This package provides stream-based readers and writers for tar files.
When working with large tar files, this library consumes considerably less memory than package:archive, although it is slightly slower.
To read entries from a tar file, use
import 'dart:io'; import 'package:tar/tar.dart'; Future<void> main() async { final reader = TarReader(File('file.tar').openRead()); while (await reader.moveNext()) { // Use reader.header to see the header of the current tar entry print(reader.header.name); // And reader.contents to read the content of the current entry as a stream print(await reader.contents.transform(utf8.decoder).first); } // Note that the reader will automatically close if moveNext() returns false or // throws. If you want to close a tar stream before that happens, use // reader.cancel(); }
To read .tar.gz
files, transform the stream with gzip.decoder
first.
To easily go through all entries in a tar file, use Reader.forEach
:
Future<void> main() async { final inputStream = File('file.tar').openRead(); await TarReader.forEach(inputStream, (entry) { print(header.name); print(await entry.contents.transform(utf8.decoder).first); }); }
Warning: Since the reader is backed by a single stream, concurrent calls to read
are not allowed! Similarly, if you‘re reading from an entry’s contents
, make sure to fully drain the stream before calling read()
again.
You can write tar files into a StreamSink<List<int>>
, such as an IOSink
:
import 'dart:io'; import 'package:tar/tar.dart'; Future<void> main() async { final output = File('test.tar').openWrite(); await Stream<tar.Entry>.value( tar.MemoryEntry( tar.Header( name: 'hello.txt', mode: int.parse('644', radix: 8), ), utf8.encode('Hello world'), ), ).pipe(tar.tarWritingSink(output)); }
Note that tar files are always written in the pax format defined by the POSIX.1-2001 specification (--format=posix
in GNU tar). When all entries have file names shorter than 100 chars and a size smaller than 8 GB, this is equivalent to the ustar
format. This library won't write PAX headers when there is no reason to do so.
To write .tar.gz
files, you can again transform the stream twice:
import 'dart:io'; import 'package:tar/tar.dart'; Future<void> write(Stream<tar.Entry> entries) { return entries .transform(tarWriter) .transform(gzip.encoder) .pipe(File('output.tar.gz').openWrite()) }
Big thanks to Garett Tok Ern Liang for writing the initial tar implementation this library is based on.