// NOTE: The order of the parameters to this method is a work around for https://github.com/dotnet/corefx/issues/4455
// and the underlying Mono bug: https://bugzilla.xamarin.com/show_bug.cgi?id=36052.
// If changing the signature of this method, ensure this issue isn't regressing on Mono.
private unsafe int EncodeIntoBuffer(char *buffer, int bufferLength, char *value, int valueLength, int firstCharacterToEncode)
{
int totalWritten = 0;
if (firstCharacterToEncode > 0)
{
int bytesToCopy = firstCharacterToEncode + firstCharacterToEncode;
//commont by jyq in 2018.7.6
//BufferInternal.MemoryCopy(value, buffer, bytesToCopy, bytesToCopy);
totalWritten += firstCharacterToEncode;
bufferLength -= firstCharacterToEncode;
buffer += firstCharacterToEncode;
}
int valueIndex = firstCharacterToEncode;
char firstChar = value[valueIndex];
char secondChar = firstChar;
bool wasSurrogatePair = false;
int charsWritten;
// this loop processes character pairs (in case they are surrogates).
// there is an if block below to process single last character.
for (int secondCharIndex = valueIndex + 1; secondCharIndex < valueLength; secondCharIndex++)
{
if (!wasSurrogatePair)
{
firstChar = secondChar;
}
else
{
firstChar = value[secondCharIndex - 1];
}
secondChar = value[secondCharIndex];
if (!WillEncode(firstChar))
{
wasSurrogatePair = false;
*buffer = firstChar;
buffer++;
bufferLength--;
totalWritten++;
}
else
{
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, secondChar, out wasSurrogatePair);
if (!TryEncodeUnicodeScalar(nextScalar, buffer, bufferLength, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
buffer += charsWritten;
bufferLength -= charsWritten;
totalWritten += charsWritten;
if (wasSurrogatePair)
{
secondCharIndex++;
}
}
}
if (!wasSurrogatePair)
{
firstChar = value[valueLength - 1];
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, null, out wasSurrogatePair);
if (!TryEncodeUnicodeScalar(nextScalar, buffer, bufferLength, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
buffer += charsWritten;
bufferLength -= charsWritten;
totalWritten += charsWritten;
}
return(totalWritten);
}