UnicodeEscaper

The amount of padding (chars) to use when growing the escape buffer.

A thread-local destination buffer to keep us from creating new buffers. The starting size is 1024 characters. If we grow past this we don't put it back in the threadlocal, we just keep going and grow as needed.

Returns the escaped form of a given literal string.

If you are escaping input in arbitrary successive chunks, then it is not generally safe to use this method. If an input string ends with an unmatched high surrogate character, then this method will throw IllegalArgumentException. You should either ensure your input is valid UTF-16 before calling this method or use an escaped Appendable (as returned by escape(Appendable)) which can cope with arbitrarily split input.

Note: When implementing an escaper it is a good idea to override this method for efficiency by inlining the implementation of nextEscapeIndex(CharSequence, int, int) directly. Doing this for PercentEscaper more than doubled the performance for unescaped strings (as measured by CharEscapersBenchmark).

Returns an Appendable instance which automatically escapes all text appended to it before passing the resulting text to an underlying Appendable.

Unlike escape(String) it is permitted to append arbitrarily split input to this Appendable, including input that is split over a surrogate pair. In this case the pending high surrogate character will not be processed until the corresponding low surrogate is appended. This means that a trailing high surrogate character at the end of the input cannot be detected and will be silently ignored. This is unavoidable since the Appendable interface has no close() method, and it is impossible to determine when the last characters have been appended.

The methods of the returned object will propagate any exceptions thrown by the underlying Appendable.

For well formed UTF-16 the escaping behavior is identical to that of escape(String) and the following code is equivalent to (but much slower than) escaper.escape(string):

StringBuilder sb = new StringBuilder();
   escaper.escape(sb).append(string);
   return sb.toString();

Returns the Unicode code point of the character at the given index.

Unlike codePointAt(CharSequence, int) or codePointAt(int) this method will never fail silently when encountering an invalid surrogate pair.

The behaviour of this method is as follows:

1. If index >= end, IndexOutOfBoundsException is thrown.
2. If the character at the specified index is not a surrogate, it is returned.
3. If the first character was a high surrogate value, then an attempt is made to read the next character.
   1. If the end of the sequence was reached, the negated value of the trailing high surrogate is returned.
   2. If the next character was a valid low surrogate, the code point value of the high/low surrogate pair is returned.
   3. If the next character was not a low surrogate value, then IllegalArgumentException is thrown.
4. If the first character was a low surrogate value, IllegalArgumentException is thrown.

Returns the escaped form of the given Unicode code point, or null if this code point does not need to be escaped. When called as part of an escaping operation, the given code point is guaranteed to be in the range 0 <= cp <= Character#MAX_CODE_POINT.

If an empty array is returned, this effectively strips the input character from the resulting text.

If the character does not need to be escaped, this method should return null, rather than an array containing the character representation of the code point. This enables the escaping algorithm to perform more efficiently.

If the implementation of this method cannot correctly handle a particular code point then it should either throw an appropriate runtime exception or return a suitable replacement character. It must never silently discard invalid input as this may constitute a security risk.

Returns the escaped form of a given literal string, starting at the given index. This method is called by the escape(String) method when it discovers that escaping is required. It is protected to allow subclasses to override the fastpath escaping function to inline their escaping test. See CharEscaperBuilder for an example usage.

This method is not reentrant and may only be invoked by the top level escape(String) method.

Scans a sub-sequence of characters from a given CharSequence, returning the index of the next character that requires escaping.

Note: When implementing an escaper, it is a good idea to override this method for efficiency. The base class implementation determines successive Unicode code points and invokes escape(int) for each of them. If the semantics of your escaper are such that code points in the supplementary range are either all escaped or all unescaped, this method can be implemented more efficiently using charAt(int).

Note however that if your escaper does not escape characters in the supplementary range, you should either continue to validate the correctness of any surrogate characters encountered or provide a clear warning to users that your escaper does not validate its input.

See PercentEscaper for an example.