394 lines
14 KiB
C++
394 lines
14 KiB
C++
/*
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**********************************************************************
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* Copyright (C) 1999 Alan Liu and others. All rights reserved.
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**********************************************************************
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* Date Name Description
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* 10/22/99 alan Creation.
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**********************************************************************
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*/
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#include "rbbi.h"
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#include "rbbi_bld.h"
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/**
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* A token used as a character-category value to identify ignore characters
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*/
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int8_t RuleBasedBreakIterator::IGNORE = -1;
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/**
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* The state number of the starting state
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*/
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int16_t RuleBasedBreakIterator::START_STATE = 1;
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/**
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* The state-transition value indicating "stop"
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*/
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int16_t RuleBasedBreakIterator::STOP_STATE = 0;
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//=======================================================================
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// constructors
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//=======================================================================
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/**
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* Constructs a RuleBasedBreakIterator according to the description
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* provided. If the description is malformed, throws an
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* IllegalArgumentException. Normally, instead of constructing a
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* RuleBasedBreakIterator directory, you'll use the factory methods
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* on BreakIterator to create one indirectly from a description
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* in the framework's resource files. You'd use this when you want
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* special behavior not provided by the built-in iterators.
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*/
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RuleBasedBreakIterator::RuleBasedBreakIterator(const UnicodeString& description) {
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this.description = description;
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// the actual work is done by the Builder class
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Builder builder;
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builder.buildBreakIterator(*this, description);
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}
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//=======================================================================
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// boilerplate
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//=======================================================================
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/**
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* Clones this iterator.
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* @return A newly-constructed RuleBasedBreakIterator with the same
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* behavior as this one.
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*/
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RuleBasedBreakIterator* RuleBasedBreakIterator::clone() const {
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return new RuleBasedBreakIterator(*this);
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}
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/**
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* Returns true if both BreakIterators are of the same class, have the same
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* rules, and iterate over the same text.
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*/
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bool_t RuleBasedBreakIterator::operator==(const RuleBasedBreakIterator& that) {
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return description.equals(((RuleBasedBreakIterator)that).description)
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&& text.equals(((RuleBasedBreakIterator)that).text);
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}
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/**
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* Returns the description used to create this iterator
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*/
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UnicodeString RuleBasedBreakIterator::toString() {
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return description;
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}
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/**
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* Compute a hashcode for this BreakIterator
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* @return A hash code
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*/
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int32_t RuleBasedBreakIterator::hashCode() {
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return description.hashCode();
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}
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//=======================================================================
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// BreakIterator overrides
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//=======================================================================
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/**
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* Sets the current iteration position to the beginning of the text.
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* (i.e., the CharacterIterator's starting offset).
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* @return The offset of the beginning of the text.
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*/
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int32_t RuleBasedBreakIterator::first() {
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CharacterIterator t = getText();
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t.first();
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return t.getIndex();
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}
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/**
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* Sets the current iteration position to the end of the text.
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* (i.e., the CharacterIterator's ending offset).
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* @return The text's past-the-end offset.
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*/
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int32_t RuleBasedBreakIterator::last() {
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CharacterIterator t = getText();
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// I'm not sure why, but t.last() returns the offset of the last character,
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// rather than the past-the-end offset
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t.setIndex(t.getEndIndex());
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return t.getIndex();
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}
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/**
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* Advances the iterator either forward or backward the specified number of steps.
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* Negative values move backward, and positive values move forward. This is
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* equivalent to repeatedly calling next() or previous().
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* @param n The number of steps to move. The sign indicates the direction
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* (negative is backwards, and positive is forwards).
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* @return The character offset of the boundary position n boundaries away from
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* the current one.
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*/
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int32_t RuleBasedBreakIterator::next(int32_t n) {
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int32_t result = current();
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while (n > 0) {
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result = handleNext();
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--n;
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}
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while (n < 0) {
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result = previous();
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++n;
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}
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return result;
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}
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/**
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* Advances the iterator to the next boundary position.
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* @return The position of the first boundary after this one.
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*/
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int32_t RuleBasedBreakIterator::next() {
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return handleNext();
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}
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/**
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* Advances the iterator backwards, to the last boundary preceding this one.
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* @return The position of the last boundary position preceding this one.
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*/
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int32_t RuleBasedBreakIterator::previous() {
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// if we're already sitting at the beginning of the text, return DONE
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CharacterIterator text = getText();
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if (current() == text.getBeginIndex())
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return BreakIterator.DONE;
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// set things up. handlePrevious() will back us up to some valid
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// break position before the current position (we back our internal
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// iterator up one step to prevent handlePrevious() from returning
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// the current position), but not necessarily the last one before
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// where we started
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int32_t start = current();
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text.previous();
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int32_t lastResult = handlePrevious();
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int32_t result = lastResult;
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// iterate forward from the known break position until we pass our
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// starting point. The last break position before the starting
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// point is our return value
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while (result != BreakIterator.DONE && result < start) {
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lastResult = result;
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result = handleNext();
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}
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// set the current iteration position to be the last break position
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// before where we started, and then return that value
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text.setIndex(lastResult);
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return lastResult;
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}
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/**
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* Sets the iterator to refer to the first boundary position following
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* the specified position.
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* @offset The position from which to begin searching for a break position.
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* @return The position of the first break after the current position.
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*/
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int32_t RuleBasedBreakIterator::following(int32_t offset) {
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// if the offset passed in is already past the end of the text,
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// just return DONE
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CharacterIterator text = getText();
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if (offset == text.getEndIndex())
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return BreakIterator.DONE;
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// otherwise, set our internal iteration position (temporarily)
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// to the position passed in. If this is the _beginning_ position,
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// then we can just use next() to get our return value
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text.setIndex(offset);
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if (offset == text.getBeginIndex())
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return handleNext();
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// otherwise, we have to sync up first. Use handlePrevious() to back
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// us up to a known break position before the specified position (if
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// we can determine that the specified position is a break position,
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// we don't back up at all). This may or may not be the last break
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// position at or before our starting position. Advance forward
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// from here until we've passed the starting position. The position
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// we stop on will be the first break position after the specified one.
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int32_t result = handlePrevious();
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while (result != BreakIterator.DONE && result <= offset)
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result = handleNext();
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return result;
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}
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/**
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* Sets the iterator to refer to the last boundary position before the
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* specified position.
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* @offset The position to begin searching for a break from.
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* @return The position of the last boundary before the starting position.
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*/
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int32_t RuleBasedBreakIterator::preceding(int32_t offset) {
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// if we start by updating the current iteration position to the
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// position specified by the caller, we can just use previous()
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// to carry out this operation
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CharacterIterator text = getText();
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text.setIndex(offset);
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return previous();
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}
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/**
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* Returns true if the specfied position is a boundary position. As a side
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* effect, leaves the iterator pointing to the first boundary position at
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* or after "offset".
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* @param offset the offset to check.
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* @return True if "offset" is a boundary position.
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*/
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bool_t RuleBasedBreakIterator::isBoundary(int32_t offset) {
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// 0 is always a boundary position (I suspect this code is wrong; I think
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// we're supposed to be comparing "offset" against text.getBeginIndex(). )
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if (offset == 0)
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return TRUE;
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// otherwise, we can use following() on the position before the specified
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// one and return true of the position we get back is the one the user
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// specified
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else
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return following(offset - 1) == offset;
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}
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/**
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* Returns the current iteration position.
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* @return The current iteration position.
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*/
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int32_t RuleBasedBreakIterator::current() {
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return getText().getIndex();
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}
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/**
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* Return a CharacterIterator over the text being analyzed. This version
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* of this method returns the actual CharacterIterator we're using internally.
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* Changing the state of this iterator can have undefined consequences. If
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* you need to change it, clone it first.
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* @return An iterator over the text being analyzed.
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*/
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CharacterIterator RuleBasedBreakIterator::getText() {
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// The iterator is initialized pointing to no text at all, so if this
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// function is called while we're in that state, we have to fudge an
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// an iterator to return.
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if (text == 0)
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text = new StringCharacterIterator("");
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return text;
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}
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/**
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* Set the iterator to analyze a new piece of text. This function resets
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* the current iteration position to the beginning of the text.
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* @param newText An iterator over the text to analyze.
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*/
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void RuleBasedBreakIterator::setText(CharacterIterator newText) {
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text = newText;
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text.first();
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}
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//=======================================================================
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// implementation
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//=======================================================================
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/**
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* This method is the actual implementation of the next() method. All iteration
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* vectors through here. This method initializes the state machine to state 1
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* and advances through the text character by character until we reach the end
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* of the text or the state machine transitions to state 0. We update our return
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* value every time the state machine passes through a possible end state.
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*/
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int32_t RuleBasedBreakIterator::handleNext() {
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// if we're already at the end of the text, return DONE.
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CharacterIterator text = getText();
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if (text.getIndex() == text.getEndIndex())
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return BreakIterator.DONE;
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// no matter what, we always advance at least one character forward
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int32_t result = text.getIndex() + 1;
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// begin in state 1
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int32_t state = START_STATE;
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int32_t category;
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UChar c = text.current();
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// loop until we reach the end of the text or transition to state 0
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while (c != CharacterIterator.DONE && state != STOP_STATE) {
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// look up the current character's character category (which tells us
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// which column in the state table to look at)
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category = lookupCategory(c);
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// if the character isn't an ignore character, look up a state
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// transition in the state table
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if (category != IGNORE) {
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state = lookupState(state, category);
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}
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// if the state we've just transitioned to is an accepting state,
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// update our return value to be the current iteration position
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if (endStates[state])
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result = text.getIndex() + 1;
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c = text.next();
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}
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text.setIndex(result);
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return result;
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}
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/**
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* This method backs the iterator back up to a "safe position" in the text.
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* This is a position that we know, without any context, must be a break position.
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* The various calling methods then iterate forward from this safe position to
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* the appropriate position to return. (For more information, see the description
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* of buildBackwardsStateTable() in RuleBasedBreakIterator.Builder.)
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*/
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int32_t RuleBasedBreakIterator::handlePrevious() {
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CharacterIterator text = getText();
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int32_t state = START_STATE;
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int32_t category = 0;
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int32_t lastCategory = 0;
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UChar c = text.current();
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// loop until we reach the beginning of the text or transition to state 0
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while (c != CharacterIterator.DONE && state != STOP_STATE) {
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// save the last character's category and look up the current
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// character's category
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lastCategory = category;
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category = lookupCategory(c);
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// if the current character isn't an ignore character, look up a
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// state transition in the backwards state table
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if (category != IGNORE)
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state = lookupBackwardState(state, category);
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// then advance one character backwards
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c = text.previous();
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}
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// if we didn't march off the beginning of the text, we're either one or two
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// positions away from the real break position. (One because of the call to
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// previous() at the end of the loop above, and another because the character
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// that takes us into the stop state will always be the character BEFORE
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// the break position.)
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if (c != CharacterIterator.DONE) {
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if (lastCategory != IGNORE)
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text.setIndex(text.getIndex() + 2);
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else
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text.next();
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}
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return text.getIndex();
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}
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/**
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* Looks up a character's category (i.e., its category for breaking purposes,
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* not its Unicode category)
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*/
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int32_t RuleBasedBreakIterator::lookupCategory(UChar c) {
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return UCharCategoryTable.elementAt(c);
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}
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/**
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* Given a current state and a character category, looks up the
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* next state to transition to in the state table.
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*/
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int32_t RuleBasedBreakIterator::lookupState(int32_t state, int32_t category) {
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return stateTable[state * numCategories + category];
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}
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/**
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* Given a current state and a character category, looks up the
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* next state to transition to in the backwards state table.
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*/
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int32_t RuleBasedBreakIterator::lookupBackwardState(int32_t state, int32_t category) {
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return backwardsStateTable[state * numCategories + category];
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}
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