add army decoder and encoder (#4)

Cargo.toml

@@ -8,6 +8,8 @@ license = "MIT OR Apache-2.0"
 
 [dependencies]
 bitflags = { version = "2.3", features = ["serde"] }
+encoding_rs = "0.8.34"
+encoding_rs_io = "0.1.7"
 glam = { version = "0.27.0", default-features = false, features = ["serde"] }
 image = "0.25.1"
 indexmap = { version = "2.2.6", features = ["serde"] }

src/army/decoder.rs

@@ -0,0 +1,277 @@
+use super::*;
+use encoding_rs::WINDOWS_1252;
+use encoding_rs_io::DecodeReaderBytesBuilder;
+use std::{
+    fmt,
+    io::{Error as IoError, Read, Seek, SeekFrom},
+    mem::size_of,
+};
+
+#[derive(Debug)]
+pub enum DecodeError {
+    IoError(IoError),
+    InvalidFormat(u32),
+    InvalidString,
+}
+
+impl std::error::Error for DecodeError {}
+
+impl From<IoError> for DecodeError {
+    fn from(error: IoError) -> Self {
+        DecodeError::IoError(error)
+    }
+}
+
+impl fmt::Display for DecodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DecodeError::IoError(e) => write!(f, "IO error: {}", e),
+            DecodeError::InvalidFormat(format) => write!(f, "invalid format: {}", format),
+            DecodeError::InvalidString => write!(f, "invalid string"),
+        }
+    }
+}
+
+pub(crate) const FORMAT: u32 = 0x0000029e;
+pub(crate) const HEADER_SIZE: usize = 192;
+const SAVE_HEADER_SIZE: usize = 504;
+pub(crate) const REGIMENT_BLOCK_SIZE: usize = 188;
+
+pub(crate) struct Header {
+    _format: u32,
+    regiment_count: u32,
+    /// The size of each regiment block in bytes.
+    ///
+    /// This is always 188 despite being encoded in the header.
+    _regiment_block_size: u32,
+    race: u8,
+    unknown1: [u8; 3],  // purpose of bytes at index 13, 14, 15 is unknown
+    unknown2: [u8; 34], // purpose of bytes at index 16-50 is unknown
+    small_banner_path: String,
+    /// There are some bytes after the null-terminated string. Not sure what
+    /// they are for.
+    small_banner_path_remainder: Vec<u8>,
+    small_banner_disabled_path: String,
+    /// There are some bytes after the null-terminated string. Not sure what
+    /// they are for.
+    small_banner_disabled_path_remainder: Vec<u8>,
+    large_banner_path: String,
+    /// There are some bytes after the null-terminated string. Not sure what
+    /// they are for.
+    large_banner_path_remainder: Vec<u8>,
+    gold_from_treasures: u16,
+    gold_in_coffers: u16,
+    magic_items: [u8; 40],
+    unknown3: [u8; 2], // purpose of bytes at index 190 and 191 is unknown
+}
+
+pub struct Decoder<R>
+where
+    R: Read + Seek,
+{
+    reader: R,
+}
+
+impl<R: Read + Seek> Decoder<R> {
+    pub fn new(reader: R) -> Self {
+        Decoder { reader }
+    }
+
+    pub fn decode(&mut self) -> Result<Army, DecodeError> {
+        let start_pos = self.maybe_read_save_file()?;
+
+        let header = self.read_header(start_pos)?;
+
+        let regiments = self.read_regiments(&header)?;
+
+        Ok(Army {
+            race: header.race,
+            unknown1: header.unknown1.to_vec(),
+            unknown2: header.unknown2.to_vec(),
+            regiments,
+            small_banner_path: header.small_banner_path,
+            small_banner_path_remainder: header.small_banner_path_remainder,
+            small_banner_disabled_path: header.small_banner_disabled_path,
+            small_banner_disabled_path_remainder: header.small_banner_disabled_path_remainder,
+            large_banner_path: header.large_banner_path,
+            large_banner_path_remainder: header.large_banner_path_remainder,
+            gold_from_treasures: header.gold_from_treasures,
+            gold_in_coffers: header.gold_in_coffers,
+            magic_items: header.magic_items.to_vec(),
+            unknown3: header.unknown3.to_vec(),
+        })
+    }
+
+    fn maybe_read_save_file(&mut self) -> Result<u64, DecodeError> {
+        let mut buf = [0; size_of::<u32>()];
+        self.reader.read_exact(&mut buf)?;
+
+        let mut start_pos = 0;
+
+        let format = u32::from_le_bytes(buf[0..size_of::<u32>()].try_into().unwrap());
+        if format != FORMAT {
+            // TODO: Skipped over reading save header.
+            start_pos = SAVE_HEADER_SIZE as u64;
+        }
+        Ok(start_pos)
+    }
+
+    fn read_header(&mut self, start_pos: u64) -> Result<Header, DecodeError> {
+        self.reader.seek(SeekFrom::Start(start_pos))?;
+
+        let mut buf = [0; HEADER_SIZE];
+        self.reader.read_exact(&mut buf)?;
+
+        let small_banner_path_buf = &buf[50..82];
+        let (small_banner_path_buf, small_banner_path_remainder) = small_banner_path_buf
+            .iter()
+            .enumerate()
+            .find(|(_, &b)| b == 0)
+            .map(|(i, _)| small_banner_path_buf.split_at(i + 1))
+            .unwrap_or((small_banner_path_buf, &[]));
+
+        let small_banner_disabled_path_buf = &buf[82..114];
+        let (small_banner_disabled_path_buf, small_banner_disabled_path_remainder) =
+            small_banner_disabled_path_buf
+                .iter()
+                .enumerate()
+                .find(|(_, &b)| b == 0)
+                .map(|(i, _)| small_banner_disabled_path_buf.split_at(i + 1))
+                .unwrap_or((small_banner_disabled_path_buf, &[]));
+
+        let large_banner_path_buf = &buf[114..146];
+        let (large_banner_path_buf, large_banner_path_remainder) = large_banner_path_buf
+            .iter()
+            .enumerate()
+            .find(|(_, &b)| b == 0)
+            .map(|(i, _)| large_banner_path_buf.split_at(i + 1))
+            .unwrap_or((large_banner_path_buf, &[]));
+
+        Ok(Header {
+            _format: u32::from_le_bytes(buf[0..4].try_into().unwrap()),
+            regiment_count: u32::from_le_bytes(buf[4..8].try_into().unwrap()),
+            _regiment_block_size: u32::from_le_bytes(buf[8..12].try_into().unwrap()),
+            race: buf[12],
+            unknown1: buf[13..16].try_into().unwrap(),
+            unknown2: buf[16..50].try_into().unwrap(),
+            small_banner_path: self.read_string(small_banner_path_buf)?,
+            small_banner_path_remainder: small_banner_path_remainder.to_vec(),
+            small_banner_disabled_path: self.read_string(small_banner_disabled_path_buf)?,
+            small_banner_disabled_path_remainder: small_banner_disabled_path_remainder.to_vec(),
+            large_banner_path: self.read_string(large_banner_path_buf)?,
+            large_banner_path_remainder: large_banner_path_remainder.to_vec(),
+            gold_from_treasures: u16::from_le_bytes(buf[146..148].try_into().unwrap()),
+            gold_in_coffers: u16::from_le_bytes(buf[148..150].try_into().unwrap()),
+            magic_items: buf[150..190].try_into().unwrap(),
+            unknown3: buf[190..192].try_into().unwrap(),
+        })
+    }
+
+    fn read_regiments(&mut self, header: &Header) -> Result<Vec<Regiment>, DecodeError> {
+        let mut regiments = Vec::with_capacity(header.regiment_count as usize);
+
+        for _ in 0..header.regiment_count {
+            regiments.push(self.read_regiment()?);
+        }
+
+        Ok(regiments)
+    }
+
+    fn read_regiment(&mut self) -> Result<Regiment, DecodeError> {
+        let mut buf = vec![0; REGIMENT_BLOCK_SIZE];
+        self.reader.read_exact(&mut buf)?;
+
+        Ok(Regiment {
+            status: buf[0..2].try_into().unwrap(),
+            unknown1: buf[2..4].try_into().unwrap(),
+            id: u16::from_le_bytes(buf[4..6].try_into().unwrap()),
+            unknown2: buf[6..8].try_into().unwrap(),
+            wizard_type: buf[8],
+            max_armor: buf[9],
+            cost: u16::from_le_bytes(buf[10..12].try_into().unwrap()),
+            banner_index: u16::from_le_bytes(buf[12..14].try_into().unwrap()),
+            unknown3: buf[14..16].try_into().unwrap(),
+            regiment_attributes: buf[16..20].try_into().unwrap(),
+            sprite_index: u16::from_le_bytes(buf[20..22].try_into().unwrap()),
+            name: self.read_string(&buf[22..54])?,
+            name_id: u16::from_le_bytes(buf[54..56].try_into().unwrap()),
+            alignment: buf[56],
+            max_troops: buf[57],
+            alive_troops: buf[58],
+            ranks: buf[59],
+            unknown4: buf[60..64].try_into().unwrap(),
+            troop_attributes: TroopAttributes {
+                movement: buf[64],
+                weapon_skill: buf[65],
+                ballistic_skill: buf[66],
+                strength: buf[67],
+                toughness: buf[68],
+                wounds: buf[69],
+                initiative: buf[70],
+                attacks: buf[71],
+                leadership: buf[72],
+            },
+            mount: buf[73],
+            armor: buf[74],
+            weapon: buf[75],
+            typ: buf[76],
+            point_value: buf[77],
+            missile_weapon: buf[78],
+            unknown5: buf[79],
+            unknown6: buf[80..84].try_into().unwrap(),
+            leader: Leader {
+                sprite_index: u16::from_le_bytes(buf[84..86].try_into().unwrap()),
+                name: self.read_string(&buf[86..118])?,
+                name_remainder: buf[118..127].to_vec(),
+                attributes: TroopAttributes {
+                    movement: buf[127],
+                    weapon_skill: buf[128],
+                    ballistic_skill: buf[129],
+                    strength: buf[130],
+                    toughness: buf[131],
+                    wounds: buf[132],
+                    initiative: buf[133],
+                    attacks: buf[134],
+                    leadership: buf[135],
+                },
+                mount: buf[136],
+                armor: buf[137],
+                weapon: buf[138],
+                unit_type: buf[139],
+                point_value: buf[140],
+                missile_weapon: buf[141],
+                unknown1: buf[142..146].try_into().unwrap(),
+                head_id: u16::from_le_bytes(buf[146..148].try_into().unwrap()),
+                x: buf[148..152].try_into().unwrap(),
+                y: buf[152..156].try_into().unwrap(),
+            },
+            experience: u16::from_le_bytes(buf[156..158].try_into().unwrap()),
+            duplicate_id: buf[158],
+            min_armor: buf[159],
+            magic_book: u16::from_le_bytes(buf[160..162].try_into().unwrap()),
+            magic_items: [
+                u16::from_le_bytes(buf[162..164].try_into().unwrap()),
+                u16::from_le_bytes(buf[164..166].try_into().unwrap()),
+                u16::from_le_bytes(buf[166..168].try_into().unwrap()),
+            ],
+            unknown7: buf[168..180].try_into().unwrap(),
+            purchased_armor: buf[180],
+            max_purchasable_armor: buf[181],
+            repurchased_troops: buf[182],
+            max_purchasable_troops: buf[183],
+            book_profile: buf[184..188].try_into().unwrap(),
+        })
+    }
+
+    fn read_string(&mut self, buf: &[u8]) -> Result<String, DecodeError> {
+        let nul_pos = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());
+        let mut decoder = DecodeReaderBytesBuilder::new()
+            .encoding(Some(WINDOWS_1252))
+            .build(&buf[..nul_pos]);
+        let mut dest = String::new();
+
+        decoder.read_to_string(&mut dest)?;
+
+        Ok(dest)
+    }
+}