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** 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.
#include "sqlite3.h"
** 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.
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 */
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 */
#endif /* _FTS3_TOKENIZER_H_ */