public unsafe override bool TryEncodeUnicodeScalar(int unicodeScalar, char *buffer, int bufferLength, out int numberOfCharactersWritten)
{
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
if (!WillEncode(unicodeScalar))
{
return(TryWriteScalarAsChar(unicodeScalar, buffer, bufferLength, out numberOfCharactersWritten));
}
numberOfCharactersWritten = 0;
uint asUtf8 = unchecked ((uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue((uint)unicodeScalar));
do
{
if (numberOfCharactersWritten + 3 > bufferLength)
{
numberOfCharactersWritten = 0;
return(false);
}
*buffer = '%'; buffer++;
*buffer = HexConverter.ToCharUpper((int)asUtf8 >> 4); buffer++;
*buffer = HexConverter.ToCharUpper((int)asUtf8); buffer++;
numberOfCharactersWritten += 3;
}while ((asUtf8 >>= 8) != 0);
return(true);
}
public unsafe override bool TryEncodeUnicodeScalar(int unicodeScalar, char *buffer, int bufferLength, out int numberOfCharactersWritten)
{
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
if (!WillEncode(unicodeScalar))
{
return(TryWriteScalarAsChar(unicodeScalar, buffer, bufferLength, out numberOfCharactersWritten));
}
numberOfCharactersWritten = 0;
uint asUtf8 = (uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue((uint)unicodeScalar);
do
{
char highNibble, lowNibble;
HexUtil.ByteToHexDigits((byte)asUtf8, out highNibble, out lowNibble);
if (numberOfCharactersWritten + 3 > bufferLength)
{
numberOfCharactersWritten = 0;
return(false);
}
*buffer = '%'; buffer++;
*buffer = highNibble; buffer++;
*buffer = lowNibble; buffer++;
numberOfCharactersWritten += 3;
}while ((asUtf8 >>= 8) != 0);
return(true);
}
public unsafe override bool TryEncodeUnicodeScalar(int unicodeScalar, char *buffer, int length, out int writtenChars)
{
if (!Encodes(unicodeScalar))
{
return(unicodeScalar.TryWriteScalarAsChar(buffer, length, out writtenChars));
}
writtenChars = 0;
uint asUtf8 = (uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue((uint)unicodeScalar);
do
{
char highNibble, lowNibble;
HexUtil.WriteHexEncodedByte((byte)asUtf8, out highNibble, out lowNibble);
if (length < 3)
{
writtenChars = 0;
return(false);
}
*buffer = '%'; buffer++;
*buffer = highNibble; buffer++;
*buffer = lowNibble; buffer++;
writtenChars += 3;
}while ((asUtf8 >>= 8) != 0);
return(true);
}
// Writes a scalar value as a percent-encoded sequence of UTF8 bytes, per RFC 3987.
protected override void WriteEncodedScalar(ref Writer writer, uint value)
{
uint asUtf8 = (uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue(value);
do
{
char highNibble, lowNibble;
HexUtil.WriteHexEncodedByte((byte)asUtf8, out highNibble, out lowNibble);
writer.Write('%');
writer.Write(highNibble);
writer.Write(lowNibble);
} while ((asUtf8 >>= 8) != 0);
}
private bool TryEncodeUnicodeScalarUtf8(uint unicodeScalar, Span <char> utf16ScratchBuffer, Span <byte> utf8Destination, out int bytesWritten)
{
if (!TryEncodeUnicodeScalar(unicodeScalar, utf16ScratchBuffer, out int charsWritten))
{
// We really don't expect any encoder to exceed 24 escaped chars per input scalar.
// If this happens, throw an exception and we can figure out if we want to support it
// in the future.
ThrowArgumentException_MaxOutputCharsPerInputChar();
}
// Transcode chars -> bytes one at a time.
utf16ScratchBuffer = utf16ScratchBuffer.Slice(0, charsWritten);
int dstIdx = 0;
while (!utf16ScratchBuffer.IsEmpty)
{
if (Rune.DecodeFromUtf16(utf16ScratchBuffer, out Rune nextScalarValue, out int scalarUtf16CodeUnitCount) != OperationStatus.Done)
{
// Wrote bad UTF-16 data, we cannot transcode to UTF-8.
ThrowArgumentException_MaxOutputCharsPerInputChar();
}
uint utf8lsb = (uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue((uint)nextScalarValue.Value);
do
{
if (SpanUtility.IsValidIndex(utf8Destination, dstIdx))
{
utf8Destination[dstIdx++] = (byte)utf8lsb;
}
else
{
bytesWritten = 0; // ran out of space in the destination
return(false);
}
} while ((utf8lsb >>= 8) != 0);
utf16ScratchBuffer = utf16ScratchBuffer.Slice(scalarUtf16CodeUnitCount);
}
bytesWritten = dstIdx;
return(true);
}
// skips the call to FindFirstCharacterToEncodeUtf8
private protected virtual OperationStatus EncodeUtf8Core(
ReadOnlySpan <byte> utf8Source,
Span <byte> utf8Destination,
out int bytesConsumed,
out int bytesWritten,
bool isFinalBlock)
{
int originalUtf8SourceLength = utf8Source.Length;
int originalUtf8DestinationLength = utf8Destination.Length;
const int TempUtf16CharBufferLength = 24; // arbitrarily chosen, but sufficient for any reasonable implementation
Span <char> utf16ScratchBuffer = stackalloc char[TempUtf16CharBufferLength];
while (!utf8Source.IsEmpty)
{
OperationStatus opStatus = Rune.DecodeFromUtf8(utf8Source, out Rune scalarValue, out int bytesConsumedJustNow);
if (opStatus != OperationStatus.Done)
{
if (!isFinalBlock && opStatus == OperationStatus.NeedMoreData)
{
goto NeedMoreData;
}
Debug.Assert(scalarValue == Rune.ReplacementChar); // DecodeFromUtf8 should've performed substitution
goto MustEncode;
}
if (!WillEncode(scalarValue.Value))
{
uint utf8lsb = (uint)UnicodeHelpers.GetUtf8RepresentationForScalarValue((uint)scalarValue.Value);
int dstIdxTemp = 0;
do
{
if ((uint)dstIdxTemp >= (uint)utf8Destination.Length)
{
goto DestinationTooSmall;
}
utf8Destination[dstIdxTemp++] = (byte)utf8lsb;
} while ((utf8lsb >>= 8) != 0);
utf8Source = utf8Source.Slice(bytesConsumedJustNow);
utf8Destination = utf8Destination.Slice(dstIdxTemp);
continue;
}
MustEncode:
if (!TryEncodeUnicodeScalarUtf8((uint)scalarValue.Value, utf16ScratchBuffer, utf8Destination, out int bytesWrittenJustNow))
{
goto DestinationTooSmall;
}
utf8Source = utf8Source.Slice(bytesConsumedJustNow);
utf8Destination = utf8Destination.Slice(bytesWrittenJustNow);
}
// And we're finished!
OperationStatus retVal = OperationStatus.Done;
ReturnCommon:
bytesConsumed = originalUtf8SourceLength - utf8Source.Length;
bytesWritten = originalUtf8DestinationLength - utf8Destination.Length;
return(retVal);
NeedMoreData:
retVal = OperationStatus.NeedMoreData;
goto ReturnCommon;
DestinationTooSmall:
retVal = OperationStatus.DestinationTooSmall;
goto ReturnCommon;
}