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1 : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 : /*
3 : * This file is part of the LibreOffice project.
4 : *
5 : * This Source Code Form is subject to the terms of the Mozilla Public
6 : * License, v. 2.0. If a copy of the MPL was not distributed with this
7 : * file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 : *
9 : * This file incorporates work covered by the following license notice:
10 : *
11 : * Licensed to the Apache Software Foundation (ASF) under one or more
12 : * contributor license agreements. See the NOTICE file distributed
13 : * with this work for additional information regarding copyright
14 : * ownership. The ASF licenses this file to you under the Apache
15 : * License, Version 2.0 (the "License"); you may not use this file
16 : * except in compliance with the License. You may obtain a copy of
17 : * the License at http://www.apache.org/licenses/LICENSE-2.0 .
18 : */
19 :
20 : /*
21 :
22 : Weighted Levenshtein Distance
23 : including wildcards
24 : '*' for any number (0 or more) of arbitrary characters
25 : '?' for exactly one arbitrary character
26 : escapeable with backslash, "\*" or "\?"
27 :
28 : Return:
29 : WLD if WLD <= nLimit, else nLimit+1
30 :
31 : or, if bSplitCount:
32 : WLD if WLD <= nLimit
33 : -WLD if Replace and Insert and Delete <= nLimit
34 : else nLimit+1
35 :
36 : Recursive definition of WLD:
37 :
38 : WLD( X(i), Y(j) ) = min( WLD( X(i-1), Y(j-1) ) + p(i,j) ,
39 : WLD( X(i) , Y(j-1) ) + q ,
40 : WLD( X(i-1), Y(j) ) + r )
41 :
42 : X(i) := the first i characters of the word X
43 : Y(j) := the first j characters of the word Y
44 : p(i,j) := 0 if i-th character of X == j-th character of Y,
45 : p else
46 :
47 : Boundary conditions:
48 : WLD( X(0), Y(j) ) := j*q (Y created by j inserts)
49 : WLD( X(i), Y(0) ) := i*r (Y created by i deletes)
50 : WLD( X(0), Y(0) ) := 0
51 :
52 : Instead of recursions a dynamic algorithm is used.
53 :
54 : See also: German computer magazine
55 : c't 07/89 pages 192-208 and c't 03/94 pages 230-239
56 : */
57 :
58 : #include <string.h>
59 :
60 : #if defined( _MSC_VER )
61 : #pragma warning(once: 4068)
62 : #endif
63 :
64 : #include "levdis.hxx"
65 :
66 : #ifdef SOLARIS
67 : #undef min
68 : #endif
69 :
70 : #define LEVDISBIG (nLimit + 1) // Return value if distance > nLimit
71 : #define LEVDISDOUBLEBUF 2048 // no doubling atop this border
72 :
73 0 : static sal_Int32 Impl_WLD_StringLen( const sal_Unicode* pStr )
74 : {
75 0 : const sal_Unicode* pTempStr = pStr;
76 0 : while( *pTempStr )
77 0 : pTempStr++;
78 0 : return (sal_Int32)(pTempStr-pStr);
79 : }
80 :
81 : // Distance from string to pattern
82 0 : int WLevDistance::WLD( const sal_Unicode* cString, sal_Int32 nStringLen )
83 : {
84 0 : int nSPMin = 0; // penalty point Minimum
85 0 : int nRepS = 0; // for SplitCount
86 :
87 : // length difference between pattern and string
88 0 : int nLenDiff = nPatternLen - nStars - nStringLen;
89 : // more insertions or deletions necessary as the limit? Then leave
90 0 : if ( (nLenDiff * nInsQ0 > nLimit)
91 0 : || ((nStars == 0) && (nLenDiff * nDelR0 < -nLimit)) )
92 0 : return LEVDISBIG;
93 :
94 : // comparative String greater than instantaneous array
95 : // -> adapt array size
96 0 : if ( nStringLen >= nArrayLen )
97 : {
98 : // increase size much more to avoid reallocation
99 0 : if ( nStringLen < LEVDISDOUBLEBUF )
100 0 : nArrayLen = 2 * nStringLen;
101 : else
102 0 : nArrayLen = nStringLen + 1;
103 0 : npDistance = aDisMem.NewMem( nArrayLen );
104 : }
105 :
106 : // Calculate start values of the second column (first pattern value).
107 : // First column (0-Len pattern) is always zero .. nStringLen * nInsQ0,
108 : // therefore the minimum is 0
109 0 : if ( nPatternLen == 0 )
110 : {
111 : // Count of deletions to reach pattern
112 0 : for ( sal_Int32 i=0; i <= nStringLen; i++ )
113 0 : npDistance[i] = i * nDelR0;
114 : }
115 0 : else if ( cpPattern[0] == '*' && bpPatIsWild[0] )
116 : {
117 : // instead of a '*' you can fit in anything
118 0 : for ( sal_Int32 i=0; i <= nStringLen; i++ )
119 0 : npDistance[i] = 0;
120 : }
121 : else
122 : {
123 : sal_Unicode c;
124 : int nP;
125 0 : c = cpPattern[0];
126 0 : if ( c == '?' && bpPatIsWild[0] )
127 0 : nP = 0; // a '?' could be any character.
128 : else
129 : // Minimum of replacement and deletion+insertion weighting
130 0 : nP = Min3( nRepP0, nRepP0, nDelR0 + nInsQ0 );
131 0 : npDistance[0] = nInsQ0; // start with simple insert
132 0 : npDistance[1] = nInsQ0;
133 0 : npDistance[2] = nInsQ0;
134 0 : int nReplacePos = -1; // tristate flag
135 0 : int nDelCnt = 0;
136 0 : for ( sal_Int32 i=1; i <= nStringLen; i++, nDelCnt += nDelR0 )
137 : {
138 0 : if ( cString[i-1] == c )
139 0 : nP = 0; // Replace from this position is 0
140 : // Deletions to match pattern + Replace
141 0 : npDistance[i] = nDelCnt + nP;
142 0 : if ( bSplitCount )
143 : {
144 0 : if ( nReplacePos < 0 && nP )
145 : { // this position will be replaced
146 0 : nRepS++;
147 0 : nReplacePos = i;
148 : }
149 0 : else if ( nReplacePos > 0 && !nP )
150 : {
151 : // same count of c
152 0 : int nBalance = levdisbalance( 0, i-1, c, cString, nStringLen );
153 0 : if ( !nBalance )
154 : { // one was replaced that was an insertion instead
155 0 : nRepS--;
156 0 : nReplacePos = 0;
157 : }
158 : }
159 : }
160 : }
161 0 : nSPMin = Min3( npDistance[0], npDistance[1], npDistance[2] );
162 : }
163 :
164 : // calculate distance matrix
165 0 : sal_Int32 j = 0; // for all columns of the pattern, till limit is not reached
166 0 : while ( (j < nPatternLen-1)
167 0 : && nSPMin <= (bSplitCount ? 2 * nLimit : nLimit) )
168 : {
169 : sal_Unicode c;
170 : int nP, nQ, nR, nPij, d2;
171 :
172 0 : j++;
173 0 : c = cpPattern[j];
174 0 : if ( bpPatIsWild[j] ) // '*' or '?' not escaped
175 0 : nP = 0; // could be replaced without penalty
176 : else
177 0 : nP = nRepP0;
178 0 : if ( c == '*' && bpPatIsWild[j] )
179 : {
180 0 : nQ = 0; // instertion and deletion without penalty
181 0 : nR = 0;
182 : }
183 : else
184 : {
185 0 : nQ = nInsQ0; // usual weighting
186 0 : nR = nDelR0;
187 : }
188 0 : d2 = npDistance[0];
189 : // increase insert count to get from null string to pattern
190 0 : npDistance[0] = npDistance[0] + nQ;
191 0 : nSPMin = npDistance[0];
192 0 : int nReplacePos = -1; // tristate flag
193 : // for each pattern column run through the string
194 0 : for ( sal_Int32 i=1; i <= nStringLen; i++ )
195 : {
196 0 : int d1 = d2; // WLD( X(i-1), Y(j-1) )
197 0 : d2 = npDistance[i]; // WLD( X(i) , Y(j-1) )
198 0 : if ( cString[i-1] == c )
199 : {
200 0 : nPij = 0; // p(i,j)
201 0 : if ( nReplacePos < 0 )
202 : {
203 : // same count of c
204 0 : int nBalance = levdisbalance( j, i-1, c, cString, nStringLen );
205 0 : if ( !nBalance )
206 0 : nReplacePos = 0; // no replacement
207 : }
208 : }
209 : else
210 0 : nPij = nP;
211 : // WLD( X(i), Y(j) ) = min( WLD( X(i-1), Y(j-1) ) + p(i,j) ,
212 : // WLD( X(i) , Y(j-1) ) + q ,
213 : // WLD( X(i-1), Y(j) ) + r )
214 0 : npDistance[i] = Min3( d1 + nPij, d2 + nQ, npDistance[i-1] + nR );
215 0 : if ( npDistance[i] < nSPMin )
216 0 : nSPMin = npDistance[i];
217 0 : if ( bSplitCount )
218 : {
219 0 : if ( nReplacePos < 0 && nPij && npDistance[i] == d1 + nPij )
220 : { // this position will be replaced
221 0 : nRepS++;
222 0 : nReplacePos = i;
223 : }
224 0 : else if ( nReplacePos > 0 && !nPij )
225 : {
226 : // character is equal in string and pattern
227 : //
228 : // If from this point:
229 : // * pattern and string have the same count of this
230 : // character
231 : // * and character count is the same before this position
232 : // then the replace was none.
233 : //
234 : // Scrambled letters are recognized here and the nRepS
235 : // replacement is withdrawn, whereby the double limit kicks
236 : // in.
237 :
238 : // Same count of c
239 0 : int nBalance = levdisbalance( j, i-1, c, cString, nStringLen );
240 0 : if ( !nBalance )
241 : { // one was replaced that was an insertion instead
242 0 : nRepS--;
243 0 : nReplacePos = 0;
244 : }
245 : }
246 : }
247 : }
248 : }
249 0 : if ( (nSPMin <= nLimit) && (npDistance[nStringLen] <= nLimit) )
250 0 : return npDistance[nStringLen];
251 : else
252 : {
253 0 : if ( bSplitCount )
254 : {
255 0 : if ( nRepS && nLenDiff > 0 )
256 0 : nRepS -= nLenDiff; // Inserts were counted
257 0 : if ( (nSPMin <= 2 * nLimit)
258 0 : && (npDistance[nStringLen] <= 2 * nLimit)
259 0 : && (nRepS * nRepP0 <= nLimit) )
260 0 : return -npDistance[nStringLen];
261 0 : return LEVDISBIG;
262 : }
263 0 : return LEVDISBIG;
264 : }
265 : }
266 :
267 : // Calculating nLimit, nReplP0, nInsQ0, nDelR0, bSplitCount
268 : // from user values nOtherX, nShorterY, nLongerZ, bRelaxed
269 0 : int WLevDistance::CalcLPQR( int nX, int nY, int nZ, bool bRelaxed )
270 : {
271 0 : if ( nX < 0 ) nX = 0; // only positive values
272 0 : if ( nY < 0 ) nY = 0;
273 0 : if ( nZ < 0 ) nZ = 0;
274 0 : if (0 == Min3( nX, nY, nZ )) // at least one 0
275 : {
276 : int nMid, nMax;
277 0 : nMax = Max3( nX, nY, nZ ); // either 0 for three 0s or Max
278 0 : if ( 0 == (nMid = Mid3( nX, nY, nZ )) ) // even two 0
279 0 : nLimit = nMax; // either 0 or the only one >0
280 : else // one is 0
281 0 : nLimit = LCM( nMid, nMax );
282 : }
283 : else // all three of them are not 0
284 0 : nLimit = LCM( LCM( nX, nY ), nZ );
285 0 : nRepP0 = ( nX ? nLimit / nX : nLimit + 1 );
286 0 : nInsQ0 = ( nY ? nLimit / nY : nLimit + 1 );
287 0 : nDelR0 = ( nZ ? nLimit / nZ : nLimit + 1 );
288 0 : bSplitCount = bRelaxed;
289 0 : return nLimit;
290 : }
291 :
292 : // greatest common divisior according to Euklid (chaindivision)
293 : // special case: 0 plus anything produces 1
294 0 : int WLevDistance::GCD( int a, int b )
295 : {
296 0 : if ( !a || !b )
297 0 : return 1;
298 0 : if ( a < 0 ) a = -a;
299 0 : if ( b < 0 ) b = -b;
300 0 : do
301 : {
302 0 : if ( a > b )
303 0 : a -= int(a / b) * b;
304 : else
305 0 : b -= int(b / a) * a;
306 0 : } while ( a && b );
307 0 : return( a ? a : b);
308 : }
309 :
310 : // least common multiple : a * b / GCD(a,b)
311 0 : int WLevDistance::LCM( int a, int b )
312 : {
313 0 : if ( a > b ) // decrease owerflow chance
314 0 : return( (a / GCD(a,b)) * b );
315 : else
316 0 : return( (b / GCD(a,b)) * a );
317 : }
318 :
319 : // Minimum of three values
320 0 : inline int WLevDistance::Min3( int x, int y, int z )
321 : {
322 0 : if ( x < y )
323 0 : return( x < z ? x : z );
324 : else
325 0 : return( y < z ? y : z );
326 : }
327 :
328 : // The value in the middle
329 0 : int WLevDistance::Mid3( int x, int y, int z )
330 : {
331 0 : int min = Min3(x,y,z);
332 0 : if ( x == min )
333 0 : return( y < z ? y : z);
334 0 : else if ( y == min )
335 0 : return( x < z ? x : z);
336 : else // z == min
337 0 : return( x < y ? x : y);
338 : }
339 :
340 : // Maximum of three values
341 0 : int WLevDistance::Max3( int x, int y, int z )
342 : {
343 0 : if ( x > y )
344 0 : return( x > z ? x : z );
345 : else
346 0 : return( y > z ? y : z );
347 : }
348 :
349 : // initialize data from CTOR
350 0 : void WLevDistance::InitData( const sal_Unicode* cPattern )
351 : {
352 0 : cpPattern = aPatMem.GetcPtr();
353 0 : bpPatIsWild = aPatMem.GetbPtr();
354 0 : npDistance = aDisMem.GetPtr();
355 0 : nStars = 0;
356 0 : const sal_Unicode* cp1 = cPattern;
357 0 : sal_Unicode* cp2 = cpPattern;
358 0 : bool* bp = bpPatIsWild;
359 : // copy pattern, count asterisks, escaped Jokers
360 0 : while ( *cp1 )
361 : {
362 0 : if ( *cp1 == '\\' ) // maybe escaped
363 : {
364 0 : if ( *(cp1+1) == '*' || *(cp1+1) == '?' ) // next Joker?
365 : {
366 0 : cp1++; // skip '\\'
367 0 : nPatternLen--;
368 : }
369 0 : *bp++ = false;
370 : }
371 0 : else if ( *cp1 == '*' || *cp1 == '?' ) // Joker
372 : {
373 0 : if ( *cp1 == '*' )
374 0 : nStars++;
375 0 : *bp++ = true;
376 : }
377 : else
378 0 : *bp++ = false;
379 0 : *cp2++ = *cp1++;
380 : }
381 0 : *cp2 = '\0';
382 0 : }
383 :
384 0 : WLevDistance::WLevDistance( const sal_Unicode* cPattern,
385 : int nOtherX, int nShorterY, int nLongerZ,
386 : bool bRelaxed ) :
387 0 : nPatternLen( Impl_WLD_StringLen(cPattern) ),
388 : aPatMem( nPatternLen + 1 ),
389 0 : nArrayLen( nPatternLen + 1 ),
390 0 : aDisMem( nArrayLen )
391 : {
392 0 : InitData( cPattern );
393 0 : CalcLPQR( nOtherX, nShorterY, nLongerZ, bRelaxed );
394 0 : }
395 :
396 : // CopyCTor
397 0 : WLevDistance::WLevDistance( const WLevDistance& rWLD ) :
398 : nPatternLen( rWLD.nPatternLen ),
399 : aPatMem( nPatternLen + 1 ),
400 0 : nArrayLen( nPatternLen + 1 ),
401 : aDisMem( nArrayLen ),
402 : nLimit( rWLD.nLimit ),
403 : nRepP0( rWLD.nRepP0 ),
404 : nInsQ0( rWLD.nInsQ0 ),
405 : nDelR0( rWLD.nDelR0 ),
406 : nStars( rWLD.nStars ),
407 0 : bSplitCount( rWLD.bSplitCount )
408 : {
409 0 : cpPattern = aPatMem.GetcPtr();
410 0 : bpPatIsWild = aPatMem.GetbPtr();
411 0 : npDistance = aDisMem.GetPtr();
412 : sal_Int32 i;
413 0 : for ( i=0; i<nPatternLen; i++ )
414 : {
415 0 : cpPattern[i] = rWLD.cpPattern[i];
416 0 : bpPatIsWild[i] = rWLD.bpPatIsWild[i];
417 : }
418 0 : cpPattern[i] = '\0';
419 0 : }
420 :
421 : // DTor
422 0 : WLevDistance::~WLevDistance()
423 : {
424 0 : }
425 :
426 : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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