fastman92 enhanced GTA SA IMG archive

Test of archive:

All files have been compressed with specified compression type and fully rebuilt.

IMG_FASTMAN92_GTASA_COMPRESSION_TYPE_NONE - 915 MB archive
IMG_FASTMAN92_GTASA_COMPRESSION_TYPE_ZLIB, highest compression level - 533 MB archive
IMG_FASTMAN92_GTASA_COMPRESSION_TYPE_LZ4, highest compression level, LZ4 HC actually - 686 MB archive


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Final specification.
Structure of IMG archive.

beginning of IMG archive, first header:

#pragma pack(push, 1)
struct tImgFastman92GTASAfirstHeader
{
    DWORD magicID;  // VERF
    DWORD archiveFlags; // bits 0-3 archive version (should be 1), bits 4-7 metadata encryption type, bits 8-10 game
    char authorName[12];    // constant value "fastman92" padded with zeros.
};
#pragma pack(pop)

VALIDATE_SIZE(tImgFastman92GTASAfirstHeader, 0x14);

------------

Second header, could be encrypted:

#pragma pack(push, 1)
struct tImgFastman92GTASAsecondHeader
{
    DWORD Check;    // constant value 1, after decryption it should have value 1. To check if decryption worked properly.
    DWORD NumberOfEntries;

    char reserved[8];   // for future use, should be NULL now.
};
#pragma pack(pop)

VALIDATE_SIZE(tImgFastman92GTASAsecondHeader, 16);


Now there comes a list of entries, each entry of type:

#define IMG_FASTMAN92_GTASA_MAX_FILENAME_LENGTH 39

#pragma pack(push, 1)
class tImgFastman92GTASAdirectoryEntry
{
public:
    unsigned __int32 PositionInSectors;
    unsigned __int16 OriginalSizeInSectors;
    unsigned __int16 NumberOfPaddedBytesInAlignedOriginalSize;
    unsigned __int16 PackedSizeInSectors;
    unsigned __int16 NumberOfPaddedBytesInAlignedPackedSize;
    unsigned __int32 Flags;
    char Name[IMG_FASTMAN92_GTASA_MAX_FILENAME_LENGTH + 1];
    char Reserved[8];   // should have NULL values when reserved.
};
#pragma pack(pop)

VALIDATE_SIZE(tImgFastman92GTASAdirectoryEntry, 64);


/////////////////
Explanation of file flags:
- bits 0-3, compression type
- bits 4-7, encryption type

///////////////////////////////////////////

Enumerations:

Game type (3 bits for this value)
    - 0: GTA SA


Compression type (4 bits for this value):
    - 0: no compression
    - 1: ZLIB compression
    - 2: LZ4 / LZ4 HC compression

Encryption type (4 bits for this value):
    - 0: no encryption
    - 1: encryption of variation 1, discouraged
    - 2: encryption of variation 2



That's all!