private static async Task ExhaustAsync(XmlDictionaryReader reader, ReadAheadWrappingStream readAheadStream, CancellationToken cancellationToken)
{
if (reader != null)
{
do
{
if (readAheadStream != null)
{
await readAheadStream.EnsureBufferedAsync(cancellationToken);
}
} while (reader.Read());
}
}
public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
{
EnsureStreamIsOpen();
if (buffer == null)
throw TraceUtility.ThrowHelperError(new ArgumentNullException("buffer"), _message);
if (offset < 0)
throw TraceUtility.ThrowHelperError(new ArgumentOutOfRangeException("offset", offset,
SR.Format(SR.ValueMustBeNonNegative)), _message);
if (count < 0)
throw TraceUtility.ThrowHelperError(new ArgumentOutOfRangeException("count", count,
SR.Format(SR.ValueMustBeNonNegative)), _message);
if (buffer.Length - offset < count)
throw TraceUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.SFxInvalidStreamOffsetLength, offset + count)), _message);
try
{
if (_reader == null)
{
_readAheadStream =
_message.Properties[ReadAheadWrappingStream.ReadAheadWrappingStreamPropertyName] as ReadAheadWrappingStream;
// Fill buffer so reading to the body contents shouldn't cause a read through to transport stream
if (_readAheadStream != null)
{
await _readAheadStream.EnsureBufferedAsync(cancellationToken);
}
_reader = _message.GetReaderAtBodyContents();
if (_wrapperName != null)
{
_reader.MoveToContent();
_reader.ReadStartElement(_wrapperName, _wrapperNs);
}
_reader.MoveToContent();
if (_reader.NodeType == XmlNodeType.EndElement)
{
return 0;
}
_reader.ReadStartElement(_elementName, _elementNs);
}
if (_reader.MoveToContent() != XmlNodeType.Text)
{
await ExhaustAsync(_reader, _readAheadStream, cancellationToken);
return 0;
}
if (_readAheadStream != null)
{
// Calculate number of UTF8 bytes needed to represent the requested bytes in base64.
// The +3 is to adjust for integer division truncating instead of rounding and the final
// == padding that can occur at the end of a base64 encoded string.
int base64EncodedBytes = (int)((8L * count) / 6L) + 3;
await _readAheadStream.EnsureBufferedAsync(base64EncodedBytes, cancellationToken);
}
int bytesRead = _reader.ReadContentAsBase64(buffer, offset, count);
_position += bytesRead;
if (bytesRead == 0)
{
await ExhaustAsync(_reader, _readAheadStream, cancellationToken);
}
return bytesRead;
}
catch (Exception ex)
{
if (Fx.IsFatal(ex))
throw;
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new IOException(SR.Format(SR.SFxStreamIOException), ex));
}
}