ICU 63.1 63.1

bytestrie.h
Go to the documentation of this file.
1 // © 2016 and later: Unicode, Inc. and others.
2 // License & terms of use: http://www.unicode.org/copyright.html
3 /*
4 *******************************************************************************
5 * Copyright (C) 2010-2012, International Business Machines
6 * Corporation and others. All Rights Reserved.
7 *******************************************************************************
8 * file name: bytestrie.h
9 * encoding: UTF-8
10 * tab size: 8 (not used)
11 * indentation:4
12 *
13 * created on: 2010sep25
14 * created by: Markus W. Scherer
15 */
16
17 #ifndef __BYTESTRIE_H__
18 #define __BYTESTRIE_H__
19
25 #include "unicode/utypes.h"
26 #include "unicode/stringpiece.h"
27 #include "unicode/uobject.h"
28 #include "unicode/ustringtrie.h"
29
30 U_NAMESPACE_BEGIN
31
32 class ByteSink;
33 class BytesTrieBuilder;
34 class CharString;
35 class UVector32;
36
50 class U_COMMON_API BytesTrie : public UMemory {
51 public:
66 BytesTrie(const void *trieBytes)
67 : ownedArray_(NULL), bytes_(static_cast<const uint8_t *>(trieBytes)),
68 pos_(bytes_), remainingMatchLength_(-1) {}
69
74 ~BytesTrie();
75
82 BytesTrie(const BytesTrie &other)
83 : ownedArray_(NULL), bytes_(other.bytes_),
84 pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
85
91 BytesTrie &reset() {
92 pos_=bytes_;
93 remainingMatchLength_=-1;
94 return *this;
95 }
96
102 class State : public UMemory {
103 public:
108 State() { bytes=NULL; }
109 private:
110 friend class BytesTrie;
111
112 const uint8_t *bytes;
113 const uint8_t *pos;
114 int32_t remainingMatchLength;
115 };
116
124 const BytesTrie &saveState(State &state) const {
125 state.bytes=bytes_;
126 state.pos=pos_;
127 state.remainingMatchLength=remainingMatchLength_;
128 return *this;
129 }
130
141 BytesTrie &resetToState(const State &state) {
142 if(bytes_==state.bytes && bytes_!=NULL) {
143 pos_=state.pos;
144 remainingMatchLength_=state.remainingMatchLength;
145 }
146 return *this;
147 }
148
155 UStringTrieResult current() const;
156
165 inline UStringTrieResult first(int32_t inByte) {
166 remainingMatchLength_=-1;
167 if(inByte<0) {
168 inByte+=0x100;
169 }
170 return nextImpl(bytes_, inByte);
171 }
172
180 UStringTrieResult next(int32_t inByte);
181
197 UStringTrieResult next(const char *s, int32_t length);
198
208 inline int32_t getValue() const {
209 const uint8_t *pos=pos_;
210 int32_t leadByte=*pos++;
211 // U_ASSERT(leadByte>=kMinValueLead);
212 return readValue(pos, leadByte>>1);
213 }
214
224 inline UBool hasUniqueValue(int32_t &uniqueValue) const {
225 const uint8_t *pos=pos_;
226 // Skip the rest of a pending linear-match node.
227 return pos!=NULL && findUniqueValue(pos+remainingMatchLength_+1, FALSE, uniqueValue);
228 }
229
238 int32_t getNextBytes(ByteSink &out) const;
239
244 class U_COMMON_API Iterator : public UMemory {
245 public:
257 Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode);
258
270 Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
271
276 ~Iterator();
277
283 Iterator &reset();
284
289 UBool hasNext() const;
290
305 UBool next(UErrorCode &errorCode);
306
311 StringPiece getString() const;
316 int32_t getValue() const { return value_; }
317
318 private:
319 UBool truncateAndStop();
320
321 const uint8_t *branchNext(const uint8_t *pos, int32_t length, UErrorCode &errorCode);
322
323 const uint8_t *bytes_;
324 const uint8_t *pos_;
325 const uint8_t *initialPos_;
326 int32_t remainingMatchLength_;
327 int32_t initialRemainingMatchLength_;
328
329 CharString *str_;
330 int32_t maxLength_;
331 int32_t value_;
332
333 // The stack stores pairs of integers for backtracking to another
334 // outbound edge of a branch node.
335 // The first integer is an offset from bytes_.
336 // The second integer has the str_->length() from before the node in bits 15..0,
337 // and the remaining branch length in bits 24..16. (Bits 31..25 are unused.)
338 // (We could store the remaining branch length minus 1 in bits 23..16 and not use bits 31..24,
339 // but the code looks more confusing that way.)
340 UVector32 *stack_;
341 };
342
343 private:
344 friend class BytesTrieBuilder;
345
352 BytesTrie(void *adoptBytes, const void *trieBytes)
353 : ownedArray_(static_cast<uint8_t *>(adoptBytes)),
354 bytes_(static_cast<const uint8_t *>(trieBytes)),
355 pos_(bytes_), remainingMatchLength_(-1) {}
356
357 // No assignment operator.
358 BytesTrie &operator=(const BytesTrie &other);
359
360 inline void stop() {
361 pos_=NULL;
362 }
363
364 // Reads a compact 32-bit integer.
365 // pos is already after the leadByte, and the lead byte is already shifted right by 1.
366 static int32_t readValue(const uint8_t *pos, int32_t leadByte);
367 static inline const uint8_t *skipValue(const uint8_t *pos, int32_t leadByte) {
368 // U_ASSERT(leadByte>=kMinValueLead);
369 if(leadByte>=(kMinTwoByteValueLead<<1)) {
370 if(leadByte<(kMinThreeByteValueLead<<1)) {
371 ++pos;
372 } else if(leadByte<(kFourByteValueLead<<1)) {
373 pos+=2;
374 } else {
375 pos+=3+((leadByte>>1)&1);
376 }
377 }
378 return pos;
379 }
380 static inline const uint8_t *skipValue(const uint8_t *pos) {
381 int32_t leadByte=*pos++;
382 return skipValue(pos, leadByte);
383 }
384
385 // Reads a jump delta and jumps.
386 static const uint8_t *jumpByDelta(const uint8_t *pos);
387
388 static inline const uint8_t *skipDelta(const uint8_t *pos) {
389 int32_t delta=*pos++;
390 if(delta>=kMinTwoByteDeltaLead) {
391 if(delta<kMinThreeByteDeltaLead) {
392 ++pos;
393 } else if(delta<kFourByteDeltaLead) {
394 pos+=2;
395 } else {
396 pos+=3+(delta&1);
397 }
398 }
399 return pos;
400 }
401
402 static inline UStringTrieResult valueResult(int32_t node) {
403 return (UStringTrieResult)(USTRINGTRIE_INTERMEDIATE_VALUE-(node&kValueIsFinal));
404 }
405
406 // Handles a branch node for both next(byte) and next(string).
407 UStringTrieResult branchNext(const uint8_t *pos, int32_t length, int32_t inByte);
408
409 // Requires remainingLength_<0.
410 UStringTrieResult nextImpl(const uint8_t *pos, int32_t inByte);
411
412 // Helper functions for hasUniqueValue().
413 // Recursively finds a unique value (or whether there is not a unique one)
414 // from a branch.
415 static const uint8_t *findUniqueValueFromBranch(const uint8_t *pos, int32_t length,
416 UBool haveUniqueValue, int32_t &uniqueValue);
417 // Recursively finds a unique value (or whether there is not a unique one)
418 // starting from a position on a node lead byte.
419 static UBool findUniqueValue(const uint8_t *pos, UBool haveUniqueValue, int32_t &uniqueValue);
420
421 // Helper functions for getNextBytes().
422 // getNextBytes() when pos is on a branch node.
423 static void getNextBranchBytes(const uint8_t *pos, int32_t length, ByteSink &out);
424 static void append(ByteSink &out, int c);
425
426 // BytesTrie data structure
427 //
428 // The trie consists of a series of byte-serialized nodes for incremental
429 // string/byte sequence matching. The root node is at the beginning of the trie data.
430 //
431 // Types of nodes are distinguished by their node lead byte ranges.
432 // After each node, except a final-value node, another node follows to
433 // encode match values or continue matching further bytes.
434 //
435 // Node types:
436 // - Value node: Stores a 32-bit integer in a compact, variable-length format.
437 // The value is for the string/byte sequence so far.
438 // One node bit indicates whether the value is final or whether
439 // matching continues with the next node.
440 // - Linear-match node: Matches a number of bytes.
441 // - Branch node: Branches to other nodes according to the current input byte.
442 // The node byte is the length of the branch (number of bytes to select from)
443 // minus 1. It is followed by a sub-node:
444 // - If the length is at most kMaxBranchLinearSubNodeLength, then
445 // there are length-1 (key, value) pairs and then one more comparison byte.
446 // If one of the key bytes matches, then the value is either a final value for
447 // the string/byte sequence so far, or a "jump" delta to the next node.
448 // If the last byte matches, then matching continues with the next node.
449 // (Values have the same encoding as value nodes.)
450 // - If the length is greater than kMaxBranchLinearSubNodeLength, then
451 // there is one byte and one "jump" delta.
452 // If the input byte is less than the sub-node byte, then "jump" by delta to
453 // the next sub-node which will have a length of length/2.
454 // (The delta has its own compact encoding.)
455 // Otherwise, skip the "jump" delta to the next sub-node
456 // which will have a length of length-length/2.
457
458 // Node lead byte values.
459
460 // 00..0f: Branch node. If node!=0 then the length is node+1, otherwise
461 // the length is one more than the next byte.
462
463 // For a branch sub-node with at most this many entries, we drop down
464 // to a linear search.
465 static const int32_t kMaxBranchLinearSubNodeLength=5;
466
467 // 10..1f: Linear-match node, match 1..16 bytes and continue reading the next node.
468 static const int32_t kMinLinearMatch=0x10;
469 static const int32_t kMaxLinearMatchLength=0x10;
470
471 // 20..ff: Variable-length value node.
472 // If odd, the value is final. (Otherwise, intermediate value or jump delta.)
473 // Then shift-right by 1 bit.
474 // The remaining lead byte value indicates the number of following bytes (0..4)
475 // and contains the value's top bits.
476 static const int32_t kMinValueLead=kMinLinearMatch+kMaxLinearMatchLength; // 0x20
477 // It is a final value if bit 0 is set.
478 static const int32_t kValueIsFinal=1;
479
480 // Compact value: After testing bit 0, shift right by 1 and then use the following thresholds.
481 static const int32_t kMinOneByteValueLead=kMinValueLead/2; // 0x10
482 static const int32_t kMaxOneByteValue=0x40; // At least 6 bits in the first byte.
483
484 static const int32_t kMinTwoByteValueLead=kMinOneByteValueLead+kMaxOneByteValue+1; // 0x51
485 static const int32_t kMaxTwoByteValue=0x1aff;
486
487 static const int32_t kMinThreeByteValueLead=kMinTwoByteValueLead+(kMaxTwoByteValue>>8)+1; // 0x6c
488 static const int32_t kFourByteValueLead=0x7e;
489
490 // A little more than Unicode code points. (0x11ffff)
491 static const int32_t kMaxThreeByteValue=((kFourByteValueLead-kMinThreeByteValueLead)<<16)-1;
492
493 static const int32_t kFiveByteValueLead=0x7f;
494
495 // Compact delta integers.
496 static const int32_t kMaxOneByteDelta=0xbf;
497 static const int32_t kMinTwoByteDeltaLead=kMaxOneByteDelta+1; // 0xc0
498 static const int32_t kMinThreeByteDeltaLead=0xf0;
499 static const int32_t kFourByteDeltaLead=0xfe;
500 static const int32_t kFiveByteDeltaLead=0xff;
501
502 static const int32_t kMaxTwoByteDelta=((kMinThreeByteDeltaLead-kMinTwoByteDeltaLead)<<8)-1; // 0x2fff
503 static const int32_t kMaxThreeByteDelta=((kFourByteDeltaLead-kMinThreeByteDeltaLead)<<16)-1; // 0xdffff
504
505 uint8_t *ownedArray_;
506
507 // Fixed value referencing the BytesTrie bytes.
508 const uint8_t *bytes_;
509
510 // Iterator variables.
511
512 // Pointer to next trie byte to read. NULL if no more matches.
513 const uint8_t *pos_;
514 // Remaining length of a linear-match node, minus 1. Negative if not in such a node.
515 int32_t remainingMatchLength_;
516 };
517
518 U_NAMESPACE_END
519
520 #endif // __BYTESTRIE_H__
icu::BytesTrieBuilder
Builder class for BytesTrie.
Definition: bytestriebuilder.h:40
icu::BytesTrie::State
BytesTrie state object, for saving a trie&#39;s current state and resetting the trie back to this state l...
Definition: bytestrie.h:102
UStringTrieResult
UStringTrieResult
Return values for BytesTrie::next(), UCharsTrie::next() and similar methods.
Definition: ustringtrie.h:35
icu::BytesTrie::BytesTrie
BytesTrie(const void *trieBytes)
Constructs a BytesTrie reader instance.
Definition: bytestrie.h:66
icu::ByteSink
A ByteSink can be filled with bytes.
Definition: bytestream.h:50
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:224
icu::BytesTrie
Light-weight, non-const reader class for a BytesTrie.
Definition: bytestrie.h:50
icu::BytesTrie::reset
BytesTrie & reset()
Resets this trie to its initial state.
Definition: bytestrie.h:91
stringpiece.h
C++ API: StringPiece: Read-only byte string wrapper class.
U_NAMESPACE_BEGIN
#define U_NAMESPACE_BEGIN
This is used to begin a declaration of a public ICU C++ API.
Definition: uversion.h:137
icu::BytesTrie::Iterator::getValue
int32_t getValue() const
Definition: bytestrie.h:316
icu::BytesTrie::first
UStringTrieResult first(int32_t inByte)
Traverses the trie from the initial state for this input byte.
Definition: bytestrie.h:165
icu::BytesTrie::getValue
int32_t getValue() const
Returns a matching byte sequence&#39;s value if called immediately after current()/first()/next() returne...
Definition: bytestrie.h:208
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:82
NULL
#define NULL
Define NULL if necessary, to nullptr for C++ and to ((void *)0) for C.
Definition: utypes.h:188
icu::BytesTrie::State::State
State()
Constructs an empty State.
Definition: bytestrie.h:108
icu::BytesTrie::Iterator
Iterator for all of the (byte sequence, value) pairs in a BytesTrie.
Definition: bytestrie.h:244
uobject.h
C++ API: Common ICU base class UObject.
U_NAMESPACE_END
#define U_NAMESPACE_END
This is used to end a declaration of a public ICU C++ API.
Definition: uversion.h:138
UErrorCode
UErrorCode
Error code to replace exception handling, so that the code is compatible with all C++ compilers...
Definition: utypes.h:401
ustringtrie.h
C API: Helper definitions for dictionary trie APIs.
icu::BytesTrie::saveState
const BytesTrie & saveState(State &state) const
Saves the state of this trie.
Definition: bytestrie.h:124
utypes.h
Basic definitions for ICU, for both C and C++ APIs.
FALSE
#define FALSE
The FALSE value of a UBool.
Definition: umachine.h:233
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:300
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
icu::StringPiece
A string-like object that points to a sized piece of memory.
Definition: stringpiece.h:54
icu::BytesTrie::resetToState
BytesTrie & resetToState(const State &state)
Resets this trie to the saved state.
Definition: bytestrie.h:141
icu::UMemory
UMemory is the common ICU base class.
Definition: uobject.h:109
UBool
int8_t UBool
The ICU boolean type.
Definition: umachine.h:225