Kaitai Struct - .DS_Store - Examples

App.java

package com.ksydsstore.app;

import java.net.*;
import java.io.*;
import java.util.*;

import io.kaitai.struct.ByteBufferKaitaiStream;

import com.ksydsstore.app.DsStore.Block;
import com.ksydsstore.app.DsStore.Block.BlockData;
import com.ksydsstore.app.DsStore.MasterBlockRef;
import com.ksydsstore.app.DsStore.MasterBlockRef.MasterBlock;

public class App {
  private DsStore dsStore;
  private Set<String> filenames;

  public static void main(String[] args) throws Exception {
    // Random .DS_Store file found on GitHub.
    URL url = new URL("https://raw.githubusercontent.com/Apress/traefik-api-gateway-microservices/main/ch07/.DS_Store");

    App parser = new App(url);
    parser.printFilenames();
  }

  public App(URL url) throws Exception {
    this.filenames = new HashSet<String>();

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    InputStream is = null;

    try {
      is = url.openStream();
      byte[] byteChunk = new byte[4096];
      int n;

      while ( (n = is.read(byteChunk)) > 0) {
        baos.write(byteChunk, 0, n);
      }
    }
    catch (IOException e) {
      System.err.printf ("Failed while reading bytes from %s: %s",
          url.toExternalForm(), e.getMessage());
      e.printStackTrace ();
    }
    finally {
      if (is != null) {
        is.close();
      }
    }

    this.dsStore = new DsStore(new ByteBufferKaitaiStream(baos.toByteArray()));

    for (MasterBlockRef masterBlockRef : this.dsStore.buddyAllocatorBody().directories()) {
      // Each B-tree directory has one master block comprising metadata.
      MasterBlock masterBlock = masterBlockRef.masterBlock();

      long blockId = masterBlock.blockId();
      long numRecords = masterBlock.numRecords();

      Block rootBlock = masterBlock.rootBlock();

      // Traverse recursively the B-tree from its root block.
      traverse(rootBlock);
    }
  }

  private void traverse(Block block) throws Exception {
    Block nextBlock = block.rightmostBlock();

    if (nextBlock != null) {
      traverse(nextBlock);
    }

    for (BlockData blockData : block.data()) {
      nextBlock = blockData.block();

      if (nextBlock != null) {
        traverse(nextBlock);
      }

      this.filenames.add(blockData.record().filename().value());
    }
  }

  public void printFilenames() {
    System.out.println("Filenames:");

    for (String filename : this.filenames) {
      System.out.println("  " + filename);
    }
  }
}

parser.py

from ds_store import DsStore

if __name__ == "__main__":
    data = DsStore.from_file("ds_store_sample_2.bin")

    # Use a set to avoid duplicates.
    filenames = set()

    def traverse(block):
        """
        Traverse recursively the B-tree from the block given as parameter.

        All filenames found in the block records are added to the global set of
        filenames.
        """

        next_block = block.rightmost_block

        if type(next_block) is DsStore.Block:
            traverse(next_block)

        for data in block.data:
            next_block = data.block

            if type(next_block) is DsStore.Block:
                traverse(next_block)

            filenames.add(data.record.filename.value)

    print(f"Number of directories: {data.buddy_allocator_body.num_directories}")
    print(f"Number of blocks: {data.buddy_allocator_body.num_blocks}")

    # One single DS_Store file can contain multiple B-tree directories.
    for directory in data.buddy_allocator_body.directories:
        # Each B-tree directory has one master block comprising metadata.
        master_block = directory.master_block

        master_block_id  = master_block.block_id
        nb_records = master_block.num_records

        print(f"Master block {master_block_id} contains {nb_records} records")

        # Traverse recursively the B-tree from its root block.
        traverse(master_block.root_block)

    # Display all filenames.
    print("Filenames:")

    for filename in filenames:
        print(f"  {filename}")