public static bool TryParse(ReadOnlySpan <byte> buffer, bool metadataOnly, out JpegScanHeader scanHeader, out int bytesConsumed)
{
bytesConsumed = 0;
if (buffer.IsEmpty)
{
scanHeader = default;
return(false);
}
byte numberOfComponents = buffer[0];
buffer = buffer.Slice(1);
bytesConsumed++;
if (buffer.Length < (2 * numberOfComponents + 3))
{
scanHeader = default;
return(false);
}
JpegScanComponentSpecificationParameters[]? components;
if (metadataOnly)
{
components = null;
buffer = buffer.Slice(2 * numberOfComponents);
bytesConsumed += 2 * numberOfComponents;
}
else
{
components = new JpegScanComponentSpecificationParameters[numberOfComponents];
for (int i = 0; i < components.Length; i++)
{
#pragma warning disable CA1806
JpegScanComponentSpecificationParameters.TryParse(buffer, out components[i]);
#pragma warning restore CA1806
buffer = buffer.Slice(2);
bytesConsumed += 2;
}
}
byte successiveApproximationBitPosition = buffer[2];
byte endOfSpectralSelection = buffer[1];
byte startOfSpectralSelection = buffer[0];
bytesConsumed += 3;
scanHeader = new JpegScanHeader(numberOfComponents, components, startOfSpectralSelection, endOfSpectralSelection, (byte)(successiveApproximationBitPosition >> 4), (byte)(successiveApproximationBitPosition & 0xf));
return(true);
}
public static bool TryParse(ReadOnlySequence <byte> buffer, bool metadataOnly, out JpegScanHeader scanHeader, out int bytesConsumed)
{
if (buffer.IsSingleSegment)
{
#if NO_READONLYSEQUENCE_FISTSPAN
return(TryParse(buffer.First.Span, metadataOnly, out scanHeader, out bytesConsumed));
#else
return(TryParse(buffer.FirstSpan, metadataOnly, out scanHeader, out bytesConsumed));
#endif
}
bytesConsumed = 0;
if (buffer.IsEmpty)
{
scanHeader = default;
return(false);
}
#if NO_READONLYSEQUENCE_FISTSPAN
byte numberOfComponents = buffer.First.Span[0];
#else
byte numberOfComponents = buffer.FirstSpan[0];
#endif
buffer = buffer.Slice(1);
bytesConsumed++;
if (buffer.Length < (2 * numberOfComponents + 3))
{
scanHeader = default;
return(false);
}
JpegScanComponentSpecificationParameters[]? components;
if (metadataOnly)
{
components = null;
buffer = buffer.Slice(2 * numberOfComponents);
bytesConsumed += 2 * numberOfComponents;
}
else
{
components = new JpegScanComponentSpecificationParameters[numberOfComponents];
for (int i = 0; i < components.Length; i++)
{
#pragma warning disable CA1806
JpegScanComponentSpecificationParameters.TryParse(buffer, out components[i]);
#pragma warning restore CA1806
buffer = buffer.Slice(2);
bytesConsumed += 2;
}
}
Span <byte> local = stackalloc byte[4];
buffer.Slice(0, 3).CopyTo(local);
byte successiveApproximationBitPosition = local[2];
byte endOfSpectralSelection = local[1];
byte startOfSpectralSelection = local[0];
bytesConsumed += 3;
scanHeader = new JpegScanHeader(numberOfComponents, components, startOfSpectralSelection, endOfSpectralSelection, (byte)(successiveApproximationBitPosition >> 4), (byte)(successiveApproximationBitPosition & 0xf));
return(true);
}
