doesn't allow it.
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if std::fs::write("/proc/self/clear_refs", "5").is_err() {
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return;
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}
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let Some(before) = peak_rss_bytes() else { return };
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let img = decode(&file).unwrap();
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let after = peak_rss_bytes().unwrap();
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assert_eq!(img.data().len() as u64, out_bytes);
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assert_eq!(img.data()[300], (300 % 251) as u8);
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// The output buffer plus slack; a `u32`-per-sample scratch copy alone would be 4× it.
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let grown = after.saturating_sub(before);
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assert!(grown < 2 * out_bytes, "decoding a {out_bytes} byte image raised peak RSS by {grown} bytes");
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}
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