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Diffstat (limited to 'fts3_tokenizer.h')
| -rw-r--r-- | fts3_tokenizer.h | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/fts3_tokenizer.h b/fts3_tokenizer.h new file mode 100644 index 0000000..708ea38 --- /dev/null +++ b/fts3_tokenizer.h @@ -0,0 +1,163 @@ +/************** Begin file fts3_tokenizer.h **********************************/ +/* +** 2006 July 10 +** +** The author disclaims copyright to this source code. +** +************************************************************************* +** Defines the interface to tokenizers used by fulltext-search. There +** are three basic components: +** +** sqlite3_tokenizer_module is a singleton defining the tokenizer +** interface functions. This is essentially the class structure for +** tokenizers. +** +** sqlite3_tokenizer is used to define a particular tokenizer, perhaps +** including customization information defined at creation time. +** +** sqlite3_tokenizer_cursor is generated by a tokenizer to generate +** tokens from a particular input. +*/ +#ifndef _FTS3_TOKENIZER_H_ +#define _FTS3_TOKENIZER_H_ + +/* TODO(shess) Only used for SQLITE_OK and SQLITE_DONE at this time. +** If tokenizers are to be allowed to call sqlite3_*() functions, then +** we will need a way to register the API consistently. +*/ + +/* +** Structures used by the tokenizer interface. When a new tokenizer +** implementation is registered, the caller provides a pointer to +** an sqlite3_tokenizer_module containing pointers to the callback +** functions that make up an implementation. +** +** When an fts3 table is created, it passes any arguments passed to +** the tokenizer clause of the CREATE VIRTUAL TABLE statement to the +** sqlite3_tokenizer_module.xCreate() function of the requested tokenizer +** implementation. The xCreate() function in turn returns an +** sqlite3_tokenizer structure representing the specific tokenizer to +** be used for the fts3 table (customized by the tokenizer clause arguments). +** +** To tokenize an input buffer, the sqlite3_tokenizer_module.xOpen() +** method is called. It returns an sqlite3_tokenizer_cursor object +** that may be used to tokenize a specific input buffer based on +** the tokenization rules supplied by a specific sqlite3_tokenizer +** object. +*/ +typedef struct sqlite3_tokenizer_module sqlite3_tokenizer_module; +typedef struct sqlite3_tokenizer sqlite3_tokenizer; +typedef struct sqlite3_tokenizer_cursor sqlite3_tokenizer_cursor; + +struct sqlite3_tokenizer_module { + + /* + ** Structure version. Should always be set to 0 or 1. + */ + int iVersion; + + /* + ** Create a new tokenizer. The values in the argv[] array are the + ** arguments passed to the "tokenizer" clause of the CREATE VIRTUAL + ** TABLE statement that created the fts3 table. For example, if + ** the following SQL is executed: + ** + ** CREATE .. USING fts3( ... , tokenizer <tokenizer-name> arg1 arg2) + ** + ** then argc is set to 2, and the argv[] array contains pointers + ** to the strings "arg1" and "arg2". + ** + ** This method should return either SQLITE_OK (0), or an SQLite error + ** code. If SQLITE_OK is returned, then *ppTokenizer should be set + ** to point at the newly created tokenizer structure. The generic + ** sqlite3_tokenizer.pModule variable should not be initialised by + ** this callback. The caller will do so. + */ + int (*xCreate)( + int argc, /* Size of argv array */ + const char *const*argv, /* Tokenizer argument strings */ + sqlite3_tokenizer **ppTokenizer /* OUT: Created tokenizer */ + ); + + /* + ** Destroy an existing tokenizer. The fts3 module calls this method + ** exactly once for each successful call to xCreate(). + */ + int (*xDestroy)(sqlite3_tokenizer *pTokenizer); + + /* + ** Create a tokenizer cursor to tokenize an input buffer. The caller + ** is responsible for ensuring that the input buffer remains valid + ** until the cursor is closed (using the xClose() method). + */ + int (*xOpen)( + sqlite3_tokenizer *pTokenizer, /* Tokenizer object */ + const char *pInput, int nBytes, /* Input buffer */ + sqlite3_tokenizer_cursor **ppCursor /* OUT: Created tokenizer cursor */ + ); + + /* + ** Destroy an existing tokenizer cursor. The fts3 module calls this + ** method exactly once for each successful call to xOpen(). + */ + int (*xClose)(sqlite3_tokenizer_cursor *pCursor); + + /* + ** Retrieve the next token from the tokenizer cursor pCursor. This + ** method should either return SQLITE_OK and set the values of the + ** "OUT" variables identified below, or SQLITE_DONE to indicate that + ** the end of the buffer has been reached, or an SQLite error code. + ** + ** *ppToken should be set to point at a buffer containing the + ** normalized version of the token (i.e. after any case-folding and/or + ** stemming has been performed). *pnBytes should be set to the length + ** of this buffer in bytes. The input text that generated the token is + ** identified by the byte offsets returned in *piStartOffset and + ** *piEndOffset. *piStartOffset should be set to the index of the first + ** byte of the token in the input buffer. *piEndOffset should be set + ** to the index of the first byte just past the end of the token in + ** the input buffer. + ** + ** The buffer *ppToken is set to point at is managed by the tokenizer + ** implementation. It is only required to be valid until the next call + ** to xNext() or xClose(). + */ + /* TODO(shess) current implementation requires pInput to be + ** nul-terminated. This should either be fixed, or pInput/nBytes + ** should be converted to zInput. + */ + int (*xNext)( + sqlite3_tokenizer_cursor *pCursor, /* Tokenizer cursor */ + const char **ppToken, int *pnBytes, /* OUT: Normalized text for token */ + int *piStartOffset, /* OUT: Byte offset of token in input buffer */ + int *piEndOffset, /* OUT: Byte offset of end of token in input buffer */ + int *piPosition /* OUT: Number of tokens returned before this one */ + ); + + /*********************************************************************** + ** Methods below this point are only available if iVersion>=1. + */ + + /* + ** Configure the language id of a tokenizer cursor. + */ + int (*xLanguageid)(sqlite3_tokenizer_cursor *pCsr, int iLangid); +}; + +struct sqlite3_tokenizer { + const sqlite3_tokenizer_module *pModule; /* The module for this tokenizer */ + /* Tokenizer implementations will typically add additional fields */ +}; + +struct sqlite3_tokenizer_cursor { + sqlite3_tokenizer *pTokenizer; /* Tokenizer for this cursor. */ + /* Tokenizer implementations will typically add additional fields */ +}; + +int fts3_global_term_cnt(int iTerm, int iCol); +int fts3_term_cnt(int iTerm, int iCol); + + +#endif /* _FTS3_TOKENIZER_H_ */ + +/************** End of fts3_tokenizer.h **************************************/ |