gameframe-turbo-pascal

The parts of the Turbo Pascal and Borland Pascal runtime that a DOS game's results depend on, rebuilt in Rust so a port gives the same numbers as the original program.

Item	What it reproduces	Why it matters
Real48	The 6-byte Real and the System unit's routines for it: conversion, *, /, +, -, compare, Int, Frac, Sin, Cos, Trunc, Round	Programs built without the 8087 option do all Real arithmetic in software, with their own rounding. IEEE doubles give different last bits
TurboRandom	RandSeed, Random, Random(range), Randomize	Games use it for everything random; the order and the values of the draws are behaviour
PascalReader, PascalWriter, PStr	Pascal data in memory and in BlockWrite files: little-endian integers, one-byte Boolean, Real, string[N]	Records in data files and saves are written field by field in this layout

It comes from Tyrian 2026, the clean-room reimplementation of Tyrian 2000. There every Real routine here matches the original program on 40,000 random operands, and 90,000 random draws match bit for bit (measured under GameFrame's DOS emulator). div is measured only for divisors of 2.0.

Use it

[dependencies]
gameframe-turbo-pascal = { git = "https://github.com/tanepiper/game-frame" }

use gameframe_turbo_pascal::{Real48, TurboRandom};

// Round(x * 0.75) as the game computes it.
let scaled = Real48::from_i32(37).mul(Real48::from_f64(0.75)).round();
assert_eq!(scaled, 28); // 27.75

// The same draws as the original, from the same seed.
let mut rng = TurboRandom::new(0x1234_5678);
let roll = rng.random(6);
assert!(roll < 6);

Check your game uses these

Turbo Pascal 5.5, 6.0 and 7.0 and Borland Pascal 7 share these algorithms, but check your game:

1. Find the System unit's routines in the decompile. With Turbo Debugger symbols, tools/dos/tdinfo.py names them; otherwise look for the Real routines that work on DX:BX:AX and CX:SI:DI.
2. Run them under GameFrame's DOS emulator on many inputs (re-emulate, dos_emu).
3. Compare with this crate bit for bit.

Programs compiled with {$N+} use the 8087 (or its emulator) for Single, Double and Extended. Those types follow the x87 FPU. This crate does not cover them.

Tests

cargo test --release -p gameframe-turbo-pascal

The tests check encodings, exact integer arithmetic, Round taking halves away from zero, Int and Frac, Sin and Cos against doubles, the generator's formula, and a data round trip. The bit-for-bit checks against the original runtime need a program compiled with it, so they live in the game project that has one.

Licence

Apache 2.0.