Saxon

There is a performance regression when escaping special characters with the UnicodeString class.

In the method writeEscape of the XMLEmitter class,

while (segstart < clength) {
    // find a maximal sequence of "ordinary" characters
    long found = chars.indexWhere(special, segstart);

that calls the indexWhere method of the UnicodeString class,

public long indexWhere(IntPredicate predicate, long from) {
    IntIterator iter = codePoints();
    long i = 0;
    while (iter.hasNext()) {
        int ch = iter.next();
        if (i >= from && predicate.test(ch)) {
            return i;
        }
        i++;
    }
    return -1;
}

the character sequence is searched from the beginning for each segment, whereas it should be searched from the position from. This is O(n²) and painful for large text nodes with many escapable characters (e.g. escaped XML).

This is a quick suggestion:

public long indexWhere(IntPredicate predicate, long from) {
    for (long i = from; i < length(); ++i) {
        int ch = codePointAt(i);
        if (predicate.test(ch)) {
            return i;
        }
    }
    return -1;
}