2
*******************************************************************************
3
* Copyright (C) 2010-2012, International Business Machines
4
* Corporation and others. All Rights Reserved.
5
*******************************************************************************
6
* file name: bytestrie.h
8
* tab size: 8 (not used)
11
* created on: 2010sep25
12
* created by: Markus W. Scherer
15
#ifndef __BYTESTRIE_H__
16
#define __BYTESTRIE_H__
20
* \brief C++ API: Trie for mapping byte sequences to integer values.
23
#include "unicode/utypes.h"
24
#include "unicode/stringpiece.h"
25
#include "unicode/uobject.h"
26
#include "unicode/ustringtrie.h"
31
class BytesTrieBuilder;
36
* Light-weight, non-const reader class for a BytesTrie.
37
* Traverses a byte-serialized data structure with minimal state,
38
* for mapping byte sequences to non-negative integer values.
40
* This class owns the serialized trie data only if it was constructed by
41
* the builder's build() method.
42
* The public constructor and the copy constructor only alias the data (only copy the pointer).
43
* There is no assignment operator.
45
* This class is not intended for public subclassing.
48
class U_COMMON_API BytesTrie : public UMemory {
51
* Constructs a BytesTrie reader instance.
53
* The trieBytes must contain a copy of a byte sequence from the BytesTrieBuilder,
54
* starting with the first byte of that sequence.
55
* The BytesTrie object will not read more bytes than
56
* the BytesTrieBuilder generated in the corresponding build() call.
58
* The array is not copied/cloned and must not be modified while
59
* the BytesTrie object is in use.
61
* @param trieBytes The byte array that contains the serialized trie.
64
BytesTrie(const void *trieBytes)
65
: ownedArray_(NULL), bytes_(static_cast<const uint8_t *>(trieBytes)),
66
pos_(bytes_), remainingMatchLength_(-1) {}
75
* Copy constructor, copies the other trie reader object and its state,
76
* but not the byte array which will be shared. (Shallow copy.)
77
* @param other Another BytesTrie object.
80
BytesTrie(const BytesTrie &other)
81
: ownedArray_(NULL), bytes_(other.bytes_),
82
pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
85
* Resets this trie to its initial state.
91
remainingMatchLength_=-1;
96
* BytesTrie state object, for saving a trie's current state
97
* and resetting the trie back to this state later.
100
class State : public UMemory {
103
* Constructs an empty State.
106
State() { bytes=NULL; }
108
friend class BytesTrie;
110
const uint8_t *bytes;
112
int32_t remainingMatchLength;
116
* Saves the state of this trie.
117
* @param state The State object to hold the trie's state.
122
const BytesTrie &saveState(State &state) const {
125
state.remainingMatchLength=remainingMatchLength_;
130
* Resets this trie to the saved state.
131
* If the state object contains no state, or the state of a different trie,
132
* then this trie remains unchanged.
133
* @param state The State object which holds a saved trie state.
139
BytesTrie &resetToState(const State &state) {
140
if(bytes_==state.bytes && bytes_!=NULL) {
142
remainingMatchLength_=state.remainingMatchLength;
148
* Determines whether the byte sequence so far matches, whether it has a value,
149
* and whether another input byte can continue a matching byte sequence.
150
* @return The match/value Result.
153
UStringTrieResult current() const;
156
* Traverses the trie from the initial state for this input byte.
157
* Equivalent to reset().next(inByte).
158
* @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
159
* Values below -0x100 and above 0xff will never match.
160
* @return The match/value Result.
163
inline UStringTrieResult first(int32_t inByte) {
164
remainingMatchLength_=-1;
168
return nextImpl(bytes_, inByte);
172
* Traverses the trie from the current state for this input byte.
173
* @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
174
* Values below -0x100 and above 0xff will never match.
175
* @return The match/value Result.
178
UStringTrieResult next(int32_t inByte);
181
* Traverses the trie from the current state for this byte sequence.
184
* Result result=current();
186
* if(!USTRINGTRIE_HAS_NEXT(result)) return USTRINGTRIE_NO_MATCH;
190
* @param s A string or byte sequence. Can be NULL if length is 0.
191
* @param length The length of the byte sequence. Can be -1 if NUL-terminated.
192
* @return The match/value Result.
195
UStringTrieResult next(const char *s, int32_t length);
198
* Returns a matching byte sequence's value if called immediately after
199
* current()/first()/next() returned USTRINGTRIE_INTERMEDIATE_VALUE or USTRINGTRIE_FINAL_VALUE.
200
* getValue() can be called multiple times.
202
* Do not call getValue() after USTRINGTRIE_NO_MATCH or USTRINGTRIE_NO_VALUE!
203
* @return The value for the byte sequence so far.
206
inline int32_t getValue() const {
207
const uint8_t *pos=pos_;
208
int32_t leadByte=*pos++;
209
// U_ASSERT(leadByte>=kMinValueLead);
210
return readValue(pos, leadByte>>1);
214
* Determines whether all byte sequences reachable from the current state
215
* map to the same value.
216
* @param uniqueValue Receives the unique value, if this function returns TRUE.
218
* @return TRUE if all byte sequences reachable from the current state
219
* map to the same value.
222
inline UBool hasUniqueValue(int32_t &uniqueValue) const {
223
const uint8_t *pos=pos_;
224
// Skip the rest of a pending linear-match node.
225
return pos!=NULL && findUniqueValue(pos+remainingMatchLength_+1, FALSE, uniqueValue);
229
* Finds each byte which continues the byte sequence from the current state.
230
* That is, each byte b for which it would be next(b)!=USTRINGTRIE_NO_MATCH now.
231
* @param out Each next byte is appended to this object.
232
* (Only uses the out.Append(s, length) method.)
233
* @return the number of bytes which continue the byte sequence from here
236
int32_t getNextBytes(ByteSink &out) const;
239
* Iterator for all of the (byte sequence, value) pairs in a BytesTrie.
242
class U_COMMON_API Iterator : public UMemory {
245
* Iterates from the root of a byte-serialized BytesTrie.
246
* @param trieBytes The trie bytes.
247
* @param maxStringLength If 0, the iterator returns full strings/byte sequences.
248
* Otherwise, the iterator returns strings with this maximum length.
249
* @param errorCode Standard ICU error code. Its input value must
250
* pass the U_SUCCESS() test, or else the function returns
251
* immediately. Check for U_FAILURE() on output or use with
252
* function chaining. (See User Guide for details.)
255
Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode);
258
* Iterates from the current state of the specified BytesTrie.
259
* @param trie The trie whose state will be copied for iteration.
260
* @param maxStringLength If 0, the iterator returns full strings/byte sequences.
261
* Otherwise, the iterator returns strings with this maximum length.
262
* @param errorCode Standard ICU error code. Its input value must
263
* pass the U_SUCCESS() test, or else the function returns
264
* immediately. Check for U_FAILURE() on output or use with
265
* function chaining. (See User Guide for details.)
268
Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
277
* Resets this iterator to its initial state.
284
* @return TRUE if there are more elements.
287
UBool hasNext() const;
290
* Finds the next (byte sequence, value) pair if there is one.
292
* If the byte sequence is truncated to the maximum length and does not
293
* have a real value, then the value is set to -1.
294
* In this case, this "not a real value" is indistinguishable from
295
* a real value of -1.
296
* @param errorCode Standard ICU error code. Its input value must
297
* pass the U_SUCCESS() test, or else the function returns
298
* immediately. Check for U_FAILURE() on output or use with
299
* function chaining. (See User Guide for details.)
300
* @return TRUE if there is another element.
303
UBool next(UErrorCode &errorCode);
306
* @return The NUL-terminated byte sequence for the last successful next().
309
const StringPiece &getString() const { return sp_; }
311
* @return The value for the last successful next().
314
int32_t getValue() const { return value_; }
317
UBool truncateAndStop();
319
const uint8_t *branchNext(const uint8_t *pos, int32_t length, UErrorCode &errorCode);
321
const uint8_t *bytes_;
323
const uint8_t *initialPos_;
324
int32_t remainingMatchLength_;
325
int32_t initialRemainingMatchLength_;
332
// The stack stores pairs of integers for backtracking to another
333
// outbound edge of a branch node.
334
// The first integer is an offset from bytes_.
335
// The second integer has the str_->length() from before the node in bits 15..0,
336
// and the remaining branch length in bits 24..16. (Bits 31..25 are unused.)
337
// (We could store the remaining branch length minus 1 in bits 23..16 and not use bits 31..24,
338
// but the code looks more confusing that way.)
343
friend class BytesTrieBuilder;
346
* Constructs a BytesTrie reader instance.
347
* Unlike the public constructor which just aliases an array,
348
* this constructor adopts the builder's array.
349
* This constructor is only called by the builder.
351
BytesTrie(void *adoptBytes, const void *trieBytes)
352
: ownedArray_(static_cast<uint8_t *>(adoptBytes)),
353
bytes_(static_cast<const uint8_t *>(trieBytes)),
354
pos_(bytes_), remainingMatchLength_(-1) {}
356
// No assignment operator.
357
BytesTrie &operator=(const BytesTrie &other);
363
// Reads a compact 32-bit integer.
364
// pos is already after the leadByte, and the lead byte is already shifted right by 1.
365
static int32_t readValue(const uint8_t *pos, int32_t leadByte);
366
static inline const uint8_t *skipValue(const uint8_t *pos, int32_t leadByte) {
367
// U_ASSERT(leadByte>=kMinValueLead);
368
if(leadByte>=(kMinTwoByteValueLead<<1)) {
369
if(leadByte<(kMinThreeByteValueLead<<1)) {
371
} else if(leadByte<(kFourByteValueLead<<1)) {
374
pos+=3+((leadByte>>1)&1);
379
static inline const uint8_t *skipValue(const uint8_t *pos) {
380
int32_t leadByte=*pos++;
381
return skipValue(pos, leadByte);
384
// Reads a jump delta and jumps.
385
static const uint8_t *jumpByDelta(const uint8_t *pos);
387
static inline const uint8_t *skipDelta(const uint8_t *pos) {
388
int32_t delta=*pos++;
389
if(delta>=kMinTwoByteDeltaLead) {
390
if(delta<kMinThreeByteDeltaLead) {
392
} else if(delta<kFourByteDeltaLead) {
401
static inline UStringTrieResult valueResult(int32_t node) {
402
return (UStringTrieResult)(USTRINGTRIE_INTERMEDIATE_VALUE-(node&kValueIsFinal));
405
// Handles a branch node for both next(byte) and next(string).
406
UStringTrieResult branchNext(const uint8_t *pos, int32_t length, int32_t inByte);
408
// Requires remainingLength_<0.
409
UStringTrieResult nextImpl(const uint8_t *pos, int32_t inByte);
411
// Helper functions for hasUniqueValue().
412
// Recursively finds a unique value (or whether there is not a unique one)
414
static const uint8_t *findUniqueValueFromBranch(const uint8_t *pos, int32_t length,
415
UBool haveUniqueValue, int32_t &uniqueValue);
416
// Recursively finds a unique value (or whether there is not a unique one)
417
// starting from a position on a node lead byte.
418
static UBool findUniqueValue(const uint8_t *pos, UBool haveUniqueValue, int32_t &uniqueValue);
420
// Helper functions for getNextBytes().
421
// getNextBytes() when pos is on a branch node.
422
static void getNextBranchBytes(const uint8_t *pos, int32_t length, ByteSink &out);
423
static void append(ByteSink &out, int c);
425
// BytesTrie data structure
427
// The trie consists of a series of byte-serialized nodes for incremental
428
// string/byte sequence matching. The root node is at the beginning of the trie data.
430
// Types of nodes are distinguished by their node lead byte ranges.
431
// After each node, except a final-value node, another node follows to
432
// encode match values or continue matching further bytes.
435
// - Value node: Stores a 32-bit integer in a compact, variable-length format.
436
// The value is for the string/byte sequence so far.
437
// One node bit indicates whether the value is final or whether
438
// matching continues with the next node.
439
// - Linear-match node: Matches a number of bytes.
440
// - Branch node: Branches to other nodes according to the current input byte.
441
// The node byte is the length of the branch (number of bytes to select from)
442
// minus 1. It is followed by a sub-node:
443
// - If the length is at most kMaxBranchLinearSubNodeLength, then
444
// there are length-1 (key, value) pairs and then one more comparison byte.
445
// If one of the key bytes matches, then the value is either a final value for
446
// the string/byte sequence so far, or a "jump" delta to the next node.
447
// If the last byte matches, then matching continues with the next node.
448
// (Values have the same encoding as value nodes.)
449
// - If the length is greater than kMaxBranchLinearSubNodeLength, then
450
// there is one byte and one "jump" delta.
451
// If the input byte is less than the sub-node byte, then "jump" by delta to
452
// the next sub-node which will have a length of length/2.
453
// (The delta has its own compact encoding.)
454
// Otherwise, skip the "jump" delta to the next sub-node
455
// which will have a length of length-length/2.
457
// Node lead byte values.
459
// 00..0f: Branch node. If node!=0 then the length is node+1, otherwise
460
// the length is one more than the next byte.
462
// For a branch sub-node with at most this many entries, we drop down
463
// to a linear search.
464
static const int32_t kMaxBranchLinearSubNodeLength=5;
466
// 10..1f: Linear-match node, match 1..16 bytes and continue reading the next node.
467
static const int32_t kMinLinearMatch=0x10;
468
static const int32_t kMaxLinearMatchLength=0x10;
470
// 20..ff: Variable-length value node.
471
// If odd, the value is final. (Otherwise, intermediate value or jump delta.)
472
// Then shift-right by 1 bit.
473
// The remaining lead byte value indicates the number of following bytes (0..4)
474
// and contains the value's top bits.
475
static const int32_t kMinValueLead=kMinLinearMatch+kMaxLinearMatchLength; // 0x20
476
// It is a final value if bit 0 is set.
477
static const int32_t kValueIsFinal=1;
479
// Compact value: After testing bit 0, shift right by 1 and then use the following thresholds.
480
static const int32_t kMinOneByteValueLead=kMinValueLead/2; // 0x10
481
static const int32_t kMaxOneByteValue=0x40; // At least 6 bits in the first byte.
483
static const int32_t kMinTwoByteValueLead=kMinOneByteValueLead+kMaxOneByteValue+1; // 0x51
484
static const int32_t kMaxTwoByteValue=0x1aff;
486
static const int32_t kMinThreeByteValueLead=kMinTwoByteValueLead+(kMaxTwoByteValue>>8)+1; // 0x6c
487
static const int32_t kFourByteValueLead=0x7e;
489
// A little more than Unicode code points. (0x11ffff)
490
static const int32_t kMaxThreeByteValue=((kFourByteValueLead-kMinThreeByteValueLead)<<16)-1;
492
static const int32_t kFiveByteValueLead=0x7f;
494
// Compact delta integers.
495
static const int32_t kMaxOneByteDelta=0xbf;
496
static const int32_t kMinTwoByteDeltaLead=kMaxOneByteDelta+1; // 0xc0
497
static const int32_t kMinThreeByteDeltaLead=0xf0;
498
static const int32_t kFourByteDeltaLead=0xfe;
499
static const int32_t kFiveByteDeltaLead=0xff;
501
static const int32_t kMaxTwoByteDelta=((kMinThreeByteDeltaLead-kMinTwoByteDeltaLead)<<8)-1; // 0x2fff
502
static const int32_t kMaxThreeByteDelta=((kFourByteDeltaLead-kMinThreeByteDeltaLead)<<16)-1; // 0xdffff
504
uint8_t *ownedArray_;
506
// Fixed value referencing the BytesTrie bytes.
507
const uint8_t *bytes_;
509
// Iterator variables.
511
// Pointer to next trie byte to read. NULL if no more matches.
513
// Remaining length of a linear-match node, minus 1. Negative if not in such a node.
514
int32_t remainingMatchLength_;
519
#endif // __BYTESTRIE_H__