internal static Zip64ExtraField GetJustZip64Block(Stream extraFieldStream,
bool readUncompressedSize, bool readCompressedSize,
bool readLocalHeaderOffset, bool readStartDiskNumber)
{
Zip64ExtraField zip64Field;
using (var reader = new BinaryReader(extraFieldStream, _utf8EncodingNoBOM))
{
while (ZipGenericExtraField.TryReadBlock(reader, extraFieldStream.Length, out var currentExtraField))
{
if (TryGetZip64BlockFromGenericExtraField(currentExtraField, readUncompressedSize,
readCompressedSize, readLocalHeaderOffset, readStartDiskNumber, out zip64Field))
{
return(zip64Field);
}
}
}
zip64Field = new Zip64ExtraField
{
CompressedSize = null,
UncompressedSize = null,
LocalHeaderOffset = null,
StartDiskNumber = null
};
return(zip64Field);
}
// if saveExtraFieldsAndComments is false, FileComment and ExtraFields will be null
// in either case, the zip64 extra field info will be incorporated into other fields
internal static bool TryReadBlock(BinaryReader reader, out ZipCentralDirectoryFileHeader header)
{
header = new ZipCentralDirectoryFileHeader();
if (reader.ReadUInt32() != SignatureConstant)
{
return(false);
}
reader.ReadByte(); // VersionMadeBySpecification
header.VersionMadeByCompatibility = reader.ReadByte();
reader.ReadUInt16(); // VersionNeededToExtract
header.GeneralPurposeBitFlag = reader.ReadUInt16();
header.CompressionMethod = reader.ReadUInt16();
header.LastModified = reader.ReadUInt32();
reader.ReadUInt32(); // Crc32
uint compressedSizeSmall = reader.ReadUInt32();
uint uncompressedSizeSmall = reader.ReadUInt32();
header.FilenameLength = reader.ReadUInt16();
header.ExtraFieldLength = reader.ReadUInt16();
header.FileCommentLength = reader.ReadUInt16();
ushort diskNumberStartSmall = reader.ReadUInt16();
reader.ReadUInt16(); // InternalFileAttributes
reader.ReadUInt32(); // ExternalFileAttributes
uint relativeOffsetOfLocalHeaderSmall = reader.ReadUInt32();
header.Filename = reader.ReadBytes(header.FilenameLength);
bool uncompressedSizeInZip64 = uncompressedSizeSmall == ZipHelper.Mask32Bit;
bool compressedSizeInZip64 = compressedSizeSmall == ZipHelper.Mask32Bit;
bool relativeOffsetInZip64 = relativeOffsetOfLocalHeaderSmall == ZipHelper.Mask32Bit;
bool diskNumberStartInZip64 = diskNumberStartSmall == ZipHelper.Mask16Bit;
Zip64ExtraField zip64;
long endExtraFields = reader.BaseStream.Position + header.ExtraFieldLength;
using (Stream str = new SubReadStream(reader.BaseStream, reader.BaseStream.Position, header.ExtraFieldLength))
{
zip64 = Zip64ExtraField.GetJustZip64Block(str,
uncompressedSizeInZip64, compressedSizeInZip64,
relativeOffsetInZip64, diskNumberStartInZip64);
}
// There are zip files that have malformed ExtraField blocks in which GetJustZip64Block() silently
// bails out without reading all the way to the end of the ExtraField block. Thus we must force the
// stream's position to the proper place.
// Fen's note: Original did a seek here, which for some reason is like 300x slower than a read, and
// also inexplicably causes ReadUInt32() to be 4x as slow and/or occur 4x as often(?!)
// Buffer alignments...? I dunno. Anyway. Speed.
// Also maybe not a good idea to use something that's faster when I don't know why it's faster.
// But my results are the same as the old method, so herpaderp.
reader.BaseStream.AdvanceToPosition(endExtraFields + header.FileCommentLength);
header.UncompressedSize = zip64.UncompressedSize ?? uncompressedSizeSmall;
header.CompressedSize = zip64.CompressedSize ?? compressedSizeSmall;
header.RelativeOffsetOfLocalHeader = zip64.LocalHeaderOffset ?? relativeOffsetOfLocalHeaderSmall;
header.DiskNumberStart = zip64.StartDiskNumber ?? diskNumberStartSmall;
return(true);
}
private static bool TryGetZip64BlockFromGenericExtraField(ZipGenericExtraField extraField,
bool readUncompressedSize, bool readCompressedSize,
bool readLocalHeaderOffset, bool readStartDiskNumber,
out Zip64ExtraField zip64Block)
{
zip64Block = new Zip64ExtraField
{
CompressedSize = null,
UncompressedSize = null,
LocalHeaderOffset = null,
StartDiskNumber = null
};
if (extraField.Tag != TagConstant)
{
return(false);
}
// this pattern needed because nested using blocks trigger CA2202
MemoryStream?ms = null;
try
{
ms = new MemoryStream(extraField.Data);
using var reader = new BinaryReader(ms);
// Why did they do this and how does it still work?!
ms = null;
zip64Block._size = extraField.Size;
ushort expectedSize = 0;
if (readUncompressedSize)
{
expectedSize += 8;
}
if (readCompressedSize)
{
expectedSize += 8;
}
if (readLocalHeaderOffset)
{
expectedSize += 8;
}
if (readStartDiskNumber)
{
expectedSize += 4;
}
// if it is not the expected size, perhaps there is another extra field that matches
if (expectedSize != zip64Block._size)
{
return(false);
}
if (readUncompressedSize)
{
zip64Block.UncompressedSize = reader.ReadInt64();
}
if (readCompressedSize)
{
zip64Block.CompressedSize = reader.ReadInt64();
}
if (readLocalHeaderOffset)
{
zip64Block.LocalHeaderOffset = reader.ReadInt64();
}
if (readStartDiskNumber)
{
zip64Block.StartDiskNumber = reader.ReadInt32();
}
// original values are unsigned, so implies value is too big to fit in signed integer
if (zip64Block.UncompressedSize < 0)
{
throw new InvalidDataException(SR.FieldTooBigUncompressedSize);
}
if (zip64Block.CompressedSize < 0)
{
throw new InvalidDataException(SR.FieldTooBigCompressedSize);
}
if (zip64Block.LocalHeaderOffset < 0)
{
throw new InvalidDataException(SR.FieldTooBigLocalHeaderOffset);
}
if (zip64Block.StartDiskNumber < 0)
{
throw new InvalidDataException(SR.FieldTooBigStartDiskNumber);
}
return(true);
}
finally
{
ms?.Dispose();
}
}