initial commit, 4.5 stable

thirdparty/icu4c/common/unicode/bytestrie.h

@@ -0,0 +1,568 @@
+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+*******************************************************************************
+*   Copyright (C) 2010-2012, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*******************************************************************************
+*   file name:  bytestrie.h
+*   encoding:   UTF-8
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2010sep25
+*   created by: Markus W. Scherer
+*/
+
+#ifndef __BYTESTRIE_H__
+#define __BYTESTRIE_H__
+
+/**
+ * \file
+ * \brief C++ API: Trie for mapping byte sequences to integer values.
+ */
+
+#include "unicode/utypes.h"
+
+#if U_SHOW_CPLUSPLUS_API
+
+#include "unicode/stringpiece.h"
+#include "unicode/uobject.h"
+#include "unicode/ustringtrie.h"
+
+class BytesTrieTest;
+
+U_NAMESPACE_BEGIN
+
+class ByteSink;
+class BytesTrieBuilder;
+class CharString;
+class UVector32;
+
+/**
+ * Light-weight, non-const reader class for a BytesTrie.
+ * Traverses a byte-serialized data structure with minimal state,
+ * for mapping byte sequences to non-negative integer values.
+ *
+ * This class owns the serialized trie data only if it was constructed by
+ * the builder's build() method.
+ * The public constructor and the copy constructor only alias the data (only copy the pointer).
+ * There is no assignment operator.
+ *
+ * This class is not intended for public subclassing.
+ * @stable ICU 4.8
+ */
+class U_COMMON_API BytesTrie : public UMemory {
+public:
+    /**
+     * Constructs a BytesTrie reader instance.
+     *
+     * The trieBytes must contain a copy of a byte sequence from the BytesTrieBuilder,
+     * starting with the first byte of that sequence.
+     * The BytesTrie object will not read more bytes than
+     * the BytesTrieBuilder generated in the corresponding build() call.
+     *
+     * The array is not copied/cloned and must not be modified while
+     * the BytesTrie object is in use.
+     *
+     * @param trieBytes The byte array that contains the serialized trie.
+     * @stable ICU 4.8
+     */
+    BytesTrie(const void *trieBytes)
+            : ownedArray_(nullptr), bytes_(static_cast<const uint8_t *>(trieBytes)),
+              pos_(bytes_), remainingMatchLength_(-1) {}
+
+    /**
+     * Destructor.
+     * @stable ICU 4.8
+     */
+    ~BytesTrie();
+
+    /**
+     * Copy constructor, copies the other trie reader object and its state,
+     * but not the byte array which will be shared. (Shallow copy.)
+     * @param other Another BytesTrie object.
+     * @stable ICU 4.8
+     */
+    BytesTrie(const BytesTrie &other)
+            : ownedArray_(nullptr), bytes_(other.bytes_),
+              pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
+
+    /**
+     * Resets this trie to its initial state.
+     * @return *this
+     * @stable ICU 4.8
+     */
+    BytesTrie &reset() {
+        pos_=bytes_;
+        remainingMatchLength_=-1;
+        return *this;
+    }
+
+    /**
+     * Returns the state of this trie as a 64-bit integer.
+     * The state value is never 0.
+     *
+     * @return opaque state value
+     * @see resetToState64
+     * @stable ICU 65
+     */
+    uint64_t getState64() const {
+        return (static_cast<uint64_t>(remainingMatchLength_ + 2) << kState64RemainingShift) |
+            static_cast<uint64_t>(pos_ - bytes_);
+    }
+
+    /**
+     * Resets this trie to the saved state.
+     * Unlike resetToState(State), the 64-bit state value
+     * must be from getState64() from the same trie object or
+     * from one initialized the exact same way.
+     * Because of no validation, this method is faster.
+     *
+     * @param state The opaque trie state value from getState64().
+     * @return *this
+     * @see getState64
+     * @see resetToState
+     * @see reset
+     * @stable ICU 65
+     */
+    BytesTrie &resetToState64(uint64_t state) {
+        remainingMatchLength_ = static_cast<int32_t>(state >> kState64RemainingShift) - 2;
+        pos_ = bytes_ + (state & kState64PosMask);
+        return *this;
+    }
+
+    /**
+     * BytesTrie state object, for saving a trie's current state
+     * and resetting the trie back to this state later.
+     * @stable ICU 4.8
+     */
+    class State : public UMemory {
+    public:
+        /**
+         * Constructs an empty State.
+         * @stable ICU 4.8
+         */
+        State() { bytes=nullptr; }
+    private:
+        friend class BytesTrie;
+
+        const uint8_t *bytes;
+        const uint8_t *pos;
+        int32_t remainingMatchLength;
+    };
+
+    /**
+     * Saves the state of this trie.
+     * @param state The State object to hold the trie's state.
+     * @return *this
+     * @see resetToState
+     * @stable ICU 4.8
+     */
+    const BytesTrie &saveState(State &state) const {
+        state.bytes=bytes_;
+        state.pos=pos_;
+        state.remainingMatchLength=remainingMatchLength_;
+        return *this;
+    }
+
+    /**
+     * Resets this trie to the saved state.
+     * If the state object contains no state, or the state of a different trie,
+     * then this trie remains unchanged.
+     * @param state The State object which holds a saved trie state.
+     * @return *this
+     * @see saveState
+     * @see reset
+     * @stable ICU 4.8
+     */
+    BytesTrie &resetToState(const State &state) {
+        if(bytes_==state.bytes && bytes_!=nullptr) {
+            pos_=state.pos;
+            remainingMatchLength_=state.remainingMatchLength;
+        }
+        return *this;
+    }
+
+    /**
+     * Determines whether the byte sequence so far matches, whether it has a value,
+     * and whether another input byte can continue a matching byte sequence.
+     * @return The match/value Result.
+     * @stable ICU 4.8
+     */
+    UStringTrieResult current() const;
+
+    /**
+     * Traverses the trie from the initial state for this input byte.
+     * Equivalent to reset().next(inByte).
+     * @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
+     *               Values below -0x100 and above 0xff will never match.
+     * @return The match/value Result.
+     * @stable ICU 4.8
+     */
+    inline UStringTrieResult first(int32_t inByte) {
+        remainingMatchLength_=-1;
+        if(inByte<0) {
+            inByte+=0x100;
+        }
+        return nextImpl(bytes_, inByte);
+    }
+
+    /**
+     * Traverses the trie from the current state for this input byte.
+     * @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
+     *               Values below -0x100 and above 0xff will never match.
+     * @return The match/value Result.
+     * @stable ICU 4.8
+     */
+    UStringTrieResult next(int32_t inByte);
+
+    /**
+     * Traverses the trie from the current state for this byte sequence.
+     * Equivalent to
+     * \code
+     * Result result=current();
+     * for(each c in s)
+     *   if(!USTRINGTRIE_HAS_NEXT(result)) return USTRINGTRIE_NO_MATCH;
+     *   result=next(c);
+     * return result;
+     * \endcode
+     * @param s A string or byte sequence. Can be nullptr if length is 0.
+     * @param length The length of the byte sequence. Can be -1 if NUL-terminated.
+     * @return The match/value Result.
+     * @stable ICU 4.8
+     */
+    UStringTrieResult next(const char *s, int32_t length);
+
+    /**
+     * Returns a matching byte sequence's value if called immediately after
+     * current()/first()/next() returned USTRINGTRIE_INTERMEDIATE_VALUE or USTRINGTRIE_FINAL_VALUE.
+     * getValue() can be called multiple times.
+     *
+     * Do not call getValue() after USTRINGTRIE_NO_MATCH or USTRINGTRIE_NO_VALUE!
+     * @return The value for the byte sequence so far.
+     * @stable ICU 4.8
+     */
+    inline int32_t getValue() const {
+        const uint8_t *pos=pos_;
+        int32_t leadByte=*pos++;
+        // U_ASSERT(leadByte>=kMinValueLead);
+        return readValue(pos, leadByte>>1);
+    }
+
+    /**
+     * Determines whether all byte sequences reachable from the current state
+     * map to the same value.
+     * @param uniqueValue Receives the unique value, if this function returns true.
+     *                    (output-only)
+     * @return true if all byte sequences reachable from the current state
+     *         map to the same value.
+     * @stable ICU 4.8
+     */
+    inline UBool hasUniqueValue(int32_t &uniqueValue) const {
+        const uint8_t *pos=pos_;
+        // Skip the rest of a pending linear-match node.
+        return pos!=nullptr && findUniqueValue(pos+remainingMatchLength_+1, false, uniqueValue);
+    }
+
+    /**
+     * Finds each byte which continues the byte sequence from the current state.
+     * That is, each byte b for which it would be next(b)!=USTRINGTRIE_NO_MATCH now.
+     * @param out Each next byte is appended to this object.
+     *            (Only uses the out.Append(s, length) method.)
+     * @return the number of bytes which continue the byte sequence from here
+     * @stable ICU 4.8
+     */
+    int32_t getNextBytes(ByteSink &out) const;
+
+    /**
+     * Iterator for all of the (byte sequence, value) pairs in a BytesTrie.
+     * @stable ICU 4.8
+     */
+    class U_COMMON_API Iterator : public UMemory {
+    public:
+        /**
+         * Iterates from the root of a byte-serialized BytesTrie.
+         * @param trieBytes The trie bytes.
+         * @param maxStringLength If 0, the iterator returns full strings/byte sequences.
+         *                        Otherwise, the iterator returns strings with this maximum length.
+         * @param errorCode Standard ICU error code. Its input value must
+         *                  pass the U_SUCCESS() test, or else the function returns
+         *                  immediately. Check for U_FAILURE() on output or use with
+         *                  function chaining. (See User Guide for details.)
+         * @stable ICU 4.8
+         */
+        Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode);
+
+        /**
+         * Iterates from the current state of the specified BytesTrie.
+         * @param trie The trie whose state will be copied for iteration.
+         * @param maxStringLength If 0, the iterator returns full strings/byte sequences.
+         *                        Otherwise, the iterator returns strings with this maximum length.
+         * @param errorCode Standard ICU error code. Its input value must
+         *                  pass the U_SUCCESS() test, or else the function returns
+         *                  immediately. Check for U_FAILURE() on output or use with
+         *                  function chaining. (See User Guide for details.)
+         * @stable ICU 4.8
+         */
+        Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
+
+        /**
+         * Destructor.
+         * @stable ICU 4.8
+         */
+        ~Iterator();
+
+        /**
+         * Resets this iterator to its initial state.
+         * @return *this
+         * @stable ICU 4.8
+         */
+        Iterator &reset();
+
+        /**
+         * @return true if there are more elements.
+         * @stable ICU 4.8
+         */
+        UBool hasNext() const;
+
+        /**
+         * Finds the next (byte sequence, value) pair if there is one.
+         *
+         * If the byte sequence is truncated to the maximum length and does not
+         * have a real value, then the value is set to -1.
+         * In this case, this "not a real value" is indistinguishable from
+         * a real value of -1.
+         * @param errorCode Standard ICU error code. Its input value must
+         *                  pass the U_SUCCESS() test, or else the function returns
+         *                  immediately. Check for U_FAILURE() on output or use with
+         *                  function chaining. (See User Guide for details.)
+         * @return true if there is another element.
+         * @stable ICU 4.8
+         */
+        UBool next(UErrorCode &errorCode);
+
+        /**
+         * @return The NUL-terminated byte sequence for the last successful next().
+         * @stable ICU 4.8
+         */
+        StringPiece getString() const;
+        /**
+         * @return The value for the last successful next().
+         * @stable ICU 4.8
+         */
+        int32_t getValue() const { return value_; }
+
+    private:
+        UBool truncateAndStop();
+
+        const uint8_t *branchNext(const uint8_t *pos, int32_t length, UErrorCode &errorCode);
+
+        const uint8_t *bytes_;
+        const uint8_t *pos_;
+        const uint8_t *initialPos_;
+        int32_t remainingMatchLength_;
+        int32_t initialRemainingMatchLength_;
+
+        CharString *str_;
+        int32_t maxLength_;
+        int32_t value_;
+
+        // The stack stores pairs of integers for backtracking to another
+        // outbound edge of a branch node.
+        // The first integer is an offset from bytes_.
+        // The second integer has the str_->length() from before the node in bits 15..0,
+        // and the remaining branch length in bits 24..16. (Bits 31..25 are unused.)
+        // (We could store the remaining branch length minus 1 in bits 23..16 and not use bits 31..24,
+        // but the code looks more confusing that way.)
+        UVector32 *stack_;
+    };
+
+private:
+    friend class BytesTrieBuilder;
+    friend class ::BytesTrieTest;
+
+    /**
+     * Constructs a BytesTrie reader instance.
+     * Unlike the public constructor which just aliases an array,
+     * this constructor adopts the builder's array.
+     * This constructor is only called by the builder.
+     */
+    BytesTrie(void *adoptBytes, const void *trieBytes)
+            : ownedArray_(static_cast<uint8_t *>(adoptBytes)),
+              bytes_(static_cast<const uint8_t *>(trieBytes)),
+              pos_(bytes_), remainingMatchLength_(-1) {}
+
+    // No assignment operator.
+    BytesTrie &operator=(const BytesTrie &other) = delete;
+
+    inline void stop() {
+        pos_=nullptr;
+    }
+
+    // Reads a compact 32-bit integer.
+    // pos is already after the leadByte, and the lead byte is already shifted right by 1.
+    static int32_t readValue(const uint8_t *pos, int32_t leadByte);
+    static inline const uint8_t *skipValue(const uint8_t *pos, int32_t leadByte) {
+        // U_ASSERT(leadByte>=kMinValueLead);
+        if(leadByte>=(kMinTwoByteValueLead<<1)) {
+            if(leadByte<(kMinThreeByteValueLead<<1)) {
+                ++pos;
+            } else if(leadByte<(kFourByteValueLead<<1)) {
+                pos+=2;
+            } else {
+                pos+=3+((leadByte>>1)&1);
+            }
+        }
+        return pos;
+    }
+    static inline const uint8_t *skipValue(const uint8_t *pos) {
+        int32_t leadByte=*pos++;
+        return skipValue(pos, leadByte);
+    }
+
+    // Reads a jump delta and jumps.
+    static const uint8_t *jumpByDelta(const uint8_t *pos);
+
+    static inline const uint8_t *skipDelta(const uint8_t *pos) {
+        int32_t delta=*pos++;
+        if(delta>=kMinTwoByteDeltaLead) {
+            if(delta<kMinThreeByteDeltaLead) {
+                ++pos;
+            } else if(delta<kFourByteDeltaLead) {
+                pos+=2;
+            } else {
+                pos+=3+(delta&1);
+            }
+        }
+        return pos;
+    }
+
+    static inline UStringTrieResult valueResult(int32_t node) {
+        return static_cast<UStringTrieResult>(USTRINGTRIE_INTERMEDIATE_VALUE - (node & kValueIsFinal));
+    }
+
+    // Handles a branch node for both next(byte) and next(string).
+    UStringTrieResult branchNext(const uint8_t *pos, int32_t length, int32_t inByte);
+
+    // Requires remainingLength_<0.
+    UStringTrieResult nextImpl(const uint8_t *pos, int32_t inByte);
+
+    // Helper functions for hasUniqueValue().
+    // Recursively finds a unique value (or whether there is not a unique one)
+    // from a branch.
+    static const uint8_t *findUniqueValueFromBranch(const uint8_t *pos, int32_t length,
+                                                    UBool haveUniqueValue, int32_t &uniqueValue);
+    // Recursively finds a unique value (or whether there is not a unique one)
+    // starting from a position on a node lead byte.
+    static UBool findUniqueValue(const uint8_t *pos, UBool haveUniqueValue, int32_t &uniqueValue);
+
+    // Helper functions for getNextBytes().
+    // getNextBytes() when pos is on a branch node.
+    static void getNextBranchBytes(const uint8_t *pos, int32_t length, ByteSink &out);
+    static void append(ByteSink &out, int c);
+
+    // BytesTrie data structure
+    //
+    // The trie consists of a series of byte-serialized nodes for incremental
+    // string/byte sequence matching. The root node is at the beginning of the trie data.
+    //
+    // Types of nodes are distinguished by their node lead byte ranges.
+    // After each node, except a final-value node, another node follows to
+    // encode match values or continue matching further bytes.
+    //
+    // Node types:
+    //  - Value node: Stores a 32-bit integer in a compact, variable-length format.
+    //    The value is for the string/byte sequence so far.
+    //    One node bit indicates whether the value is final or whether
+    //    matching continues with the next node.
+    //  - Linear-match node: Matches a number of bytes.
+    //  - Branch node: Branches to other nodes according to the current input byte.
+    //    The node byte is the length of the branch (number of bytes to select from)
+    //    minus 1. It is followed by a sub-node:
+    //    - If the length is at most kMaxBranchLinearSubNodeLength, then
+    //      there are length-1 (key, value) pairs and then one more comparison byte.
+    //      If one of the key bytes matches, then the value is either a final value for
+    //      the string/byte sequence so far, or a "jump" delta to the next node.
+    //      If the last byte matches, then matching continues with the next node.
+    //      (Values have the same encoding as value nodes.)
+    //    - If the length is greater than kMaxBranchLinearSubNodeLength, then
+    //      there is one byte and one "jump" delta.
+    //      If the input byte is less than the sub-node byte, then "jump" by delta to
+    //      the next sub-node which will have a length of length/2.
+    //      (The delta has its own compact encoding.)
+    //      Otherwise, skip the "jump" delta to the next sub-node
+    //      which will have a length of length-length/2.
+
+    // Node lead byte values.
+
+    // 00..0f: Branch node. If node!=0 then the length is node+1, otherwise
+    // the length is one more than the next byte.
+
+    // For a branch sub-node with at most this many entries, we drop down
+    // to a linear search.
+    static const int32_t kMaxBranchLinearSubNodeLength=5;
+
+    // 10..1f: Linear-match node, match 1..16 bytes and continue reading the next node.
+    static const int32_t kMinLinearMatch=0x10;
+    static const int32_t kMaxLinearMatchLength=0x10;
+
+    // 20..ff: Variable-length value node.
+    // If odd, the value is final. (Otherwise, intermediate value or jump delta.)
+    // Then shift-right by 1 bit.
+    // The remaining lead byte value indicates the number of following bytes (0..4)
+    // and contains the value's top bits.
+    static const int32_t kMinValueLead=kMinLinearMatch+kMaxLinearMatchLength;  // 0x20
+    // It is a final value if bit 0 is set.
+    static const int32_t kValueIsFinal=1;
+
+    // Compact value: After testing bit 0, shift right by 1 and then use the following thresholds.
+    static const int32_t kMinOneByteValueLead=kMinValueLead/2;  // 0x10
+    static const int32_t kMaxOneByteValue=0x40;  // At least 6 bits in the first byte.
+
+    static const int32_t kMinTwoByteValueLead=kMinOneByteValueLead+kMaxOneByteValue+1;  // 0x51
+    static const int32_t kMaxTwoByteValue=0x1aff;
+
+    static const int32_t kMinThreeByteValueLead=kMinTwoByteValueLead+(kMaxTwoByteValue>>8)+1;  // 0x6c
+    static const int32_t kFourByteValueLead=0x7e;
+
+    // A little more than Unicode code points. (0x11ffff)
+    static const int32_t kMaxThreeByteValue=((kFourByteValueLead-kMinThreeByteValueLead)<<16)-1;
+
+    static const int32_t kFiveByteValueLead=0x7f;
+
+    // Compact delta integers.
+    static const int32_t kMaxOneByteDelta=0xbf;
+    static const int32_t kMinTwoByteDeltaLead=kMaxOneByteDelta+1;  // 0xc0
+    static const int32_t kMinThreeByteDeltaLead=0xf0;
+    static const int32_t kFourByteDeltaLead=0xfe;
+    static const int32_t kFiveByteDeltaLead=0xff;
+
+    static const int32_t kMaxTwoByteDelta=((kMinThreeByteDeltaLead-kMinTwoByteDeltaLead)<<8)-1;  // 0x2fff
+    static const int32_t kMaxThreeByteDelta=((kFourByteDeltaLead-kMinThreeByteDeltaLead)<<16)-1;  // 0xdffff
+
+    // For getState64():
+    // The remainingMatchLength_ is -1..14=(kMaxLinearMatchLength=0x10)-2
+    // so we need at least 5 bits for that.
+    // We add 2 to store it as a positive value 1..16=kMaxLinearMatchLength.
+    static constexpr int32_t kState64RemainingShift = 59;
+    static constexpr uint64_t kState64PosMask = (UINT64_C(1) << kState64RemainingShift) - 1;
+
+    uint8_t *ownedArray_;
+
+    // Fixed value referencing the BytesTrie bytes.
+    const uint8_t *bytes_;
+
+    // Iterator variables.
+
+    // Pointer to next trie byte to read. nullptr if no more matches.
+    const uint8_t *pos_;
+    // Remaining length of a linear-match node, minus 1. Negative if not in such a node.
+    int32_t remainingMatchLength_;
+};
+
+U_NAMESPACE_END
+
+#endif /* U_SHOW_CPLUSPLUS_API */
+
+#endif  // __BYTESTRIE_H__