#pragma warning disable IDE0060 // 'this' taken explicitly to avoid argument shuffling by caller
static int TryEncodeScalarAsHex(object @this, uint scalarValue, Span <char> destination)
#pragma warning restore IDE0060
{
UnicodeDebug.AssertIsValidScalar(scalarValue);
// For inputs 0x0000..0x10FFFF, log2 will return 0..20.
// (It counts the number of bits following the highest set bit.)
//
// We divide by 4 to get the number of nibbles (this rounds down),
// then +1 to account for rounding effects. This also accounts for
// that when log2 results in an exact multiple of 4, no rounding has
// taken place, but we need to include a char for the preceding '0x1'.
// Finally, we +4 to account for the "&#x" prefix and the ";" suffix,
// then -1 to get the index of the last legal location we want to write to.
// >> +1 +4 -1 = +4
int idxOfSemicolon = (int)((uint)BitOperations.Log2(scalarValue) / 4) + 4;
Debug.Assert(4 <= idxOfSemicolon && idxOfSemicolon <= 9, "Expected '�'..''.");
if (!SpanUtility.IsValidIndex(destination, idxOfSemicolon))
{
goto OutOfSpaceInner;
}
destination[idxOfSemicolon] = ';';
// It's more efficient to write 4 chars at a time instead of 1 char.
// The '0' at the end will be overwritten.
if (!SpanUtility.TryWriteChars(destination, '&', '#', 'x', '0'))
{
Debug.Fail("We should've had enough room to write 4 chars.");
}
destination = destination.Slice(3, idxOfSemicolon - 3);
for (int i = destination.Length - 1; SpanUtility.IsValidIndex(destination, i); i--)
{
char asUpperHex = HexConverter.ToCharUpper((int)scalarValue);
destination[i] = asUpperHex;
scalarValue >>= 4; // write a nibble - not a byte - at a time
}
return(destination.Length + 4);
OutOfSpaceInner:
return(-1);
}
internal override int EncodeUtf16(Rune value, Span <char> destination)
{
if (value.Value == '<')
{
if (!SpanUtility.TryWriteChars(destination, '&', 'l', 't', ';'))
{
goto OutOfSpace;
}
return(4);
}
else if (value.Value == '>')
{
if (!SpanUtility.TryWriteChars(destination, '&', 'g', 't', ';'))
{
goto OutOfSpace;
}
return(4);
}
else if (value.Value == '&')
{
if (!SpanUtility.TryWriteChars(destination, '&', 'a', 'm', 'p', ';'))
{
goto OutOfSpace;
}
return(5);
}
else if (value.Value == '\"')
{
if (!SpanUtility.TryWriteChars(destination, '&', 'q', 'u', 'o', 't', ';'))
{
goto OutOfSpace;
}
return(6);
}
else
{
return(TryEncodeScalarAsHex(this, (uint)value.Value, destination));
}
OutOfSpace:
return(-1);
