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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__