initial commit, 4.5 stable

thirdparty/icu4c/common/locdistance.h

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+// © 2019 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+// locdistance.h
+// created: 2019may08 Markus W. Scherer
+
+#ifndef __LOCDISTANCE_H__
+#define __LOCDISTANCE_H__
+
+#include "unicode/utypes.h"
+#include "unicode/bytestrie.h"
+#include "unicode/localematcher.h"
+#include "unicode/locid.h"
+#include "unicode/uobject.h"
+#include "lsr.h"
+
+U_NAMESPACE_BEGIN
+
+struct LocaleDistanceData;
+
+/**
+ * Offline-built data for LocaleMatcher.
+ * Mostly but not only the data for mapping locales to their maximized forms.
+ */
+class LocaleDistance final : public UMemory {
+public:
+    static const LocaleDistance *getSingleton(UErrorCode &errorCode);
+
+    static int32_t shiftDistance(int32_t distance) {
+        return distance << DISTANCE_SHIFT;
+    }
+
+    static int32_t getShiftedDistance(int32_t indexAndDistance) {
+        return indexAndDistance & DISTANCE_MASK;
+    }
+
+    static double getDistanceDouble(int32_t indexAndDistance) {
+        double shiftedDistance = getShiftedDistance(indexAndDistance);
+        return shiftedDistance / (1 << DISTANCE_SHIFT);
+    }
+
+    static int32_t getDistanceFloor(int32_t indexAndDistance) {
+        return (indexAndDistance & DISTANCE_MASK) >> DISTANCE_SHIFT;
+    }
+
+    static int32_t getIndex(int32_t indexAndDistance) {
+        // assert indexAndDistance >= 0;
+        return indexAndDistance >> INDEX_SHIFT;
+    }
+
+    /**
+     * Finds the supported LSR with the smallest distance from the desired one.
+     * Equivalent LSR subtags must be normalized into a canonical form.
+     *
+     * <p>Returns the index of the lowest-distance supported LSR in the high bits
+     * (negative if none has a distance below the threshold),
+     * and its distance (0..ABOVE_THRESHOLD) in the low bits.
+     */
+    int32_t getBestIndexAndDistance(const LSR &desired,
+                                    const LSR **supportedLSRs, int32_t supportedLSRsLength,
+                                    int32_t shiftedThreshold,
+                                    ULocMatchFavorSubtag favorSubtag,
+                                    ULocMatchDirection direction) const;
+
+    bool isParadigmLSR(const LSR &lsr) const;
+
+    int32_t getDefaultScriptDistance() const {
+        return defaultScriptDistance;
+    }
+
+    int32_t getDefaultDemotionPerDesiredLocale() const {
+        return defaultDemotionPerDesiredLocale;
+    }
+
+private:
+    // The distance is shifted left to gain some fraction bits.
+    static constexpr int32_t DISTANCE_SHIFT = 3;
+    static constexpr int32_t DISTANCE_FRACTION_MASK = 7;
+    // 7 bits for 0..100
+    static constexpr int32_t DISTANCE_INT_SHIFT = 7;
+    static constexpr int32_t INDEX_SHIFT = DISTANCE_INT_SHIFT + DISTANCE_SHIFT;
+    static constexpr int32_t DISTANCE_MASK = 0x3ff;
+    // tic constexpr int32_t MAX_INDEX = 0x1fffff;  // avoids sign bit
+    static constexpr int32_t INDEX_NEG_1 = 0xfffffc00;
+
+    LocaleDistance(const LocaleDistanceData &data, const LikelySubtags &likely);
+    LocaleDistance(const LocaleDistance &other) = delete;
+    LocaleDistance &operator=(const LocaleDistance &other) = delete;
+
+    static void initLocaleDistance(UErrorCode &errorCode);
+
+    bool isMatch(const LSR &desired, const LSR &supported,
+                 int32_t shiftedThreshold, ULocMatchFavorSubtag favorSubtag) const {
+        const LSR *pSupp = &supported;
+        return getBestIndexAndDistance(
+            desired, &pSupp, 1,
+            shiftedThreshold, favorSubtag, ULOCMATCH_DIRECTION_WITH_ONE_WAY) >= 0;
+    }
+
+    static int32_t getDesSuppScriptDistance(BytesTrie &iter, uint64_t startState,
+                                            const char *desired, const char *supported);
+
+    static int32_t getRegionPartitionsDistance(
+        BytesTrie &iter, uint64_t startState,
+        const char *desiredPartitions, const char *supportedPartitions,
+        int32_t threshold);
+
+    static int32_t getFallbackRegionDistance(BytesTrie &iter, uint64_t startState);
+
+    static int32_t trieNext(BytesTrie &iter, const char *s, bool wantValue);
+
+    const char *partitionsForRegion(const LSR &lsr) const {
+        // ill-formed region -> one non-matching string
+        int32_t pIndex = regionToPartitionsIndex[lsr.regionIndex];
+        return partitionArrays[pIndex];
+    }
+
+    int32_t getDefaultRegionDistance() const {
+        return defaultRegionDistance;
+    }
+
+    const LikelySubtags &likelySubtags;
+
+    // The trie maps each dlang+slang+dscript+sscript+dregion+sregion
+    // (encoded in ASCII with bit 7 set on the last character of each subtag) to a distance.
+    // There is also a trie value for each subsequence of whole subtags.
+    // One '*' is used for a (desired, supported) pair of "und", "Zzzz"/"", or "ZZ"/"".
+    BytesTrie trie;
+
+    /**
+     * Maps each region to zero or more single-character partitions.
+     */
+    const uint8_t *regionToPartitionsIndex;
+    const char **partitionArrays;
+
+    /**
+     * Used to get the paradigm region for a cluster, if there is one.
+     */
+    const LSR *paradigmLSRs;
+    int32_t paradigmLSRsLength;
+
+    int32_t defaultLanguageDistance;
+    int32_t defaultScriptDistance;
+    int32_t defaultRegionDistance;
+    int32_t minRegionDistance;
+    int32_t defaultDemotionPerDesiredLocale;
+};
+
+U_NAMESPACE_END
+
+#endif  // __LOCDISTANCE_H__