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 /*

 *******************************************************************************

 *   Copyright (C) 2010-2012, International Business Machines

 *   Corporation and others.  All Rights Reserved.

 *******************************************************************************

 *   file name:  ucharstrie.h

 *   encoding:   US-ASCII

 *   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"

 #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 UChar-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 UChar sequence from the UCharsTrieBuilder,

      * starting with the first UChar of that sequence.

      * The UCharsTrie object will not read more UChars 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 UChar array that contains the serialized trie.

      * @stable ICU 4.8

      */

     UCharsTrie(const UChar *trieUChars)

             : ownedArray_(NULL), 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 UChar array which will be shared. (Shallow copy.)

      * @param other Another UCharsTrie object.

      * @stable ICU 4.8

      */

     UCharsTrie(const UCharsTrie &other)

             : ownedArray_(NULL), 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;

     }

     /**

      * 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=NULL; }

     private:

         friend class UCharsTrie;

         const UChar *uchars;

         const UChar *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_!=NULL) {

             pos_=state.pos;

             remainingMatchLength_=state.remainingMatchLength;

         }

         return *this;

     }

     /**

      * Determines whether the string so far matches, whether it has a value,

      * and whether another input UChar 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 UChar.

      * 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 UChar.

      * @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 NULL 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(const UChar *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 UChar *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 UChar *pos=pos_;

         // Skip the rest of a pending linear-match node.

         return pos!=NULL && findUniqueValue(pos+remainingMatchLength_+1, FALSE, uniqueValue);

     }

     /**

      * Finds each UChar which continues the string from the current state.

      * That is, each UChar c for which it would be next(c)!=USTRINGTRIE_NO_MATCH now.

      * @param out Each next UChar is appended to this object.

      * @return the number of UChars 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 UChar-serialized UCharsTrie.

          * @param trieUChars The trie UChars.

          * @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 UChar *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_=NULL;

             value_=-1;  // no real value for str

             return TRUE;

         }

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

         const UChar *uchars_;

         const UChar *pos_;

         const UChar *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(UChar *adoptUChars, const UChar *trieUChars)

             : ownedArray_(adoptUChars), uchars_(trieUChars),

               pos_(uchars_), remainingMatchLength_(-1) {}

     // No assignment operator.

     UCharsTrie &operator=(const UCharsTrie &other);

     inline void stop() {

         pos_=NULL;

     }

     // 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 UChar *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 UChar *skipValue(const UChar *pos, int32_t leadUnit) {

         if(leadUnit>=kMinTwoUnitValueLead) {

             if(leadUnit<kThreeUnitValueLead) {

                 ++pos;

             } else {

                 pos+=2;

             }

         }

         return pos;

     }

     static inline const UChar *skipValue(const UChar *pos) {

         int32_t leadUnit=*pos++;

         return skipValue(pos, leadUnit&0x7fff);

     }

     static inline int32_t readNodeValue(const UChar *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 UChar *skipNodeValue(const UChar *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 UChar *jumpByDelta(const UChar *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 UChar *skipDelta(const UChar *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 (UStringTrieResult)(USTRINGTRIE_INTERMEDIATE_VALUE-(node>>15));

     }

     // Handles a branch node for both next(uchar) and next(string).

     UStringTrieResult branchNext(const UChar *pos, int32_t length, int32_t uchar);

     // Requires remainingLength_<0.

     UStringTrieResult nextImpl(const UChar *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 UChar *findUniqueValueFromBranch(const UChar *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 UChar *pos, UBool haveUniqueValue, int32_t &uniqueValue);

     // Helper functions for getNextUChars().

     // getNextUChars() when pos is on a branch node.

     static void getNextBranchUChars(const UChar *pos, int32_t length, Appendable &out);

     // UCharsTrie data structure

     //

     // The trie consists of a series of UChar-serialized nodes for incremental

     // Unicode string/UChar sequence matching. (UChar=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/UChar sequence so far.

     //  - Match node, optionally with an intermediate value in a different compact format.

     //    The value, if present, is for the string/UChar 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

     UChar *ownedArray_;

     // Fixed value referencing the UCharsTrie words.

     const UChar *uchars_;

     // Iterator variables.

     // Pointer to next trie unit to read. NULL if no more matches.

     const UChar *pos_;

     // Remaining length of a linear-match node, minus 1. Negative if not in such a node.

     int32_t remainingMatchLength_;

 };

 U_NAMESPACE_END

 #endif  // __UCHARSTRIE_H__