Fix level extents read as bytes, and extract the level geometry

A defect in the Phase 1 extractor, found by reading the data extent's contents:
level extents are declared in sector counts, the generic G/ pair table uses byte
counts, and level containers were being routed through the generic path. So
LEVEL0.WAD's data extent -- 6,484 sectors -- was taken as 6,484 bytes. Every
test still passed, because a truncated file is still a file.

The extent's own header gave it away: it declares an uncompressed total of
13,277,920 bytes, and 13,277,920 / 6,484 is 2047.7. A ratio landing on 2048 is
a unit error, not a compression ratio. Across 27 levels this had been discarding
roughly 300 MB of level content.

Level containers now go through the typed LevelHeader instead. Level 0 yields:

  data.bin         13,279,232   the data extent
  core_data.wad     9,738,678   the geometry, compressed
  core_data.bin    16,969,296   the geometry, decompressed
  core_index.bin       31,600   the geometry directory
  gameplay.bin       659,456
  sound_bank.bin   1,503,232

core_data is a WAD LZ77 stream -- the format already implemented for the game --
and it decompresses cleanly. The first real level content this project has
recovered.

New: LevelDataHeader parses the data extent's own header, a table of byte ranges
naming the level overlay executable, the geometry directory, the GS RAM image,
the HUD banks and the geometry. Note this is a third meaning for a "size" field
on the same disc, after sector counts in the level header and byte counts in the
generic table; all three are documented together in level-data.md so the next
parser does not rediscover this the hard way.

The geometry directory's offsets were checked against the geometry rather than
taken on trust: all twelve land inside the 16.9 MB of decompressed core_data,
which is what confirms the header is being read correctly. The class tables
themselves do not yet decode under the documented layout, and that is recorded
as open work in plan/level-assets.md rather than papered over.

75 unit tests, 9 integration tests against the real disc. Hash table regenerated
at 5,159 files and 5,671,915,799 bytes -- hashes only, no content. Extraction
now writes to ~/Documents/gc-extracted rather than /tmp, which is 16 GB and did
not have room for a 5.3 GB output.

crates/gc-extract/data/gc-files.tsv

@@ -2498,149 +2498,173 @@ e5f948087847e7d4a98b2a069599ea39b32fb996	14	hud/0776.bin
 bf9fdc4cdb7924599d6eeaf380e6198542390245	15	hud/0778.bin
 c25009da53bbe1163360026f14958e95baf0096e	15	hud/0779.bin
 e1baca5f8178da95e7dc496305a36f984be542aa	15	hud/0780.bin
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+84723c80beedd7e55143a424a1b2f6255a200ab0	1654784	level16/sound_bank.bin
+485e5343a6f146179b319fb7d76388eee6e21276	20920320	level17/core_data.bin
+fc90583b7560be17115f57c8ecf6fc14ec2e59d8	10922651	level17/core_data.wad
+5f9496629cf8c32071c2d4a125fee1ca7b89f73e	35856	level17/core_index.bin
+d7669eec9eb3cf36bf4f649333ae79864c1a7043	14575616	level17/data.bin
+10a5f5e2862f7364a9bbe886dadb9ebca8ab0381	796672	level17/gameplay.bin
+37c76a37d9e3cbbed6dfc324b0b90d3498ecb0e7	1347584	level17/sound_bank.bin
+f9240e2bd6406f206e155b09cc5c914b6574e41e	20268640	level18/core_data.bin
+f44add8374224a84070995ecb4b1be8cfb58aa9f	11721139	level18/core_data.wad
+6ab43f9167d67246e18394eef5b732589fcaff66	33088	level18/core_index.bin
+d0f931677cb6589a564937c3d15c13344b923969	15501312	level18/data.bin
+2adc53f721fca95dd1012994d243e0704edd034c	675840	level18/gameplay.bin
+b26483cc29ecb8b6d2c71919ff7cd56b09522bc1	1492992	level18/sound_bank.bin
+0918d824b72b892a24f46108bbc60f6e875236f6	20233504	level19/core_data.bin
+b79df8e074db7d3c75bc2b3b9c2a4de61e5dd9cd	11797811	level19/core_data.wad
+b0ea377a39a616dbd2b15224a9996925c7b28f4d	31536	level19/core_index.bin
+3218aa99e3ea4e9f4a050a5117413261defded4e	15386624	level19/data.bin
+8700a93086450328f2693b553e1df447a79fcd83	825344	level19/gameplay.bin
+877ca7fb8e80d810d6c37fb993795aa10b5b1033	47104	level19/occlusion.bin
+8298f799c394542e912e41ff3321ee55c70e0c8f	1570816	level19/sound_bank.bin
+6d56189ad74f04d366116b736ab12888154de833	20209408	level2/core_data.bin
+f0eb5c033e84092748cf3457818b0d4c85da7a0a	11372886	level2/core_data.wad
+73411362c1cfa8faec733705d93e953f1381ef30	33808	level2/core_index.bin
+14c7c5cd788c0bebe531029bc1f8f8d570ea1771	15089664	level2/data.bin
+bfc9f6bc73edfa7deb46505f187c274dcf7b863a	790528	level2/gameplay.bin
+01c7d4c7b0ecb44a91694ffde796ff941057191a	28672	level2/occlusion.bin
+bce56b3b899d72c5d89f612bd70447f066c10757	1118208	level2/sound_bank.bin
+daf162b58756e2661f3ec891c8736a1611b4dc52	19637472	level20/core_data.bin
+7e7203ac3a2dbf578546573a34fa6dce4c336d35	10449039	level20/core_data.wad
+b12e8599d211addc85cbe138e58157ade380a575	37360	level20/core_index.bin
+640e6a62f3795bb285663364c2929f4640dacf33	14237696	level20/data.bin
+7368af71bc6c070fc6422fd69a354b2f3518ed2b	833536	level20/gameplay.bin
+61ae37031d1df746bffb4a0bddeaee85558c894e	36864	level20/occlusion.bin
+abce77e8841c0ed0fa006db81840b35ea4c75afd	1335296	level20/sound_bank.bin
+5e850ab42d2dc3e8fa1f9ae74d401be1658c9ba7	14483120	level21/core_data.bin
+f10321014e7ccd61a65f294baefaf35875d6294b	8178784	level21/core_data.wad
+728b90cdbb44f1b94c140d82fc03268ca54408ac	25456	level21/core_index.bin
+4a3ebd058fe62df17ed4d74fe190442ff2993474	11722752	level21/data.bin
+6c2b9faaef23c142a61316190852251404734c39	448512	level21/gameplay.bin
+8fbcb2360d5244e92bfd7c2ccd453eec44cd042b	1167360	level21/sound_bank.bin
+7b0733a07f28e7d7cf5d8a19b1058a98a5563c9f	14288048	level22/core_data.bin
+34a2d1ac57f13cacdf46cd7d73f356951f87dd43	8186976	level22/core_data.wad
+edb2fd7c72d0a517613fd813429aa9036e2eb509	25152	level22/core_index.bin
+3519cac29e6371802b40e3d8234ef7064abee336	11683840	level22/data.bin
+a8760bb193082c5e85faeb5f799ab8585f366805	557056	level22/gameplay.bin
+dba3b2b5856efbd28a8aeaa15fbee6f4fb479895	1363968	level22/sound_bank.bin
+c6b6f4087f4c9cd374a587b13777f9575953838a	12647664	level23/core_data.bin
+dbdca886def506bd2e6fd189c0fc4ca8d2834b97	6900832	level23/core_data.wad
+ed196a1541e056da4433d366c1a096143ea87ca0	23024	level23/core_index.bin
+9a26194ba7d5930279a62113b1377ffeb1294269	10414080	level23/data.bin
+336b3c864d1aa317003499e7d1d2d5a8cee13d58	505856	level23/gameplay.bin
+e254322f1d87d2650c21ec2c118546df1a56d9e8	1675264	level23/sound_bank.bin
+508808939296de54fee8928824bdcc6d37204d01	6386608	level24/core_data.bin
+c44701fc0a229dc8071a30594231d5edfb6b4119	3805312	level24/core_data.wad
+c526f84012360c24a07e4bbd6823dd18ce8b3181	16608	level24/core_index.bin
+f38883faa65e74f67a44da4a55b9b476848d7cae	6981632	level24/data.bin
+3bf88b1d1c455ab90bbacc3270a3f54c94b900ef	937984	level24/sound_bank.bin
+c81ea8c485748fccec6619bacc75afe8ce2f7e20	5898736	level25/core_data.bin
+80d763434b9dda1224c446de67e4907cfbdcfbe7	3513706	level25/core_data.wad
+c493407fb493ff359e90d1bdfc1b379a2a6c540a	16592	level25/core_index.bin
+e57a615ccce4afd0a3de13f638ecaa19f88d0789	6852608	level25/data.bin
+e9d246c13a7198b42a71f081d767b9e9598d01a1	1370112	level25/sound_bank.bin
+948974c4fd10e7ca7ad1a362af9cb46aa6c81773	9530880	level26/core_data.bin
+6140efd9a7ebbcd81bfddf1ce0a5395ffb136d2e	5894651	level26/core_data.wad
+d71c13701f26cd0a4bbcb9508fb0387ba54d2d62	20704	level26/core_index.bin
+4fdd7d88a5d3db63418c968f8a5f53ac370b86be	9224192	level26/data.bin
+0d63ad0bc2edcd958b1c7dbec303c256ed8850e1	679936	level26/gameplay.bin
+8f6a74b8008a9ebc9e92853d0b339a8e725c9992	1073152	level26/sound_bank.bin
+f5d3cd4480fe6a52a019d04401a360018b279b81	21148480	level3/core_data.bin
+690209848c64647194548d5e81f329d471392a8e	11383592	level3/core_data.wad
+351819059a5b74d8e17f50ee87974e5c30504c3e	37568	level3/core_index.bin
+eb8366046b5643cc54d42d800c06bf66ccd4ef36	15157248	level3/data.bin
+55cc4acecac6ba19232e6505fdc06a22b0633a45	749568	level3/gameplay.bin
+d986825dfc2bed713eb9699504536346658aaa3f	1705984	level3/sound_bank.bin
+f8c0aa3778b5bcb1995e516045b28ca6ac35502f	21107088	level4/core_data.bin
+ec75f324670188af581c4fceaa4cb285353f95b8	12171908	level4/core_data.wad
+cc4997acbdc0a6ac85d427227c04e6af6e34cd46	38080	level4/core_index.bin
+67a114e12f840f4c01e3f96b48c504f93b839b03	15998976	level4/data.bin
+eeee7ebf8d9980f9afc6d9c2bc2156bcca015ddd	960512	level4/gameplay.bin
+fed269c2d706a2ba11cab965e090fd41d434055c	49152	level4/occlusion.bin
+bdd446767b1a84043d65ff968278cd2d5808705a	1236992	level4/sound_bank.bin
+cb07a102a92b887d06d9314c07ce1db50e14c1fb	16715440	level5/core_data.bin
+e5cc08e39cb6883b391605bdcff8ba3bb8423699	11205994	level5/core_data.wad
+d41e06bc7086ed6876bef602420cca8d52492b1e	23536	level5/core_index.bin
+b241ea9d8fe18dd5bdbc8a4255ba8450a66b3c6a	14772224	level5/data.bin
+c71539e0f8b0e2d666d9382475539c7a590fee04	514048	level5/gameplay.bin
+5c2fd4470dd8c892af7686770af8cf3e2396373c	1390592	level5/sound_bank.bin
+8ea18c5a51e4ae07ca56d92d65ffde60f4bcce12	20935696	level6/core_data.bin
+f2962a73cfb15ab1bef23253d863d2433b264383	12810673	level6/core_data.wad
+29284ba33a151cb45df0b4d074fa7ccc9d2c0667	38080	level6/core_index.bin
+ccb0a4e8c51be81fbcd8ad325ab8d521bbdb7604	16777216	level6/data.bin
+b9ff3b4b8fb6308aac7f5ddba1c4b1099d484dd5	929792	level6/gameplay.bin
+82fcce964396eb508768933d092a557bc1b05c89	1669120	level6/sound_bank.bin
+6692290d78706a2b92cba541264ddea9a764e2f2	18209392	level7/core_data.bin
+f1cae801f1050c57258f93a7035148b3094ece03	10780010	level7/core_data.wad
+79e3957d149ce3b00f713eb1757fec89d7db86c4	32736	level7/core_index.bin
+9b18673cac7d7d6c3d64bebca909f3bb76ff9f39	14366720	level7/data.bin
+bc8f542a56d4795c77774201903e25b01962c039	636928	level7/gameplay.bin
+e02d1b0d2339d72ed5d07abfe105f41e2288f59f	16384	level7/occlusion.bin
+8e07c803b709100023c3b44c8842eec9b8f49898	1556480	level7/sound_bank.bin
+264a306c3a83b9137d9753b282e9c773cd386713	21086224	level8/core_data.bin
+0a96094edd63dc4dd940894b007f85b21874cfeb	9700660	level8/core_data.wad
+8d1b6c3a05e9b2140c056df3e538ed537b9d3a33	30624	level8/core_index.bin
+ee6f0ca2c15e1e0828d63547a8c19d2c45b8c0e2	13375488	level8/data.bin
+ff4c7dd1924165ddc7dbb9494a166eb3e140c95c	899072	level8/gameplay.bin
+afeb717c151befdabfcf6297b0dbb1772ac13fdb	22528	level8/occlusion.bin
+1f65f6b44e4e4a146aaac3d63b7f459657de0010	1593344	level8/sound_bank.bin
+fd39207fd776cb3ba6b8d5f6d3b10d61610c5e49	21592016	level9/core_data.bin
+314f79d0a1d9ae630d67da9e3259a658c3c5642b	12578171	level9/core_data.wad
+ffed974844aa0bef984bc33c86ff6757e0f9c5bc	34976	level9/core_index.bin
+db530147f5d900e5a85294070a0a5e707c086213	16232448	level9/data.bin
+3839c295b0408460f50032ff166cac27c0bdf411	864256	level9/gameplay.bin
+bc38b5983d8717ff4c7a35fac3cd1042ef7bd675	1697792	level9/sound_bank.bin
 f666c702e75052034d72125db6bd5d6821ac8379	9	misc/0000.bin
 2af38bb5b2fe77af4ed2a6079ebe5857247082a5	367	misc/0001.bin
 ccc75282e2a72f7adbe1ba7bee744c0799f41b04	62	misc/0002.bin

crates/gc-extract/src/main.rs

@@ -22,6 +22,9 @@ fn main() -> ExitCode {
         Some("identify") => run_identify(&args[1..]),
         Some("unpack") => run_unpack(&args[1..]),
         Some("verify") => run_verify(&args[1..]),
+        // Scratch helper used while reversing the level formats: decompress a
+        // byte range of an already-unpacked file with the WAD decoder.
+        Some("wad") => run_wad(&args[1..]),
         Some("--help") | Some("-h") | Some("help") | None => {
             usage();
             ExitCode::SUCCESS
@@ -187,6 +190,56 @@ fn run_unpack(args: &[String]) -> ExitCode {
     }
 }
 
+fn run_wad(args: &[String]) -> ExitCode {
+    if args.len() < 4 {
+        eprintln!("usage: gc-extract wad <file> <offset> <size> <out>");
+        return ExitCode::FAILURE;
+    }
+    let data = match std::fs::read(&args[0]) {
+        Ok(d) => d,
+        Err(e) => {
+            eprintln!("error: {}", e);
+            return ExitCode::FAILURE;
+        }
+    };
+    let off: usize = match args[1].parse() {
+        Ok(v) => v,
+        Err(e) => {
+            eprintln!("error: bad offset: {e}");
+            return ExitCode::FAILURE;
+        }
+    };
+    let sz: usize = match args[2].parse() {
+        Ok(v) => v,
+        Err(e) => {
+            eprintln!("error: bad size: {e}");
+            return ExitCode::FAILURE;
+        }
+    };
+    if off + sz > data.len() {
+        eprintln!(
+            "error: range {off}..{} is outside the {} byte file",
+            off + sz,
+            data.len()
+        );
+        return ExitCode::FAILURE;
+    }
+    match gc_formats::wad::decompress(&data[off..off + sz]) {
+        Ok(out) => {
+            if let Err(e) = std::fs::write(&args[3], &out) {
+                eprintln!("error: cannot write {}: {e}", args[3]);
+                return ExitCode::FAILURE;
+            }
+            println!("{} bytes -> {} bytes -> {}", sz, out.len(), args[3]);
+            ExitCode::SUCCESS
+        }
+        Err(e) => {
+            eprintln!("error: {e}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
 fn run_verify(args: &[String]) -> ExitCode {
     if args.len() < 2 {
         eprintln!("usage: gc-extract verify <out-dir> <table.tsv>");

crates/gc-extract/src/unpack.rs

@@ -13,6 +13,8 @@ use std::path::{Path, PathBuf};
 
 use gc_formats::global_wad::{GlobalWad, RangeKind};
 use gc_formats::iso9660::IsoImage;
+use gc_formats::level_data::{LevelDataHeader, LevelDataPart};
+use gc_formats::level_wad::LevelHeader;
 
 /// One unpacked asset, with the identity we record for verification.
 pub struct Extracted {
@@ -76,6 +78,106 @@ pub fn unpack(iso_path: &Path, out_dir: &Path) -> Result<Vec<Extracted>, String>
             continue;
         }
 
+        // Level containers have a typed header whose extents use sector counts,
+        // not the byte counts of the generic `G/` pair table. Reading them
+        // through the generic path would take a 6,484-sector extent as 6,484
+        // bytes and silently lose 13 MB of every level, so they go through the
+        // typed parser.
+        if stem.starts_with("level")
+            && stem
+                .trim_start_matches("level")
+                .chars()
+                .all(|c| c.is_ascii_digit())
+        {
+            match LevelHeader::parse(&raw) {
+                Ok(header) => {
+                    let mut parts = 0usize;
+                    for (part, range) in header.ordered_extents() {
+                        let Some(offset) = range.byte_offset() else {
+                            continue;
+                        };
+                        let len = range.byte_len() as usize;
+                        if offset + len as u64 > raw.len() as u64 {
+                            eprintln!(
+                                "  {stem}/{}: runs past the end of the container; skipped",
+                                part.name()
+                            );
+                            continue;
+                        }
+                        write_file(
+                            out_dir,
+                            &format!("{stem}/{}.bin", part.name()),
+                            &raw[offset as usize..offset as usize + len],
+                            &mut written,
+                        );
+                        parts += 1;
+                    }
+                    // The `data` extent is itself a container of byte ranges.
+                    // Split out the geometry directory and the geometry, so the
+                    // latter is usable without re-deriving the layout later.
+                    // `data_extent` is the `data` slice; `raw` is the whole
+                    // level container and its offsets are unrelated.
+                    let data_extent: &[u8] = &raw[header.data.offset as usize * 2048
+                        ..(header.data.offset as usize + header.data.size as usize) * 2048];
+                    match LevelDataHeader::parse(data_extent) {
+                        Ok(data_header) => {
+                            let core = data_header.part(LevelDataPart::CoreData);
+                            let index = data_header.part(LevelDataPart::CoreIndex);
+                            if let Ok(bytes) = core.slice(data_extent, data_extent.len()) {
+                                // `core_data` is a WAD stream: keep both the
+                                // compressed original and the decoded form,
+                                // because the hash table covers the original.
+                                write_file(
+                                    out_dir,
+                                    &format!("{stem}/core_data.wad"),
+                                    bytes,
+                                    &mut written,
+                                );
+                                match gc_formats::wad::decompress(bytes) {
+                                    Ok(decoded) => {
+                                        write_file(
+                                            out_dir,
+                                            &format!("{stem}/core_data.bin"),
+                                            &decoded,
+                                            &mut written,
+                                        );
+                                    }
+                                    Err(e) => eprintln!(
+                                        "  {stem}: core_data did not decompress ({e}); the \
+                                         compressed form was kept"
+                                    ),
+                                }
+                                parts += 1;
+                            }
+                            if let Ok(bytes) = index.slice(data_extent, data_extent.len()) {
+                                write_file(
+                                    out_dir,
+                                    &format!("{stem}/core_index.bin"),
+                                    bytes,
+                                    &mut written,
+                                );
+                                parts += 1;
+                            }
+                        }
+                        Err(e) => eprintln!("  {stem}: data extent header did not parse: {e}"),
+                    }
+
+                    println!(
+                        "  {:<16} {} bytes, level id {} -> {} parts",
+                        stem,
+                        raw.len(),
+                        header.id,
+                        parts
+                    );
+                }
+                Err(e) => {
+                    skipped.push((relative.clone(), e.to_string()));
+                    write_file(out_dir, &relative, &raw, &mut written);
+                }
+            }
+            continue;
+        }
+
         let container = match GlobalWad::parse_with(&raw, RangeKind::for_container(&relative)) {
             Ok(c) => c,
             Err(e) => {

crates/gc-extract/tests/disc.rs

@@ -306,3 +306,82 @@ fn level_extent_sizes_are_sector_counts() {
     // Read as bytes, 734 would be under four sectors and the tiling would break.
     assert_eq!(h.sound_bank.byte_len(), 734 * 2048);
 }
+
+/// The level data extent is a container of byte ranges. Its header locates the
+/// geometry index and the compressed geometry, and every range must lie inside
+/// the extent on all 27 levels.
+#[test]
+fn level_data_extents_are_in_range() {
+    let path = require_disc!();
+    let iso = gc_formats::iso9660::IsoImage::open(&path).expect("ISO should open");
+
+    let mut checked = 0;
+    for entry in iso.files.iter().filter(|e| e.name.starts_with("G/LEVEL")) {
+        let raw =
+            gc_formats::iso9660::read_at(&path, entry.lba, entry.size).expect("read container");
+        let lh = gc_formats::level_wad::LevelHeader::parse(&raw).expect("level header");
+        let data = lh.data;
+        let Some(offset) = data.byte_offset() else {
+            continue;
+        };
+        let len = data.byte_len() as usize;
+        let extent = &raw[offset as usize..offset as usize + len];
+
+        let dh = gc_formats::level_data::LevelDataHeader::parse(extent)
+            .unwrap_or_else(|e| panic!("{}: data extent header: {e}", entry.name));
+
+        for (part, r) in dh.present_parts() {
+            assert!(
+                r.end() <= extent.len() as u64,
+                "{}: {part:?} ends at {} but the extent is {} bytes",
+                entry.name,
+                r.end(),
+                extent.len()
+            );
+        }
+
+        // The geometry is the big one and must be substantial.
+        assert!(
+            dh.core_data.size > 1_000_000,
+            "{}: core_data is only {} bytes",
+            entry.name,
+            dh.core_data.size
+        );
+        checked += 1;
+    }
+    assert_eq!(checked, 27, "expected 27 level containers");
+}
+
+/// The geometry must decompress. This is the first test that touches real level
+/// content rather than headers.
+#[test]
+fn level_geometry_decompresses() {
+    let path = require_disc!();
+    let iso = gc_formats::iso9660::IsoImage::open(&path).expect("ISO should open");
+    let entry = iso.find("G/LEVEL0.WAD").expect("level 0");
+
+    let raw = gc_formats::iso9660::read_at(&path, entry.lba, entry.size).expect("read container");
+    let lh = gc_formats::level_wad::LevelHeader::parse(&raw).expect("level header");
+    let data = lh.data;
+    let extent = &raw[data.byte_offset().unwrap() as usize
+        ..(data.byte_offset().unwrap() + data.byte_len()) as usize];
+
+    let dh = gc_formats::level_data::LevelDataHeader::parse(extent).expect("data header");
+    let core = dh
+        .core_data
+        .slice(extent, extent.len())
+        .expect("core_data slice");
+
+    assert!(
+        gc_formats::wad::is_wad(core),
+        "core_data should start with the WAD magic"
+    );
+
+    let decoded = gc_formats::wad::decompress(core).expect("core_data should decompress");
+    assert!(
+        decoded.len() > core.len(),
+        "decompressed geometry ({}) should exceed the compressed size ({})",
+        decoded.len(),
+        core.len()
+    );
+}