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IonFx-Miasmata-RS5-file-format.md

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IonFx Miasmata RS5 file format

The RS5 file format is a ZLib-compressed Tagged file format created by Joe Johnson of IonFx for the addictive survival game Miasmata.

Note that fixed-size fields containing variable-size data (such as the name fields in the central directory) will have garbage after the end of the variable-size data.

All data in the file is stored in little-endian order.

Types are expressed as DotNet types:

  • byte: unsigned 8-bit integer
  • short: signed 16-bit integer
  • int: signed 32-bit integer
  • long: signed 64-bit integer
  • float: 32-bit floating-point
  • ASCIZ: Null-terminated 8-bit ASCII string - note that the space after the string in a field is not zeroed, and may contain garbage.
  • FILETIME: 64-bit Win32 FILETIME value
  • ARGB: 8-bit Alpha, Red, Green and Blue values (32bpp)

File Header

The file starts with a 24 byte header pointing to the central directory.

Offset Size Type Meaning
0x0000 8 byte[] Magic value CFILEHDR
0x0008 8 long Absolute offset of central directory within file
0x0010 4 int Size of each entry in central directory
0x0014 4 int Unknown

Central Directory

The central directory consists of one or more consecutive directory entries, each pointing to either nothing (offset = length = 0) or a tagged information object. The first entry is always a pointer to the central directory itself. Each directory entry appears to always be 168 bytes long.

Offset Size Type Meaning
0x0000 8 long Absolute offset of object within file
0x0008 4 int Compressed length of object
0x000C 4 ??? Unknown - seems to always be 0x80000000 for present entries
0x0010 4 ??? Unknown - seems to always be 0x00000300 for present entries
0x0014 4 byte[] FourCC - identifies type of object
0x0018 8 long The size of the uncompressed data shifted left by one bit. The low bit is always 1 for a valid entry and 0 otherwise.
0x0020 8 FILETIME Appears to be the modification time of the object
0x0028 128 ASCIZ Null-terminated name of object

Tagged information format

Each object is compressed using the RFC1950 Zlib compression format. Each object is wrapped in a tagged chunk and can contain either data or one or more tagged chunks. All chunks within the compressed objects are aligned to 8 bytes. The chunk size in the chunk header does not include this alignment padding.

Offset Size Type Meaning
0x0000 4 byte[] FourCC - identifies type of chunk
0x0004 2 ??? Unknown - always appears to be zero
0x0006 1 byte Length of name including terminating zero
0x0007 1 byte zero if the chunk contains data; 1 if the chunk either contains no data or contains tagged chunks.
0x0008 4 int Size of the chunk
0x000c variable ASCIZ Null-terminated name of chunk
align(8) variable Chunk data or tagged chunks

Objects

Object types are identified by a few tags. Anything that doesn't fit in these tags (such as terrain height maps) is tagged as RAW..

Object types:

Special objects: