internal static void ToLower(char h, char l, out char hr, out char lr)
{
Debug.Assert(char.IsHighSurrogate(h));
Debug.Assert(char.IsLowSurrogate(l));
UnicodeUtility.GetUtf16SurrogatesFromSupplementaryPlaneScalar(CharUnicodeInfo.ToLower(UnicodeUtility.GetScalarFromUtf16SurrogatePair(h, l)), out hr, out lr);
}
public bool MoveNext()
{
// Make copies of fields to avoid tearing issues since we're
// about to perform unsafe accesses.
uint currentCharPair = _currentCharPair;
if (currentCharPair > char.MaxValue)
{
// There was a surrogate pair smuggled in here from a previous operation.
// Shift out the high surrogate value and return immediately.
_currentCharPair = currentCharPair >> 16;
return(true);
}
ReadOnlySpan <byte> bytes = _obj.AsBytesSkipNullCheck();
int nextByteIdx = _nextByteIdx;
if ((uint)nextByteIdx >= (uint)bytes.Length)
{
return(false); // no more data
}
// TODO_UTF8STRING: Can we skip correctness checks below?
// Perhaps not, this enumerator struct is potentially tearable.
OperationStatus status = Rune.DecodeFromUtf8(bytes.Slice(nextByteIdx), out Rune currentRune, out int bytesConsumedJustNow);
Debug.Assert(status == OperationStatus.Done);
_nextByteIdx = nextByteIdx + bytesConsumedJustNow;
if (currentRune.IsBmp)
{
// Common case - BMP scalar value.
_currentCharPair = (uint)currentRune.Value;
}
else
{
// Uncommon case - supplementary (astral) plane scalar value.
// We'll smuggle the two UTF-16 code units into a single 32-bit value,
// with the leading surrogate packed into the low 16 bits of the value,
// and the trailing surrogate packed into the high 16 bits of the value.
UnicodeUtility.GetUtf16SurrogatesFromSupplementaryPlaneScalar((uint)currentRune.Value, out char leadingCodeUnit, out char trailingCodeUnit);
_currentCharPair = (uint)leadingCodeUnit + ((uint)trailingCodeUnit << 16);
}
return(true);
}
