private void EncodeCore(ref Writer writer, char *input, uint charsRemaining)
{
while (charsRemaining != 0)
{
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(input, endOfString: (charsRemaining == 1));
if (UnicodeHelpers.IsSupplementaryCodePoint(nextScalar))
{
// Supplementary characters should always be encoded numerically.
WriteEncodedScalar(ref writer, (uint)nextScalar);
// We consume two UTF-16 characters for a single supplementary character.
input += 2;
charsRemaining -= 2;
}
else
{
// Otherwise, this was a BMP character.
input++;
charsRemaining--;
char c = (char)nextScalar;
if (IsCharacterAllowed(c))
{
writer.Write(c);
}
else
{
WriteEncodedScalar(ref writer, (uint)nextScalar);
}
}
}
}
// Writes an encoded scalar value (in the BMP) as a JavaScript-escaped character.
private static void WriteEncodedSingleCharacter(ref Writer writer, uint value)
{
Debug.Assert(!UnicodeHelpers.IsSupplementaryCodePoint((int)value), "The incoming value should've been in the BMP.");
// Encode this as 6 chars "\uFFFF".
writer.Write('\\');
writer.Write('u');
writer.Write(HexUtil.IntToChar(value >> 12));
writer.Write(HexUtil.IntToChar((value >> 8) & 0xFU));
writer.Write(HexUtil.IntToChar((value >> 4) & 0xFU));
writer.Write(HexUtil.IntToChar(value & 0xFU));
}
// Writes a scalar value as an JavaScript-escaped character (or sequence of characters).
private static void WriteEncodedScalarAsNumericEntity(ref Writer writer, uint value)
{
if (UnicodeHelpers.IsSupplementaryCodePoint((int)value))
{
// Convert this back to UTF-16 and write out both characters.
char leadingSurrogate, trailingSurrogate;
UnicodeHelpers.GetUtf16SurrogatePairFromAstralScalarValue((int)value, out leadingSurrogate, out trailingSurrogate);
WriteEncodedSingleCharacter(ref writer, leadingSurrogate);
WriteEncodedSingleCharacter(ref writer, trailingSurrogate);
}
else
{
// This is only a single character.
WriteEncodedSingleCharacter(ref writer, value);
}
}