Implement our own gba header

agb-gbafix/Cargo.lock

@@ -7,10 +7,8 @@ name = "agb-gbafix"
 version = "0.16.0"
 dependencies = [
  "anyhow",
- "bytemuck",
  "clap",
  "elf",
- "gbafix",
 ]
 
 [[package]]
@@ -74,12 +72,6 @@ version = "2.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "630be753d4e58660abd17930c71b647fe46c27ea6b63cc59e1e3851406972e42"
 
-[[package]]
-name = "bytemuck"
-version = "1.13.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "17febce684fd15d89027105661fec94afb475cb995fbc59d2865198446ba2eea"
-
 [[package]]
 name = "cc"
 version = "1.0.79"
@@ -146,15 +138,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "gbafix"
-version = "1.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f7e47af9d5377b8b0def53d9916f6c28521f2e5b97c5fec137797417c26ab4b7"
-dependencies = [
- "bytemuck",
-]
-
 [[package]]
 name = "hermit-abi"
 version = "0.3.1"

agb-gbafix/Cargo.toml

@@ -9,8 +9,6 @@ repository = "https://github.com/agbrs/agb"
 
 [dependencies]
 elf = "0.7"
-gbafix = "1"
-bytemuck = "1"
 anyhow = "1"
 clap = "4"
 

agb-gbafix/src/lib.rs

@@ -1,11 +1,66 @@
 use anyhow::{anyhow, bail, ensure, Result};
 use std::io::Write;
 
-pub fn write_gba_file<W: Write>(
-    input: &[u8],
-    mut header: gbafix::GBAHeader,
-    output: &mut W,
-) -> Result<()> {
+const GBA_HEADER_SIZE: usize = 192;
+
+const NINTENDO_LOGO: &[u8] = &[
+    0x24, 0xFF, 0xAE, 0x51, 0x69, 0x9A, 0xA2, 0x21, 0x3D, 0x84, 0x82, 0x0A, 0x84, 0xE4, 0x09, 0xAD,
+    0x11, 0x24, 0x8B, 0x98, 0xC0, 0x81, 0x7F, 0x21, 0xA3, 0x52, 0xBE, 0x19, 0x93, 0x09, 0xCE, 0x20,
+    0x10, 0x46, 0x4A, 0x4A, 0xF8, 0x27, 0x31, 0xEC, 0x58, 0xC7, 0xE8, 0x33, 0x82, 0xE3, 0xCE, 0xBF,
+    0x85, 0xF4, 0xDF, 0x94, 0xCE, 0x4B, 0x09, 0xC1, 0x94, 0x56, 0x8A, 0xC0, 0x13, 0x72, 0xA7, 0xFC,
+    0x9F, 0x84, 0x4D, 0x73, 0xA3, 0xCA, 0x9A, 0x61, 0x58, 0x97, 0xA3, 0x27, 0xFC, 0x03, 0x98, 0x76,
+    0x23, 0x1D, 0xC7, 0x61, 0x03, 0x04, 0xAE, 0x56, 0xBF, 0x38, 0x84, 0x00, 0x40, 0xA7, 0x0E, 0xFD,
+    0xFF, 0x52, 0xFE, 0x03, 0x6F, 0x95, 0x30, 0xF1, 0x97, 0xFB, 0xC0, 0x85, 0x60, 0xD6, 0x80, 0x25,
+    0xA9, 0x63, 0xBE, 0x03, 0x01, 0x4E, 0x38, 0xE2, 0xF9, 0xA2, 0x34, 0xFF, 0xBB, 0x3E, 0x03, 0x44,
+    0x78, 0x00, 0x90, 0xCB, 0x88, 0x11, 0x3A, 0x94, 0x65, 0xC0, 0x7C, 0x63, 0x87, 0xF0, 0x3C, 0xAF,
+    0xD6, 0x25, 0xE4, 0x8B, 0x38, 0x0A, 0xAC, 0x72, 0x21, 0xD4, 0xF8, 0x07,
+];
+
+#[derive(Debug, Default)]
+pub struct GbaHeader {
+    pub start_code: [u8; 4],
+    pub game_title: [u8; 12],
+    pub game_code: [u8; 4],
+    pub maker_code: [u8; 2],
+    pub software_version: u8,
+}
+
+impl GbaHeader {
+    fn produce_header(&self) -> Vec<u8> {
+        let mut header_result = vec![];
+
+        header_result.extend_from_slice(&self.start_code);
+        header_result.extend_from_slice(NINTENDO_LOGO);
+        header_result.extend_from_slice(&self.game_title);
+        header_result.extend_from_slice(&self.game_code);
+        header_result.extend_from_slice(&self.maker_code);
+        header_result.push(0x96); // must be 96
+        header_result.push(0); // main unit code (0 for current GBA models)
+        header_result.push(0); // device type, usually 0
+        header_result.extend_from_slice(&[0; 7]); // reserved area, should be zero filled
+        header_result.push(self.software_version);
+
+        let checksum = Self::calculate_checksum(&header_result);
+        header_result.push(checksum); // checksum
+        header_result.extend_from_slice(&[0; 2]); // reserved area, should be zero filled
+
+        assert_eq!(header_result.len(), GBA_HEADER_SIZE);
+
+        header_result
+    }
+
+    fn calculate_checksum(header: &[u8]) -> u8 {
+        let mut chk = 0u8;
+        for value in header.iter().take(0xBC).skip(0xA0) {
+            chk = chk.wrapping_sub(*value);
+        }
+
+        chk = chk.wrapping_sub(0x19);
+        chk
+    }
+}
+
+pub fn write_gba_file<W: Write>(input: &[u8], mut header: GbaHeader, output: &mut W) -> Result<()> {
     let elf_file = elf::ElfBytes::<elf::endian::AnyEndian>::minimal_parse(input)?;
 
     let section_headers = elf_file
@@ -38,18 +93,15 @@ pub fn write_gba_file<W: Write>(
         }
 
         if bytes_written == 0 {
-            const GBA_HEADER_SIZE: usize = 192;
-
             ensure!(
                 data.len() > GBA_HEADER_SIZE,
                 "first section must be at least as big as the gba header"
             );
 
             header.start_code = data[0..4].try_into().unwrap();
-            header.update_checksum();
 
-            let header_bytes = bytemuck::bytes_of(&header);
-            output.write_all(header_bytes)?;
+            let header_bytes = header.produce_header();
+            output.write_all(&header_bytes)?;
 
             data = &data[GBA_HEADER_SIZE..];
             bytes_written += GBA_HEADER_SIZE as u64;

agb-gbafix/src/main.rs

@@ -7,7 +7,7 @@ use std::{
     path::PathBuf,
 };
 
-use agb_gbafix::write_gba_file;
+use agb_gbafix::{write_gba_file, GbaHeader};
 
 fn main() -> Result<()> {
     let matches = clap::Command::new("agb-gbafix")
@@ -27,7 +27,7 @@ fn main() -> Result<()> {
         None => input.with_extension("gba"),
     };
 
-    let mut header = gbafix::GBAHeader::default();
+    let mut header = GbaHeader::default();
 
     {
         let title = if let Some(title) = matches.get_one::<String>("title") {
@@ -41,7 +41,7 @@ fn main() -> Result<()> {
         };
 
         for (i, &c) in title.as_bytes().iter().enumerate().take(12) {
-            header.title[i] = c;
+            header.game_title[i] = c;
         }
     }
 
@@ -61,7 +61,7 @@ fn main() -> Result<()> {
     }
 
     if let Some(game_version) = matches.get_one::<u8>("gameversion") {
-        header.version = *game_version;
+        header.software_version = *game_version;
     }
 
     if let Some(game_code) = matches.get_one::<String>("gamecode") {