/// <summary>
/// Flush the TIFF file header into the stream.
/// </summary>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> that fires if the user has requested to abort this operation.</param>
/// <returns></returns>
public async Task FlushAsync(CancellationToken cancellationToken = default)
{
EnsureNotDisposed();
cancellationToken.ThrowIfCancellationRequested();
Debug.Assert(_writer != null);
if (_requireBigTiff && !_useBigTiff)
{
throw new InvalidOperationException("Must use BigTIFF format. But it is disabled.");
}
byte[] buffer = ArrayPool <byte> .Shared.Rent(SmallBufferSize);
try
{
Array.Clear(buffer, 0, 16);
TiffFileHeader.Write(buffer, _imageFileDirectoryOffset, BitConverter.IsLittleEndian, _useBigTiff);
await _writer !.WriteAsync(0, new ArraySegment <byte>(buffer, 0, _useBigTiff ? 16 : 8), cancellationToken).ConfigureAwait(false);
await _writer.FlushAsync(cancellationToken).ConfigureAwait(false);
}
finally
{
ArrayPool <byte> .Shared.Return(buffer);
}
}
/// <summary>
/// Try to parse TIFF file header from the specified buffer.
/// </summary>
/// <param name="data">The buffer to use.</param>
/// <param name="header">The parsed TIFF file header.</param>
/// <returns>True if the TIFF file header is successfully parsed. Otherwise, false.</returns>
public static bool TryParse(ReadOnlySpan <byte> data, out TiffFileHeader header)
{
if (data.Length < 8)
{
header = default;
return(false);
}
// Read byte order
short byteOrderFlag = MemoryMarshal.Read <short>(data);
bool reverseEndianRequired;
if (byteOrderFlag == LittleEndianByteOrderFlag)
{
reverseEndianRequired = !BitConverter.IsLittleEndian;
}
else if (byteOrderFlag == BigEndianByteOrderFlag)
{
reverseEndianRequired = BitConverter.IsLittleEndian;
}
else
{
header = default;
return(false);
}
// Read TIFF version
short version = MemoryMarshal.Read <short>(data.Slice(2));
if (reverseEndianRequired)
{
version = BinaryPrimitives.ReverseEndianness(version);
}
if (version == StandardTiffVersion)
{
// Standard TIFF
int imageFileDirectoryOffset32 = MemoryMarshal.Read <int>(data.Slice(4));
if (reverseEndianRequired)
{
imageFileDirectoryOffset32 = BinaryPrimitives.ReverseEndianness(imageFileDirectoryOffset32);
}
// An IFD can be at any location in the file after the header but must begin on a word boundary.
if (imageFileDirectoryOffset32 < 8 || (imageFileDirectoryOffset32 & 0b1) == 1)
{
header = default;
return(false);
}
header = new TiffFileHeader(byteOrderFlag, imageFileDirectoryOffset32);
return(true);
}
else if (version == BigTiffVersion)
{
// BigTIFF
data = data.Slice(4);
if (data.Length < 12)
{
header = default;
return(false);
}
short byteSizeOfOffsets = MemoryMarshal.Read <short>(data);
short bigTiffConstant = MemoryMarshal.Read <short>(data.Slice(2));
long imageFileDirectoryOffset64 = MemoryMarshal.Read <long>(data.Slice(4));
if (reverseEndianRequired)
{
byteSizeOfOffsets = BinaryPrimitives.ReverseEndianness(byteSizeOfOffsets);
// Uncomment this when we support BigTIFF constant other than zero.
// bigTiffConstant = BinaryPrimitives.ReverseEndianness(bigTiffConstant);
imageFileDirectoryOffset64 = BinaryPrimitives.ReverseEndianness(imageFileDirectoryOffset64);
}
if (byteSizeOfOffsets != 8)
{
// Unsupported byte size of offsets
header = default;
return(false);
}
if (bigTiffConstant != 0)
{
header = default;
return(false);
}
// An IFD can be at any location in the file after the header but must begin on a word boundary.
if (imageFileDirectoryOffset64 < 16 || (imageFileDirectoryOffset64 & 0b1) == 1)
{
header = default;
return(false);
}
header = new TiffFileHeader(byteOrderFlag, BigTiffVersion, byteSizeOfOffsets, imageFileDirectoryOffset64);
return(true);
}
else
{
header = default;
return(false);
}
}
