/// <summary>
/// Read values of type <see cref="TiffFieldType.IFD"/> from the specified tag.
/// </summary>
/// <param name="tag">The tag to read.</param>
/// <param name="sizeLimit">The maximum number of values to read.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> that fires if the user want to stop the current task.</param>
/// <returns>A <see cref="ValueTask{TiffValueCollection}"/> that completes when the values are read and return the read values.</returns>
public ValueTask <TiffValueCollection <TiffStreamOffset> > ReadIFDFieldAsync(TiffTag tag, int sizeLimit, CancellationToken cancellationToken = default)
{
if (Reader is null)
{
throw new InvalidOperationException();
}
if (ImageFileDirectory is null)
{
throw new InvalidOperationException();
}
TiffImageFileDirectoryEntry entry = ImageFileDirectory.FindEntry(tag);
if (entry.Tag == TiffTag.None)
{
return(new ValueTask <TiffValueCollection <TiffStreamOffset> >(TiffValueCollection.Empty <TiffStreamOffset>()));
}
return(Reader.ReadIFDFieldAsync(entry, sizeLimit, cancellationToken: cancellationToken));
}
/// <summary>
/// Read values of type <see cref="TiffFieldType.SLong"/> from the specified tag.
/// </summary>
/// <param name="tag">The tag to read.</param>
/// <returns>The values read.</returns>
public TiffValueCollection <int> ReadSLongField(TiffTag tag)
{
if (Reader is null)
{
throw new InvalidOperationException();
}
if (ImageFileDirectory is null)
{
throw new InvalidOperationException();
}
TiffImageFileDirectoryEntry entry = ImageFileDirectory.FindEntry(tag);
if (entry.Tag == TiffTag.None)
{
return(TiffValueCollection.Empty <int>());
}
return(Reader.ReadSLongField(entry));
}
/// <summary>
/// Read values of type <see cref="TiffFieldType.SRational"/> from the specified tag.
/// </summary>
/// <param name="tag">The tag to read.</param>
/// <param name="sizeLimit">The maximum number of values to read.</param>
/// <returns>The values read.</returns>
public TiffValueCollection <TiffSRational> ReadSRationalField(TiffTag tag, int sizeLimit)
{
if (Reader is null)
{
throw new InvalidOperationException();
}
if (ImageFileDirectory is null)
{
throw new InvalidOperationException();
}
TiffImageFileDirectoryEntry entry = ImageFileDirectory.FindEntry(tag);
if (entry.Tag == TiffTag.None)
{
return(TiffValueCollection.Empty <TiffSRational>());
}
return(Reader.ReadSRationalField(entry, sizeLimit));
}
/// <summary>
/// Read values of type <see cref="TiffFieldType.ASCII"/> from the specified tag.
/// </summary>
/// <param name="tag">The tag to read.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> that fires if the user want to stop the current task.</param>
/// <returns>A <see cref="ValueTask{TiffValueCollection}"/> that completes when the values are read and return the read values.</returns>
public ValueTask <TiffValueCollection <string> > ReadASCIIFieldAsync(TiffTag tag, CancellationToken cancellationToken = default)
{
if (Reader is null)
{
throw new InvalidOperationException();
}
if (ImageFileDirectory is null)
{
throw new InvalidOperationException();
}
TiffImageFileDirectoryEntry entry = ImageFileDirectory.FindEntry(tag);
if (entry.Tag == TiffTag.None)
{
return(new ValueTask <TiffValueCollection <string> >(TiffValueCollection.Empty <string>()));
}
return(Reader.ReadASCIIFieldAsync(entry, cancellationToken: cancellationToken));
}
private static TiffValueCollection <string> ParseASCIIArray(ReadOnlySpan <byte> buffer)
{
int startIndex = 0;
int count = buffer.Length;
if (count == 0)
{
return(TiffValueCollection.Empty <string>());
}
// Find the null terminator of the first string.
int endIndex = startIndex + count - 1;
int nullIndex = endIndex + 1;
for (int i = startIndex; i <= endIndex; i++)
{
if (buffer[i] == 0)
{
nullIndex = i;
break;
}
}
string firstValue = EncodingASCIIGetString(buffer.Slice(startIndex, nullIndex - startIndex));
if (nullIndex >= endIndex)
{
return(TiffValueCollection.Single(firstValue));
}
// Find the count of all strings.
startIndex = nullIndex + 1;
int strCount = 1;
for (int i = startIndex; i <= endIndex; i++)
{
if (buffer[i] == 0)
{
strCount++;
}
}
if (buffer[endIndex] != 0)
{
strCount++;
}
// Read all strings.
string[] values = new string[strCount];
values[0] = firstValue;
int index = 1;
for (int i = startIndex; i <= endIndex; i++)
{
if (buffer[i] == 0)
{
values[index] = EncodingASCIIGetString(buffer.Slice(startIndex, i - startIndex));
index++;
startIndex = i + 1;
}
}
if (buffer[endIndex] != 0)
{
values[index] = EncodingASCIIGetString(buffer.Slice(startIndex, endIndex - startIndex + 1));
}
return(TiffValueCollection.UnsafeWrap(values));
}