atom feed19 messages in net.php.lists.internals[PHP-DEV] BreakIterator
FromSent OnAttachments
Gustavo LopesMay 31, 2012 4:21 am 
David MuirMay 31, 2012 4:39 pm 
Gustavo LopesJun 1, 2012 12:56 am 
Benjamin EberleiJun 1, 2012 1:02 am 
Pierre JoyeJun 1, 2012 3:58 am 
Gustavo LopesJun 1, 2012 4:34 am 
Maciek SokolewiczJun 1, 2012 6:34 am 
Pierre JoyeJun 1, 2012 6:37 am 
Nikita PopovJun 1, 2012 6:56 am 
Gustavo LopesJun 1, 2012 7:41 am 
Gustavo LopesJun 1, 2012 7:55 am 
Gustavo LopesJun 1, 2012 8:02 am 
Pierre JoyeJun 1, 2012 10:41 am 
Stas MalyshevJun 1, 2012 11:30 am 
Gustavo LopesJun 1, 2012 2:28 pm 
Stas MalyshevJun 4, 2012 12:09 pm 
Gustavo LopesJun 4, 2012 2:08 pm 
Stas MalyshevJun 4, 2012 3:00 pm 
Gustavo LopesJun 22, 2012 12:47 pm 
Subject:[PHP-DEV] BreakIterator
From:Gustavo Lopes (glo@nebm.ist.utl.pt)
Date:May 31, 2012 4:21:32 am
List:net.php.lists.internals

Hi

I've wrapped ICU's BreakIterator and RuleBasedBreakIterator. I stopped short of adding a procedural interface. I think there's a larger expectation of a having an OOP interface when working with iterators. What do you think? If there's no procedural interface, I'll change the instances of zend_parse_methods to zpp for performance.

Now I'll copy the commit message here if someone want to comment on a specific point inline:

---- BreakIterator and RuleBasedBreakiterator added This commit adds wrappers for the classes BreakIterator and RuleBasedbreakIterator. The C++ ICU classes are described here: <http://icu-project.org/apiref/icu4c/classBreakIterator.html> <http://icu-project.org/apiref/icu4c/classRuleBasedBreakIterator.html>

Additionally, a tutorial is available at: <http://userguide.icu-project.org/boundaryanalysis>

This implementation wraps UTF-8 text in a UText. The text is iterated without any copying or conversion to UTF-16. There is also no validation that the input is actually UTF-8; where there are malformed sequences, the UText will simply U+FFFD.

The class BreakIterator cannot be instantiated directly (has a private constructor). It provides the interface exposed by the ICU abstract class with the same name. The PHP class is not abstract because we may use it to wrap native subclasses of BreakIterator that we don't know how to wrap. This class includes methods to move the iterator position to the beginning (first()), to the end (last()), forward (next()), backwards (previous()), to the boundary preceding a certain position (preceding()) and following a certain position (following()) and to obtain the current position (current()). next() can also be used to advance or recede an arbitrary number of positions.

BreakIterator also exposes other native methods: getAvailableLocales(), getLocale() and factory methods to build several predefined types of BreakIterators: createWordInstance() for word boundaries, createCharacterInstance() for locale dependent notions of "characters", createSentenceInstance() for sentences, createLineInstance() and createTitleInstance() -- for title casing breaks. These factories currently return RuleBasedbreakIterators where the names of the rule sets are found in the ICU data, observing the passed locale (although the locale is taken into considering there are very few exceptions to the root rules).

The clone and compare_object PHP object handlers are also implemented, though the comparison does not yield meaningful results when used with >, <, >= and <=.

Note that BreakIterator is an iterator only in the sense of the first 'Iterator' in 'IteratorIterator', i.e., it does not implement the Iterator interface. The reason is that there is no sensible implementation for Iterator::key(). Using it for an ordinal of the current boundary is not feasible because we are allowed to move to any boundary at any time. It we were to determine the current ordinal when last() is called we'd have to traverse the whole input text to find out how many breaks there were before. Therefore, BreakIterator implements only Traversable. It can be wrapped in an IteratorIterator, but the usual warnings apply.

Finally, I added a convenience method to BreakIterator: getPartsIterator(). This provides an IntlIterator, backed by the BreakIterator PHP object (i.e. moving the pointer or changing the text in BreakIterator affects the iterator and also moving the iterator affects the backing BreakIterator), which allows traversing the text between each boundary. This iterator uses the original text to retrieve the text between two positions, not the code points returned by the wrapping UText. Therefore, if the text includes invalid code unit sequences, these invalid sequences will be in the output of this iterator, not U+FFFD code points.

The class RuleBasedIterator exposes a constructor that allows building an iterator from arbitrary compiled or non-compiled rules. The form of these rules in described in the tutorial linked above. The rest of the methods allow retrieving the rules -- getRules() and getCompiledRules() --, a hash code of the rule set (hashCode()) and the rules statuses (getRuleStatus() and getRuleStatusVec()).

Because the RuleBasedBreakIterator constructor may return parse errors, I reuse the UParseError to text function that was in the transliterator files. Therefore, I move that function to intl_error.c.

common_enum.cpp was also changed, mainly to expose previously static functions. This avoided code duplication when implementing the BreakIterator iterator and the IntlIterator returned by BreakIterator::getPartsIterator().