Anda harus ingat bahwa perancang di Microsoft adalah orang pintar dan semua yang mereka tambahkan ke C # memiliki setidaknya 1 kasing. Proyek FParsec menggunakan kode yang tidak aman untuk mengeluarkan setiap tetes kinerja terakhir yang mampu dilakukan oleh C #. Perhatikan penggunaan fixeddan stackalloc.
private char* ReadCharsFromStream(char* buffer, int maxCount, out string overhangChars) {
Debug.Assert(maxCount >= 0);
fixed (byte* byteBuffer = ByteBuffer) {
overhangChars = null;
try {
while (maxCount >= MaxCharCountForOneByte) {// if maxCount < MaxCharCountForOneByte, Convert could throw
int nBytesInByteBuffer = FillByteBuffer();
bool flush = nBytesInByteBuffer == 0;
int bytesUsed, charsUsed; bool completed = false;
Decoder.Convert(byteBuffer + ByteBufferIndex, nBytesInByteBuffer,
buffer, maxCount, flush,
out bytesUsed, out charsUsed, out completed);
ByteBufferIndex += bytesUsed; // GetChars consumed bytesUsed bytes from the byte buffer
buffer += charsUsed;
maxCount -= charsUsed;
if (flush && completed) return buffer;
}
if (maxCount == 0) return buffer;
char* cs = stackalloc char[MaxCharCountForOneByte];
for (;;) {
int nBytesInByteBuffer = FillByteBuffer();
bool flush = nBytesInByteBuffer == 0;
int bytesUsed, charsUsed; bool completed;
Decoder.Convert(byteBuffer + ByteBufferIndex, nBytesInByteBuffer,
cs, MaxCharCountForOneByte, flush,
out bytesUsed, out charsUsed, out completed);
ByteBufferIndex += bytesUsed;
if (charsUsed > 0) {
int i = 0;
do {
*(buffer++) = cs[i++];
if (--maxCount == 0) {
if (i < charsUsed) overhangChars = new string(cs, i, charsUsed - i);
return buffer;
}
} while (i < charsUsed);
}
if (flush && completed) return buffer;
}
} catch (DecoderFallbackException e) {
e.Data.Add("Stream.Position", ByteIndex + e.Index);
throw;
}
}
}