4 ** The author disclaims copyright to this source code.
6 *************************************************************************
7 ** Defines the interface to tokenizers used by fulltext-search. There
8 ** are three basic components:
10 ** sqlite3_tokenizer_module is a singleton defining the tokenizer
11 ** interface functions. This is essentially the class structure for
14 ** sqlite3_tokenizer is used to define a particular tokenizer, perhaps
15 ** including customization information defined at creation time.
17 ** sqlite3_tokenizer_cursor is generated by a tokenizer to generate
18 ** tokens from a particular input.
20 #ifndef _FTS3_TOKENIZER_H_
21 #define _FTS3_TOKENIZER_H_
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.
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.
35 ** When an fts3 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 fts3 table (customized by the tokenizer clause arguments).
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
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;
52 struct sqlite3_tokenizer_module {
55 ** Structure version. Should always be set to 0.
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 fts3 table. For example, if
63 ** the following SQL is executed:
65 ** CREATE .. USING fts3( ... , tokenizer <tokenizer-name> arg1 arg2)
67 ** then argc is set to 2, and the argv[] array contains pointers
68 ** to the strings "arg1" and "arg2".
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.
77 int argc, /* Size of argv array */
78 const char *const*argv, /* Tokenizer argument strings */
79 sqlite3_tokenizer **ppTokenizer /* OUT: Created tokenizer */
83 ** Destroy an existing tokenizer. The fts3 module calls this method
84 ** exactly once for each successful call to xCreate().
86 int (*xDestroy)(sqlite3_tokenizer *pTokenizer);
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).
94 sqlite3_tokenizer *pTokenizer, /* Tokenizer object */
95 const char *pInput, int nBytes, /* Input buffer */
96 sqlite3_tokenizer_cursor **ppCursor /* OUT: Created tokenizer cursor */
100 ** Destroy an existing tokenizer cursor. The fts3 module calls this
101 ** method exactly once for each successful call to xOpen().
103 int (*xClose)(sqlite3_tokenizer_cursor *pCursor);
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.
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
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().
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.
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 */
135 struct sqlite3_tokenizer {
136 const sqlite3_tokenizer_module *pModule; /* The module for this tokenizer */
137 /* Tokenizer implementations will typically add additional fields */
140 struct sqlite3_tokenizer_cursor {
141 sqlite3_tokenizer *pTokenizer; /* Tokenizer for this cursor. */
142 /* Tokenizer implementations will typically add additional fields */
145 #endif /* _FTS3_TOKENIZER_H_ */