gwc_spec.md

Source : https://github.com/WFoundation/WF.Compiler

File format of GWC files:

@0000:                          ; Signature
    BYTE     0x02               ; Version
    BYTE     0x0a               ; 2.10 or 2.11
    BYTE     "CART"
    BYTE     0x00

@0007:
    USHORT   NumberOfObjects    ; Number of objects ("media files") in cartridge:

@0009:
    ; References to individual objects in cartridge.
    ; Object 0 is always Lua bytecode for cartridge.
    ; There is exactly [number_of_objects] blocks like this:
    repeat <NumberOfObjects> times
    {
        USHORT   ObjectID       ; Distinct ID for each object, duplicates are forbidden
        INT      Address          ; Address of object in GWC file
    }

@xxxx:                          ; 0009 + <NumberOfObjects> * 0006 bytes from begining
    ; Header with all important informations for this cartridge
    INT      HeaderLength       ; Length of information header (following block):

    DOUBLE   Latitude           ; N+/S-
    DOUBLE   Longitude          ; E+/W-
    DOUBLE   Altitude           ; Meters

    LONG     Date of creation   ; Seconds since 2004-02-10 01:00:00

    ; MediaID of icon and splashscreen
    SHORT    ObjectID of splashscreen    ; -1 = without splashscreen/poster
    SHORT    ObjectID of icon            ; -1 = without icon

    ASCIIZ   TypeOfCartridge             ; "Tour guide", "Wherigo cache", etc.
    ASCIIZ   Player                      ; Name of player downloaded cartridge
    LONG     PlayerID                    ; ID of player in the Groundspeak database

    ASCIIZ   CartridgeName               ; "Name of this cartridge"
    ASCIIZ   CartridgeGUID
    ASCIIZ   CartridgeDescription        ; "This is a sample cartridge"
    ASCIIZ   StartingLocationDescription ; "Nice parking"
    ASCIIZ   Version                     ; "1.2"
    ASCIIZ   Author                      ; Author of cartridge
    ASCIIZ   Company                     ; Company of cartridge author
    ASCIIZ   RecommendedDevice           ; "Garmin Colorado", "Windows PPC", etc.

    INT      Length                      ; Length of CompletionCode
    ASCIIZ   CompletionCode              ; Normally 15/16 characters

@address_of_FIRST_object (with ObjectID = 0):
    ; always Lua bytecode
    INT      Length                      ; Length of Lua bytecode
    BYTE[Length]    ContentOfObject      ; Lua bytecode

@address_of_ALL_OTHER_objects (with ID > 0):
    BYTE     ValidObject
    if (ValidObject == 0)
    {
        ; when ValidObject == 0, it means that object is DELETED and does
        ; not exist in cartridge. Nothing else follows.
    }
    else
    {
        ; Object type: 1=bmp, 2=png, 3=jpg, 4=gif, 17=wav, 18=mp3, 19=fdl, 
        ; 20=snd, 21=ogg, 33=swf, 49=txt, other values have unknown meaning
        INT           ObjectType               
        INT           Length
        BYTE[Length]  content_of_object
    }

@end

Varibles

    BYTE   = unsigned char (1 byte)
    SHORT  = signed short (2 bytes, little endian)
    USHORT = unsigned short (2 bytes, little endian)
    INT    = signed long (4 bytes, little endian)
    UINT   = unsigned long (4 bytes, little endian)
    LONG   = signed long (8 bytes, little endian)
    DOUBLE = double-precision floating point number (8 bytes)
    ASCIIZ = zero-terminated string ("hello world!", 0x00)