private static unsafe void EncodeCore(this TextEncoder encoder, TextWriter output, char *value, int valueLength)
{
Debug.Assert(encoder != null && value != null & output != null);
Debug.Assert(valueLength >= 0);
int bufferLength = encoder.MaxOutputCharactersPerInputCharacter;
char *buffer = stackalloc char[bufferLength];
char firstChar = *value;
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 = 1; secondCharIndex < valueLength; secondCharIndex++)
{
if (!wasSurrogatePair)
{
firstChar = secondChar;
}
else
{
firstChar = value[secondCharIndex - 1];
}
secondChar = value[secondCharIndex];
if (!encoder.Encodes(firstChar))
{
wasSurrogatePair = false;
output.Write(firstChar);
}
else
{
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, secondChar, out wasSurrogatePair);
if (!encoder.TryEncodeUnicodeScalar(nextScalar, buffer, bufferLength, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
output.Write(buffer, charsWritten);
if (wasSurrogatePair)
{
secondCharIndex++;
}
}
}
if (!wasSurrogatePair)
{
firstChar = value[valueLength - 1];
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, null, out wasSurrogatePair);
if (!encoder.TryEncodeUnicodeScalar(nextScalar, buffer, bufferLength, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
output.Write(buffer, charsWritten);
}
}
public static string Encode(this TextEncoder encoder, string value)
{
if (value == null)
{
return(value);
}
unsafe
{
fixed(char *valuePointer = value)
{
int firstCharacterToEncode = encoder.FindFirstCharacterToEncode(valuePointer, value.Length);
if (firstCharacterToEncode == -1)
{
return(value);
}
int bufferSize = encoder.MaxOutputCharsPerInputChar * value.Length;
char *wholebuffer = stackalloc char[bufferSize];
char *buffer = wholebuffer;
int totalWritten = 0;
if (firstCharacterToEncode > 0)
{
int bytesToCopy = firstCharacterToEncode + firstCharacterToEncode;
Buffer.MemoryCopy(valuePointer, buffer, bytesToCopy, bytesToCopy);
totalWritten += firstCharacterToEncode;
bufferSize -= 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 < value.Length; secondCharIndex++)
{
if (!wasSurrogatePair)
{
firstChar = secondChar;
}
else
{
firstChar = value[secondCharIndex - 1];
}
secondChar = value[secondCharIndex];
if (!encoder.Encodes(firstChar))
{
wasSurrogatePair = false;
*buffer = firstChar;
buffer++;
bufferSize--;
totalWritten++;
}
else
{
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, secondChar, out wasSurrogatePair);
if (!encoder.TryEncodeUnicodeScalar(nextScalar, buffer, bufferSize, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
buffer += charsWritten;
bufferSize -= charsWritten;
totalWritten += charsWritten;
if (wasSurrogatePair)
{
secondCharIndex++;
}
}
}
if (!wasSurrogatePair)
{
firstChar = value[value.Length - 1];
int nextScalar = UnicodeHelpers.GetScalarValueFromUtf16(firstChar, null, out wasSurrogatePair);
if (!encoder.TryEncodeUnicodeScalar(nextScalar, buffer, bufferSize, out charsWritten))
{
throw new ArgumentException("Argument encoder does not implement MaxOutputCharsPerInputChar correctly.");
}
buffer += charsWritten;
bufferSize -= charsWritten;
totalWritten += charsWritten;
}
var result = new String(wholebuffer, 0, totalWritten);
return(result);
}
}
}