dictzip_reader 0.1.3

A Dart package to read and decompress dictzip (.dict.dz) files with random access support.

dictzip_reader

A Dart package to read and decompress dictzip (.dict.dz) files with random access support.

Dictzip is a gzip variant that stores a Random Access (RA) chunk index in the gzip Extra Field. The uncompressed data is divided into fixed-size chunks, each chunk independently deflated. This allows efficient random access: only the chunk(s) covering the requested byte range need to be decompressed.

Usage

Standard File Reading

import 'package:dictzip_reader/dictzip_reader.dart';

void main() async {
  final reader = DictzipReader('/path/to/file.dict.dz');
  await reader.open();
  
  // Read 100 bytes starting at uncompressed offset 500
  final text = await reader.read(500, 100);
  print(text);
  
  await reader.close();
}

Built-in Memory Source

For small files that fit in memory, use MemoryRandomAccessSource for maximum speed:

final fileBytes = await File('test.dict.dz').readAsBytes();
final source = MemoryRandomAccessSource(fileBytes);
final reader = DictzipReader(null);

await reader.openSource(source);
final text = await reader.read(0, 50);
print(text);

await reader.close();

Advanced: Custom Data Sources (SAF, Network)

To support other non-file sources (like Android Storage Access Framework content:// URIs), implement the RandomAccessSource interface.

class MyCustomSource implements RandomAccessSource {
  @override
  Future<Uint8List> read(int offset, int length) async {
    // Implement your read logic here
  }

  @override
  Future<int> get length async => 12345; // total size

  @override
  Future<void> open() async {
    // Check and open source if necessary
  }

  @override
  Future<void> close() async {
    // Cleanup
  }
}

void main() async {
  final reader = DictzipReader(null); // No path needed
  await reader.openSource(MyCustomSource());
  
  final text = await reader.read(0, 50);
  print(text);
  
  await reader.close();
}

Features

• Parses dictzip RA (Random Access) headers.
• Supports efficient random access to compressed files.
• Handles standard gzip files (though without random access optimization if RA header is missing).
• Low memory footprint by only decompressing necessary chunks.

Github repository

https://github.com/drdhaval2785/dictzip_reader