SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the SQLite library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.190 2006/09/10 17:08:30 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.

/*
** Every module implementation uses a subclass of the following structure
** to describe a particular instance of the module.  Each subclass will
** be taylored to the specific needs of the module implementation.   The
** purpose of this superclass is to define certain fields that are common
** to all module implementations.
**
** Virtual tables methods can set an error message by assigning a
** string obtained from sqlite3_mprintf() to zErrMsg.  The method should
** take care that any prior string is freed by a call to sqlite3_free()
** prior to assigning a new string to zErrMsg.  After the error message
** is delivered up to the client application, the string will be automatically
** freed by sqlite3_free() and the zErrMsg field will be zeroed.  Note
** that sqlite3_mprintf() and sqlite3_free() are used on the zErrMsg field
** since virtual tables are commonly implemented in loadable extensions which
** do not have access to sqlite3MPrintf() or sqlite3Free().
*/
struct sqlite3_vtab {
  const sqlite3_module *pModule;  /* The module for this virtual table */
  int nRef;                       /* Used internally */
  char *zErrMsg;                  /* Error message text */
  /* Virtual table implementations will typically add additional fields */
};

/* Every module implementation uses a subclass of the following structure
** to describe cursors that point into the virtual table and are used
** to loop through the virtual table.  Cursors are created using the
** xOpen method of the module.  Each module implementation will define

/*
** 2006 June 10
**
** 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.
**
*************************************************************************
** This file contains code used to help implement virtual tables.
**
** $Id: vtab.c,v 1.32 2006/09/10 17:08:30 drh Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

/*
** External API function used to create a new virtual-table module.
*/

/*
** Unlock a virtual table.  When the last lock is removed,
** disconnect the virtual table.
*/
void sqlite3VtabUnlock(sqlite3_vtab *pVtab){
  pVtab->nRef--;
  if( pVtab->nRef==0 ){
    sqlite3_free(pVtab->zErrMsg);
    pVtab->zErrMsg = 0;
    pVtab->pModule->xDisconnect(pVtab);
  }
}

/*
** Clear any and all virtual-table information from the Table record.
** This routine is called, for example, just before deleting the Table

  Table *pTab,
  Module *pMod,
  int (*xConstruct)(sqlite3*, void *, int, char **, sqlite3_vtab **),
  char **pzErr
){
  int rc;
  int rc2;
  sqlite3_vtab *pVtab;
  char **azArg = pTab->azModuleArg;
  int nArg = pTab->nModuleArg;
  char *zErr = sqlite3MPrintf("vtable constructor failed: %s", pTab->zName);

  assert( !db->pVTab );
  assert( xConstruct );

  db->pVTab = pTab;
  rc = sqlite3SafetyOff(db);
  assert( rc==SQLITE_OK );
  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pTab->pVtab);
  rc2 = sqlite3SafetyOn(db);
  pVtab = pTab->pVtab;
  if( rc==SQLITE_OK && pVtab ){
    pVtab->pModule = pMod->pModule;
    pVtab->nRef = 1;
  }

  if( SQLITE_OK!=rc ){
    if( pVtab && pVtab->zErrMsg ){
      *pzErr = sqlite3MPrintf("%s", pVtab->zErrMsg);
      sqlite3_free(pVtab->zErrMsg);
      pVtab->zErrMsg = 0;
    }else{
      *pzErr = zErr;
      zErr = 0;
    }
  }else if( db->pVTab ){
    const char *zFormat = "vtable constructor did not declare schema: %s";
    *pzErr = sqlite3MPrintf(zFormat, pTab->zName);
    rc = SQLITE_ERROR;
  } 
  if( rc==SQLITE_OK ){
    rc = rc2;
  }