Annotation of embedaddon/sqlite3/ext/fts3/fts3_tokenizer.h, revision 1.1.1.1
1.1 misho 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 _FTS3_TOKENIZER_H_
21: #define _FTS3_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 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).
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 fts3 table. For example, if
63: ** the following SQL is executed:
64: **
65: ** CREATE .. USING fts3( ... , 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 fts3 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 fts3 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. *piStartOffset should be set to the index of the first
117: ** byte of the token in the input buffer. *piEndOffset should be set
118: ** to the index of the first byte just past the end of the token in
119: ** the input buffer.
120: **
121: ** The buffer *ppToken is set to point at is managed by the tokenizer
122: ** implementation. It is only required to be valid until the next call
123: ** to xNext() or xClose().
124: */
125: /* TODO(shess) current implementation requires pInput to be
126: ** nul-terminated. This should either be fixed, or pInput/nBytes
127: ** should be converted to zInput.
128: */
129: int (*xNext)(
130: sqlite3_tokenizer_cursor *pCursor, /* Tokenizer cursor */
131: const char **ppToken, int *pnBytes, /* OUT: Normalized text for token */
132: int *piStartOffset, /* OUT: Byte offset of token in input buffer */
133: int *piEndOffset, /* OUT: Byte offset of end of token in input buffer */
134: int *piPosition /* OUT: Number of tokens returned before this one */
135: );
136: };
137:
138: struct sqlite3_tokenizer {
139: const sqlite3_tokenizer_module *pModule; /* The module for this tokenizer */
140: /* Tokenizer implementations will typically add additional fields */
141: };
142:
143: struct sqlite3_tokenizer_cursor {
144: sqlite3_tokenizer *pTokenizer; /* Tokenizer for this cursor. */
145: /* Tokenizer implementations will typically add additional fields */
146: };
147:
148: int fts3_global_term_cnt(int iTerm, int iCol);
149: int fts3_term_cnt(int iTerm, int iCol);
150:
151:
152: #endif /* _FTS3_TOKENIZER_H_ */
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