archive/lib/src/tar_decoder.dart

import 'dart:convert';

import 'archive.dart';
import 'archive_file.dart';
import 'tar/tar_file.dart';
import 'util/input_stream.dart';

final paxRecordRegexp = RegExp(r"(\d+) (\w+)=(.*)");

/// Decode a tar formatted buffer into an [Archive] object.
class TarDecoder {
  List<TarFile> files = [];

  Archive decodeBytes(List<int> data,
      {bool verify = false, bool storeData = true}) {
    return decodeBuffer(InputStream(data),
        verify: verify, storeData: storeData);
  }

  Archive decodeBuffer(InputStreamBase input,
      {bool verify = false, bool storeData = true}) {
    final archive = Archive();
    files.clear();

    String? nextName;
    String? nextLinkName;

    // TarFile paxHeader = null;
    while (!input.isEOS) {
      // End of archive when two consecutive 0's are found.
      final endCheck = input.peekBytes(2).toUint8List();
      if (endCheck.length < 2 || (endCheck[0] == 0 && endCheck[1] == 0)) {
        break;
      }

      final tf = TarFile.read(input, storeData: storeData);
      // GNU tar puts filenames in files when they exceed tar's native length.
      if (tf.filename == '././@LongLink') {
        nextName = tf.rawContent!.readString();
        continue;
      }

      // In POSIX formatted tar files, a separate 'PAX' file contains extended
      // metadata for files. These are identified by having a type flag 'X'.
      // TODO: parse these metadata values.
      if (tf.typeFlag == TarFile.TYPE_G_EX_HEADER ||
          tf.typeFlag == TarFile.TYPE_G_EX_HEADER2) {
        // TODO handle PAX global header.
        continue;
      }
      if (tf.typeFlag == TarFile.TYPE_EX_HEADER ||
          tf.typeFlag == TarFile.TYPE_EX_HEADER2) {
        utf8
            .decode(tf.rawContent!.toUint8List())
            .split('\n')
            .where((s) => paxRecordRegexp.hasMatch(s))
            .forEach((record) {
          var match = paxRecordRegexp.firstMatch(record)!;
          var keyword = match.group(2);
          var value = match.group(3)!;
          switch (keyword) {
            case 'path':
              nextName = value;
              break;
            case 'linkpath':
              nextLinkName = value;
              break;
            default:
            // TODO: support other pax headers.
          }
        });
        continue;
      }

      // Fix file attributes.
      if (nextName != null) {
        tf.filename = nextName!;
        nextName = null;
      }
      if (nextLinkName != null) {
        tf.nameOfLinkedFile = nextLinkName!;
        nextLinkName = null;
      }
      files.add(tf);

      final file = ArchiveFile(tf.filename, tf.fileSize, tf.rawContent);

      file.mode = tf.mode;
      file.ownerId = tf.ownerId;
      file.groupId = tf.groupId;
      file.lastModTime = tf.lastModTime;
      file.isFile = tf.isFile;
      file.isSymbolicLink = tf.typeFlag == TarFile.TYPE_SYMBOLIC_LINK;
      file.nameOfLinkedFile = tf.nameOfLinkedFile;

      archive.addFile(file);
    }

    return archive;
  }
}