1 /*
2 ** 2006 Oct 10
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
10 **
11 ******************************************************************************
12 **
13 ** Implementation of the "simple" full-text-search tokenizer.
14 */
15
16 /*
17 ** The code in this file is only compiled if:
18 **
19 ** * The FTS2 module is being built as an extension
20 ** (in which case SQLITE_CORE is not defined), or
21 **
22 ** * The FTS2 module is being built into the core of
23 ** SQLite (in which case SQLITE_ENABLE_FTS2 is defined).
24 */
25 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2)
26
27
28 #include <assert.h>
29 #include <stdlib.h>
30 #include <stdio.h>
31 #include <string.h>
32
33 #include "fts2_tokenizer.h"
34
35 typedef struct simple_tokenizer {
36 sqlite3_tokenizer base;
37 char delim[128]; /* flag ASCII delimiters */
38 } simple_tokenizer;
39
40 typedef struct simple_tokenizer_cursor {
41 sqlite3_tokenizer_cursor base;
42 const char *pInput; /* input we are tokenizing */
43 int nBytes; /* size of the input */
44 int iOffset; /* current position in pInput */
45 int iToken; /* index of next token to be returned */
46 char *pToken; /* storage for current token */
47 int nTokenAllocated; /* space allocated to zToken buffer */
48 } simple_tokenizer_cursor;
49
50
51 /* Forward declaration */
52 static const sqlite3_tokenizer_module simpleTokenizerModule;
53
simpleDelim(simple_tokenizer * t,unsigned char c)54 static int simpleDelim(simple_tokenizer *t, unsigned char c){
55 return c<0x80 && t->delim[c];
56 }
57
58 /*
59 ** Create a new tokenizer instance.
60 */
simpleCreate(int argc,const char * const * argv,sqlite3_tokenizer ** ppTokenizer)61 static int simpleCreate(
62 int argc, const char * const *argv,
63 sqlite3_tokenizer **ppTokenizer
64 ){
65 simple_tokenizer *t;
66
67 t = (simple_tokenizer *) sqlite3_malloc(sizeof(*t));
68 if( t==NULL ) return SQLITE_NOMEM;
69 memset(t, 0, sizeof(*t));
70
71 /* TODO(shess) Delimiters need to remain the same from run to run,
72 ** else we need to reindex. One solution would be a meta-table to
73 ** track such information in the database, then we'd only want this
74 ** information on the initial create.
75 */
76 if( argc>1 ){
77 int i, n = strlen(argv[1]);
78 for(i=0; i<n; i++){
79 unsigned char ch = argv[1][i];
80 /* We explicitly don't support UTF-8 delimiters for now. */
81 if( ch>=0x80 ){
82 sqlite3_free(t);
83 return SQLITE_ERROR;
84 }
85 t->delim[ch] = 1;
86 }
87 } else {
88 /* Mark non-alphanumeric ASCII characters as delimiters */
89 int i;
90 for(i=1; i<0x80; i++){
91 t->delim[i] = !((i>='0' && i<='9') || (i>='A' && i<='Z') ||
92 (i>='a' && i<='z'));
93 }
94 }
95
96 *ppTokenizer = &t->base;
97 return SQLITE_OK;
98 }
99
100 /*
101 ** Destroy a tokenizer
102 */
simpleDestroy(sqlite3_tokenizer * pTokenizer)103 static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
104 sqlite3_free(pTokenizer);
105 return SQLITE_OK;
106 }
107
108 /*
109 ** Prepare to begin tokenizing a particular string. The input
110 ** string to be tokenized is pInput[0..nBytes-1]. A cursor
111 ** used to incrementally tokenize this string is returned in
112 ** *ppCursor.
113 */
simpleOpen(sqlite3_tokenizer * pTokenizer,const char * pInput,int nBytes,sqlite3_tokenizer_cursor ** ppCursor)114 static int simpleOpen(
115 sqlite3_tokenizer *pTokenizer, /* The tokenizer */
116 const char *pInput, int nBytes, /* String to be tokenized */
117 sqlite3_tokenizer_cursor **ppCursor /* OUT: Tokenization cursor */
118 ){
119 simple_tokenizer_cursor *c;
120
121 c = (simple_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
122 if( c==NULL ) return SQLITE_NOMEM;
123
124 c->pInput = pInput;
125 if( pInput==0 ){
126 c->nBytes = 0;
127 }else if( nBytes<0 ){
128 c->nBytes = (int)strlen(pInput);
129 }else{
130 c->nBytes = nBytes;
131 }
132 c->iOffset = 0; /* start tokenizing at the beginning */
133 c->iToken = 0;
134 c->pToken = NULL; /* no space allocated, yet. */
135 c->nTokenAllocated = 0;
136
137 *ppCursor = &c->base;
138 return SQLITE_OK;
139 }
140
141 /*
142 ** Close a tokenization cursor previously opened by a call to
143 ** simpleOpen() above.
144 */
simpleClose(sqlite3_tokenizer_cursor * pCursor)145 static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
146 simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
147 sqlite3_free(c->pToken);
148 sqlite3_free(c);
149 return SQLITE_OK;
150 }
151
152 /*
153 ** Extract the next token from a tokenization cursor. The cursor must
154 ** have been opened by a prior call to simpleOpen().
155 */
simpleNext(sqlite3_tokenizer_cursor * pCursor,const char ** ppToken,int * pnBytes,int * piStartOffset,int * piEndOffset,int * piPosition)156 static int simpleNext(
157 sqlite3_tokenizer_cursor *pCursor, /* Cursor returned by simpleOpen */
158 const char **ppToken, /* OUT: *ppToken is the token text */
159 int *pnBytes, /* OUT: Number of bytes in token */
160 int *piStartOffset, /* OUT: Starting offset of token */
161 int *piEndOffset, /* OUT: Ending offset of token */
162 int *piPosition /* OUT: Position integer of token */
163 ){
164 simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
165 simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
166 unsigned char *p = (unsigned char *)c->pInput;
167
168 while( c->iOffset<c->nBytes ){
169 int iStartOffset;
170
171 /* Scan past delimiter characters */
172 while( c->iOffset<c->nBytes && simpleDelim(t, p[c->iOffset]) ){
173 c->iOffset++;
174 }
175
176 /* Count non-delimiter characters. */
177 iStartOffset = c->iOffset;
178 while( c->iOffset<c->nBytes && !simpleDelim(t, p[c->iOffset]) ){
179 c->iOffset++;
180 }
181
182 if( c->iOffset>iStartOffset ){
183 int i, n = c->iOffset-iStartOffset;
184 if( n>c->nTokenAllocated ){
185 c->nTokenAllocated = n+20;
186 c->pToken = sqlite3_realloc(c->pToken, c->nTokenAllocated);
187 if( c->pToken==NULL ) return SQLITE_NOMEM;
188 }
189 for(i=0; i<n; i++){
190 /* TODO(shess) This needs expansion to handle UTF-8
191 ** case-insensitivity.
192 */
193 unsigned char ch = p[iStartOffset+i];
194 c->pToken[i] = (ch>='A' && ch<='Z') ? (ch - 'A' + 'a') : ch;
195 }
196 *ppToken = c->pToken;
197 *pnBytes = n;
198 *piStartOffset = iStartOffset;
199 *piEndOffset = c->iOffset;
200 *piPosition = c->iToken++;
201
202 return SQLITE_OK;
203 }
204 }
205 return SQLITE_DONE;
206 }
207
208 /*
209 ** The set of routines that implement the simple tokenizer
210 */
211 static const sqlite3_tokenizer_module simpleTokenizerModule = {
212 0,
213 simpleCreate,
214 simpleDestroy,
215 simpleOpen,
216 simpleClose,
217 simpleNext,
218 };
219
220 /*
221 ** Allocate a new simple tokenizer. Return a pointer to the new
222 ** tokenizer in *ppModule
223 */
sqlite3Fts2SimpleTokenizerModule(sqlite3_tokenizer_module const ** ppModule)224 void sqlite3Fts2SimpleTokenizerModule(
225 sqlite3_tokenizer_module const**ppModule
226 ){
227 *ppModule = &simpleTokenizerModule;
228 }
229
230 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2) */
231