public static void Encode(this TextEncoder encoder, TextWriter output, char[] value, int startIndex, int characterCount)
{
if (encoder == null)
{
throw new ArgumentNullException("encoder");
}
if (value == null)
{
throw new ArgumentNullException("value");
}
if (output == null)
{
throw new ArgumentNullException("output");
}
ValidateRanges(startIndex, characterCount, actualInputLength: value.Length);
unsafe
{
fixed(char *valuePointer = value)
{
char *substring = valuePointer + startIndex;
int firstIndexToEncode = encoder.FindFirstCharacterToEncode(substring, characterCount);
if (firstIndexToEncode == -1) // nothing to encode;
{
if (startIndex == 0 && characterCount == value.Length) // write whole string
{
output.Write(value);
return;
}
for (int i = 0; i < characterCount; i++) // write substring
{
output.Write(*substring);
substring++;
}
return;
}
// write prefix, then encode
for (int i = 0; i < firstIndexToEncode; i++)
{
output.Write(*substring);
substring++;
}
EncodeCore(encoder, output, substring, characterCount - firstIndexToEncode);
}
}
}
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);
}
}
}