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