xpath.c File Reference

SQLite extension module to select parts of XML documents using libxml2 XPath and SQLite's virtual table mechanism. More...

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <libxml/parser.h>
#include <libxml/tree.h>
#include <libxml/xpath.h>
#include <sqlite3ext.h>

Go to the source code of this file.

Data Structures
struct	XDOC
	Structure to cache XML document. More...
struct	XMOD
	Structure holding per module/database data. More...
struct	XTAB
	Structure to describe virtual table. More...
struct	XEXP
	Structure to describe XPath expression. More...
struct	XCSR
	Structure to describe virtual table cursor. More...
Typedefs
typedef struct XDOC	XDOC
typedef struct XMOD	XMOD
typedef struct XTAB	XTAB
typedef struct XEXP	XEXP
typedef struct XCSR	XCSR
Functions
static int	xpath_connect (sqlite3 *db, void *aux, int argc, const char *const *argv, sqlite3_vtab **vtabp, char **errp)
	Connect to virtual table.
static int	xpath_create (sqlite3 *db, void *aux, int argc, const char *const *argv, sqlite3_vtab **vtabp, char **errp)
	Create virtual table.
static int	xpath_disconnect (sqlite3_vtab *vtab)
	Disconnect virtual table.
static int	xpath_destroy (sqlite3_vtab *vtab)
	Destroy virtual table.
static int	xpath_bestindex (sqlite3_vtab *vtab, sqlite3_index_info *info)
	Determines information for filter function according to constraints.
static int	xpath_open (sqlite3_vtab *vtab, sqlite3_vtab_cursor **cursorp)
	Open virtual table and return cursor.
static int	xpath_close (sqlite3_vtab_cursor *cursor)
	Close virtual table cursor.
static int	xpath_next (sqlite3_vtab_cursor *cursor)
	Retrieve next row from virtual table cursor.
static int	xpath_filter (sqlite3_vtab_cursor *cursor, int idxNum, const char *idxStr, int argc, sqlite3_value **argv)
	Filter function for virtual table.
static int	xpath_eof (sqlite3_vtab_cursor *cursor)
	Return end of table state of virtual table cursor.
static int	xpath_column (sqlite3_vtab_cursor *cursor, sqlite3_context *ctx, int n)
	Return column data of virtual table.
static int	xpath_rowid (sqlite3_vtab_cursor *cursor, sqlite3_int64 *rowidp)
	Return current rowid of virtual table cursor.
static int	xpath_update (sqlite3_vtab *vtab, int argc, sqlite3_value **argv, sqlite3_int64 *rowidp)
	Insert/delete row into/from virtual table.
static void	xpath_vfunc_common (sqlite3_context *ctx, int conv, int argc, sqlite3_value **argv)
	Common XPath select function for virtual table.
static void	xpath_vfunc_string (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning string value from virtual table.
static void	xpath_vfunc_boolean (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning boolean value from virtual table.
static void	xpath_vfunc_number (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning number from virtual table.
static void	xpath_vfunc_xml (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning XML from virtual table.
static int	xpath_findfunc (sqlite3_vtab *vtab, int nargs, const char *name, void(**pfunc)(sqlite3_context *, int, sqlite3_value **), void **parg)
	Find overloaded function on virtual table.
static void	xpath_func_common (sqlite3_context *ctx, int conv, int argc, sqlite3_value **argv)
	Common XPath select function.
static void	xpath_func_string (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning string value.
static void	xpath_func_boolean (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning boolean value.
static void	xpath_func_number (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning number.
static void	xpath_func_xml (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	XPath select function returning XML.
static void	xpath_func_dump (sqlite3_context *ctx, int argc, sqlite3_value **argv)
	Function to dump XML document.
static void	xpath_fini (void *aux)
	Module finalizer.
static int	xpath_init (sqlite3 *db)
	Module initializer creating SQLite module and functions.
int	sqlite3_extension_init (sqlite3 *db, char **errmsg, const sqlite3_api_routines *api)
	Initializer for SQLite extension load mechanism.
Variables
static int	initialized = 0
static XMOD *	xmod = 0
static sqlite3_module	xpath_mod
	SQLite module descriptor.

---

Detailed Description

SQLite extension module to select parts of XML documents using libxml2 XPath and SQLite's virtual table mechanism.

2013 March 15

The author disclaims copyright to this source code. In place of a legal notice, here is a blessing:

May you do good and not evil. May you find forgiveness for yourself and forgive others. May you share freely, never taking more than you give.

Definition in file xpath.c.

---

Typedef Documentation

XCSR

typedef struct XDOC XDOC

XEXP

XMOD

XTAB

---

Function Documentation

int sqlite3_extension_init	(	sqlite3 *	db,
		char **	errmsg,
		const sqlite3_api_routines *	api
	)

Initializer for SQLite extension load mechanism.

Parameters:

db	SQLite database pointer
errmsg	pointer receiving error message
api	SQLite API routines

Returns:

SQLite error code

Definition at line 1658 of file xpath.c.

References xpath_init().

static int xpath_bestindex	(	sqlite3_vtab *	vtab,
		sqlite3_index_info *	info
	)		[static]

Determines information for filter function according to constraints.

Parameters:

vtab	virtual table
info	index/constraint information

Returns:

SQLite error code

Definition at line 255 of file xpath.c.

static int xpath_close

(

sqlite3_vtab_cursor *

cursor

)

[static]

Close virtual table cursor.

Parameters:

cursor

cursor pointer

Returns:

SQLite error code

Definition at line 290 of file xpath.c.

References XCSR::cursor, XCSR::first, XEXP::next, XEXP::pctx, XEXP::pobj, and XTAB::xc.

static int xpath_column	(	sqlite3_vtab_cursor *	cursor,
		sqlite3_context *	ctx,
		int	n
	)		[static]

Return column data of virtual table.

Parameters:

cursor	virtual table cursor
ctx	SQLite function context
n	column index

Returns:

SQLite error code

Definition at line 461 of file xpath.c.

References XCSR::cursor, XTAB::idocs, XTAB::ndoc, XCSR::pos, and XTAB::xm.

static int xpath_connect	(	sqlite3 *	db,
		void *	aux,
		int	argc,
		const char *const *	argv,
		sqlite3_vtab **	vtabp,
		char **	errp
	)		[static]

Connect to virtual table.

Parameters:

db	SQLite database pointer
aux	user specific pointer
argc	argument count
argv	argument vector
vtabp	pointer receiving virtual table pointer
errp	pointer receiving error messag

Returns:

SQLite error code

Argument vector contains:

argv[0] - module name
argv[1] - database name
argv[2] - table name (virtual table)

Definition at line 135 of file xpath.c.

References XTAB::db, XTAB::idocs, XTAB::ndoc, nomem(), XTAB::sdoc, XTAB::vtab, XTAB::xc, and XTAB::xm.

Referenced by xpath_create().

static int xpath_create	(	sqlite3 *	db,
		void *	aux,
		int	argc,
		const char *const *	argv,
		sqlite3_vtab **	vtabp,
		char **	errp
	)		[static]

Create virtual table.

Parameters:

db	SQLite database pointer
aux	user specific pointer
argc	argument count
argv	argument vector
vtabp	pointer receiving virtual table pointer
errp	pointer receiving error messag

Returns:

SQLite error code

Definition at line 191 of file xpath.c.

References xpath_connect().

static int xpath_destroy

(

sqlite3_vtab *

vtab

)

[static]

Destroy virtual table.

Parameters:

vtab	virtual table pointer

Returns:

always SQLITE_OK

Definition at line 242 of file xpath.c.

References xpath_disconnect().

static int xpath_disconnect

(

sqlite3_vtab *

vtab

)

[static]

Disconnect virtual table.

Parameters:

vtab	virtual table pointer

Returns:

always SQLITE_OK

Definition at line 205 of file xpath.c.

References XDOC::doc, XMOD::docs, XTAB::idocs, XMOD::mutex, XMOD::ndoc, XTAB::ndoc, XDOC::refcnt, XMOD::sdoc, and XTAB::xm.

Referenced by xpath_destroy().

static int xpath_eof

(

sqlite3_vtab_cursor *

cursor

)

[static]

Return end of table state of virtual table cursor.

Parameters:

cursor

virtual table cursor

Returns:

true/false

Definition at line 444 of file xpath.c.

References XCSR::cursor, XTAB::ndoc, and XCSR::pos.

static int xpath_filter	(	sqlite3_vtab_cursor *	cursor,
		int	idxNum,
		const char *	idxStr,
		int	argc,
		sqlite3_value **	argv
	)		[static]

Filter function for virtual table.

Parameters:

cursor	virtual table cursor
idxNum	not used
idxStr	nod used
argc	number arguments (not used)
argv	argument (nothing or RHS of filter expression, not used)

Returns:

SQLite error code

Definition at line 426 of file xpath.c.

References XCSR::cursor, XCSR::pos, XTAB::xc, and xpath_next().

static int xpath_findfunc	(	sqlite3_vtab *	vtab,
		int	nargs,
		const char *	name,
		void(**)(sqlite3_context *, int, sqlite3_value **)	pfunc,
		void **	parg
	)		[static]

Find overloaded function on virtual table.

Parameters:

vtab	virtual table
nargs	number arguments
name	function name
pfunc	pointer to function (value return)
parg	pointer to function's argument (value return)

Returns:

0 or 1

Definition at line 1008 of file xpath.c.

References xpath_vfunc_boolean(), xpath_vfunc_number(), xpath_vfunc_string(), and xpath_vfunc_xml().

static void xpath_fini

(

void *

aux

)

[static]

Module finalizer.

Parameters:

aux	pointer to module data

Returns:

SQLite error code

Definition at line 1518 of file xpath.c.

References XDOC::doc, XMOD::docs, initialized, XMOD::mutex, XMOD::ndoc, XDOC::refcnt, XMOD::refcnt, and XMOD::sdoc.

Referenced by xpath_init().

static void xpath_func_boolean	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning boolean value.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 1259 of file xpath.c.

References xpath_func_common().

Referenced by xpath_init().

static void xpath_func_common	(	sqlite3_context *	ctx,
		int	conv,
		int	argc,
		sqlite3_value **	argv
	)		[static]

Common XPath select function.

Parameters:

ctx	SQLite function context
conv	conversion (0=string, 1=boolean, 2=number)
argc	number of arguments
argv	argument vector

Examples:

SELECT xpath_string(<docid>, '//book/title');
SELECT xpath_number(<xml-string>, '//book/price', <options;&gt, <encoding>, <base-url>);

The <docid> argument is the DOCID value of a row in a virtual table. Otherwise a string containing an XML document is expected. The optional arguments are
<options> - parser options, see libxml's XML_PARSE_* defines
<encoding> - encoding of the XML document
<base-url> - base URL of the XML document

Definition at line 1106 of file xpath.c.

References XDOC::doc, XMOD::docs, XMOD::mutex, XDOC::refcnt, and XMOD::sdoc.

Referenced by xpath_func_boolean(), xpath_func_number(), xpath_func_string(), and xpath_func_xml().

static void xpath_func_dump	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

Function to dump XML document.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Examples:

SELECT xml_dump(<docid>, <encoding> <fmt>)

The <docid> argument is the DOCID value of a row in a virtual table. The <encoding> argument is the optional encoding (default UTF-8). The <fmt> argument is the optional formatting flag for the xmlDocDumpFormatMemoryEnc() libxml2 function.

Definition at line 1308 of file xpath.c.

References XDOC::doc, XMOD::docs, XMOD::mutex, and XMOD::sdoc.

Referenced by xpath_init().

static void xpath_func_number	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning number.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 1272 of file xpath.c.

References xpath_func_common().

Referenced by xpath_init().

static void xpath_func_string	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning string value.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 1246 of file xpath.c.

References xpath_func_common().

Referenced by xpath_init().

static void xpath_func_xml	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning XML.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 1285 of file xpath.c.

References xpath_func_common().

Referenced by xpath_init().

static int xpath_init

(

sqlite3 *

db

)

[static]

Module initializer creating SQLite module and functions.

Parameters:

db	database pointer

Returns:

SQLite error code

Definition at line 1571 of file xpath.c.

References XMOD::docs, initialized, XMOD::mutex, XMOD::ndoc, XMOD::refcnt, XMOD::sdoc, xmod, xpath_fini(), xpath_func_boolean(), xpath_func_dump(), xpath_func_number(), xpath_func_string(), and xpath_func_xml().

Referenced by sqlite3_extension_init().

static int xpath_next

(

sqlite3_vtab_cursor *

cursor

)

[static]

Retrieve next row from virtual table cursor.

Parameters:

cursor

virtual table cursor

Returns:

SQLite error code

Definition at line 321 of file xpath.c.

References XCSR::cursor, XCSR::first, XTAB::ndoc, XCSR::nexpr, XEXP::parent, XEXP::pos, and XCSR::pos.

Referenced by xpath_filter().

static int xpath_open	(	sqlite3_vtab *	vtab,
		sqlite3_vtab_cursor **	cursorp
	)		[static]

Open virtual table and return cursor.

Parameters:

vtab	virtual table pointer
cursorp	pointer receiving cursor pointer

Returns:

SQLite error code

Definition at line 268 of file xpath.c.

References XCSR::cursor, XCSR::first, XCSR::last, XCSR::nexpr, and XCSR::pos.

static int xpath_rowid	(	sqlite3_vtab_cursor *	cursor,
		sqlite3_int64 *	rowidp
	)		[static]

Return current rowid of virtual table cursor.

Parameters:

cursor	virtual table cursor
rowidp	value buffer to receive current rowid

Returns:

SQLite error code

Definition at line 505 of file xpath.c.

References XCSR::cursor, XTAB::idocs, XCSR::pos, and XTAB::xm.

static int xpath_update	(	sqlite3_vtab *	vtab,
		int	argc,
		sqlite3_value **	argv,
		sqlite3_int64 *	rowidp
	)		[static]

Insert/delete row into/from virtual table.

Parameters:

vtab	virtual table pointer
argc	number of arguments
argv	argument vector
rowidp	value buffer to receive rowid

Returns:

SQLite error code

Examples:

CREATE VIRTUAL TABLE X USING xpath();
INSERT INTO X(XML) VALUES('xml-string ...');
INSERT INTO X(PATH,OPTIONS) VALUES(<url>,0);
DELETE FROM X WHERE DOCID=<docid>;

Virtual table columns:

DOCID - document identifier and ROWID
XML - XML string
PATH - pathname or URL
OPTIONS - parser options, see libxml's XML_PARSE_* defines
ENCODING - optional document encoding, default UTF-8
BASEURL - optional base URL when XML string given
XMLDUMP - output column, XML dump of document tree

All columns except DOCID are hidden. UPDATE on the virtual table is not supported. Default parser options are XML_PARSE_NOERROR, XML_PARSE_NOWARNING, and XML_PARSE_NONET.

Definition at line 550 of file xpath.c.

References XDOC::doc, XMOD::docs, XTAB::idocs, XMOD::mutex, XMOD::ndoc, XTAB::ndoc, nomem(), XDOC::refcnt, XMOD::sdoc, XTAB::sdoc, and XTAB::xm.

static void xpath_vfunc_boolean	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning boolean value from virtual table.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 966 of file xpath.c.

References xpath_vfunc_common().

Referenced by xpath_findfunc().

static void xpath_vfunc_common	(	sqlite3_context *	ctx,
		int	conv,
		int	argc,
		sqlite3_value **	argv
	)		[static]

Common XPath select function for virtual table.

Parameters:

ctx	SQLite function context
conv	conversion (0=string, 1=boolean, 2=number)
argc	number of arguments
argv	argument vector

Examples:

CREATE VIRTUAL TABLE X USING xpath();
INSERT INTO X(XML) VALUES('xml-string ...');
SELECT xpath_string(docid, '//book/title') FROM X;
SELECT xpath_number(docid, '//book/price') FROM X;

The RHS of the xpath_* functions should be a constant string.

Definition at line 757 of file xpath.c.

References XEXP::conv, XEXP::doc, XDOC::doc, XMOD::docs, XEXP::expr, XCSR::first, XTAB::idocs, XCSR::last, XTAB::ndoc, XCSR::nexpr, XEXP::next, XEXP::parent, XEXP::pctx, XEXP::pobj, XEXP::pos, XCSR::pos, XEXP::prev, XTAB::xc, and XTAB::xm.

Referenced by xpath_vfunc_boolean(), xpath_vfunc_number(), xpath_vfunc_string(), and xpath_vfunc_xml().

static void xpath_vfunc_number	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning number from virtual table.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 979 of file xpath.c.

References xpath_vfunc_common().

Referenced by xpath_findfunc().

static void xpath_vfunc_string	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning string value from virtual table.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 953 of file xpath.c.

References xpath_vfunc_common().

Referenced by xpath_findfunc().

static void xpath_vfunc_xml	(	sqlite3_context *	ctx,
		int	argc,
		sqlite3_value **	argv
	)		[static]

XPath select function returning XML from virtual table.

Parameters:

ctx	SQLite function context
argc	number of arguments
argv	argument vector

Definition at line 992 of file xpath.c.

References xpath_vfunc_common().

Referenced by xpath_findfunc().

---

Variable Documentation

int initialized = 0 [static]

Definition at line 66 of file xpath.c.

Referenced by xpath_fini(), and xpath_init().

XMOD* xmod = 0 [static]

Definition at line 67 of file xpath.c.

Referenced by xpath_init().

sqlite3_module xpath_mod [static]

Initial value:

 {
    1,                  
    xpath_create,       
    xpath_connect,      
    xpath_bestindex,    
    xpath_disconnect,   
    xpath_destroy,      
    xpath_open,         
    xpath_close,        
    xpath_filter,       
    xpath_next,         
    xpath_eof,          
    xpath_column,       
    xpath_rowid,        
    xpath_update,       
    0,                  
    0,                  
    0,                  
    0,                  
    xpath_findfunc,     



}

SQLite module descriptor.

Definition at line 1058 of file xpath.c.