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goujichengandDeepSeek V3.2
ab438b05ca
A grid thumbnail and a loupe preview of an unedited raw show the camera's embedded JPEG, which sits near the start of the file — for a 24 MP Fuji RAF, 5.6 MB of a 56 MB file (measured: DSCF9492.RAF). The loader read the file whole and threw the sensor data away, so every preview paid for 50 MB nobody looked at. On a local disk that is merely wasteful; on a network share, where photographers keep libraries, it is the wait: the same preview took 10 s over a GVFS/SMB Wi-Fi share against 0.96 s after this change. - `lightcraft_raw::bounded_preview(bytes)` locates the preview from the header alone and reports its byte range; `embedded_preview_from_range` extracts it, byte for byte what `embedded_preview` returns for the whole file (the pointer is read from the RAF header's fixed u32s at 84/88). - `engine::files::preview_window` reads a 4 KiB prefix, then — because the container reader clamps a slice to the buffer it was given, so a short prefix reports a plausible but truncated 3948 bytes — re-reads exactly the extent the header declares, and takes the window out of the prefix rather than reading those bytes twice. `LIGHTCRAFT_PROFILE=1` prints what each preview cost. - Formats whose preview only the whole file reveals (CR3 boxes, TIFF pointer tags past the prefix, CRW/MRW/X3F scans), a lying pointer, a short read and a file that changes underneath us all fall back to the whole-file path: a damaged header never costs the user their preview. - Tests: the header range matches `embedded_preview` byte for byte, with a clamped prefix, a padded extent, a late pointer, a lying pointer and a non-JPEG window covered; on a synthetic RAF with a 200 KB tail the quick path and the whole-file path produce identical pixels and the read stays under half the file; `crates/engine/tests/preview_read.rs` (opt-in, `#[ignore]`) measures a real file on a share. No raw fixture is committed. - `docs/raw-preview-reads.md` records the mechanism and the numbers. Co-Authored-By: DeepSeek V3.2 <noreply@deepseek.com>
43 lines
2.0 KiB
Rust
43 lines
2.0 KiB
Rust
//! Opt-in test of the embedded-preview read path on a **real file the user has** — typically one on a
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//! network share, which is where reading only the header instead of the whole raw matters:
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//!
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//! LC_PREVIEW_RAW="/run/user/1000/gvfs/smb-share:.../DSCF0001.RAF" \
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//! cargo test --release -p lightcraft-engine --test preview_read -- --ignored --nocapture
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//!
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//! It reports what the preview cost and fails when the read is not the small part of the file the
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//! header path promises. Skipped without `LC_PREVIEW_RAW` (there is no committed raw fixture: media
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//! is never committed, see AGENTS.md).
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use std::time::Instant;
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#[test]
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#[ignore = "needs LC_PREVIEW_RAW pointing at a real raw file"]
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fn a_preview_reads_only_the_header_and_the_preview() {
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let Ok(path) = std::env::var("LC_PREVIEW_RAW") else {
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eprintln!("skipped: set LC_PREVIEW_RAW=<path to a raw file>");
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return;
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};
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let file_len = std::fs::metadata(&path).expect("the file exists").len();
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assert!(file_len > 0, "empty file");
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let started = Instant::now();
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let window =
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lightcraft_engine::files::preview_window(&path).expect("the file reads").expect("it carries an embedded preview the header can point at");
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let elapsed = started.elapsed();
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let (_, preview, read) = window;
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let frac = read.fraction();
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println!(
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"preview of {path}\n read {} of {} bytes ({:.1} %) in {:.2} s{}",
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read.read,
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read.total,
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frac * 100.0,
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elapsed.as_secs_f64(),
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if read.header_path { " [header path]" } else { " [whole file]" }
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);
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assert!(read.header_path, "the header path must answer for a raw whose pointer is in its header");
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assert_eq!(read.total, file_len, "the report covers the whole file");
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assert!(frac < 0.5, "a preview must not cost most of the file: read {} of {} bytes", read.read, read.total);
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assert!(preview.starts_with(&[0xff, 0xd8]), "the preview bytes are a JPEG: {:?}", preview.get(..4));
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}
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