ext/fts3/fts3_tokenizer1.c

   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 FTS3 module is being built as an extension
  20 **       (in which case SQLITE_CORE is not defined), or
  21 **
  22 **     * The FTS3 module is being built into the core of
  23 **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
  24 */
  25 #include "fts3Int.h"
  26 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
  27
  28 #include <assert.h>
  29 #include <stdlib.h>
  30 #include <stdio.h>
  31 #include <string.h>
  32
  33 #include "fts3_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 static int simpleDelim(simple_tokenizer *t, unsigned char c){
  52   return c<0x80 && t->delim[c];
  53 }
  54 static int fts3_isalnum(int x){
  55   return (x>='0' && x<='9') || (x>='A' && x<='Z') || (x>='a' && x<='z');
  56 }
  57
  58 /*
  59 ** Create a new tokenizer instance.
  60 */
  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 = (int)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] = !fts3_isalnum(i) ? -1 : 0;
  92     }
  93   }
  94
  95   *ppTokenizer = &t->base;
  96   return SQLITE_OK;
  97 }
  98
  99 /*
 100 ** Destroy a tokenizer
 101 */
 102 static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
 103   sqlite3_free(pTokenizer);
 104   return SQLITE_OK;
 105 }
 106
 107 /*
 108 ** Prepare to begin tokenizing a particular string.  The input
 109 ** string to be tokenized is pInput[0..nBytes-1].  A cursor
 110 ** used to incrementally tokenize this string is returned in
 111 ** *ppCursor.
 112 */
 113 static int simpleOpen(
 114   sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
 115   const char *pInput, int nBytes,        /* String to be tokenized */
 116   sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
 117 ){
 118   simple_tokenizer_cursor *c;
 119
 120   UNUSED_PARAMETER(pTokenizer);
 121
 122   c = (simple_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
 123   if( c==NULL ) return SQLITE_NOMEM;
 124
 125   c->pInput = pInput;
 126   if( pInput==0 ){
 127     c->nBytes = 0;
 128   }else if( nBytes<0 ){
 129     c->nBytes = (int)strlen(pInput);
 130   }else{
 131     c->nBytes = nBytes;
 132   }
 133   c->iOffset = 0;                 /* start tokenizing at the beginning */
 134   c->iToken = 0;
 135   c->pToken = NULL;               /* no space allocated, yet. */
 136   c->nTokenAllocated = 0;
 137
 138   *ppCursor = &c->base;
 139   return SQLITE_OK;
 140 }
 141
 142 /*
 143 ** Close a tokenization cursor previously opened by a call to
 144 ** simpleOpen() above.
 145 */
 146 static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
 147   simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
 148   sqlite3_free(c->pToken);
 149   sqlite3_free(c);
 150   return SQLITE_OK;
 151 }
 152
 153 /*
 154 ** Extract the next token from a tokenization cursor.  The cursor must
 155 ** have been opened by a prior call to simpleOpen().
 156 */
 157 static int simpleNext(
 158   sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
 159   const char **ppToken,               /* OUT: *ppToken is the token text */
 160   int *pnBytes,                       /* OUT: Number of bytes in token */
 161   int *piStartOffset,                 /* OUT: Starting offset of token */
 162   int *piEndOffset,                   /* OUT: Ending offset of token */
 163   int *piPosition                     /* OUT: Position integer of token */
 164 ){
 165   simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
 166   simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
 167   unsigned char *p = (unsigned char *)c->pInput;
 168
 169   while( c->iOffset<c->nBytes ){
 170     int iStartOffset;
 171
 172     /* Scan past delimiter characters */
 173     while( c->iOffset<c->nBytes && simpleDelim(t, p[c->iOffset]) ){
 174       c->iOffset++;
 175     }
 176
 177     /* Count non-delimiter characters. */
 178     iStartOffset = c->iOffset;
 179     while( c->iOffset<c->nBytes && !simpleDelim(t, p[c->iOffset]) ){
 180       c->iOffset++;
 181     }
 182
 183     if( c->iOffset>iStartOffset ){
 184       int i, n = c->iOffset-iStartOffset;
 185       if( n>c->nTokenAllocated ){
 186         char *pNew;
 187         c->nTokenAllocated = n+20;
 188         pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
 189         if( !pNew ) return SQLITE_NOMEM;
 190         c->pToken = pNew;
 191       }
 192       for(i=0; i<n; i++){
 193         /* TODO(shess) This needs expansion to handle UTF-8
 194         ** case-insensitivity.
 195         */
 196         unsigned char ch = p[iStartOffset+i];
 197         c->pToken[i] = (char)((ch>='A' && ch<='Z') ? ch-'A'+'a' : ch);
 198       }
 199       *ppToken = c->pToken;
 200       *pnBytes = n;
 201       *piStartOffset = iStartOffset;
 202       *piEndOffset = c->iOffset;
 203       *piPosition = c->iToken++;
 204
 205       return SQLITE_OK;
 206     }
 207   }
 208   return SQLITE_DONE;
 209 }
 210
 211 /*
 212 ** The set of routines that implement the simple tokenizer
 213 */
 214 static const sqlite3_tokenizer_module simpleTokenizerModule = {
 215   0,
 216   simpleCreate,
 217   simpleDestroy,
 218   simpleOpen,
 219   simpleClose,
 220   simpleNext,
 221   0,
 222 };
 223
 224 /*
 225 ** Allocate a new simple tokenizer.  Return a pointer to the new
 226 ** tokenizer in *ppModule
 227 */
 228 void sqlite3Fts3SimpleTokenizerModule(
 229   sqlite3_tokenizer_module const**ppModule
 230 ){
 231   *ppModule = &simpleTokenizerModule;
 232 }
 233
 234 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */