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 /*

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

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

 *   Corporation and others.  All Rights Reserved.

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

 *   file name:  bytestrie.h

 *   encoding:   US-ASCII

 *   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"

 #include "unicode/stringpiece.h"

 #include "unicode/uobject.h"

 #include "unicode/ustringtrie.h"

 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_(NULL), 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_(NULL), 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;

     }

     /**

      * 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=NULL; }

     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_!=NULL) {

             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 NULL 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!=NULL && 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

          */

         const StringPiece &getString() const { return sp_; }

         /**

          * @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_;

         StringPiece sp_;

         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;

     /**

      * 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);

     inline void stop() {

         pos_=NULL;

     }

     // 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 (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

     uint8_t *ownedArray_;

     // Fixed value referencing the BytesTrie bytes.

     const uint8_t *bytes_;

     // Iterator variables.

     // Pointer to next trie byte to read. NULL 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  // __BYTESTRIE_H__