Add support to read embbed control block (tested game: https://vndb.org/v19829 )

msg_tool_build/src/simple_pack.rs

@@ -0,0 +1,66 @@
+//! A simple implementation of a pack file
+use std::fs::File;
+use std::io::{BufWriter, Read, Result, Seek, Write};
+use std::path::{Path, PathBuf};
+
+pub struct SimplePack {
+    file: File,
+    path: PathBuf,
+    tmp_path: PathBuf,
+}
+
+impl SimplePack {
+    pub fn new<P: AsRef<Path> + ?Sized>(path: &P) -> Result<Self> {
+        let mut file = File::create(path.as_ref())?;
+        file.write_all(b"SPCK")?;
+        file.write_all(&[0])?; // No compression
+        Ok(Self {
+            file,
+            path: path.as_ref().to_path_buf(),
+            tmp_path: path.as_ref().with_added_extension(".tmp"),
+        })
+    }
+    pub fn add_file<R: Read>(&mut self, name: &str, mut data: R) -> Result<()> {
+        let mut writer = BufWriter::new(&mut self.file);
+        writer.write_all(name.as_bytes())?;
+        writer.write_all(&[0])?; // Null terminator for the name
+        let file_size_loc = writer.stream_position()?;
+        writer.write_all(&0u64.to_le_bytes())?; // Placeholder for file size
+        let size = std::io::copy(&mut data, &mut writer)?;
+        let current_pos = writer.stream_position()?;
+        writer.seek(std::io::SeekFrom::Start(file_size_loc))?;
+        writer.write_all(&size.to_le_bytes())?; // Write the actual file size
+        writer.seek(std::io::SeekFrom::Start(current_pos))?; // Move back to the end of the file
+        writer.flush()?;
+        Ok(())
+    }
+    pub fn compress(mut self, level: i32) -> Result<()> {
+        self.file.flush()?;
+        std::mem::drop(self.file); // Close the file before renaming
+        // Move the file to a temporary location
+        std::fs::rename(&self.path, &self.tmp_path)?;
+        {
+            let tmp_file = File::open(&self.tmp_path)?;
+            let mut reader = std::io::BufReader::new(tmp_file);
+            reader.seek_relative(5)?; // Skip header
+            let original_size = reader.get_ref().metadata()?.len() - 5;
+            let outfile = File::create(&self.path)?;
+            let mut writer = std::io::BufWriter::new(outfile);
+            writer.write_all(b"SPCK")?;
+            writer.write_all(&[1])?; // Compression flag
+            let compress_size_loc = writer.stream_position()?;
+            writer.write_all(&0u64.to_le_bytes())?; // Placeholder for compressed size
+            writer.write_all(&original_size.to_le_bytes())?;
+            let cur_loc = writer.stream_position()?;
+            let mut encoder = zstd::stream::write::Encoder::new(&mut writer, level)?;
+            std::io::copy(&mut reader, &mut encoder)?;
+            encoder.finish()?;
+            writer.flush()?;
+            let compressed_size = writer.stream_position()? - cur_loc;
+            writer.seek(std::io::SeekFrom::Start(compress_size_loc))?;
+            writer.write_all(&compressed_size.to_le_bytes())?; // Write the actual compressed size
+        }
+        std::fs::remove_file(&self.tmp_path)?; // Clean up the temporary file
+        Ok(())
+    }
+}