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rbbi_cache.h (7953B)

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// Copyright (C) 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html

// file: rbbi_cache.h
//
#ifndef RBBI_CACHE_H
#define RBBI_CACHE_H

#include "unicode/utypes.h"

#if !UCONFIG_NO_BREAK_ITERATION

#include "unicode/rbbi.h"
#include "unicode/uobject.h"

#include "uvectr32.h"

U_NAMESPACE_BEGIN

/* DictionaryCache  stores the boundaries obtained from a run of dictionary characters.
*                 Dictionary boundaries are moved first to this cache, then from here
*                 to the main BreakCache, where they may inter-leave with non-dictionary
*                 boundaries. The public BreakIterator API always fetches directly
*                 from the main BreakCache, not from here.
*
*                 In common situations, the number of boundaries in a single dictionary run
*                 should be quite small, it will be terminated by punctuation, spaces,
*                 or any other non-dictionary characters. The main BreakCache may end
*                 up with boundaries from multiple dictionary based runs.
*
*                 The boundaries are stored in a simple ArrayList (vector), with the
*                 assumption that they will be accessed sequentially.
*/                 
class RuleBasedBreakIterator::DictionaryCache: public UMemory {
 public:
    DictionaryCache(RuleBasedBreakIterator *bi, UErrorCode &status);
    ~DictionaryCache();

    void reset();

    UBool following(int32_t fromPos, int32_t *pos, int32_t *statusIndex);
    UBool preceding(int32_t fromPos, int32_t *pos, int32_t *statusIndex);

   /**
    * Populate the cache with the dictionary based boundaries within a region of text.
    * @param startPos  The start position of a range of text
    * @param endPos    The end position of a range of text
    * @param firstRuleStatus The rule status index that applies to the break at startPos
    * @param otherRuleStatus The rule status index that applies to boundaries other than startPos
    * @internal
    */
   void populateDictionary(int32_t startPos, int32_t endPos,
                        int32_t firstRuleStatus, int32_t otherRuleStatus);



   RuleBasedBreakIterator *fBI;
   
   UVector32           fBreaks;                // A vector containing the boundaries.
   int32_t             fPositionInCache;       // Index in fBreaks of last boundary returned by following()
                                               //    or preceding(). Optimizes sequential access.
   int32_t             fStart;                 // Text position of first boundary in cache.
   int32_t             fLimit;                 // Last boundary in cache. Which is the limit of the
                                               //    text segment being handled by the dictionary.
   int32_t             fFirstRuleStatusIndex;  // Rule status info for first boundary.
   int32_t             fOtherRuleStatusIndex;  // Rule status info for 2nd through last boundaries.
};


/*
* class BreakCache
*
* Cache of break boundary positions and rule status values.
* Break iterator API functions, next(), previous(), etc., will use cached results
* when possible, and otherwise cache new results as they are obtained.
*
* Uniformly caches both dictionary and rule based (non-dictionary) boundaries.
*
* The cache is implemented as a single circular buffer.
*/

/*
* size of the circular cache buffer.
*/

class RuleBasedBreakIterator::BreakCache: public UMemory {
 public:
               BreakCache(RuleBasedBreakIterator *bi, UErrorCode &status);
   virtual     ~BreakCache();
   void        reset(int32_t pos = 0, int32_t ruleStatus = 0);
   void        next() {    if (fBufIdx == fEndBufIdx) {
                               nextOL();
                           } else {
                               fBufIdx = modChunkSize(fBufIdx + 1);
                               fTextIdx = fBI->fPosition = fBoundaries[fBufIdx];
                               fBI->fRuleStatusIndex = fStatuses[fBufIdx];
                           }
               }


   void        nextOL();
   void        previous(UErrorCode &status);

   // Move the iteration state to the position following the startPosition.
   // Input position must be pinned to the input length.
   void        following(int32_t startPosition, UErrorCode &status);

   void        preceding(int32_t startPosition, UErrorCode &status);

   /*
    * Update the state of the public BreakIterator (fBI) to reflect the
    * current state of the break iterator cache (this).
    */
   int32_t     current();

   /**
    * Add boundaries to the cache near the specified position.
    * The given position need not be a boundary itself.
    * The input position must be within the range of the text, and
    * on a code point boundary.
    * If the requested position is a break boundary, leave the iteration
    * position on it.
    * If the requested position is not a boundary, leave the iteration
    * position on the preceding boundary and include both the
    * preceding and following boundaries in the cache.
    * Additional boundaries, either preceding or following, may be added
    * to the cache as a side effect.
    *
    * Return false if the operation failed.
    */
   UBool populateNear(int32_t position, UErrorCode &status);

   /**
    *  Add boundary(s) to the cache following the current last boundary.
    *  Return false if at the end of the text, and no more boundaries can be added.
    *  Leave iteration position at the first newly added boundary, or unchanged if no boundary was added.
    */
   UBool populateFollowing();

   /**
    *  Add one or more boundaries to the cache preceding the first currently cached boundary.
    *  Leave the iteration position on the first added boundary.
    *  Return false if no boundaries could be added (if at the start of the text.)
    */
   UBool populatePreceding(UErrorCode &status);

   enum UpdatePositionValues {
       RetainCachePosition = 0,
       UpdateCachePosition = 1
   };

   /*
    * Add the boundary following the current position.
    * The current position can be left as it was, or changed to the newly added boundary,
    * as specified by the update parameter.
    */
   void addFollowing(int32_t position, int32_t ruleStatusIdx, UpdatePositionValues update);


   /*
    * Add the boundary preceding the current position.
    * The current position can be left as it was, or changed to the newly added boundary,
    * as specified by the update parameter.
    */
   bool addPreceding(int32_t position, int32_t ruleStatusIdx, UpdatePositionValues update);

   /**
    *  Set the cache position to the specified position, or, if the position
    *  falls between to cached boundaries, to the preceding boundary.
    *  Fails if the requested position is outside of the range of boundaries currently held by the cache.
    *  The startPosition must be on a code point boundary.
    *
    *  Return true if successful, false if the specified position is after
    *  the last cached boundary or before the first.
    */
   UBool                   seek(int32_t startPosition);

   void dumpCache();

 private:
   static inline int32_t   modChunkSize(int index) { return index & (CACHE_SIZE - 1); }

   static constexpr int32_t CACHE_SIZE = 128;
   static_assert((CACHE_SIZE & (CACHE_SIZE-1)) == 0, "CACHE_SIZE must be power of two.");

   RuleBasedBreakIterator *fBI;
   int32_t                 fStartBufIdx;
   int32_t                 fEndBufIdx;    // inclusive

   int32_t                 fTextIdx;
   int32_t                 fBufIdx;

   int32_t                 fBoundaries[CACHE_SIZE];
   uint16_t                fStatuses[CACHE_SIZE];

   UVector32               fSideBuffer;
};

U_NAMESPACE_END

#endif // #if !UCONFIG_NO_BREAK_ITERATION

#endif // RBBI_CACHE_H