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| 1 /* | |
| 2 ** 2013-02-28 | |
| 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 ** This file contains code to implement the next_char(A,T,F,W,C) SQL function. | |
| 14 ** | |
| 15 ** The next_char(A,T,F,W,C) function finds all valid "next" characters for | |
| 16 ** string A given the vocabulary in T.F. If the W value exists and is a | |
| 17 ** non-empty string, then it is an SQL expression that limits the entries | |
| 18 ** in T.F that will be considered. If C exists and is a non-empty string, | |
| 19 ** then it is the name of the collating sequence to use for comparison. If | |
| 20 ** | |
| 21 ** Only the first three arguments are required. If the C parameter is | |
| 22 ** omitted or is NULL or is an empty string, then the default collating | |
| 23 ** sequence of T.F is used for comparision. If the W parameter is omitted | |
| 24 ** or is NULL or is an empty string, then no filtering of the output is | |
| 25 ** done. | |
| 26 ** | |
| 27 ** The T.F column should be indexed using collation C or else this routine | |
| 28 ** will be quite slow. | |
| 29 ** | |
| 30 ** For example, suppose an application has a dictionary like this: | |
| 31 ** | |
| 32 ** CREATE TABLE dictionary(word TEXT UNIQUE); | |
| 33 ** | |
| 34 ** Further suppose that for user keypad entry, it is desired to disable | |
| 35 ** (gray out) keys that are not valid as the next character. If the | |
| 36 ** the user has previously entered (say) 'cha' then to find all allowed | |
| 37 ** next characters (and thereby determine when keys should not be grayed | |
| 38 ** out) run the following query: | |
| 39 ** | |
| 40 ** SELECT next_char('cha','dictionary','word'); | |
| 41 ** | |
| 42 ** IMPLEMENTATION NOTES: | |
| 43 ** | |
| 44 ** The next_char function is implemented using recursive SQL that makes | |
| 45 ** use of the table name and column name as part of a query. If either | |
| 46 ** the table name or column name are keywords or contain special characters, | |
| 47 ** then they should be escaped. For example: | |
| 48 ** | |
| 49 ** SELECT next_char('cha','[dictionary]','[word]'); | |
| 50 ** | |
| 51 ** This also means that the table name can be a subquery: | |
| 52 ** | |
| 53 ** SELECT next_char('cha','(SELECT word AS w FROM dictionary)','w'); | |
| 54 */ | |
| 55 #include "sqlite3ext.h" | |
| 56 SQLITE_EXTENSION_INIT1 | |
| 57 #include <string.h> | |
| 58 | |
| 59 /* | |
| 60 ** A structure to hold context of the next_char() computation across | |
| 61 ** nested function calls. | |
| 62 */ | |
| 63 typedef struct nextCharContext nextCharContext; | |
| 64 struct nextCharContext { | |
| 65 sqlite3 *db; /* Database connection */ | |
| 66 sqlite3_stmt *pStmt; /* Prepared statement used to query */ | |
| 67 const unsigned char *zPrefix; /* Prefix to scan */ | |
| 68 int nPrefix; /* Size of zPrefix in bytes */ | |
| 69 int nAlloc; /* Space allocated to aResult */ | |
| 70 int nUsed; /* Space used in aResult */ | |
| 71 unsigned int *aResult; /* Array of next characters */ | |
| 72 int mallocFailed; /* True if malloc fails */ | |
| 73 int otherError; /* True for any other failure */ | |
| 74 }; | |
| 75 | |
| 76 /* | |
| 77 ** Append a result character if the character is not already in the | |
| 78 ** result. | |
| 79 */ | |
| 80 static void nextCharAppend(nextCharContext *p, unsigned c){ | |
| 81 int i; | |
| 82 for(i=0; i<p->nUsed; i++){ | |
| 83 if( p->aResult[i]==c ) return; | |
| 84 } | |
| 85 if( p->nUsed+1 > p->nAlloc ){ | |
| 86 unsigned int *aNew; | |
| 87 int n = p->nAlloc*2 + 30; | |
| 88 aNew = sqlite3_realloc(p->aResult, n*sizeof(unsigned int)); | |
| 89 if( aNew==0 ){ | |
| 90 p->mallocFailed = 1; | |
| 91 return; | |
| 92 }else{ | |
| 93 p->aResult = aNew; | |
| 94 p->nAlloc = n; | |
| 95 } | |
| 96 } | |
| 97 p->aResult[p->nUsed++] = c; | |
| 98 } | |
| 99 | |
| 100 /* | |
| 101 ** Write a character into z[] as UTF8. Return the number of bytes needed | |
| 102 ** to hold the character | |
| 103 */ | |
| 104 static int writeUtf8(unsigned char *z, unsigned c){ | |
| 105 if( c<0x00080 ){ | |
| 106 z[0] = (unsigned char)(c&0xff); | |
| 107 return 1; | |
| 108 } | |
| 109 if( c<0x00800 ){ | |
| 110 z[0] = 0xC0 + (unsigned char)((c>>6)&0x1F); | |
| 111 z[1] = 0x80 + (unsigned char)(c & 0x3F); | |
| 112 return 2; | |
| 113 } | |
| 114 if( c<0x10000 ){ | |
| 115 z[0] = 0xE0 + (unsigned char)((c>>12)&0x0F); | |
| 116 z[1] = 0x80 + (unsigned char)((c>>6) & 0x3F); | |
| 117 z[2] = 0x80 + (unsigned char)(c & 0x3F); | |
| 118 return 3; | |
| 119 } | |
| 120 z[0] = 0xF0 + (unsigned char)((c>>18) & 0x07); | |
| 121 z[1] = 0x80 + (unsigned char)((c>>12) & 0x3F); | |
| 122 z[2] = 0x80 + (unsigned char)((c>>6) & 0x3F); | |
| 123 z[3] = 0x80 + (unsigned char)(c & 0x3F); | |
| 124 return 4; | |
| 125 } | |
| 126 | |
| 127 /* | |
| 128 ** Read a UTF8 character out of z[] and write it into *pOut. Return | |
| 129 ** the number of bytes in z[] that were used to construct the character. | |
| 130 */ | |
| 131 static int readUtf8(const unsigned char *z, unsigned *pOut){ | |
| 132 static const unsigned char validBits[] = { | |
| 133 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, | |
| 134 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, | |
| 135 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, | |
| 136 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, | |
| 137 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, | |
| 138 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, | |
| 139 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, | |
| 140 0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00, | |
| 141 }; | |
| 142 unsigned c = z[0]; | |
| 143 if( c<0xc0 ){ | |
| 144 *pOut = c; | |
| 145 return 1; | |
| 146 }else{ | |
| 147 int n = 1; | |
| 148 c = validBits[c-0xc0]; | |
| 149 while( (z[n] & 0xc0)==0x80 ){ | |
| 150 c = (c<<6) + (0x3f & z[n++]); | |
| 151 } | |
| 152 if( c<0x80 || (c&0xFFFFF800)==0xD800 || (c&0xFFFFFFFE)==0xFFFE ){ | |
| 153 c = 0xFFFD; | |
| 154 } | |
| 155 *pOut = c; | |
| 156 return n; | |
| 157 } | |
| 158 } | |
| 159 | |
| 160 /* | |
| 161 ** The nextCharContext structure has been set up. Add all "next" characters | |
| 162 ** to the result set. | |
| 163 */ | |
| 164 static void findNextChars(nextCharContext *p){ | |
| 165 unsigned cPrev = 0; | |
| 166 unsigned char zPrev[8]; | |
| 167 int n, rc; | |
| 168 | |
| 169 for(;;){ | |
| 170 sqlite3_bind_text(p->pStmt, 1, (char*)p->zPrefix, p->nPrefix, | |
| 171 SQLITE_STATIC); | |
| 172 n = writeUtf8(zPrev, cPrev+1); | |
| 173 sqlite3_bind_text(p->pStmt, 2, (char*)zPrev, n, SQLITE_STATIC); | |
| 174 rc = sqlite3_step(p->pStmt); | |
| 175 if( rc==SQLITE_DONE ){ | |
| 176 sqlite3_reset(p->pStmt); | |
| 177 return; | |
| 178 }else if( rc!=SQLITE_ROW ){ | |
| 179 p->otherError = rc; | |
| 180 return; | |
| 181 }else{ | |
| 182 const unsigned char *zOut = sqlite3_column_text(p->pStmt, 0); | |
| 183 unsigned cNext; | |
| 184 n = readUtf8(zOut+p->nPrefix, &cNext); | |
| 185 sqlite3_reset(p->pStmt); | |
| 186 nextCharAppend(p, cNext); | |
| 187 cPrev = cNext; | |
| 188 if( p->mallocFailed ) return; | |
| 189 } | |
| 190 } | |
| 191 } | |
| 192 | |
| 193 | |
| 194 /* | |
| 195 ** next_character(A,T,F,W) | |
| 196 ** | |
| 197 ** Return a string composted of all next possible characters after | |
| 198 ** A for elements of T.F. If W is supplied, then it is an SQL expression | |
| 199 ** that limits the elements in T.F that are considered. | |
| 200 */ | |
| 201 static void nextCharFunc( | |
| 202 sqlite3_context *context, | |
| 203 int argc, | |
| 204 sqlite3_value **argv | |
| 205 ){ | |
| 206 nextCharContext c; | |
| 207 const unsigned char *zTable = sqlite3_value_text(argv[1]); | |
| 208 const unsigned char *zField = sqlite3_value_text(argv[2]); | |
| 209 const unsigned char *zWhere; | |
| 210 const unsigned char *zCollName; | |
| 211 char *zWhereClause = 0; | |
| 212 char *zColl = 0; | |
| 213 char *zSql; | |
| 214 int rc; | |
| 215 | |
| 216 memset(&c, 0, sizeof(c)); | |
| 217 c.db = sqlite3_context_db_handle(context); | |
| 218 c.zPrefix = sqlite3_value_text(argv[0]); | |
| 219 c.nPrefix = sqlite3_value_bytes(argv[0]); | |
| 220 if( zTable==0 || zField==0 || c.zPrefix==0 ) return; | |
| 221 if( argc>=4 | |
| 222 && (zWhere = sqlite3_value_text(argv[3]))!=0 | |
| 223 && zWhere[0]!=0 | |
| 224 ){ | |
| 225 zWhereClause = sqlite3_mprintf("AND (%s)", zWhere); | |
| 226 if( zWhereClause==0 ){ | |
| 227 sqlite3_result_error_nomem(context); | |
| 228 return; | |
| 229 } | |
| 230 }else{ | |
| 231 zWhereClause = ""; | |
| 232 } | |
| 233 if( argc>=5 | |
| 234 && (zCollName = sqlite3_value_text(argv[4]))!=0 | |
| 235 && zCollName[0]!=0 | |
| 236 ){ | |
| 237 zColl = sqlite3_mprintf("collate \"%w\"", zCollName); | |
| 238 if( zColl==0 ){ | |
| 239 sqlite3_result_error_nomem(context); | |
| 240 if( zWhereClause[0] ) sqlite3_free(zWhereClause); | |
| 241 return; | |
| 242 } | |
| 243 }else{ | |
| 244 zColl = ""; | |
| 245 } | |
| 246 zSql = sqlite3_mprintf( | |
| 247 "SELECT %s FROM %s" | |
| 248 " WHERE %s>=(?1 || ?2) %s" | |
| 249 " AND %s<=(?1 || char(1114111)) %s" /* 1114111 == 0x10ffff */ | |
| 250 " %s" | |
| 251 " ORDER BY 1 %s ASC LIMIT 1", | |
| 252 zField, zTable, zField, zColl, zField, zColl, zWhereClause, zColl | |
| 253 ); | |
| 254 if( zWhereClause[0] ) sqlite3_free(zWhereClause); | |
| 255 if( zColl[0] ) sqlite3_free(zColl); | |
| 256 if( zSql==0 ){ | |
| 257 sqlite3_result_error_nomem(context); | |
| 258 return; | |
| 259 } | |
| 260 | |
| 261 rc = sqlite3_prepare_v2(c.db, zSql, -1, &c.pStmt, 0); | |
| 262 sqlite3_free(zSql); | |
| 263 if( rc ){ | |
| 264 sqlite3_result_error(context, sqlite3_errmsg(c.db), -1); | |
| 265 return; | |
| 266 } | |
| 267 findNextChars(&c); | |
| 268 if( c.mallocFailed ){ | |
| 269 sqlite3_result_error_nomem(context); | |
| 270 }else{ | |
| 271 unsigned char *pRes; | |
| 272 pRes = sqlite3_malloc( c.nUsed*4 + 1 ); | |
| 273 if( pRes==0 ){ | |
| 274 sqlite3_result_error_nomem(context); | |
| 275 }else{ | |
| 276 int i; | |
| 277 int n = 0; | |
| 278 for(i=0; i<c.nUsed; i++){ | |
| 279 n += writeUtf8(pRes+n, c.aResult[i]); | |
| 280 } | |
| 281 pRes[n] = 0; | |
| 282 sqlite3_result_text(context, (const char*)pRes, n, sqlite3_free); | |
| 283 } | |
| 284 } | |
| 285 sqlite3_finalize(c.pStmt); | |
| 286 sqlite3_free(c.aResult); | |
| 287 } | |
| 288 | |
| 289 #ifdef _WIN32 | |
| 290 __declspec(dllexport) | |
| 291 #endif | |
| 292 int sqlite3_nextchar_init( | |
| 293 sqlite3 *db, | |
| 294 char **pzErrMsg, | |
| 295 const sqlite3_api_routines *pApi | |
| 296 ){ | |
| 297 int rc = SQLITE_OK; | |
| 298 SQLITE_EXTENSION_INIT2(pApi); | |
| 299 (void)pzErrMsg; /* Unused parameter */ | |
| 300 rc = sqlite3_create_function(db, "next_char", 3, SQLITE_UTF8, 0, | |
| 301 nextCharFunc, 0, 0); | |
| 302 if( rc==SQLITE_OK ){ | |
| 303 rc = sqlite3_create_function(db, "next_char", 4, SQLITE_UTF8, 0, | |
| 304 nextCharFunc, 0, 0); | |
| 305 } | |
| 306 if( rc==SQLITE_OK ){ | |
| 307 rc = sqlite3_create_function(db, "next_char", 5, SQLITE_UTF8, 0, | |
| 308 nextCharFunc, 0, 0); | |
| 309 } | |
| 310 return rc; | |
| 311 } | |
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Chromium Code Reviews
Issue 2363173002:
[sqlite] Remove obsolete reference version 3.8.7.4. (Closed)
