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);
}
// shouldn't ever read the byte at position endExtraField
// assumes we are positioned at the beginning of an extra field subfield
internal static bool TryReadBlock(BinaryReader reader, long endExtraField, out ZipGenericExtraField field)
{
field = new ZipGenericExtraField();
// not enough bytes to read tag + size
if (endExtraField - reader.BaseStream.Position < 4)
{
return(false);
}
field.Tag = reader.ReadUInt16();
field.Size = reader.ReadUInt16();
// not enough bytes to read the data
if (endExtraField - reader.BaseStream.Position < field.Size)
{
return(false);
}
field.Data = reader.ReadBytes(field.Size);
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();
}
}