Check in the pristine copy of ICU 4.6...

icu46/source/common/dictbe.cpp

+/**
+ *******************************************************************************
+ * Copyright (C) 2006-2008, International Business Machines Corporation and others. *
+ * All Rights Reserved.                                                        *
+ *******************************************************************************
+ */
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_BREAK_ITERATION
+
+#include "brkeng.h"
+#include "dictbe.h"
+#include "unicode/uniset.h"
+#include "unicode/chariter.h"
+#include "unicode/ubrk.h"
+#include "uvector.h"
+#include "triedict.h"
+
+U_NAMESPACE_BEGIN
+
+/*
+ ******************************************************************
+ */
+
+/*DictionaryBreakEngine::DictionaryBreakEngine() {
+    fTypes = 0;
+}*/
+
+DictionaryBreakEngine::DictionaryBreakEngine(uint32_t breakTypes) {
+    fTypes = breakTypes;
+}
+
+DictionaryBreakEngine::~DictionaryBreakEngine() {
+}
+
+UBool
+DictionaryBreakEngine::handles(UChar32 c, int32_t breakType) const {
+    return (breakType >= 0 && breakType < 32 && (((uint32_t)1 << breakType) & fTypes)
+            && fSet.contains(c));
+}
+
+int32_t
+DictionaryBreakEngine::findBreaks( UText *text,
+                                 int32_t startPos,
+                                 int32_t endPos,
+                                 UBool reverse,
+                                 int32_t breakType,
+                                 UStack &foundBreaks ) const {
+    int32_t result = 0;
+
+    // Find the span of characters included in the set.
+    int32_t start = (int32_t)utext_getNativeIndex(text);
+    int32_t current;
+    int32_t rangeStart;
+    int32_t rangeEnd;
+    UChar32 c = utext_current32(text);
+    if (reverse) {
+        UBool   isDict = fSet.contains(c);
+        while((current = (int32_t)utext_getNativeIndex(text)) > startPos && isDict) {
+            c = utext_previous32(text);
+            isDict = fSet.contains(c);
+        }
+        rangeStart = (current < startPos) ? startPos : current+(isDict ? 0 : 1);
+        rangeEnd = start + 1;
+    }
+    else {
+        while((current = (int32_t)utext_getNativeIndex(text)) < endPos && fSet.contains(c)) {
+            utext_next32(text);         // TODO:  recast loop for postincrement
+            c = utext_current32(text);
+        }
+        rangeStart = start;
+        rangeEnd = current;
+    }
+    if (breakType >= 0 && breakType < 32 && (((uint32_t)1 << breakType) & fTypes)) {
+        result = divideUpDictionaryRange(text, rangeStart, rangeEnd, foundBreaks);
+        utext_setNativeIndex(text, current);
+    }
+    
+    return result;
+}
+
+void
+DictionaryBreakEngine::setCharacters( const UnicodeSet &set ) {
+    fSet = set;
+    // Compact for caching
+    fSet.compact();
+}
+
+/*void
+DictionaryBreakEngine::setBreakTypes( uint32_t breakTypes ) {
+    fTypes = breakTypes;
+}*/
+
+/*
+ ******************************************************************
+ */
+
+
+// Helper class for improving readability of the Thai word break
+// algorithm. The implementation is completely inline.
+
+// List size, limited by the maximum number of words in the dictionary
+// that form a nested sequence.
+#define POSSIBLE_WORD_LIST_MAX 20
+
+class PossibleWord {
+ private:
+  // list of word candidate lengths, in increasing length order
+  int32_t   lengths[POSSIBLE_WORD_LIST_MAX];
+  int       count;      // Count of candidates
+  int32_t   prefix;     // The longest match with a dictionary word
+  int32_t   offset;     // Offset in the text of these candidates
+  int       mark;       // The preferred candidate's offset
+  int       current;    // The candidate we're currently looking at
+
+ public:
+  PossibleWord();
+  ~PossibleWord();
+  
+  // Fill the list of candidates if needed, select the longest, and return the number found
+  int       candidates( UText *text, const TrieWordDictionary *dict, int32_t rangeEnd );
+  
+  // Select the currently marked candidate, point after it in the text, and invalidate self
+  int32_t   acceptMarked( UText *text );
+  
+  // Back up from the current candidate to the next shorter one; return TRUE if that exists
+  // and point the text after it
+  UBool     backUp( UText *text );
+  
+  // Return the longest prefix this candidate location shares with a dictionary word
+  int32_t   longestPrefix();
+  
+  // Mark the current candidate as the one we like
+  void      markCurrent();
+};
+
+inline
+PossibleWord::PossibleWord() {
+    offset = -1;
+}
+
+inline
+PossibleWord::~PossibleWord() {
+}
+
+inline int
+PossibleWord::candidates( UText *text, const TrieWordDictionary *dict, int32_t rangeEnd ) {
+    // TODO: If getIndex is too slow, use offset < 0 and add discardAll()
+    int32_t start = (int32_t)utext_getNativeIndex(text);
+    if (start != offset) {
+        offset = start;
+        prefix = dict->matches(text, rangeEnd-start, lengths, count, sizeof(lengths)/sizeof(lengths[0]));
+        // Dictionary leaves text after longest prefix, not longest word. Back up.
+        if (count <= 0) {
+            utext_setNativeIndex(text, start);
+        }
+    }
+    if (count > 0) {
+        utext_setNativeIndex(text, start+lengths[count-1]);
+    }
+    current = count-1;
+    mark = current;
+    return count;
+}
+
+inline int32_t
+PossibleWord::acceptMarked( UText *text ) {
+    utext_setNativeIndex(text, offset + lengths[mark]);
+    return lengths[mark];
+}
+
+inline UBool
+PossibleWord::backUp( UText *text ) {
+    if (current > 0) {
+        utext_setNativeIndex(text, offset + lengths[--current]);
+        return TRUE;
+    }
+    return FALSE;
+}
+
+inline int32_t
+PossibleWord::longestPrefix() {
+    return prefix;
+}
+
+inline void
+PossibleWord::markCurrent() {
+    mark = current;
+}
+
+// How many words in a row are "good enough"?
+#define THAI_LOOKAHEAD 3
+
+// Will not combine a non-word with a preceding dictionary word longer than this
+#define THAI_ROOT_COMBINE_THRESHOLD 3
+
+// Will not combine a non-word that shares at least this much prefix with a
+// dictionary word, with a preceding word
+#define THAI_PREFIX_COMBINE_THRESHOLD 3
+
+// Ellision character
+#define THAI_PAIYANNOI 0x0E2F
+
+// Repeat character
+#define THAI_MAIYAMOK 0x0E46
+
+// Minimum word size
+#define THAI_MIN_WORD 2
+
+// Minimum number of characters for two words
+#define THAI_MIN_WORD_SPAN (THAI_MIN_WORD * 2)
+
+ThaiBreakEngine::ThaiBreakEngine(const TrieWordDictionary *adoptDictionary, UErrorCode &status)
+    : DictionaryBreakEngine((1<<UBRK_WORD) | (1<<UBRK_LINE)),
+      fDictionary(adoptDictionary)
+{
+    fThaiWordSet.applyPattern(UNICODE_STRING_SIMPLE("[[:Thai:]&[:LineBreak=SA:]]"), status);
+    if (U_SUCCESS(status)) {
+        setCharacters(fThaiWordSet);
+    }
+    fMarkSet.applyPattern(UNICODE_STRING_SIMPLE("[[:Thai:]&[:LineBreak=SA:]&[:M:]]"), status);
+    fMarkSet.add(0x0020);
+    fEndWordSet = fThaiWordSet;
+    fEndWordSet.remove(0x0E31);             // MAI HAN-AKAT
+    fEndWordSet.remove(0x0E40, 0x0E44);     // SARA E through SARA AI MAIMALAI
+    fBeginWordSet.add(0x0E01, 0x0E2E);      // KO KAI through HO NOKHUK
+    fBeginWordSet.add(0x0E40, 0x0E44);      // SARA E through SARA AI MAIMALAI
+    fSuffixSet.add(THAI_PAIYANNOI);
+    fSuffixSet.add(THAI_MAIYAMOK);
+
+    // Compact for caching.
+    fMarkSet.compact();
+    fEndWordSet.compact();
+    fBeginWordSet.compact();
+    fSuffixSet.compact();
+}
+
+ThaiBreakEngine::~ThaiBreakEngine() {
+    delete fDictionary;
+}
+
+int32_t
+ThaiBreakEngine::divideUpDictionaryRange( UText *text,
+                                                int32_t rangeStart,
+                                                int32_t rangeEnd,
+                                                UStack &foundBreaks ) const {
+    if ((rangeEnd - rangeStart) < THAI_MIN_WORD_SPAN) {
+        return 0;       // Not enough characters for two words
+    }
+
+    uint32_t wordsFound = 0;
+    int32_t wordLength;
+    int32_t current;
+    UErrorCode status = U_ZERO_ERROR;
+    PossibleWord words[THAI_LOOKAHEAD];
+    UChar32 uc;
+    
+    utext_setNativeIndex(text, rangeStart);
+    
+    while (U_SUCCESS(status) && (current = (int32_t)utext_getNativeIndex(text)) < rangeEnd) {
+        wordLength = 0;
+
+        // Look for candidate words at the current position
+        int candidates = words[wordsFound%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd);
+        
+        // If we found exactly one, use that
+        if (candidates == 1) {
+            wordLength = words[wordsFound%THAI_LOOKAHEAD].acceptMarked(text);
+            wordsFound += 1;
+        }
+        
+        // If there was more than one, see which one can take us forward the most words
+        else if (candidates > 1) {
+            // If we're already at the end of the range, we're done
+            if ((int32_t)utext_getNativeIndex(text) >= rangeEnd) {
+                goto foundBest;
+            }
+            do {
+                int wordsMatched = 1;
+                if (words[(wordsFound+1)%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd) > 0) {
+                    if (wordsMatched < 2) {
+                        // Followed by another dictionary word; mark first word as a good candidate
+                        words[wordsFound%THAI_LOOKAHEAD].markCurrent();
+                        wordsMatched = 2;
+                    }
+                    
+                    // If we're already at the end of the range, we're done
+                    if ((int32_t)utext_getNativeIndex(text) >= rangeEnd) {
+                        goto foundBest;
+                    }
+                    
+                    // See if any of the possible second words is followed by a third word
+                    do {
+                        // If we find a third word, stop right away
+                        if (words[(wordsFound+2)%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd)) {
+                            words[wordsFound%THAI_LOOKAHEAD].markCurrent();
+                            goto foundBest;
+                        }
+                    }
+                    while (words[(wordsFound+1)%THAI_LOOKAHEAD].backUp(text));
+                }
+            }
+            while (words[wordsFound%THAI_LOOKAHEAD].backUp(text));
+foundBest:
+            wordLength = words[wordsFound%THAI_LOOKAHEAD].acceptMarked(text);
+            wordsFound += 1;
+        }
+        
+        // We come here after having either found a word or not. We look ahead to the
+        // next word. If it's not a dictionary word, we will combine it withe the word we
+        // just found (if there is one), but only if the preceding word does not exceed
+        // the threshold.
+        // The text iterator should now be positioned at the end of the word we found.
+        if ((int32_t)utext_getNativeIndex(text) < rangeEnd && wordLength < THAI_ROOT_COMBINE_THRESHOLD) {
+            // if it is a dictionary word, do nothing. If it isn't, then if there is
+            // no preceding word, or the non-word shares less than the minimum threshold
+            // of characters with a dictionary word, then scan to resynchronize
+            if (words[wordsFound%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd) <= 0
+                  && (wordLength == 0
+                      || words[wordsFound%THAI_LOOKAHEAD].longestPrefix() < THAI_PREFIX_COMBINE_THRESHOLD)) {
+                // Look for a plausible word boundary
+                //TODO: This section will need a rework for UText.
+                int32_t remaining = rangeEnd - (current+wordLength);
+                UChar32 pc = utext_current32(text);
+                int32_t chars = 0;
+                for (;;) {
+                    utext_next32(text);
+                    uc = utext_current32(text);
+                    // TODO: Here we're counting on the fact that the SA languages are all
+                    // in the BMP. This should get fixed with the UText rework.
+                    chars += 1;
+                    if (--remaining <= 0) {
+                        break;
+                    }
+                    if (fEndWordSet.contains(pc) && fBeginWordSet.contains(uc)) {
+                        // Maybe. See if it's in the dictionary.
+                        // NOTE: In the original Apple code, checked that the next
+                        // two characters after uc were not 0x0E4C THANTHAKHAT before
+                        // checking the dictionary. That is just a performance filter,
+                        // but it's not clear it's faster than checking the trie.
+                        int candidates = words[(wordsFound+1)%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd);
+                        utext_setNativeIndex(text, current+wordLength+chars);
+                        if (candidates > 0) {
+                            break;
+                        }
+                    }
+                    pc = uc;
+                }
+                
+                // Bump the word count if there wasn't already one
+                if (wordLength <= 0) {
+                    wordsFound += 1;
+                }
+                
+                // Update the length with the passed-over characters
+                wordLength += chars;
+            }
+            else {
+                // Back up to where we were for next iteration
+                utext_setNativeIndex(text, current+wordLength);
+            }
+        }
+        
+        // Never stop before a combining mark.
+        int32_t currPos;
+        while ((currPos = (int32_t)utext_getNativeIndex(text)) < rangeEnd && fMarkSet.contains(utext_current32(text))) {
+            utext_next32(text);
+            wordLength += (int32_t)utext_getNativeIndex(text) - currPos;
+        }
+        
+        // Look ahead for possible suffixes if a dictionary word does not follow.
+        // We do this in code rather than using a rule so that the heuristic
+        // resynch continues to function. For example, one of the suffix characters
+        // could be a typo in the middle of a word.
+        if ((int32_t)utext_getNativeIndex(text) < rangeEnd && wordLength > 0) {
+            if (words[wordsFound%THAI_LOOKAHEAD].candidates(text, fDictionary, rangeEnd) <= 0
+                && fSuffixSet.contains(uc = utext_current32(text))) {
+                if (uc == THAI_PAIYANNOI) {
+                    if (!fSuffixSet.contains(utext_previous32(text))) {
+                        // Skip over previous end and PAIYANNOI
+                        utext_next32(text);
+                        utext_next32(text);
+                        wordLength += 1;            // Add PAIYANNOI to word
+                        uc = utext_current32(text);     // Fetch next character
+                    }
+                    else {
+                        // Restore prior position
+                        utext_next32(text);
+                    }
+                }
+                if (uc == THAI_MAIYAMOK) {
+                    if (utext_previous32(text) != THAI_MAIYAMOK) {
+                        // Skip over previous end and MAIYAMOK
+                        utext_next32(text);
+                        utext_next32(text);
+                        wordLength += 1;            // Add MAIYAMOK to word
+                    }
+                    else {
+                        // Restore prior position
+                        utext_next32(text);
+                    }
+                }
+            }
+            else {
+                utext_setNativeIndex(text, current+wordLength);
+            }
+        }
+        
+        // Did we find a word on this iteration? If so, push it on the break stack
+        if (wordLength > 0) {
+            foundBreaks.push((current+wordLength), status);
+        }
+    }
+    
+    // Don't return a break for the end of the dictionary range if there is one there.
+    if (foundBreaks.peeki() >= rangeEnd) {
+        (void) foundBreaks.popi();
+        wordsFound -= 1;
+    }
+
+    return wordsFound;
+}
+
+U_NAMESPACE_END
+
+#endif /* #if !UCONFIG_NO_BREAK_ITERATION */