tor-browser

ucharstrie.h (23128B)

---

// © 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:  ucharstrie.h
*   encoding:   UTF-8
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 2010nov14
*   created by: Markus W. Scherer
*/

#ifndef __UCHARSTRIE_H__
#define __UCHARSTRIE_H__

/**
* \file
* \brief C++ API: Trie for mapping Unicode strings (or 16-bit-unit sequences)
*                 to integer values.
*/

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#include "unicode/unistr.h"
#include "unicode/uobject.h"
#include "unicode/ustringtrie.h"

U_NAMESPACE_BEGIN

class Appendable;
class UCharsTrieBuilder;
class UVector32;

/**
* Light-weight, non-const reader class for a UCharsTrie.
* Traverses a char16_t-serialized data structure with minimal state,
* for mapping strings (16-bit-unit 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 UCharsTrie : public UMemory {
public:
   /**
    * Constructs a UCharsTrie reader instance.
    *
    * The trieUChars must contain a copy of a char16_t sequence from the UCharsTrieBuilder,
    * starting with the first char16_t of that sequence.
    * The UCharsTrie object will not read more char16_ts than
    * the UCharsTrieBuilder generated in the corresponding build() call.
    *
    * The array is not copied/cloned and must not be modified while
    * the UCharsTrie object is in use.
    *
    * @param trieUChars The char16_t array that contains the serialized trie.
    * @stable ICU 4.8
    */
   UCharsTrie(ConstChar16Ptr trieUChars)
           : ownedArray_(nullptr), uchars_(trieUChars),
             pos_(uchars_), remainingMatchLength_(-1) {}

   /**
    * Destructor.
    * @stable ICU 4.8
    */
   ~UCharsTrie();

   /**
    * Copy constructor, copies the other trie reader object and its state,
    * but not the char16_t array which will be shared. (Shallow copy.)
    * @param other Another UCharsTrie object.
    * @stable ICU 4.8
    */
   UCharsTrie(const UCharsTrie &other)
           : ownedArray_(nullptr), uchars_(other.uchars_),
             pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}

   /**
    * Resets this trie to its initial state.
    * @return *this
    * @stable ICU 4.8
    */
   UCharsTrie &reset() {
       pos_=uchars_;
       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_ - uchars_);
   }

   /**
    * 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
    */
   UCharsTrie &resetToState64(uint64_t state) {
       remainingMatchLength_ = static_cast<int32_t>(state >> kState64RemainingShift) - 2;
       pos_ = uchars_ + (state & kState64PosMask);
       return *this;
   }

   /**
    * UCharsTrie 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() { uchars=nullptr; }
   private:
       friend class UCharsTrie;

       const char16_t *uchars;
       const char16_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 UCharsTrie &saveState(State &state) const {
       state.uchars=uchars_;
       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
    */
   UCharsTrie &resetToState(const State &state) {
       if(uchars_==state.uchars && uchars_!=nullptr) {
           pos_=state.pos;
           remainingMatchLength_=state.remainingMatchLength;
       }
       return *this;
   }

   /**
    * Determines whether the string so far matches, whether it has a value,
    * and whether another input char16_t can continue a matching string.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   UStringTrieResult current() const;

   /**
    * Traverses the trie from the initial state for this input char16_t.
    * Equivalent to reset().next(uchar).
    * @param uchar Input char value. Values below 0 and above 0xffff will never match.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   inline UStringTrieResult first(int32_t uchar) {
       remainingMatchLength_=-1;
       return nextImpl(uchars_, uchar);
   }

   /**
    * Traverses the trie from the initial state for the
    * one or two UTF-16 code units for this input code point.
    * Equivalent to reset().nextForCodePoint(cp).
    * @param cp A Unicode code point 0..0x10ffff.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   UStringTrieResult firstForCodePoint(UChar32 cp);

   /**
    * Traverses the trie from the current state for this input char16_t.
    * @param uchar Input char value. Values below 0 and above 0xffff will never match.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   UStringTrieResult next(int32_t uchar);

   /**
    * Traverses the trie from the current state for the
    * one or two UTF-16 code units for this input code point.
    * @param cp A Unicode code point 0..0x10ffff.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   UStringTrieResult nextForCodePoint(UChar32 cp);

   /**
    * Traverses the trie from the current state for this string.
    * 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. Can be nullptr if length is 0.
    * @param length The length of the string. Can be -1 if NUL-terminated.
    * @return The match/value Result.
    * @stable ICU 4.8
    */
   UStringTrieResult next(ConstChar16Ptr s, int32_t length);

   /**
    * Returns a matching string'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 string so far.
    * @stable ICU 4.8
    */
   inline int32_t getValue() const {
       const char16_t *pos=pos_;
       int32_t leadUnit=*pos++;
       // U_ASSERT(leadUnit>=kMinValueLead);
       return leadUnit&kValueIsFinal ?
           readValue(pos, leadUnit&0x7fff) : readNodeValue(pos, leadUnit);
   }

   /**
    * Determines whether all strings 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 strings reachable from the current state
    *         map to the same value.
    * @stable ICU 4.8
    */
   inline UBool hasUniqueValue(int32_t &uniqueValue) const {
       const char16_t *pos=pos_;
       // Skip the rest of a pending linear-match node.
       return pos!=nullptr && findUniqueValue(pos+remainingMatchLength_+1, false, uniqueValue);
   }

   /**
    * Finds each char16_t which continues the string from the current state.
    * That is, each char16_t c for which it would be next(c)!=USTRINGTRIE_NO_MATCH now.
    * @param out Each next char16_t is appended to this object.
    * @return the number of char16_ts which continue the string from here
    * @stable ICU 4.8
    */
   int32_t getNextUChars(Appendable &out) const;

   /**
    * Iterator for all of the (string, value) pairs in a UCharsTrie.
    * @stable ICU 4.8
    */
   class U_COMMON_API Iterator : public UMemory {
   public:
       /**
        * Iterates from the root of a char16_t-serialized UCharsTrie.
        * @param trieUChars The trie char16_ts.
        * @param maxStringLength If 0, the iterator returns full strings.
        *                        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(ConstChar16Ptr trieUChars, int32_t maxStringLength, UErrorCode &errorCode);

       /**
        * Iterates from the current state of the specified UCharsTrie.
        * @param trie The trie whose state will be copied for iteration.
        * @param maxStringLength If 0, the iterator returns full strings.
        *                        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 UCharsTrie &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 (string, value) pair if there is one.
        *
        * If the string 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 string for the last successful next().
        * @stable ICU 4.8
        */
       const UnicodeString &getString() const { return str_; }
       /**
        * @return The value for the last successful next().
        * @stable ICU 4.8
        */
       int32_t getValue() const { return value_; }

   private:
       UBool truncateAndStop() {
           pos_=nullptr;
           value_=-1;  // no real value for str
           return true;
       }

       const char16_t *branchNext(const char16_t *pos, int32_t length, UErrorCode &errorCode);

       const char16_t *uchars_;
       const char16_t *pos_;
       const char16_t *initialPos_;
       int32_t remainingMatchLength_;
       int32_t initialRemainingMatchLength_;
       UBool skipValue_;  // Skip intermediate value which was already delivered.

       UnicodeString 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 uchars_.
       // The second integer has the str_.length() from before the node in bits 15..0,
       // and the remaining branch length in bits 31..16.
       // (We could store the remaining branch length minus 1 in bits 30..16 and not use the sign bit,
       // but the code looks more confusing that way.)
       UVector32 *stack_;
   };

private:
   friend class UCharsTrieBuilder;

   /**
    * Constructs a UCharsTrie 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.
    */
   UCharsTrie(char16_t *adoptUChars, const char16_t *trieUChars)
           : ownedArray_(adoptUChars), uchars_(trieUChars),
             pos_(uchars_), remainingMatchLength_(-1) {}

   // No assignment operator.
   UCharsTrie &operator=(const UCharsTrie &other) = delete;

   inline void stop() {
       pos_=nullptr;
   }

   // Reads a compact 32-bit integer.
   // pos is already after the leadUnit, and the lead unit has bit 15 reset.
   static inline int32_t readValue(const char16_t *pos, int32_t leadUnit) {
       int32_t value;
       if(leadUnit<kMinTwoUnitValueLead) {
           value=leadUnit;
       } else if(leadUnit<kThreeUnitValueLead) {
           value=((leadUnit-kMinTwoUnitValueLead)<<16)|*pos;
       } else {
           value=(pos[0]<<16)|pos[1];
       }
       return value;
   }
   static inline const char16_t *skipValue(const char16_t *pos, int32_t leadUnit) {
       if(leadUnit>=kMinTwoUnitValueLead) {
           if(leadUnit<kThreeUnitValueLead) {
               ++pos;
           } else {
               pos+=2;
           }
       }
       return pos;
   }
   static inline const char16_t *skipValue(const char16_t *pos) {
       int32_t leadUnit=*pos++;
       return skipValue(pos, leadUnit&0x7fff);
   }

   static inline int32_t readNodeValue(const char16_t *pos, int32_t leadUnit) {
       // U_ASSERT(kMinValueLead<=leadUnit && leadUnit<kValueIsFinal);
       int32_t value;
       if(leadUnit<kMinTwoUnitNodeValueLead) {
           value=(leadUnit>>6)-1;
       } else if(leadUnit<kThreeUnitNodeValueLead) {
           value=(((leadUnit&0x7fc0)-kMinTwoUnitNodeValueLead)<<10)|*pos;
       } else {
           value=(pos[0]<<16)|pos[1];
       }
       return value;
   }
   static inline const char16_t *skipNodeValue(const char16_t *pos, int32_t leadUnit) {
       // U_ASSERT(kMinValueLead<=leadUnit && leadUnit<kValueIsFinal);
       if(leadUnit>=kMinTwoUnitNodeValueLead) {
           if(leadUnit<kThreeUnitNodeValueLead) {
               ++pos;
           } else {
               pos+=2;
           }
       }
       return pos;
   }

   static inline const char16_t *jumpByDelta(const char16_t *pos) {
       int32_t delta=*pos++;
       if(delta>=kMinTwoUnitDeltaLead) {
           if(delta==kThreeUnitDeltaLead) {
               delta=(pos[0]<<16)|pos[1];
               pos+=2;
           } else {
               delta=((delta-kMinTwoUnitDeltaLead)<<16)|*pos++;
           }
       }
       return pos+delta;
   }

   static const char16_t *skipDelta(const char16_t *pos) {
       int32_t delta=*pos++;
       if(delta>=kMinTwoUnitDeltaLead) {
           if(delta==kThreeUnitDeltaLead) {
               pos+=2;
           } else {
               ++pos;
           }
       }
       return pos;
   }

   static inline UStringTrieResult valueResult(int32_t node) {
       return static_cast<UStringTrieResult>(USTRINGTRIE_INTERMEDIATE_VALUE - (node >> 15));
   }

   // Handles a branch node for both next(uchar) and next(string).
   UStringTrieResult branchNext(const char16_t *pos, int32_t length, int32_t uchar);

   // Requires remainingLength_<0.
   UStringTrieResult nextImpl(const char16_t *pos, int32_t uchar);

   // Helper functions for hasUniqueValue().
   // Recursively finds a unique value (or whether there is not a unique one)
   // from a branch.
   static const char16_t *findUniqueValueFromBranch(const char16_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 unit.
   static UBool findUniqueValue(const char16_t *pos, UBool haveUniqueValue, int32_t &uniqueValue);

   // Helper functions for getNextUChars().
   // getNextUChars() when pos is on a branch node.
   static void getNextBranchUChars(const char16_t *pos, int32_t length, Appendable &out);

   // UCharsTrie data structure
   //
   // The trie consists of a series of char16_t-serialized nodes for incremental
   // Unicode string/char16_t sequence matching. (char16_t=16-bit unsigned integer)
   // The root node is at the beginning of the trie data.
   //
   // Types of nodes are distinguished by their node lead unit ranges.
   // After each node, except a final-value node, another node follows to
   // encode match values or continue matching further units.
   //
   // Node types:
   //  - Final-value node: Stores a 32-bit integer in a compact, variable-length format.
   //    The value is for the string/char16_t sequence so far.
   //  - Match node, optionally with an intermediate value in a different compact format.
   //    The value, if present, is for the string/char16_t sequence so far.
   //
   //  Aside from the value, which uses the node lead unit's high bits:
   //
   //  - Linear-match node: Matches a number of units.
   //  - Branch node: Branches to other nodes according to the current input unit.
   //    The node unit is the length of the branch (number of units 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 unit.
   //      If one of the key units matches, then the value is either a final value for
   //      the string so far, or a "jump" delta to the next node.
   //      If the last unit matches, then matching continues with the next node.
   //      (Values have the same encoding as final-value nodes.)
   //    - If the length is greater than kMaxBranchLinearSubNodeLength, then
   //      there is one unit and one "jump" delta.
   //      If the input unit is less than the sub-node unit, 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.

   // Match-node lead unit values, after masking off intermediate-value bits:

   // 0000..002f: Branch node. If node!=0 then the length is node+1, otherwise
   // the length is one more than the next unit.

   // For a branch sub-node with at most this many entries, we drop down
   // to a linear search.
   static const int32_t kMaxBranchLinearSubNodeLength=5;

   // 0030..003f: Linear-match node, match 1..16 units and continue reading the next node.
   static const int32_t kMinLinearMatch=0x30;
   static const int32_t kMaxLinearMatchLength=0x10;

   // Match-node lead unit bits 14..6 for the optional intermediate value.
   // If these bits are 0, then there is no intermediate value.
   // Otherwise, see the *NodeValue* constants below.
   static const int32_t kMinValueLead=kMinLinearMatch+kMaxLinearMatchLength;  // 0x0040
   static const int32_t kNodeTypeMask=kMinValueLead-1;  // 0x003f

   // A final-value node has bit 15 set.
   static const int32_t kValueIsFinal=0x8000;

   // Compact value: After testing and masking off bit 15, use the following thresholds.
   static const int32_t kMaxOneUnitValue=0x3fff;

   static const int32_t kMinTwoUnitValueLead=kMaxOneUnitValue+1;  // 0x4000
   static const int32_t kThreeUnitValueLead=0x7fff;

   static const int32_t kMaxTwoUnitValue=((kThreeUnitValueLead-kMinTwoUnitValueLead)<<16)-1;  // 0x3ffeffff

   // Compact intermediate-value integer, lead unit shared with a branch or linear-match node.
   static const int32_t kMaxOneUnitNodeValue=0xff;
   static const int32_t kMinTwoUnitNodeValueLead=kMinValueLead+((kMaxOneUnitNodeValue+1)<<6);  // 0x4040
   static const int32_t kThreeUnitNodeValueLead=0x7fc0;

   static const int32_t kMaxTwoUnitNodeValue=
       ((kThreeUnitNodeValueLead-kMinTwoUnitNodeValueLead)<<10)-1;  // 0xfdffff

   // Compact delta integers.
   static const int32_t kMaxOneUnitDelta=0xfbff;
   static const int32_t kMinTwoUnitDeltaLead=kMaxOneUnitDelta+1;  // 0xfc00
   static const int32_t kThreeUnitDeltaLead=0xffff;

   static const int32_t kMaxTwoUnitDelta=((kThreeUnitDeltaLead-kMinTwoUnitDeltaLead)<<16)-1;  // 0x03feffff

   // 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;

   char16_t *ownedArray_;

   // Fixed value referencing the UCharsTrie words.
   const char16_t *uchars_;

   // Iterator variables.

   // Pointer to next trie unit to read. nullptr if no more matches.
   const char16_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  // __UCHARSTRIE_H__