1/*
2** The author disclaims copyright to this source code.
3**
4*************************************************************************
5** Implementation of the "simple" full-text-search tokenizer.
6*/
7
8/*
9** The code in this file is only compiled if:
10**
11**     * The FTS1 module is being built as an extension
12**       (in which case SQLITE_CORE is not defined), or
13**
14**     * The FTS1 module is being built into the core of
15**       SQLite (in which case SQLITE_ENABLE_FTS1 is defined).
16*/
17#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1)
18
19
20#include <assert.h>
21#include <stdlib.h>
22#include <stdio.h>
23#include <string.h>
24#include <ctype.h>
25
26#include "fts1_tokenizer.h"
27
28typedef struct simple_tokenizer {
29  sqlite3_tokenizer base;
30  char delim[128];             /* flag ASCII delimiters */
31} simple_tokenizer;
32
33typedef struct simple_tokenizer_cursor {
34  sqlite3_tokenizer_cursor base;
35  const char *pInput;          /* input we are tokenizing */
36  int nBytes;                  /* size of the input */
37  int iOffset;                 /* current position in pInput */
38  int iToken;                  /* index of next token to be returned */
39  char *pToken;                /* storage for current token */
40  int nTokenAllocated;         /* space allocated to zToken buffer */
41} simple_tokenizer_cursor;
42
43
44/* Forward declaration */
45static const sqlite3_tokenizer_module simpleTokenizerModule;
46
47static int isDelim(simple_tokenizer *t, unsigned char c){
48  return c<0x80 && t->delim[c];
49}
50
51/*
52** Create a new tokenizer instance.
53*/
54static int simpleCreate(
55  int argc, const char * const *argv,
56  sqlite3_tokenizer **ppTokenizer
57){
58  simple_tokenizer *t;
59
60  t = (simple_tokenizer *) calloc(sizeof(*t), 1);
61  if( t==NULL ) return SQLITE_NOMEM;
62
63  /* TODO(shess) Delimiters need to remain the same from run to run,
64  ** else we need to reindex.  One solution would be a meta-table to
65  ** track such information in the database, then we'd only want this
66  ** information on the initial create.
67  */
68  if( argc>1 ){
69    int i, n = strlen(argv[1]);
70    for(i=0; i<n; i++){
71      unsigned char ch = argv[1][i];
72      /* We explicitly don't support UTF-8 delimiters for now. */
73      if( ch>=0x80 ){
74        free(t);
75        return SQLITE_ERROR;
76      }
77      t->delim[ch] = 1;
78    }
79  } else {
80    /* Mark non-alphanumeric ASCII characters as delimiters */
81    int i;
82    for(i=1; i<0x80; i++){
83      t->delim[i] = !isalnum(i);
84    }
85  }
86
87  *ppTokenizer = &t->base;
88  return SQLITE_OK;
89}
90
91/*
92** Destroy a tokenizer
93*/
94static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
95  free(pTokenizer);
96  return SQLITE_OK;
97}
98
99/*
100** Prepare to begin tokenizing a particular string.  The input
101** string to be tokenized is pInput[0..nBytes-1].  A cursor
102** used to incrementally tokenize this string is returned in
103** *ppCursor.
104*/
105static int simpleOpen(
106  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
107  const char *pInput, int nBytes,        /* String to be tokenized */
108  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
109){
110  simple_tokenizer_cursor *c;
111
112  c = (simple_tokenizer_cursor *) malloc(sizeof(*c));
113  if( c==NULL ) return SQLITE_NOMEM;
114
115  c->pInput = pInput;
116  if( pInput==0 ){
117    c->nBytes = 0;
118  }else if( nBytes<0 ){
119    c->nBytes = (int)strlen(pInput);
120  }else{
121    c->nBytes = nBytes;
122  }
123  c->iOffset = 0;                 /* start tokenizing at the beginning */
124  c->iToken = 0;
125  c->pToken = NULL;               /* no space allocated, yet. */
126  c->nTokenAllocated = 0;
127
128  *ppCursor = &c->base;
129  return SQLITE_OK;
130}
131
132/*
133** Close a tokenization cursor previously opened by a call to
134** simpleOpen() above.
135*/
136static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
137  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
138  free(c->pToken);
139  free(c);
140  return SQLITE_OK;
141}
142
143/*
144** Extract the next token from a tokenization cursor.  The cursor must
145** have been opened by a prior call to simpleOpen().
146*/
147static int simpleNext(
148  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
149  const char **ppToken,               /* OUT: *ppToken is the token text */
150  int *pnBytes,                       /* OUT: Number of bytes in token */
151  int *piStartOffset,                 /* OUT: Starting offset of token */
152  int *piEndOffset,                   /* OUT: Ending offset of token */
153  int *piPosition                     /* OUT: Position integer of token */
154){
155  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
156  simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
157  unsigned char *p = (unsigned char *)c->pInput;
158
159  while( c->iOffset<c->nBytes ){
160    int iStartOffset;
161
162    /* Scan past delimiter characters */
163    while( c->iOffset<c->nBytes && isDelim(t, p[c->iOffset]) ){
164      c->iOffset++;
165    }
166
167    /* Count non-delimiter characters. */
168    iStartOffset = c->iOffset;
169    while( c->iOffset<c->nBytes && !isDelim(t, p[c->iOffset]) ){
170      c->iOffset++;
171    }
172
173    if( c->iOffset>iStartOffset ){
174      int i, n = c->iOffset-iStartOffset;
175      if( n>c->nTokenAllocated ){
176        c->nTokenAllocated = n+20;
177        c->pToken = realloc(c->pToken, c->nTokenAllocated);
178        if( c->pToken==NULL ) return SQLITE_NOMEM;
179      }
180      for(i=0; i<n; i++){
181        /* TODO(shess) This needs expansion to handle UTF-8
182        ** case-insensitivity.
183        */
184        unsigned char ch = p[iStartOffset+i];
185        c->pToken[i] = ch<0x80 ? tolower(ch) : ch;
186      }
187      *ppToken = c->pToken;
188      *pnBytes = n;
189      *piStartOffset = iStartOffset;
190      *piEndOffset = c->iOffset;
191      *piPosition = c->iToken++;
192
193      return SQLITE_OK;
194    }
195  }
196  return SQLITE_DONE;
197}
198
199/*
200** The set of routines that implement the simple tokenizer
201*/
202static const sqlite3_tokenizer_module simpleTokenizerModule = {
203  0,
204  simpleCreate,
205  simpleDestroy,
206  simpleOpen,
207  simpleClose,
208  simpleNext,
209};
210
211/*
212** Allocate a new simple tokenizer.  Return a pointer to the new
213** tokenizer in *ppModule
214*/
215void sqlite3Fts1SimpleTokenizerModule(
216  sqlite3_tokenizer_module const**ppModule
217){
218  *ppModule = &simpleTokenizerModule;
219}
220
221#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1) */
222