77 lines
2.8 KiB
C#
77 lines
2.8 KiB
C#
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using System;
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using System.Collections.Generic;
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using System.IO;
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using SharpCompress.Common.Zip.Headers;
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using SharpCompress.IO;
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namespace SharpCompress.Common.Zip
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{
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internal class SeekableZipHeaderFactory : ZipHeaderFactory
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{
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private const int MAX_ITERATIONS_FOR_DIRECTORY_HEADER = 1000;
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internal SeekableZipHeaderFactory(string password)
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: base(StreamingMode.Seekable, password)
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{
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}
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internal IEnumerable<DirectoryEntryHeader> ReadSeekableHeader(Stream stream)
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{
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long offset = 0;
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uint signature;
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BinaryReader reader = new BinaryReader(stream);
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int iterationCount = 0;
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do
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{
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if ((stream.Length + offset) - 4 < 0)
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{
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throw new ArchiveException("Failed to locate the Zip Header");
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}
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stream.Seek(offset - 4, SeekOrigin.End);
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signature = reader.ReadUInt32();
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offset--;
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iterationCount++;
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if (iterationCount > MAX_ITERATIONS_FOR_DIRECTORY_HEADER)
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{
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throw new ArchiveException(
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"Could not find Zip file Directory at the end of the file. File may be corrupted.");
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}
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} while (signature != DIRECTORY_END_HEADER_BYTES);
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var entry = new DirectoryEndHeader();
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entry.Read(reader);
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stream.Seek(entry.DirectoryStartOffsetRelativeToDisk, SeekOrigin.Begin);
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DirectoryEntryHeader directoryEntryHeader = null;
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long position = stream.Position;
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while (true)
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{
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stream.Position = position;
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signature = reader.ReadUInt32();
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directoryEntryHeader = ReadHeader(signature, reader) as DirectoryEntryHeader;
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position = stream.Position;
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if (directoryEntryHeader == null)
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{
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yield break;
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}
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//entry could be zero bytes so we need to know that.
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directoryEntryHeader.HasData = directoryEntryHeader.CompressedSize != 0;
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yield return directoryEntryHeader;
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}
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}
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internal LocalEntryHeader GetLocalHeader(Stream stream, DirectoryEntryHeader directoryEntryHeader)
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{
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stream.Seek(directoryEntryHeader.RelativeOffsetOfEntryHeader, SeekOrigin.Begin);
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BinaryReader reader = new BinaryReader(stream);
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uint signature = reader.ReadUInt32();
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var localEntryHeader = ReadHeader(signature, reader) as LocalEntryHeader;
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if (localEntryHeader == null)
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{
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throw new InvalidOperationException();
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}
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return localEntryHeader;
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}
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}
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}
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