BFL containers

Almost every data file of the game (.bfl, but also the loose .c3d, .cin, .rpl and .tga files) uses the same two wrapper layers, and most .bfl files are archives of named member files. Reference reader: tools/bfl.py (list, or extract with an output directory).

Layers

Layer	Detection	Content
gzip	bytes 1f 8b	RFC 1952 gzip, one member, deflate, no file name. The game reads every file through zlib 1.1.3's gzopen/gzread, which passes non-gzip files through unchanged, so the gzip layer is optional.
CMPR	ASCII CMPR	u32 payload size (little endian), then exactly that many payload bytes.
payload		One file, or an archive (below).

File_Load 0x4aa220 opens the file with gzopen, reads 8 bytes, and if they are CMPR + size, allocates the size and reads the payload. Otherwise it closes the gz stream and reads the file as it is with ReadFile. On a failed open it shows the "Make sure the CMR2 CD is in the CD-ROM drive" dialog and retries.

Every file on the disc except Sounds/surface.bfl (a plain RIFF WAVE) and the .adp music has both layers.

Archive

An archive payload is the member files back to back, followed by a directory and a final u32:

member data ...                    (each member starts 4-byte aligned in practice)
directory:
  repeat:
    u32 size
    u32 offset                     (from the start of the payload)
    u32 name_length                (without terminator)
    char name[name_length]         (padded with zeros to a multiple of 4)
u32 directory_offset               (last 4 bytes of the payload)

The directory runs from directory_offset to payload_size - 4. There is no entry count. Names are lower case, without directories (move.wav, t_1a.dds, fra02.tre).

Bfl_Find 0x4a9c70 lower-cases the requested name and walks the directory linearly with a byte compare; the first match wins and the size is returned through an out parameter. Bfl_FindFile 0x4a9df0 strips the directory part of the requested path first (after the last / or \), so the game can ask for \NEWIMAGE\Exhaust\exhst02.tga and get the member exhst02.tga.

Texture lookup

Bfl_FindTexture 0x4a9e60 strips the extension and tries <name>.dds, then <name>.tga. Archives therefore come in pairs: one with uncompressed TGA members and a C variant with DXT5 DDS members of the same names (res640.bfl / res640C.bfl, Com640.bfl / Com640C.bfl, ukDay1.bfl / ukDay1C.bfl). Which one is mounted depends on the texture-compression setting (FUN_004a9700, true when the device reports DXT support and the option is on). Track textures (<country>hit.bfl, <country>lot.bfl) and the car a sets exist only as DXT5, so the port needs a DXT decoder whatever the setting.

Archive slots

Mounted archives live in fixed slots {u8 *data, u32 size, u32 loaded} (16 bytes) that the code reaches through accessors:

Accessor	Slot	Mounted from
FUN_00455290	0x541f08	Game\BigFiles\Common.bfl (sounds, effect textures)
FUN_004552a0	0x541f18	Game\BigFiles\Com<640|1024>[C].bfl (HUD textures and fonts)
FUN_004552b0	0x541f28	CountrySpecific\<region>\<language>speech.bfl
FUN_004552c0	0x541f38	the stage archive Game\Tracks\<country>\<stage><Hi|Lo>.bfl
FUN_004552d0	0x541f48	Game\BigFiles\FireWork.bfl (only when fireworks are enabled)
FUN_004552e0		Sounds\surface.bfl
FUN_004552f0		CountrySpecific\<region>\<language>text.bfl

Bfl_MountCommon 0x455080 mounts the common set; Bfl_MountStage 0x455260 the stage. The resolution in Com<n> is 1024 when the configured screen width (FUN_00405c10) is at least 1024 and two capability checks pass (FUN_004b7560(1024), FUN_004b7590(1024); not read yet), else 640.

What is where

Path	Archive members
FrontEnd/res640[C].bfl, res1024[C].bfl	Front-end screens, car pictures (f99b01.tga, f99f01.tga), country flags and backgrounds, fonts (hel_12pt.pcf + .tga)
FrontEnd/common.bfl	Stage "diamond" files <stage>.dmd (324 bytes each), menu sounds
FrontEnd/exittexture.tga	Single file: the exit screen
CountrySpecific/Europe/<language>text.bfl	f<language>.txt (front end), s<language>.txt (stage screens), g<language>.txt (in game)
CountrySpecific/Europe/<language>speech.bfl	Co-driver pace-note samples (100.wav, left.wav, ...)
CountrySpecific/Europe/FEres640E[C].bfl	Localised front-end textures (copyright screens)
Game/Bigfiles/common.bfl	In-game sounds (collisions, rolls, landings, rain), effect textures (rain.dds, splat.dds, lights, skid marks)
Game/Bigfiles/Com<res>[C].bfl	HUD: rev counter, speedo, pace-note arrows, fonts (hel_13pt, lcd_14pt, ocr_60pt)
Game/Bigfiles/FireWork.bfl	Fireworks textures and sounds (championship end)
Game/Cars/<car><set><n>.bfl	Car textures for one model set (cars.md)
Game/Tracks/<country>/<stage>Hi.bfl, Lo.bfl	One stage (stage.md)
Game/Tracks/<country>/<country>hit.bfl, lot.bfl	Track textures for the country, high and low detail (DXT5 only)
Game/Tracks/Clouds/pc/cloud_<light|med|heavy>.bfl	Sky/cloud textures (PCLow/ for low detail)
SetupRep/<640|1024>/<country>Day<n>[C].bfl	Service-area and stage-map screens per rally day; common[C].bfl
Sounds/Car/<engine>.bfl	Engine sound sets (205.bfl, focus.bfl, ...)
Sounds/surface.bfl	Not an archive: one RIFF WAVE

Member counts over the whole disc: 7,804 DDS, 4,003 TGA, 609 WAV (5 of them empty), 94 .dmd, 72 .pcf, 20 .txt, and the stage member types (188 of each, two per stage).