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| 1 /* |
| 2 ** 2006 July 10 |
| 3 ** |
| 4 ** The author disclaims copyright to this source code. |
| 5 ** |
| 6 ************************************************************************* |
| 7 ** Defines the interface to tokenizers used by fulltext-search. There |
| 8 ** are three basic components: |
| 9 ** |
| 10 ** sqlite3_tokenizer_module is a singleton defining the tokenizer |
| 11 ** interface functions. This is essentially the class structure for |
| 12 ** tokenizers. |
| 13 ** |
| 14 ** sqlite3_tokenizer is used to define a particular tokenizer, perhaps |
| 15 ** including customization information defined at creation time. |
| 16 ** |
| 17 ** sqlite3_tokenizer_cursor is generated by a tokenizer to generate |
| 18 ** tokens from a particular input. |
| 19 */ |
| 20 #ifndef _FTS2_TOKENIZER_H_ |
| 21 #define _FTS2_TOKENIZER_H_ |
| 22 |
| 23 /* TODO(shess) Only used for SQLITE_OK and SQLITE_DONE at this time. |
| 24 ** If tokenizers are to be allowed to call sqlite3_*() functions, then |
| 25 ** we will need a way to register the API consistently. |
| 26 */ |
| 27 #include "sqlite3.h" |
| 28 |
| 29 /* |
| 30 ** Structures used by the tokenizer interface. When a new tokenizer |
| 31 ** implementation is registered, the caller provides a pointer to |
| 32 ** an sqlite3_tokenizer_module containing pointers to the callback |
| 33 ** functions that make up an implementation. |
| 34 ** |
| 35 ** When an fts2 table is created, it passes any arguments passed to |
| 36 ** the tokenizer clause of the CREATE VIRTUAL TABLE statement to the |
| 37 ** sqlite3_tokenizer_module.xCreate() function of the requested tokenizer |
| 38 ** implementation. The xCreate() function in turn returns an |
| 39 ** sqlite3_tokenizer structure representing the specific tokenizer to |
| 40 ** be used for the fts2 table (customized by the tokenizer clause arguments). |
| 41 ** |
| 42 ** To tokenize an input buffer, the sqlite3_tokenizer_module.xOpen() |
| 43 ** method is called. It returns an sqlite3_tokenizer_cursor object |
| 44 ** that may be used to tokenize a specific input buffer based on |
| 45 ** the tokenization rules supplied by a specific sqlite3_tokenizer |
| 46 ** object. |
| 47 */ |
| 48 typedef struct sqlite3_tokenizer_module sqlite3_tokenizer_module; |
| 49 typedef struct sqlite3_tokenizer sqlite3_tokenizer; |
| 50 typedef struct sqlite3_tokenizer_cursor sqlite3_tokenizer_cursor; |
| 51 |
| 52 struct sqlite3_tokenizer_module { |
| 53 |
| 54 /* |
| 55 ** Structure version. Should always be set to 0. |
| 56 */ |
| 57 int iVersion; |
| 58 |
| 59 /* |
| 60 ** Create a new tokenizer. The values in the argv[] array are the |
| 61 ** arguments passed to the "tokenizer" clause of the CREATE VIRTUAL |
| 62 ** TABLE statement that created the fts2 table. For example, if |
| 63 ** the following SQL is executed: |
| 64 ** |
| 65 ** CREATE .. USING fts2( ... , tokenizer <tokenizer-name> arg1 arg2) |
| 66 ** |
| 67 ** then argc is set to 2, and the argv[] array contains pointers |
| 68 ** to the strings "arg1" and "arg2". |
| 69 ** |
| 70 ** This method should return either SQLITE_OK (0), or an SQLite error |
| 71 ** code. If SQLITE_OK is returned, then *ppTokenizer should be set |
| 72 ** to point at the newly created tokenizer structure. The generic |
| 73 ** sqlite3_tokenizer.pModule variable should not be initialised by |
| 74 ** this callback. The caller will do so. |
| 75 */ |
| 76 int (*xCreate)( |
| 77 int argc, /* Size of argv array */ |
| 78 const char *const*argv, /* Tokenizer argument strings */ |
| 79 sqlite3_tokenizer **ppTokenizer /* OUT: Created tokenizer */ |
| 80 ); |
| 81 |
| 82 /* |
| 83 ** Destroy an existing tokenizer. The fts2 module calls this method |
| 84 ** exactly once for each successful call to xCreate(). |
| 85 */ |
| 86 int (*xDestroy)(sqlite3_tokenizer *pTokenizer); |
| 87 |
| 88 /* |
| 89 ** Create a tokenizer cursor to tokenize an input buffer. The caller |
| 90 ** is responsible for ensuring that the input buffer remains valid |
| 91 ** until the cursor is closed (using the xClose() method). |
| 92 */ |
| 93 int (*xOpen)( |
| 94 sqlite3_tokenizer *pTokenizer, /* Tokenizer object */ |
| 95 const char *pInput, int nBytes, /* Input buffer */ |
| 96 sqlite3_tokenizer_cursor **ppCursor /* OUT: Created tokenizer cursor */ |
| 97 ); |
| 98 |
| 99 /* |
| 100 ** Destroy an existing tokenizer cursor. The fts2 module calls this |
| 101 ** method exactly once for each successful call to xOpen(). |
| 102 */ |
| 103 int (*xClose)(sqlite3_tokenizer_cursor *pCursor); |
| 104 |
| 105 /* |
| 106 ** Retrieve the next token from the tokenizer cursor pCursor. This |
| 107 ** method should either return SQLITE_OK and set the values of the |
| 108 ** "OUT" variables identified below, or SQLITE_DONE to indicate that |
| 109 ** the end of the buffer has been reached, or an SQLite error code. |
| 110 ** |
| 111 ** *ppToken should be set to point at a buffer containing the |
| 112 ** normalized version of the token (i.e. after any case-folding and/or |
| 113 ** stemming has been performed). *pnBytes should be set to the length |
| 114 ** of this buffer in bytes. The input text that generated the token is |
| 115 ** identified by the byte offsets returned in *piStartOffset and |
| 116 ** *piEndOffset. |
| 117 ** |
| 118 ** The buffer *ppToken is set to point at is managed by the tokenizer |
| 119 ** implementation. It is only required to be valid until the next call |
| 120 ** to xNext() or xClose(). |
| 121 */ |
| 122 /* TODO(shess) current implementation requires pInput to be |
| 123 ** nul-terminated. This should either be fixed, or pInput/nBytes |
| 124 ** should be converted to zInput. |
| 125 */ |
| 126 int (*xNext)( |
| 127 sqlite3_tokenizer_cursor *pCursor, /* Tokenizer cursor */ |
| 128 const char **ppToken, int *pnBytes, /* OUT: Normalized text for token */ |
| 129 int *piStartOffset, /* OUT: Byte offset of token in input buffer */ |
| 130 int *piEndOffset, /* OUT: Byte offset of end of token in input buffer */ |
| 131 int *piPosition /* OUT: Number of tokens returned before this one */ |
| 132 ); |
| 133 }; |
| 134 |
| 135 struct sqlite3_tokenizer { |
| 136 const sqlite3_tokenizer_module *pModule; /* The module for this tokenizer */ |
| 137 /* Tokenizer implementations will typically add additional fields */ |
| 138 }; |
| 139 |
| 140 struct sqlite3_tokenizer_cursor { |
| 141 sqlite3_tokenizer *pTokenizer; /* Tokenizer for this cursor. */ |
| 142 /* Tokenizer implementations will typically add additional fields */ |
| 143 }; |
| 144 |
| 145 #endif /* _FTS2_TOKENIZER_H_ */ |
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