initial commit, 4.5 stable

thirdparty/icu4c/common/rbbi_cache.h

@@ -0,0 +1,203 @@
+// 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