146 lines
5.7 KiB
C
146 lines
5.7 KiB
C
/*
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** 2006 July 10
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**
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** The author disclaims copyright to this source code.
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**
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*************************************************************************
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** Defines the interface to tokenizers used by fulltext-search. There
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** are three basic components:
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**
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** sqlite3_tokenizer_module is a singleton defining the tokenizer
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** interface functions. This is essentially the class structure for
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** tokenizers.
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**
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** sqlite3_tokenizer is used to define a particular tokenizer, perhaps
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** including customization information defined at creation time.
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**
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** sqlite3_tokenizer_cursor is generated by a tokenizer to generate
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** tokens from a particular input.
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*/
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#ifndef _FTS2_TOKENIZER_H_
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#define _FTS2_TOKENIZER_H_
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/* TODO(shess) Only used for SQLITE_OK and SQLITE_DONE at this time.
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** If tokenizers are to be allowed to call sqlite3_*() functions, then
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** we will need a way to register the API consistently.
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*/
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#include "sqlite3.h"
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/*
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** Structures used by the tokenizer interface. When a new tokenizer
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** implementation is registered, the caller provides a pointer to
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** an sqlite3_tokenizer_module containing pointers to the callback
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** functions that make up an implementation.
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**
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** When an fts2 table is created, it passes any arguments passed to
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** the tokenizer clause of the CREATE VIRTUAL TABLE statement to the
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** sqlite3_tokenizer_module.xCreate() function of the requested tokenizer
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** implementation. The xCreate() function in turn returns an
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** sqlite3_tokenizer structure representing the specific tokenizer to
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** be used for the fts2 table (customized by the tokenizer clause arguments).
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**
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** To tokenize an input buffer, the sqlite3_tokenizer_module.xOpen()
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** method is called. It returns an sqlite3_tokenizer_cursor object
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** that may be used to tokenize a specific input buffer based on
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** the tokenization rules supplied by a specific sqlite3_tokenizer
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** object.
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*/
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typedef struct sqlite3_tokenizer_module sqlite3_tokenizer_module;
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typedef struct sqlite3_tokenizer sqlite3_tokenizer;
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typedef struct sqlite3_tokenizer_cursor sqlite3_tokenizer_cursor;
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struct sqlite3_tokenizer_module {
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/*
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** Structure version. Should always be set to 0.
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*/
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int iVersion;
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/*
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** Create a new tokenizer. The values in the argv[] array are the
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** arguments passed to the "tokenizer" clause of the CREATE VIRTUAL
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** TABLE statement that created the fts2 table. For example, if
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** the following SQL is executed:
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**
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** CREATE .. USING fts2( ... , tokenizer <tokenizer-name> arg1 arg2)
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**
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** then argc is set to 2, and the argv[] array contains pointers
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** to the strings "arg1" and "arg2".
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**
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** This method should return either SQLITE_OK (0), or an SQLite error
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** code. If SQLITE_OK is returned, then *ppTokenizer should be set
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** to point at the newly created tokenizer structure. The generic
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** sqlite3_tokenizer.pModule variable should not be initialized by
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** this callback. The caller will do so.
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*/
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int (*xCreate)(
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int argc, /* Size of argv array */
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const char *const*argv, /* Tokenizer argument strings */
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sqlite3_tokenizer **ppTokenizer /* OUT: Created tokenizer */
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);
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/*
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** Destroy an existing tokenizer. The fts2 module calls this method
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** exactly once for each successful call to xCreate().
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*/
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int (*xDestroy)(sqlite3_tokenizer *pTokenizer);
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/*
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** Create a tokenizer cursor to tokenize an input buffer. The caller
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** is responsible for ensuring that the input buffer remains valid
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** until the cursor is closed (using the xClose() method).
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*/
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int (*xOpen)(
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sqlite3_tokenizer *pTokenizer, /* Tokenizer object */
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const char *pInput, int nBytes, /* Input buffer */
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sqlite3_tokenizer_cursor **ppCursor /* OUT: Created tokenizer cursor */
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);
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/*
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** Destroy an existing tokenizer cursor. The fts2 module calls this
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** method exactly once for each successful call to xOpen().
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*/
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int (*xClose)(sqlite3_tokenizer_cursor *pCursor);
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/*
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** Retrieve the next token from the tokenizer cursor pCursor. This
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** method should either return SQLITE_OK and set the values of the
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** "OUT" variables identified below, or SQLITE_DONE to indicate that
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** the end of the buffer has been reached, or an SQLite error code.
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**
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** *ppToken should be set to point at a buffer containing the
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** normalized version of the token (i.e. after any case-folding and/or
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** stemming has been performed). *pnBytes should be set to the length
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** of this buffer in bytes. The input text that generated the token is
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** identified by the byte offsets returned in *piStartOffset and
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** *piEndOffset.
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**
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** The buffer *ppToken is set to point at is managed by the tokenizer
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** implementation. It is only required to be valid until the next call
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** to xNext() or xClose().
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*/
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/* TODO(shess) current implementation requires pInput to be
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** nul-terminated. This should either be fixed, or pInput/nBytes
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** should be converted to zInput.
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*/
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int (*xNext)(
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sqlite3_tokenizer_cursor *pCursor, /* Tokenizer cursor */
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const char **ppToken, int *pnBytes, /* OUT: Normalized text for token */
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int *piStartOffset, /* OUT: Byte offset of token in input buffer */
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int *piEndOffset, /* OUT: Byte offset of end of token in input buffer */
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int *piPosition /* OUT: Number of tokens returned before this one */
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);
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};
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struct sqlite3_tokenizer {
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const sqlite3_tokenizer_module *pModule; /* The module for this tokenizer */
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/* Tokenizer implementations will typically add additional fields */
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};
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struct sqlite3_tokenizer_cursor {
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sqlite3_tokenizer *pTokenizer; /* Tokenizer for this cursor. */
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/* Tokenizer implementations will typically add additional fields */
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};
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#endif /* _FTS2_TOKENIZER_H_ */
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