448 lines
18 KiB
C++
448 lines
18 KiB
C++
/*
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**********************************************************************
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* Copyright (C) 1999-2000 IBM Corp. All rights reserved.
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**********************************************************************
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* Date Name Description
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* 12/1/99 rgillam Complete port from Java.
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* 01/13/2000 helena Added UErrorCode to ctors.
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**********************************************************************
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*/
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#include "ucmp8.h"
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#include "unicode/dbbi.h"
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#include "dbbi_tbl.h"
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#include "uvector.h"
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char DictionaryBasedBreakIterator::fgClassID = 0;
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//=======================================================================
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// constructors
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//=======================================================================
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DictionaryBasedBreakIterator::DictionaryBasedBreakIterator(const void* tablesImage,
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char* dictionaryFilename,
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UErrorCode& status)
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: RuleBasedBreakIterator((const void*)NULL),
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dictionaryCharCount(0),
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cachedBreakPositions(NULL),
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numCachedBreakPositions(0),
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positionInCache(0)
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{
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tables = new DictionaryBasedBreakIteratorTables(tablesImage, dictionaryFilename, status);
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if (U_FAILURE(status)) {
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delete tables;
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return;
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}
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tables->addReference();
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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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* Destructor
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*/
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DictionaryBasedBreakIterator::~DictionaryBasedBreakIterator()
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{
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delete [] cachedBreakPositions;
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}
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/**
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* Assignment operator. Sets this iterator to have the same behavior,
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* and iterate over the same text, as the one passed in.
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*/
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DictionaryBasedBreakIterator&
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DictionaryBasedBreakIterator::operator=(const DictionaryBasedBreakIterator& that) {
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reset();
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RuleBasedBreakIterator::operator=(that);
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return *this;
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}
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/**
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* Returns a newly-constructed RuleBasedBreakIterator with the same
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* behavior, and iterating over the same text, as this one.
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*/
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BreakIterator*
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DictionaryBasedBreakIterator::clone() const {
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return new DictionaryBasedBreakIterator(*this);
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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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* Advances the iterator one step backwards.
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* @return The position of the last boundary position before the
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* current iteration position
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*/
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int32_t
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DictionaryBasedBreakIterator::previous()
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{
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// if we have cached break positions and we're still in the range
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// covered by them, just move one step backward in the cache
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if (cachedBreakPositions != NULL && positionInCache > 0) {
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--positionInCache;
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text->setIndex(cachedBreakPositions[positionInCache]);
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return cachedBreakPositions[positionInCache];
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}
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// otherwise, dump the cache and use the inherited previous() method to move
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// backward. This may fill up the cache with new break positions, in which
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// case we have to mark our position in the cache
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else {
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reset();
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int32_t result = RuleBasedBreakIterator::previous();
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if (cachedBreakPositions != NULL) {
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positionInCache = numCachedBreakPositions - 2;
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}
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return result;
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}
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}
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/**
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* Sets the current iteration position to the last boundary position
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* before the specified position.
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* @param offset The position to begin searching from
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* @return The position of the last boundary before "offset"
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*/
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int32_t
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DictionaryBasedBreakIterator::preceding(int32_t offset)
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{
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// if the offset passed in is already past the end of the text,
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// just return DONE; if it's before the beginning, return the
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// text's starting offset
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if (text == NULL || offset > text->endIndex()) {
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return BreakIterator::DONE;
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}
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else if (offset < text->startIndex()) {
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return text->startIndex();
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}
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// if we have no cached break positions, or "offset" is outside the
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// range covered by the cache, we can just call the inherited routine
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// (which will eventually call other routines in this class that may
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// refresh the cache)
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if (cachedBreakPositions == NULL || offset <= cachedBreakPositions[0] ||
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offset > cachedBreakPositions[numCachedBreakPositions - 1]) {
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reset();
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return RuleBasedBreakIterator::preceding(offset);
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}
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// on the other hand, if "offset" is within the range covered by the cache,
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// then all we have to do is search the cache for the last break position
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// before "offset"
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else {
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positionInCache = 0;
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while (positionInCache < numCachedBreakPositions
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&& offset > cachedBreakPositions[positionInCache])
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++positionInCache;
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--positionInCache;
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text->setIndex(cachedBreakPositions[positionInCache]);
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return text->getIndex();
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}
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}
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/**
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* Sets the current iteration position to the first boundary position after
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* the specified position.
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* @param offset The position to begin searching forward from
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* @return The position of the first boundary after "offset"
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*/
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int32_t
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DictionaryBasedBreakIterator::following(int32_t offset)
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{
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// if the offset passed in is already past the end of the text,
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// just return DONE; if it's before the beginning, return the
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// text's starting offset
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if (text == NULL || offset > text->endIndex()) {
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return BreakIterator::DONE;
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}
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else if (offset < text->startIndex()) {
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return text->startIndex();
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}
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// if we have no cached break positions, or if "offset" is outside the
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// range covered by the cache, then dump the cache and call our
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// inherited following() method. This will call other methods in this
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// class that may refresh the cache.
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if (cachedBreakPositions == NULL || offset < cachedBreakPositions[0] ||
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offset >= cachedBreakPositions[numCachedBreakPositions - 1]) {
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reset();
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return RuleBasedBreakIterator::following(offset);
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}
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// on the other hand, if "offset" is within the range covered by the
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// cache, then just search the cache for the first break position
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// after "offset"
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else {
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positionInCache = 0;
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while (positionInCache < numCachedBreakPositions
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&& offset >= cachedBreakPositions[positionInCache])
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++positionInCache;
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text->setIndex(cachedBreakPositions[positionInCache]);
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return text->getIndex();
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}
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}
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/**
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* This is the implementation function for next().
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*/
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int32_t
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DictionaryBasedBreakIterator::handleNext()
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{
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// if there are no cached break positions, or if we've just moved
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// off the end of the range covered by the cache, we have to dump
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// and possibly regenerate the cache
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if (cachedBreakPositions == NULL || positionInCache == numCachedBreakPositions - 1) {
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// start by using the inherited handleNext() to find a tentative return
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// value. dictionaryCharCount tells us how many dictionary characters
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// we passed over on our way to the tentative return value
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int32_t startPos = text->getIndex();
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dictionaryCharCount = 0;
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int32_t result = RuleBasedBreakIterator::handleNext();
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// if we passed over more than one dictionary character, then we use
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// divideUpDictionaryRange() to regenerate the cached break positions
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// for the new range
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if (dictionaryCharCount > 1 && result - startPos > 1) {
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divideUpDictionaryRange(startPos, result);
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}
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// otherwise, the value we got back from the inherited fuction
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// is our return value, and we can dump the cache
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else {
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reset();
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return result;
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}
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}
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// if the cache of break positions has been regenerated (or existed all
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// along), then just advance to the next break position in the cache
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// and return it
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if (cachedBreakPositions != NULL) {
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++positionInCache;
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text->setIndex(cachedBreakPositions[positionInCache]);
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return cachedBreakPositions[positionInCache];
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}
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return -9999; // SHOULD NEVER GET HERE!
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}
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void
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DictionaryBasedBreakIterator::reset()
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{
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delete [] cachedBreakPositions;
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cachedBreakPositions = NULL;
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numCachedBreakPositions = 0;
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dictionaryCharCount = 0;
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positionInCache = 0;
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}
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/**
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* This is the function that actually implements the dictionary-based
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* algorithm. Given the endpoints of a range of text, it uses the
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* dictionary to determine the positions of any boundaries in this
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* range. It stores all the boundary positions it discovers in
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* cachedBreakPositions so that we only have to do this work once
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* for each time we enter the range.
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*/
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void
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DictionaryBasedBreakIterator::divideUpDictionaryRange(int32_t startPos, int32_t endPos)
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{
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// to avoid casts throughout the rest of this function
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DictionaryBasedBreakIteratorTables* tables
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= (DictionaryBasedBreakIteratorTables*)(this->tables);
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// the range we're dividing may begin or end with non-dictionary characters
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// (i.e., for line breaking, we may have leading or trailing punctuation
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// that needs to be kept with the word). Seek from the beginning of the
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// range to the first dictionary character
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text->setIndex(startPos);
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UChar c = text->current();
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int category = tables->lookupCategory(c, this);
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while (category == IGNORE || !tables->categoryFlags[category]) {
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c = text->next();
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category = tables->lookupCategory(c, this);
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}
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// initialize. We maintain two stacks: currentBreakPositions contains
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// the list of break positions that will be returned if we successfully
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// finish traversing the whole range now. possibleBreakPositions lists
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// all other possible word ends we've passed along the way. (Whenever
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// we reach an error [a sequence of characters that can't begin any word
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// in the dictionary], we back up, possibly delete some breaks from
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// currentBreakPositions, move a break from possibleBreakPositions
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// to currentBreakPositions, and start over from there. This process
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// continues in this way until we either successfully make it all the way
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// across the range, or exhaust all of our combinations of break
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// positions.) wrongBreakPositions is used to keep track of paths we've
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// tried on previous iterations. As the iterator backs up further and
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// further, this saves us from having to follow each possible path
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// through the text all the way to the error (hopefully avoiding many
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// future recursive calls as well).
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UStack currentBreakPositions;
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UStack possibleBreakPositions;
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UVector wrongBreakPositions;
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// the dictionary is implemented as a trie, which is treated as a state
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// machine. -1 represents the end of a legal word. Every word in the
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// dictionary is represented by a path from the root node to -1. A path
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// that ends in state 0 is an illegal combination of characters.
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int16_t state = 0;
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// these two variables are used for error handling. We keep track of the
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// farthest we've gotten through the range being divided, and the combination
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// of breaks that got us that far. If we use up all possible break
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// combinations, the text contains an error or a word that's not in the
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// dictionary. In this case, we "bless" the break positions that got us the
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// farthest as real break positions, and then start over from scratch with
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// the character where the error occurred.
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int32_t farthestEndPoint = text->getIndex();
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UStack bestBreakPositions;
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bool_t bestBreakPositionsInitialized = FALSE;
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// initialize (we always exit the loop with a break statement)
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c = text->current();
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while (TRUE) {
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// if we can transition to state "-1" from our current state, we're
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// on the last character of a legal word. Push that position onto
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// the possible-break-positions stack
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if (tables->dictionary.at(state, (int32_t)0) == -1) {
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possibleBreakPositions.push((void*)text->getIndex());
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}
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// look up the new state to transition to in the dictionary
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state = tables->dictionary.at(state, c);
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// if the character we're sitting on causes us to transition to
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// the "end of word" state, then it was a non-dictionary character
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// and we've successfully traversed the whole range. Drop out
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// of the loop.
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if (state == -1) {
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currentBreakPositions.push((void*)text->getIndex());
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break;
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}
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// if the character we're sitting on causes us to transition to
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// the error state, or if we've gone off the end of the range
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// without transitioning to the "end of word" state, we've hit
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// an error...
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else if (state == 0 || text->getIndex() >= endPos) {
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// if this is the farthest we've gotten, take note of it in
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// case there's an error in the text
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if (text->getIndex() > farthestEndPoint) {
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farthestEndPoint = text->getIndex();
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bestBreakPositions.removeAllElements();
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bestBreakPositionsInitialized = TRUE;
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for (int32_t i = 0; i < currentBreakPositions.size(); i++) {
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bestBreakPositions.push(currentBreakPositions.elementAt(i));
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}
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}
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// wrongBreakPositions is a list of all break positions we've tried starting
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// that didn't allow us to traverse all the way through the text. Every time
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// we pop a break position off of currentBreakPositions, we put it into
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// wrongBreakPositions to avoid trying it again later. If we make it to this
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// spot, we're either going to back up to a break in possibleBreakPositions
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// and try starting over from there, or we've exhausted all possible break
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// positions and are going to do the fallback procedure. This loop prevents
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// us from messing with anything in possibleBreakPositions that didn't work as
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// a starting point the last time we tried it (this is to prevent a bunch of
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// repetitive checks from slowing down some extreme cases)
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while (!possibleBreakPositions.isEmpty() && wrongBreakPositions.contains(
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possibleBreakPositions.peek())) {
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possibleBreakPositions.pop();
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}
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// if we've used up all possible break-position combinations, there's
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// an error or an unknown word in the text. In this case, we start
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// over, treating the farthest character we've reached as the beginning
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// of the range, and "blessing" the break positions that got us that
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// far as real break positions
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if (possibleBreakPositions.isEmpty()) {
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if (bestBreakPositionsInitialized) {
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currentBreakPositions.removeAllElements();
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for (int32_t i = 0; i < bestBreakPositions.size(); i++) {
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currentBreakPositions.push(bestBreakPositions.elementAt(i));
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}
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bestBreakPositions.removeAllElements();
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if (farthestEndPoint < endPos) {
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text->setIndex(farthestEndPoint + 1);
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}
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else {
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break;
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}
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}
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else {
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if ((currentBreakPositions.isEmpty()
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|| (int32_t)(unsigned long)currentBreakPositions.peek() != text->getIndex())
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&& text->getIndex() != startPos) {
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currentBreakPositions.push((void*)text->getIndex());
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}
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text->next();
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currentBreakPositions.push((void*)text->getIndex());
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}
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}
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// if we still have more break positions we can try, then promote the
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// last break in possibleBreakPositions into currentBreakPositions,
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// and get rid of all entries in currentBreakPositions that come after
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// it. Then back up to that position and start over from there (i.e.,
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// treat that position as the beginning of a new word)
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else {
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int32_t temp = (int32_t)(unsigned long)possibleBreakPositions.pop();
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void* temp2 = NULL;
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while (!currentBreakPositions.isEmpty() && temp <
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(int32_t)(unsigned long)currentBreakPositions.peek()) {
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temp2 = currentBreakPositions.pop();
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wrongBreakPositions.addElement(temp2);
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}
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currentBreakPositions.push((void*)temp);
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text->setIndex((int32_t)(unsigned long)currentBreakPositions.peek());
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}
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// re-sync "c" for the next go-round, and drop out of the loop if
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// we've made it off the end of the range
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c = text->current();
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if (text->getIndex() >= endPos) {
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break;
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}
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}
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// if we didn't hit any exceptional conditions on this last iteration,
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// just advance to the next character and loop
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else {
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c = text->next();
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}
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}
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// dump the last break position in the list, and replace it with the actual
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// end of the range (which may be the same character, or may be further on
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// because the range actually ended with non-dictionary characters we want to
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// keep with the word)
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if (!currentBreakPositions.isEmpty()) {
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currentBreakPositions.pop();
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}
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currentBreakPositions.push((void*)endPos);
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// create a regular array to hold the break positions and copy
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// the break positions from the stack to the array (in addition,
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// our starting position goes into this array as a break position).
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// This array becomes the cache of break positions used by next()
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// and previous(), so this is where we actually refresh the cache.
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cachedBreakPositions = new int32_t[currentBreakPositions.size() + 1];
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numCachedBreakPositions = currentBreakPositions.size() + 1;
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cachedBreakPositions[0] = startPos;
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for (int32_t i = 0; i < currentBreakPositions.size(); i++) {
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cachedBreakPositions[i + 1] = (int32_t)(unsigned long)currentBreakPositions.elementAt(i);
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}
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positionInCache = 0;
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}
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