Write start of ZZT preprocessor

It's messy, but it can parse worlds now!

.gitignore

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+target/

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "assembler"
+version = "0.1.0"
+dependencies = [
+ "byteorder",
+]
+
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"

Cargo.toml

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+[package]
+name = "assembler"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+byteorder = "1.5.0"

src/main.rs

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+use byteorder::{ByteOrder, LittleEndian};
+use std::{env, error::Error, fs, process::exit};
+
+struct World {
+    header: Vec<u8>,
+    boards: Vec<Board>,
+}
+
+struct Board {
+    name: Vec<u8>,
+    terrain: Vec<[u8; 2]>,
+    info: Vec<u8>,
+    stats: Vec<Stat>,
+}
+
+struct Stat {
+    info: Vec<u8>,
+    code: Vec<u8>,
+}
+
+impl World {
+    fn from(bytes: &[u8]) -> Result<World, Box<dyn Error>> {
+        let mut world = World {
+            header: Vec::from(&bytes[0..512]),
+            boards: vec![],
+        };
+        // TODO: Remove LittleEndian entirely?
+        let num_boards = 1 + LittleEndian::read_u16(&world.header[2..4]);
+        let mut offset = world.header.len();
+        for _ in 0..num_boards {
+            // Ideally, this wouldn't panic if we run out of bytes
+            let board_len =
+                u16::from_le_bytes((&bytes[offset..offset + 2]).try_into().unwrap()) as usize;
+            offset += 2;
+            world
+                .boards
+                .push(Board::from(&bytes[offset..offset + board_len])?);
+            offset += board_len;
+        }
+        Ok(world)
+    }
+}
+
+impl Board {
+    fn from(bytes: &[u8]) -> Result<Board, Box<dyn Error>> {
+        // Read board name
+        let name_len = bytes[0] as usize;
+        let name = Vec::from(&bytes[1..name_len + 1]);
+        let mut offset = 51; // skip Pascal string[50]
+
+        // Read terrain
+        let mut terrain = vec![[0; 2]; 60 * 25];
+        let mut i = 0;
+        while i < terrain.len() {
+            let times = if bytes[offset] == 0 {
+                256
+            } else {
+                bytes[offset] as usize
+            };
+            let tile = (&bytes[offset + 1..offset + 3]).try_into().unwrap();
+            offset += 3;
+            for _ in 0..times {
+                terrain[i] = tile;
+                i += 1
+            }
+        }
+
+        // Read board info
+        let info = Vec::from(&bytes[offset..offset + 86]);
+        offset += 86;
+
+        // Read stats
+        let num_stats =
+            u16::from_le_bytes((&bytes[offset..offset + 2]).try_into().unwrap()) as usize + 1;
+        offset += 2;
+        let mut stats = Vec::with_capacity(num_stats);
+        for _ in 0..num_stats {
+            let mut stat = Stat {
+                info: Vec::from(&bytes[offset..offset + 25]),
+                code: vec![],
+            };
+            offset += 25 + 8;
+            let code_len = i16::from_le_bytes((&stat.info[23..25]).try_into().unwrap());
+            if code_len > 0 {
+                let code_len = code_len as usize;
+                stat.code = Vec::from(&bytes[offset..offset + code_len]);
+                offset += code_len;
+            }
+            stats.push(stat);
+        }
+        Ok(Board {
+            name,
+            terrain,
+            info,
+            stats,
+        })
+    }
+}
+
+fn to_latin1(bytes: &[u8]) -> String {
+    bytes.iter().map(|&x| x as char).collect()
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        eprintln!("Usage: {} WORLD_FILE", args[0]);
+        exit(1);
+    }
+
+    let bytes = fs::read(&args[1])?;
+    let world = World::from(&bytes)?;
+
+    println!("num boards: {}", &world.boards.len());
+    for board in &world.boards {
+        println!("board: {}", to_latin1(&board.name));
+        for stat in &board.stats {
+            let (x, y) = (stat.info[0] as usize, stat.info[1] as usize);
+            println!(
+                "  stat at ({}, {}): {:?}, {:?}",
+                x,
+                y,
+                board.terrain[(x - 1) + (y - 1) * 60],
+                to_latin1(&stat.code)
+            );
+        }
+    }
+    Ok(())
+}