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