public static CharacterMap /*!*/ Create(MutableString /*!*/ from, MutableString /*!*/ to)
{
Debug.Assert(!from.IsEmpty);
int fromLength = from.GetCharCount();
bool complemental = from.StartsWith('^') && fromLength > 1;
// TODO: kcodings
// TODO: surrogates
// TODO: max - min > threshold
int min, max;
if (from.DetectByteCharacters())
{
min = 0;
max = 255;
}
else
{
min = Int32.MaxValue;
max = -1;
for (int i = (complemental ? 1 : 0); i < fromLength; i++)
{
int c = from.GetChar(i);
if (c < min)
{
min = c;
}
if (c > max)
{
max = c;
}
}
}
BitArray map;
char[] image;
if (complemental || to.IsEmpty)
{
image = null;
map = MakeBitmap(from, fromLength, complemental, min, max);
}
else
{
map = null;
image = new char[max - min + 1];
// no need to initialize the array:
Debug.Assert(Unmapped == 0);
bool needMap = false;
var toEnum = ExpandRanges(to, 0, to.GetCharCount(), true).GetEnumerator();
foreach (var f in ExpandRanges(from, 0, fromLength, false))
{
toEnum.MoveNext();
needMap |= (image[f - min] = toEnum.Current) == Unmapped;
}
if (needMap)
{
map = MakeBitmap(from, fromLength, false, min, max);
}
}
return(new CharacterMap(map, image, complemental ? to.GetLastChar() : -1, complemental, min, max));
}
