Disc hashing (HashDisc.cs + CdReader.cs — port of hash_disc.c + cdreader.c)

Disc hashing reads files inside an optical disc image: track selection, sector math, ISO9660 lookups, and console-specific boot-file rules. The default CD reader (CdReader.cs) provides the .cue/.gdi/.bin parsing and the track abstraction.

Track selection

The engine opens tracks by logical selection, mirroring RC_HASH_CDTRACK_*:

Selection	Meaning
FIRST_DATA	first track whose mode is MODE*
LAST	last track in the table
LARGEST	largest data track (by file size)
FIRST_OF_SECOND_SESSION	first track of session 2 (Jaguar CD)

Sector math (the part most likely to surprise)

• MSF ↔ LBA: the C computes msf_to_lba = (m*60+s)*75 + f − 150 (LBA 0 = MSF 00:02:00). Raw 2352-byte images must carry real MSF in the sector headers — a synthetic image whose sector 0 says 00:00:00 yields track_first_sector = −150, which breaks absolute-LBA reads.
• Cue INDEX 01 00:00:00 parses to sector offset 0 (the cue parser does not subtract 150); real-world cues use 00:02:00.
• Sector sizes: MODE1/2048 (2048, header 0), MODE2/2336 (2336, header 8), MODE1/2352 (2352, header 16), MODE2/2352 (2352, header 24 — includes the 8-byte XA subheader), AUDIO (2352, header 0, raw stream).
• Sector-size probe (cdreader_determine_sector_size): reads 32 bytes at (16 + pregap) · 2352 looking for the 12-byte sync pattern, then CD001 at +25 (XA) / +17 / +1, falling back to file-size heuristics.

ISO9660 mini-parser

HashDisc.CdFindFileSector is the port of rc_cd_find_file_sector:

• reads the PVD at LBA 16 (256 bytes);
• root directory extent + size from the PVD record;
• walks directory records (name, version ;1 handling, case-insensitive compare), recursing through subdirectories;
• returns the file's sector and size for rc_hash_cd_file.

The walker is deliberately tolerant (it does not require spec-perfect directory records) — this is the default backend. The alternative backend is FileSystemResolver (VideoGameFileSystemParser), which is spec-strict and CHD-bound (see the porting guide).

Per-console rules

Console	Algorithm
PSX	first data track; read SYSTEM.CNF, parse BOOT=cdrom:\..., MD5 of the boot file with the exe name prefixed; fallback to PSX.EXE
PS2	BOOT2 = cdrom0:\... via ISO9660; MD5 of the ELF (with ELF marker check)
PSP	PSP_GAME\PARAM.SFO + PSP_GAME\SYSDIR\EBOOT.BIN (MD5 of both); .pbp = whole-file
Saturn / Sega CD	first 512 bytes of sector 0, magic-checked (SEGA SEGASATURN / SEGADISCSYSTEM)
PCE-CD	first data track, header check PC Engine CD-ROM SYSTEM
PC-FX	largest data track, sector-0 marker check
3DO	OperaFS: LAUNCHME lookup (case-insensitive), volume header included in the hash
Jaguar CD	second-session first track; ATARI APPROVED DATA HEADER scan, byteswap variants, homebrew KART-track logic
Neo Geo CD	IPL.TXT contents lookup (lowercase variant), hash the listed executables
Dreamcast	OperaFS IP.BIN + largest track rules
GameCube	0xC2339F3D magic at 0x1C, then disc-partition reading
Wii	disc partition path vs WiiWare TMD/content

rc_hash_cd_file

The shared helper streams a file region (sector + size) into the MD5 across sector boundaries, handling 2352/2048 conversions and the 64 MiB cap — ported 1:1.

12.4.0 changes ported in Part II

• 3DO short-read guard: the OperaFS magic is only checked when the sector read returned ≥ 132 bytes (rc_hash_3do).
• GDI filename bounds: an unterminated quoted filename errors with Quoted string without closing quote; filenames ≥ 256 bytes error with Cannot copy %u byte filename into %u byte buffer (previously an unbounded copy).
• Wii/WiiWare malloc-failure checks are N/A in managed code (noted in comments).