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bytestrie.h
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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 2010-2012, International Business Machines
* Corporation and others. All Rights Reserved.
*******************************************************************************
* file name: bytestrie.h
* encoding: UTF-8
* tab size: 8 (not used)
* indentation:4
*
* created on: 2010sep25
* created by: Markus W. Scherer
*/
#ifndef __BYTESTRIE_H__
#define __BYTESTRIE_H__
#include "unicode/utypes.h"
#if U_SHOW_CPLUSPLUS_API
#include "unicode/stringpiece.h"
#include "unicode/uobject.h"
#include "unicode/ustringtrie.h"
class BytesTrieTest;
U_NAMESPACE_BEGIN
class ByteSink;
class BytesTrieBuilder;
class CharString;
class UVector32;
class U_COMMON_API BytesTrie : public UMemory {
public:
BytesTrie(const void *trieBytes)
: ownedArray_(nullptr), bytes_(static_cast<const uint8_t *>(trieBytes)),
pos_(bytes_), remainingMatchLength_(-1) {}
~BytesTrie();
BytesTrie(const BytesTrie &other)
: ownedArray_(nullptr), bytes_(other.bytes_),
pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
BytesTrie &reset() {
pos_=bytes_;
remainingMatchLength_=-1;
return *this;
}
uint64_t getState64() const {
return (static_cast<uint64_t>(remainingMatchLength_ + 2) << kState64RemainingShift) |
static_cast<uint64_t>(pos_ - bytes_);
}
BytesTrie &resetToState64(uint64_t state) {
remainingMatchLength_ = static_cast<int32_t>(state >> kState64RemainingShift) - 2;
pos_ = bytes_ + (state & kState64PosMask);
return *this;
}
class State : public UMemory {
public:
State() { bytes=nullptr; }
private:
friend class BytesTrie;
const uint8_t *bytes;
const uint8_t *pos;
int32_t remainingMatchLength;
};
const BytesTrie &saveState(State &state) const {
state.bytes=bytes_;
state.pos=pos_;
state.remainingMatchLength=remainingMatchLength_;
return *this;
}
BytesTrie &resetToState(const State &state) {
if(bytes_==state.bytes && bytes_!=nullptr) {
pos_=state.pos;
remainingMatchLength_=state.remainingMatchLength;
}
return *this;
}
UStringTrieResult current() const;
inline UStringTrieResult first(int32_t inByte) {
remainingMatchLength_=-1;
if(inByte<0) {
inByte+=0x100;
}
return nextImpl(bytes_, inByte);
}
UStringTrieResult next(int32_t inByte);
UStringTrieResult next(const char *s, int32_t length);
inline int32_t getValue() const {
const uint8_t *pos=pos_;
int32_t leadByte=*pos++;
// U_ASSERT(leadByte>=kMinValueLead);
return readValue(pos, leadByte>>1);
}
inline UBool hasUniqueValue(int32_t &uniqueValue) const {
const uint8_t *pos=pos_;
// Skip the rest of a pending linear-match node.
return pos!=nullptr && findUniqueValue(pos+remainingMatchLength_+1, false, uniqueValue);
}
int32_t getNextBytes(ByteSink &out) const;
class U_COMMON_API Iterator : public UMemory {
public:
Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode);
Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
~Iterator();
Iterator &reset();
UBool hasNext() const;
UBool next(UErrorCode &errorCode);
StringPiece getString() const;
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_;
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;
friend class ::BytesTrieTest;
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) = delete;
inline void stop() {
pos_=nullptr;
}
// 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 static_cast<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
// For getState64():
// The remainingMatchLength_ is -1..14=(kMaxLinearMatchLength=0x10)-2
// so we need at least 5 bits for that.
// We add 2 to store it as a positive value 1..16=kMaxLinearMatchLength.
static constexpr int32_t kState64RemainingShift = 59;
static constexpr uint64_t kState64PosMask = (UINT64_C(1) << kState64RemainingShift) - 1;
uint8_t *ownedArray_;
// Fixed value referencing the BytesTrie bytes.
const uint8_t *bytes_;
// Iterator variables.
// Pointer to next trie byte to read. nullptr 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 /* U_SHOW_CPLUSPLUS_API */
#endif // __BYTESTRIE_H__
BytesTrieBuilder
Builder class for BytesTrie.
Definition bytestriebuilder.h:45
icu::ByteSink
A ByteSink can be filled with bytes.
Definition bytestream.h:55
icu::BytesTrie::Iterator::hasNext
UBool hasNext() const
icu::BytesTrie::Iterator::getString
StringPiece getString() const
icu::BytesTrie::Iterator::reset
Iterator & reset()
Resets this iterator to its initial state.
icu::BytesTrie::Iterator::~Iterator
~Iterator()
Destructor.
icu::BytesTrie::Iterator::getValue
int32_t getValue() const
Definition bytestrie.h:354
icu::BytesTrie::Iterator::Iterator
Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode)
Iterates from the root of a byte-serialized BytesTrie.
icu::BytesTrie::Iterator::next
UBool next(UErrorCode &errorCode)
Finds the next (byte sequence, value) pair if there is one.
icu::BytesTrie::Iterator::Iterator
Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode)
Iterates from the current state of the specified BytesTrie.
icu::BytesTrie::State
BytesTrie state object, for saving a trie's current state and resetting the trie back to this state l...
Definition bytestrie.h:140
icu::BytesTrie::State::State
State()
Constructs an empty State.
Definition bytestrie.h:146
icu::BytesTrie
Light-weight, non-const reader class for a BytesTrie.
Definition bytestrie.h:55
icu::BytesTrie::getValue
int32_t getValue() const
Returns a matching byte sequence's value if called immediately after current()/first()/next() returne...
Definition bytestrie.h:246
icu::BytesTrie::current
UStringTrieResult current() const
Determines whether the byte sequence so far matches, whether it has a value, and whether another inpu...
icu::BytesTrie::next
UStringTrieResult next(const char *s, int32_t length)
Traverses the trie from the current state for this byte sequence.
icu::BytesTrie::first
UStringTrieResult first(int32_t inByte)
Traverses the trie from the initial state for this input byte.
Definition bytestrie.h:203
icu::BytesTrie::hasUniqueValue
UBool hasUniqueValue(int32_t &uniqueValue) const
Determines whether all byte sequences reachable from the current state map to the same value.
Definition bytestrie.h:262
icu::BytesTrie::~BytesTrie
~BytesTrie()
Destructor.
icu::BytesTrie::resetToState64
BytesTrie & resetToState64(uint64_t state)
Resets this trie to the saved state.
Definition bytestrie.h:129
icu::BytesTrie::saveState
const BytesTrie & saveState(State &state) const
Saves the state of this trie.
Definition bytestrie.h:162
icu::BytesTrie::BytesTrie
BytesTrie(const BytesTrie &other)
Copy constructor, copies the other trie reader object and its state, but not the byte array which wil...
Definition bytestrie.h:87
icu::BytesTrie::getNextBytes
int32_t getNextBytes(ByteSink &out) const
Finds each byte which continues the byte sequence from the current state.
icu::BytesTrie::getState64
uint64_t getState64() const
Returns the state of this trie as a 64-bit integer.
Definition bytestrie.h:110
icu::BytesTrie::resetToState
BytesTrie & resetToState(const State &state)
Resets this trie to the saved state.
Definition bytestrie.h:179
icu::BytesTrie::BytesTrie
BytesTrie(const void *trieBytes)
Constructs a BytesTrie reader instance.
Definition bytestrie.h:71
icu::BytesTrie::next
UStringTrieResult next(int32_t inByte)
Traverses the trie from the current state for this input byte.
icu::BytesTrie::reset
BytesTrie & reset()
Resets this trie to its initial state.
Definition bytestrie.h:96
icu::StringPiece
A string-like object that points to a sized piece of memory.
Definition stringpiece.h:61
icu::UMemory
UMemory is the common ICU base class.
Definition uobject.h:115
stringpiece.h
C++ API: StringPiece: Read-only byte string wrapper class.
UINT64_C
#define UINT64_C(c)
Provides a platform independent way to specify an unsigned 64-bit integer constant.
Definition umachine.h:241
UBool
int8_t UBool
The ICU boolean type, a signed-byte integer.
Definition umachine.h:269
uobject.h
C++ API: Common ICU base class UObject.
ustringtrie.h
C API: Helper definitions for dictionary trie APIs.
UStringTrieResult
UStringTrieResult
Return values for BytesTrie::next(), UCharsTrie::next() and similar methods.
Definition ustringtrie.h:35
USTRINGTRIE_INTERMEDIATE_VALUE
@ USTRINGTRIE_INTERMEDIATE_VALUE
The input unit(s) continued a matching string and there is a value for the string so far.
Definition ustringtrie.h:66
utypes.h
Basic definitions for ICU, for both C and C++ APIs.
UErrorCode
UErrorCode
Standard ICU4C error code type, a substitute for exceptions.
Definition utypes.h:509
U_COMMON_API
#define U_COMMON_API
Set to export library symbols from inside the common library, and to import them from outside.
Definition utypes.h:315