public static bool TryDecodeCodePoint(ByteSpan buffer, out UnicodeCodePoint codePoint, out int encodedBytes)
{
if (buffer.Length < 2)
{
codePoint = default(UnicodeCodePoint);
encodedBytes = default(int);
// buffer too small
return false;
}
uint codePointValue = (uint)buffer[0] | ((uint)buffer[1] << 8);
encodedBytes = 2;
// Notice: This is any surrogate, not only high surrogate
bool isSurrogate = codePointValue >= SpecConstants.HighSurrogateFirstCodePoint && codePointValue <= SpecConstants.LowSurrogateLastCodePoint;
if (isSurrogate)
{
isSurrogate = codePointValue <= SpecConstants.HighSurrogateLastCodePoint;
if (!isSurrogate || buffer.Length < 4)
{
codePoint = default(UnicodeCodePoint);
encodedBytes = default(int);
// invalid high surrogate or buffer too small
return false;
}
unchecked
{
codePointValue -= SpecConstants.HighSurrogateFirstCodePoint;
encodedBytes += 2;
}
// high surrogate contains 10 first bits of the code point
codePointValue <<= 10;
uint lowSurrogate = (uint)buffer[2] | ((uint)buffer[3] << 8);
if (lowSurrogate < SpecConstants.LowSurrogateFirstCodePoint || lowSurrogate > SpecConstants.LowSurrogateLastCodePoint)
{
codePoint = default(UnicodeCodePoint);
encodedBytes = default(int);
// invalid low surrogate character
return false;
}
unchecked
{
lowSurrogate -= SpecConstants.LowSurrogateFirstCodePoint;
}
codePointValue |= lowSurrogate;
}
codePoint = (UnicodeCodePoint)codePointValue;
return true;
}
public static bool TryEncodeCodePoint(UnicodeCodePoint codePoint, ByteSpan buffer, out int encodedBytes)
{
if ((uint)codePoint > 0x10FFFF)
{
encodedBytes = default(int);
return false;
}
// is Surrogate?
encodedBytes = ((uint)codePoint >= 0x10000) ? 4 : 2;
if (buffer.Length < encodedBytes)
{
codePoint = default(UnicodeCodePoint);
encodedBytes = default(int);
// buffer too small
return false;
}
if (encodedBytes == 2)
{
unchecked
{
buffer[0] = (byte)((uint)codePoint);
buffer[1] = (byte)((uint)codePoint >> 8);
}
}
else
{
unchecked
{
uint highSurrogate = ((uint)codePoint >> 10) + 0xD800;
uint lowSurrogate = ((uint)codePoint & MaskLow10Bits) + 0xDC00;
buffer[0] = (byte)highSurrogate;
buffer[1] = (byte)(highSurrogate >> 8);
buffer[2] = (byte)lowSurrogate;
buffer[3] = (byte)(lowSurrogate >> 8);
}
}
return true;
}
public static bool IsSupportedCodePoint(UnicodeCodePoint codePoint)
{
// TODO: Check this value, written from head
return codePoint.Value < 17 * (1 << 16);
}
public static bool IsSupportedCodePoint(UnicodeCodePoint codePoint)
{
// TODO: Check this value, written from head
return(codePoint.Value < 17 * (1 << 16));
}