Middleware

Middleware is a library that a game licenses for one job. In most cases it does not need to be reverse engineered. Identify it, label its functions, and replace it in the port with a library that does the same job. Check whether the game depends on any exact behaviour of the library, such as its random numbers, its rounding or its timing.

Common libraries of the era

Job	Library	Signs in the files	In the port
Video	Smacker (RAD Game Tools, 1994)	.SMK files starting SMK2 or SMK4; smackw32.dll	FFmpeg decodes Smacker
Video	Bink (RAD, 1999)	.BIK files starting BIK; binkw32.dll	FFmpeg decodes most Bink 1 files
Video	Westwood VQA, Sierra VMD, Cinepak in AVI	.VQA, .VMD, .AVI	FFmpeg, or a small decoder from the documented format
Sound	Miles Sound System (RAD), earlier the Audio Interface Library	mss32.dll, MSS strings; in DOS, AIL driver files (.DIG, .MDI)	A modern audio library; MIDI through a software synthesiser
Sound	DIGPAK and MIDPAK, HMI Sound Operating System	DIGPAK drivers as .COM files and MIDPAK music drivers as .ADV files, called through INT 66h; HMI*.386; SOS strings	The same
Sound	FMOD	fmod.dll, fmodex.dll; FMOD strings	A modern library; FMOD's tracker-module playback has its own quirks to match
Sound	DirectSound, DirectMusic, A3D, EAX	imports from dsound.dll, dmusic; a3d.dll; EAX strings	See Sound hardware
3D graphics	Direct3D, OpenGL, Glide	imports from ddraw.dll, d3d8.dll, opengl32.dll, glide2x.dll	See 3D accelerators
Physics	Havok (from 2000), MathEngine, PhysX (from 2005)	hk prefixes in RTTI and strings; PhysX DLLs	Physics middleware results must be matched only if the game's rules depend on them; often they are cosmetic
Animation	Granny 3D (RAD)	.gr2 files; granny2.dll	A reader for the format, documented by modders
Scripting	Lua (from 1993), Python, Tcl	lua_pcall, Lua 5.0 strings; python2x.dll	Use the same language version; decompile compiled scripts (unluac)
Compression	zlib, LZSS, LZW, Huffman, PKWARE DCL ("implode")	zlib's version strings and CRC table; PKWARE strings	A standard library, or the documented algorithm
Online	GameSpy SDK, DirectPlay, Kali	gamespy strings; dplayx.dll	Replace with your own networking; do not contact old services (Online games)
Protection	SafeDisc, SecuROM, StarForce, CD checks	.icd files, secdrv.sys, ~df394b.tmp; checks for a disc label	Breaking it is restricted in many countries (Legal); the port reads the player's files and does not need it

When the port must match the middleware

Most middleware can be replaced freely. A few cases need care:

• Music timing. If the game logic waits for the music (a level ends when a song ends, a cut scene follows the music), the port must match the music library's timing. Measure it.
• Random numbers. A few libraries use the C runtime's rand. If the game also uses rand, the library's calls change the game's sequence. Trace every caller of the random function.
• Video frame counts. Some games count video frames to time events. Use the same frame rate and frame count as the original file.
• Scripting. Use the same script language version as the game. Lua 4.0 and 5.0 differ in their libraries and byte code, and Lua 5.3 added an integer type.
• Physics. If physics sets a game result (a ball's bounce in a sports game), the port must match the physics library's exact results. This is hard to match without the same library. Decide early whether your project can accept a deviation and record it.

How to identify a library inside the executable

Libraries are often linked statically, so there is no separate DLL.

1. Search the strings for version and copyright notices. Most libraries include one.
2. Look for the library's constant tables: CRC tables, Huffman tables, DCT coefficients.
3. Compare the function with the library's source if it is open (zlib, Lua). The structure of a compiled zlib inflate loop is easy to recognise once you have seen it.
4. Label the whole library's functions in Ghidra with a prefix (zlib_, lua_, smk_), so you can skip them while tracing.