1 // Copyright (C) 2016 and later: Unicode, Inc. and others.
2 // License & terms of use: http://www.unicode.org/copyright.html
4 *******************************************************************************
5 * Copyright (C) 2010-2012, International Business Machines
6 * Corporation and others. All Rights Reserved.
7 *******************************************************************************
8 * file name: bytestrie.h
10 * tab size: 8 (not used)
13 * created on: 2010sep25
14 * created by: Markus W. Scherer
17 #ifndef __BYTESTRIE_H__
18 #define __BYTESTRIE_H__
22 * \brief C++ API: Trie for mapping byte sequences to integer values.
25 #include "unicode/utypes.h"
26 #include "unicode/stringpiece.h"
27 #include "unicode/uobject.h"
28 #include "unicode/ustringtrie.h"
33 class BytesTrieBuilder;
38 * Light-weight, non-const reader class for a BytesTrie.
39 * Traverses a byte-serialized data structure with minimal state,
40 * for mapping byte sequences to non-negative integer values.
42 * This class owns the serialized trie data only if it was constructed by
43 * the builder's build() method.
44 * The public constructor and the copy constructor only alias the data (only copy the pointer).
45 * There is no assignment operator.
47 * This class is not intended for public subclassing.
50 class U_COMMON_API BytesTrie : public UMemory {
53 * Constructs a BytesTrie reader instance.
55 * The trieBytes must contain a copy of a byte sequence from the BytesTrieBuilder,
56 * starting with the first byte of that sequence.
57 * The BytesTrie object will not read more bytes than
58 * the BytesTrieBuilder generated in the corresponding build() call.
60 * The array is not copied/cloned and must not be modified while
61 * the BytesTrie object is in use.
63 * @param trieBytes The byte array that contains the serialized trie.
66 BytesTrie(const void *trieBytes)
67 : ownedArray_(NULL), bytes_(static_cast<const uint8_t *>(trieBytes)),
68 pos_(bytes_), remainingMatchLength_(-1) {}
77 * Copy constructor, copies the other trie reader object and its state,
78 * but not the byte array which will be shared. (Shallow copy.)
79 * @param other Another BytesTrie object.
82 BytesTrie(const BytesTrie &other)
83 : ownedArray_(NULL), bytes_(other.bytes_),
84 pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
87 * Resets this trie to its initial state.
93 remainingMatchLength_=-1;
98 * BytesTrie state object, for saving a trie's current state
99 * and resetting the trie back to this state later.
102 class State : public UMemory {
105 * Constructs an empty State.
108 State() { bytes=NULL; }
110 friend class BytesTrie;
112 const uint8_t *bytes;
114 int32_t remainingMatchLength;
118 * Saves the state of this trie.
119 * @param state The State object to hold the trie's state.
124 const BytesTrie &saveState(State &state) const {
127 state.remainingMatchLength=remainingMatchLength_;
132 * Resets this trie to the saved state.
133 * If the state object contains no state, or the state of a different trie,
134 * then this trie remains unchanged.
135 * @param state The State object which holds a saved trie state.
141 BytesTrie &resetToState(const State &state) {
142 if(bytes_==state.bytes && bytes_!=NULL) {
144 remainingMatchLength_=state.remainingMatchLength;
150 * Determines whether the byte sequence so far matches, whether it has a value,
151 * and whether another input byte can continue a matching byte sequence.
152 * @return The match/value Result.
155 UStringTrieResult current() const;
158 * Traverses the trie from the initial state for this input byte.
159 * Equivalent to reset().next(inByte).
160 * @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
161 * Values below -0x100 and above 0xff will never match.
162 * @return The match/value Result.
165 inline UStringTrieResult first(int32_t inByte) {
166 remainingMatchLength_=-1;
170 return nextImpl(bytes_, inByte);
174 * Traverses the trie from the current state for this input byte.
175 * @param inByte Input byte value. Values -0x100..-1 are treated like 0..0xff.
176 * Values below -0x100 and above 0xff will never match.
177 * @return The match/value Result.
180 UStringTrieResult next(int32_t inByte);
183 * Traverses the trie from the current state for this byte sequence.
186 * Result result=current();
188 * if(!USTRINGTRIE_HAS_NEXT(result)) return USTRINGTRIE_NO_MATCH;
192 * @param s A string or byte sequence. Can be NULL if length is 0.
193 * @param length The length of the byte sequence. Can be -1 if NUL-terminated.
194 * @return The match/value Result.
197 UStringTrieResult next(const char *s, int32_t length);
200 * Returns a matching byte sequence's value if called immediately after
201 * current()/first()/next() returned USTRINGTRIE_INTERMEDIATE_VALUE or USTRINGTRIE_FINAL_VALUE.
202 * getValue() can be called multiple times.
204 * Do not call getValue() after USTRINGTRIE_NO_MATCH or USTRINGTRIE_NO_VALUE!
205 * @return The value for the byte sequence so far.
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);
216 * Determines whether all byte sequences reachable from the current state
217 * map to the same value.
218 * @param uniqueValue Receives the unique value, if this function returns TRUE.
220 * @return TRUE if all byte sequences reachable from the current state
221 * map to the same value.
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);
231 * Finds each byte which continues the byte sequence from the current state.
232 * That is, each byte b for which it would be next(b)!=USTRINGTRIE_NO_MATCH now.
233 * @param out Each next byte is appended to this object.
234 * (Only uses the out.Append(s, length) method.)
235 * @return the number of bytes which continue the byte sequence from here
238 int32_t getNextBytes(ByteSink &out) const;
241 * Iterator for all of the (byte sequence, value) pairs in a BytesTrie.
244 class U_COMMON_API Iterator : public UMemory {
247 * Iterates from the root of a byte-serialized BytesTrie.
248 * @param trieBytes The trie bytes.
249 * @param maxStringLength If 0, the iterator returns full strings/byte sequences.
250 * Otherwise, the iterator returns strings with this maximum length.
251 * @param errorCode Standard ICU error code. Its input value must
252 * pass the U_SUCCESS() test, or else the function returns
253 * immediately. Check for U_FAILURE() on output or use with
254 * function chaining. (See User Guide for details.)
257 Iterator(const void *trieBytes, int32_t maxStringLength, UErrorCode &errorCode);
260 * Iterates from the current state of the specified BytesTrie.
261 * @param trie The trie whose state will be copied for iteration.
262 * @param maxStringLength If 0, the iterator returns full strings/byte sequences.
263 * Otherwise, the iterator returns strings with this maximum length.
264 * @param errorCode Standard ICU error code. Its input value must
265 * pass the U_SUCCESS() test, or else the function returns
266 * immediately. Check for U_FAILURE() on output or use with
267 * function chaining. (See User Guide for details.)
270 Iterator(const BytesTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
279 * Resets this iterator to its initial state.
286 * @return TRUE if there are more elements.
289 UBool hasNext() const;
292 * Finds the next (byte sequence, value) pair if there is one.
294 * If the byte sequence is truncated to the maximum length and does not
295 * have a real value, then the value is set to -1.
296 * In this case, this "not a real value" is indistinguishable from
297 * a real value of -1.
298 * @param errorCode Standard ICU error code. Its input value must
299 * pass the U_SUCCESS() test, or else the function returns
300 * immediately. Check for U_FAILURE() on output or use with
301 * function chaining. (See User Guide for details.)
302 * @return TRUE if there is another element.
305 UBool next(UErrorCode &errorCode);
308 * @return The NUL-terminated byte sequence for the last successful next().
311 StringPiece getString() const;
313 * @return The value for the last successful next().
316 int32_t getValue() const { return value_; }
319 UBool truncateAndStop();
321 const uint8_t *branchNext(const uint8_t *pos, int32_t length, UErrorCode &errorCode);
323 const uint8_t *bytes_;
325 const uint8_t *initialPos_;
326 int32_t remainingMatchLength_;
327 int32_t initialRemainingMatchLength_;
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.)
344 friend class BytesTrieBuilder;
347 * Constructs a BytesTrie reader instance.
348 * Unlike the public constructor which just aliases an array,
349 * this constructor adopts the builder's array.
350 * This constructor is only called by the builder.
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) {}
357 // No assignment operator.
358 BytesTrie &operator=(const BytesTrie &other);
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)) {
372 } else if(leadByte<(kFourByteValueLead<<1)) {
375 pos+=3+((leadByte>>1)&1);
380 static inline const uint8_t *skipValue(const uint8_t *pos) {
381 int32_t leadByte=*pos++;
382 return skipValue(pos, leadByte);
385 // Reads a jump delta and jumps.
386 static const uint8_t *jumpByDelta(const uint8_t *pos);
388 static inline const uint8_t *skipDelta(const uint8_t *pos) {
389 int32_t delta=*pos++;
390 if(delta>=kMinTwoByteDeltaLead) {
391 if(delta<kMinThreeByteDeltaLead) {
393 } else if(delta<kFourByteDeltaLead) {
402 static inline UStringTrieResult valueResult(int32_t node) {
403 return (UStringTrieResult)(USTRINGTRIE_INTERMEDIATE_VALUE-(node&kValueIsFinal));
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);
409 // Requires remainingLength_<0.
410 UStringTrieResult nextImpl(const uint8_t *pos, int32_t inByte);
412 // Helper functions for hasUniqueValue().
413 // Recursively finds a unique value (or whether there is not a unique one)
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);
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);
426 // BytesTrie data structure
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.
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.
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.
458 // Node lead byte values.
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.
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;
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;
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;
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.
484 static const int32_t kMinTwoByteValueLead=kMinOneByteValueLead+kMaxOneByteValue+1; // 0x51
485 static const int32_t kMaxTwoByteValue=0x1aff;
487 static const int32_t kMinThreeByteValueLead=kMinTwoByteValueLead+(kMaxTwoByteValue>>8)+1; // 0x6c
488 static const int32_t kFourByteValueLead=0x7e;
490 // A little more than Unicode code points. (0x11ffff)
491 static const int32_t kMaxThreeByteValue=((kFourByteValueLead-kMinThreeByteValueLead)<<16)-1;
493 static const int32_t kFiveByteValueLead=0x7f;
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;
502 static const int32_t kMaxTwoByteDelta=((kMinThreeByteDeltaLead-kMinTwoByteDeltaLead)<<8)-1; // 0x2fff
503 static const int32_t kMaxThreeByteDelta=((kFourByteDeltaLead-kMinThreeByteDeltaLead)<<16)-1; // 0xdffff
505 uint8_t *ownedArray_;
507 // Fixed value referencing the BytesTrie bytes.
508 const uint8_t *bytes_;
510 // Iterator variables.
512 // Pointer to next trie byte to read. NULL if no more matches.
514 // Remaining length of a linear-match node, minus 1. Negative if not in such a node.
515 int32_t remainingMatchLength_;
520 #endif // __BYTESTRIE_H__