mattercontrol/Community.CsharpSqlite/src/vtab_c.cs

using System;
using System.Diagnostics;
using System.Text;

namespace Community.CsharpSqlite
{
	public partial class Sqlite3
	{
		/*
		** 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.
		*************************************************************************
		**  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
		**  C#-SQLite is an independent reimplementation of the SQLite software library
		**
		**  SQLITE_SOURCE_ID: 2011-06-23 19:49:22 4374b7e83ea0a3fbc3691f9c0c936272862f32f2
		**
		*************************************************************************
		*/
#if !SQLITE_OMIT_VIRTUALTABLE
		//#include "sqliteInt.h"

		/*
		** Before a virtual table xCreate() or xConnect() method is invoked, the
		** sqlite3.pVtabCtx member variable is set to point to an instance of
		** this struct allocated on the stack. It is used by the implementation of
		** the sqlite3_declare_vtab() and sqlite3_vtab_config() APIs, both of which
		** are invoked only from within xCreate and xConnect methods.
		*/

		public class VtabCtx
		{
			public Table pTab;
			public VTable pVTable;
		};

		/*
		** The actual function that does the work of creating a new module.
		** This function implements the sqlite3_create_module() and
		** sqlite3_create_module_v2() interfaces.
		*/

		private static int createModule(
		  sqlite3 db,              /* Database in which module is registered */
		  string zName,            /* Name assigned to this module */
		  sqlite3_module pModule,  /* The definition of the module */
		  object pAux,             /* Context pointer for xCreate/xConnect */
		  smdxDestroy xDestroy     /* Module destructor function */
		)
		{
			int rc, nName;
			Module pMod;

			sqlite3_mutex_enter(db.mutex);
			nName = sqlite3Strlen30(zName);
			pMod = new Module();//  (Module)sqlite3DbMallocRaw( db, sizeof( Module ) + nName + 1 );
			if (pMod != null)
			{
				Module pDel;
				string zCopy;// = (char )(&pMod[1]);
				zCopy = zName;//memcpy(zCopy, zName, nName+1);
				pMod.zName = zCopy;
				pMod.pModule = pModule;
				pMod.pAux = pAux;
				pMod.xDestroy = xDestroy;
				pDel = (Module)sqlite3HashInsert(ref db.aModule, zCopy, nName, pMod);
				if (pDel != null && pDel.xDestroy != null)
				{
					sqlite3ResetInternalSchema(db, -1);
					pDel.xDestroy(ref pDel.pAux);
				}
				sqlite3DbFree(db, ref pDel);
				//if( pDel==pMod ){
				//  db.mallocFailed = 1;
				//}
			}
			else if (xDestroy != null)
			{
				xDestroy(ref pAux);
			}
			rc = sqlite3ApiExit(db, SQLITE_OK);
			sqlite3_mutex_leave(db.mutex);
			return rc;
		}

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

		private static int sqlite3_create_module(
		  sqlite3 db,               /* Database in which module is registered */
		  string zName,             /* Name assigned to this module */
		  sqlite3_module pModule,   /* The definition of the module */
		  object pAux               /* Context pointer for xCreate/xConnect */
		)
		{
			return createModule(db, zName, pModule, pAux, null);
		}

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

		private static int sqlite3_create_module_v2(
		  sqlite3 db,               /* Database in which module is registered */
		  string zName,             /* Name assigned to this module */
		  sqlite3_module pModule,   /* The definition of the module */
		  sqlite3_vtab pAux,        /* Context pointer for xCreate/xConnect */
		  smdxDestroy xDestroy      /* Module destructor function */
		)
		{
			return createModule(db, zName, pModule, pAux, xDestroy);
		}

		/*
		** Lock the virtual table so that it cannot be disconnected.
		** Locks nest.  Every lock should have a corresponding unlock.
		** If an unlock is omitted, resources leaks will occur.
		**
		** If a disconnect is attempted while a virtual table is locked,
		** the disconnect is deferred until all locks have been removed.
		*/

		private static void sqlite3VtabLock(VTable pVTab)
		{
			pVTab.nRef++;
		}

		/*
		** pTab is a pointer to a Table structure representing a virtual-table.
		** Return a pointer to the VTable object used by connection db to access
		** this virtual-table, if one has been created, or NULL otherwise.
		*/

		private static VTable sqlite3GetVTable(sqlite3 db, Table pTab)
		{
			VTable pVtab;
			Debug.Assert(IsVirtual(pTab));
			for (pVtab = pTab.pVTable; pVtab != null && pVtab.db != db; pVtab = pVtab.pNext)
				;
			return pVtab;
		}

		/*
		** Decrement the ref-count on a virtual table object. When the ref-count
		** reaches zero, call the xDisconnect() method to delete the object.
		*/

		private static void sqlite3VtabUnlock(VTable pVTab)
		{
			sqlite3 db = pVTab.db;

			Debug.Assert(db != null);
			Debug.Assert(pVTab.nRef > 0);
			Debug.Assert(sqlite3SafetyCheckOk(db));

			pVTab.nRef--;
			if (pVTab.nRef == 0)
			{
				object p = pVTab.pVtab;
				if (p != null)
				{
					((sqlite3_vtab)p).pModule.xDisconnect(ref p);
				}
				sqlite3DbFree(db, ref pVTab);
			}
		}

		/*
		** Table p is a virtual table. This function moves all elements in the
		** p.pVTable list to the sqlite3.pDisconnect lists of their associated
		** database connections to be disconnected at the next opportunity.
		** Except, if argument db is not NULL, then the entry associated with
		** connection db is left in the p.pVTable list.
		*/

		private static VTable vtabDisconnectAll(sqlite3 db, Table p)
		{
			VTable pRet = null;
			VTable pVTable = p.pVTable;
			p.pVTable = null;

			/* Assert that the mutex (if any) associated with the BtShared database
			** that contains table p is held by the caller. See header comments
			** above function sqlite3VtabUnlockList() for an explanation of why
			** this makes it safe to access the sqlite3.pDisconnect list of any
			** database connection that may have an entry in the p.pVTable list.
			*/
			Debug.Assert(db == null || sqlite3SchemaMutexHeld(db, 0, p.pSchema));

			while (pVTable != null)
			{
				sqlite3 db2 = pVTable.db;
				VTable pNext = pVTable.pNext;
				Debug.Assert(db2 != null);
				if (db2 == db)
				{
					pRet = pVTable;
					p.pVTable = pRet;
					pRet.pNext = null;
				}
				else
				{
					pVTable.pNext = db2.pDisconnect;
					db2.pDisconnect = pVTable;
				}
				pVTable = pNext;
			}

			Debug.Assert(null == db || pRet != null);
			return pRet;
		}

		/*
		** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
		**
		** This function may only be called when the mutexes associated with all
		** shared b-tree databases opened using connection db are held by the
		** caller. This is done to protect the sqlite3.pDisconnect list. The
		** sqlite3.pDisconnect list is accessed only as follows:
		**
		**   1) By this function. In this case, all BtShared mutexes and the mutex
		**      associated with the database handle itself must be held.
		**
		**   2) By function vtabDisconnectAll(), when it adds a VTable entry to
		**      the sqlite3.pDisconnect list. In this case either the BtShared mutex
		**      associated with the database the virtual table is stored in is held
		**      or, if the virtual table is stored in a non-sharable database, then
		**      the database handle mutex is held.
		**
		** As a result, a sqlite3.pDisconnect cannot be accessed simultaneously
		** by multiple threads. It is thread-safe.
		*/

		private static void sqlite3VtabUnlockList(sqlite3 db)
		{
			VTable p = db.pDisconnect;
			db.pDisconnect = null;

			Debug.Assert(sqlite3BtreeHoldsAllMutexes(db));
			Debug.Assert(sqlite3_mutex_held(db.mutex));

			if (p != null)
			{
				sqlite3ExpirePreparedStatements(db);
				do
				{
					VTable pNext = p.pNext;
					sqlite3VtabUnlock(p);
					p = pNext;
				} while (p != null);
			}
		}

		/*
		** Clear any and all virtual-table information from the Table record.
		** This routine is called, for example, just before deleting the Table
		** record.
		**
		** Since it is a virtual-table, the Table structure contains a pointer
		** to the head of a linked list of VTable structures. Each VTable
		** structure is associated with a single sqlite3* user of the schema.
		** The reference count of the VTable structure associated with database
		** connection db is decremented immediately (which may lead to the
		** structure being xDisconnected and free). Any other VTable structures
		** in the list are moved to the sqlite3.pDisconnect list of the associated
		** database connection.
		*/

		private static void sqlite3VtabClear(sqlite3 db, Table p)
		{
			if (null == db || db.pnBytesFreed == 0)
				vtabDisconnectAll(null, p);
			if (p.azModuleArg != null)
			{
				int i;
				for (i = 0; i < p.nModuleArg; i++)
				{
					sqlite3DbFree(db, ref p.azModuleArg[i]);
				}
				sqlite3DbFree(db, ref p.azModuleArg);
			}
		}

		/*
		** Add a new module argument to pTable.azModuleArg[].
		** The string is not copied - the pointer is stored.  The
		** string will be freed automatically when the table is
		** deleted.
		*/

		private static void addModuleArgument(sqlite3 db, Table pTable, string zArg)
		{
			int i = pTable.nModuleArg++;
			//int nBytes = sizeof(char )*(1+pTable.nModuleArg);
			//string[] azModuleArg;
			//sqlite3DbRealloc( db, pTable.azModuleArg, nBytes );
			if (pTable.azModuleArg == null || pTable.azModuleArg.Length < pTable.nModuleArg)
				Array.Resize(ref pTable.azModuleArg, 3 + pTable.nModuleArg);
			//if ( azModuleArg == null )
			//{
			//  int j;
			//  for ( j = 0; j < i; j++ )
			//  {
			//    sqlite3DbFree( db, ref pTable.azModuleArg[j] );
			//  }
			//  sqlite3DbFree( db, ref zArg );
			//  sqlite3DbFree( db, ref pTable.azModuleArg );
			//  pTable.nModuleArg = 0;
			//}
			//else
			{
				pTable.azModuleArg[i] = zArg;
				//pTable.azModuleArg[i + 1] = null;
				//azModuleArg[i+1] = 0;
			}
			//pTable.azModuleArg = azModuleArg;
		}

		/*
		** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE
		** statement.  The module name has been parsed, but the optional list
		** of parameters that follow the module name are still pending.
		*/

		private static void sqlite3VtabBeginParse(
		  Parse pParse,        /* Parsing context */
		  Token pName1,        /* Name of new table, or database name */
		  Token pName2,        /* Name of new table or NULL */
		  Token pModuleName    /* Name of the module for the virtual table */
		)
		{
			int iDb;              /* The database the table is being created in */
			Table pTable;        /* The new virtual table */
			sqlite3 db;          /* Database connection */

			sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, 0);
			pTable = pParse.pNewTable;
			if (pTable == null)
				return;
			Debug.Assert(null == pTable.pIndex);

			db = pParse.db;
			iDb = sqlite3SchemaToIndex(db, pTable.pSchema);
			Debug.Assert(iDb >= 0);

			pTable.tabFlags |= TF_Virtual;
			pTable.nModuleArg = 0;
			addModuleArgument(db, pTable, sqlite3NameFromToken(db, pModuleName));
			addModuleArgument(db, pTable, db.aDb[iDb].zName);//sqlite3DbStrDup( db, db.aDb[iDb].zName ) );
			addModuleArgument(db, pTable, pTable.zName);//sqlite3DbStrDup( db, pTable.zName ) );
			pParse.sNameToken.n = pParse.sNameToken.z.Length;//      (int)[pModuleName.n] - pName1.z );

#if !SQLITE_OMIT_AUTHORIZATION
  /* Creating a virtual table invokes the authorization callback twice.
  ** The first invocation, to obtain permission to INSERT a row into the
  ** sqlite_master table, has already been made by sqlite3StartTable().
  ** The second call, to obtain permission to create the table, is made now.
  */
  if( pTable->azModuleArg ){
    sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName,
            pTable->azModuleArg[0], pParse->db->aDb[iDb].zName);
  }
#endif
		}

		/*
		** This routine takes the module argument that has been accumulating
		** in pParse.zArg[] and appends it to the list of arguments on the
		** virtual table currently under construction in pParse.pTable.
		*/

		private static void addArgumentToVtab(Parse pParse)
		{
			if (pParse.sArg.z != null && ALWAYS(pParse.pNewTable))
			{
				string z = pParse.sArg.z.Substring(0, pParse.sArg.n);
				////int n = pParse.sArg.n;
				sqlite3 db = pParse.db;
				addModuleArgument(db, pParse.pNewTable, z);////sqlite3DbStrNDup( db, z, n ) );
			}
		}

		/*
		** The parser calls this routine after the CREATE VIRTUAL TABLE statement
		** has been completely parsed.
		*/

		private static void sqlite3VtabFinishParse(Parse pParse, Token pEnd)
		{
			Table pTab = pParse.pNewTable;  /* The table being constructed */
			sqlite3 db = pParse.db;         /* The database connection */

			if (pTab == null)
				return;
			addArgumentToVtab(pParse);
			pParse.sArg.z = "";
			if (pTab.nModuleArg < 1)
				return;

			/* If the CREATE VIRTUAL TABLE statement is being entered for the
			** first time (in other words if the virtual table is actually being
			** created now instead of just being read out of sqlite_master) then
			** do additional initialization work and store the statement text
			** in the sqlite_master table.
			*/
			if (0 == db.init.busy)
			{
				string zStmt;
				string zWhere;
				int iDb;
				Vdbe v;

				/* Compute the complete text of the CREATE VIRTUAL TABLE statement */
				if (pEnd != null)
				{
					pParse.sNameToken.n = pParse.sNameToken.z.Length;//(int)( pEnd.z - pParse.sNameToken.z ) + pEnd.n;
				}
				zStmt = sqlite3MPrintf(db, "CREATE VIRTUAL TABLE %T", pParse.sNameToken.z.Substring(0, pParse.sNameToken.n));

				/* A slot for the record has already been allocated in the
				** SQLITE_MASTER table.  We just need to update that slot with all
				** the information we've collected.
				**
				** The VM register number pParse.regRowid holds the rowid of an
				** entry in the sqlite_master table tht was created for this vtab
				** by sqlite3StartTable().
				*/
				iDb = sqlite3SchemaToIndex(db, pTab.pSchema);
				sqlite3NestedParse(pParse,
				  "UPDATE %Q.%s " +
					 "SET type='table', name=%Q, tbl_name=%Q, rootpage=0, sql=%Q " +
				   "WHERE rowid=#%d",
				  db.aDb[iDb].zName, SCHEMA_TABLE(iDb),
				  pTab.zName,
				  pTab.zName,
				  zStmt,
				  pParse.regRowid
				);
				sqlite3DbFree(db, ref zStmt);
				v = sqlite3GetVdbe(pParse);
				sqlite3ChangeCookie(pParse, iDb);

				sqlite3VdbeAddOp2(v, OP_Expire, 0, 0);
				zWhere = sqlite3MPrintf(db, "name='%q' AND type='table'", pTab.zName);
				sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);
				sqlite3VdbeAddOp4(v, OP_VCreate, iDb, 0, 0,
									 pTab.zName, sqlite3Strlen30(pTab.zName) + 1);
			}

			/* If we are rereading the sqlite_master table create the in-memory
			** record of the table. The xConnect() method is not called until
			** the first time the virtual table is used in an SQL statement. This
			** allows a schema that contains virtual tables to be loaded before
			** the required virtual table implementations are registered.  */
			else
			{
				Table pOld;
				Schema pSchema = pTab.pSchema;
				string zName = pTab.zName;
				int nName = sqlite3Strlen30(zName);
				Debug.Assert(sqlite3SchemaMutexHeld(db, 0, pSchema));
				pOld = sqlite3HashInsert(ref pSchema.tblHash, zName, nName, pTab);
				if (pOld != null)
				{
					//db.mallocFailed = 1;
					Debug.Assert(pTab == pOld);  /* Malloc must have failed inside HashInsert() */
					return;
				}
				pParse.pNewTable = null;
			}
		}

		/*
		** The parser calls this routine when it sees the first token
		** of an argument to the module name in a CREATE VIRTUAL TABLE statement.
		*/

		private static void sqlite3VtabArgInit(Parse pParse)
		{
			addArgumentToVtab(pParse);
			pParse.sArg.z = null;
			pParse.sArg.n = 0;
		}

		/*
		** The parser calls this routine for each token after the first token
		** in an argument to the module name in a CREATE VIRTUAL TABLE statement.
		*/

		private static void sqlite3VtabArgExtend(Parse pParse, Token p)
		{
			Token pArg = pParse.sArg;
			if (pArg.z == null)
			{
				pArg.z = p.z;
				pArg.n = p.n;
			}
			else
			{
				//Debug.Assert( pArg.z< p.z );
				pArg.n += p.n + 1;//(int)( p.z[p.n] - pArg.z );
			}
		}

		/*
		** Invoke a virtual table constructor (either xCreate or xConnect). The
		** pointer to the function to invoke is passed as the fourth parameter
		** to this procedure.
		*/

		private static int vtabCallConstructor(
		  sqlite3 db,
		  Table pTab,
		  Module pMod,
		  smdxCreateConnect xConstruct,
		  ref string pzErr
		)
		{
			VtabCtx sCtx = new VtabCtx();
			VTable pVTable;
			int rc;
			string[] azArg = pTab.azModuleArg;
			int nArg = pTab.nModuleArg;
			string zErr = null;
			string zModuleName = sqlite3MPrintf(db, "%s", pTab.zName);

			//if ( String.IsNullOrEmpty( zModuleName ) )
			//{
			//  return SQLITE_NOMEM;
			//}

			pVTable = new VTable();//sqlite3DbMallocZero( db, sizeof( VTable ) );
			//if ( null == pVTable )
			//{
			//  sqlite3DbFree( db, ref zModuleName );
			//  return SQLITE_NOMEM;
			//}
			pVTable.db = db;
			pVTable.pMod = pMod;

			/* Invoke the virtual table constructor */
			//assert( &db->pVtabCtx );
			Debug.Assert(xConstruct != null);
			sCtx.pTab = pTab;
			sCtx.pVTable = pVTable;
			db.pVtabCtx = sCtx;
			rc = xConstruct(db, pMod.pAux, nArg, azArg, out pVTable.pVtab, out zErr);
			db.pVtabCtx = null;
			//if ( rc == SQLITE_NOMEM )
			//  db.mallocFailed = 1;

			if (SQLITE_OK != rc)
			{
				if (zErr == "")
				{
					pzErr = sqlite3MPrintf(db, "vtable constructor failed: %s", zModuleName);
				}
				else
				{
					pzErr = sqlite3MPrintf(db, "%s", zErr);
					zErr = null;//sqlite3_free( zErr );
				}
				sqlite3DbFree(db, ref pVTable);
			}
			else if (ALWAYS(pVTable.pVtab))
			{
				/* Justification of ALWAYS():  A correct vtab constructor must allocate
				** the sqlite3_vtab object if successful.  */
				pVTable.pVtab.pModule = pMod.pModule;
				pVTable.nRef = 1;
				if (sCtx.pTab != null)
				{
					string zFormat = "vtable constructor did not declare schema: %s";
					pzErr = sqlite3MPrintf(db, zFormat, pTab.zName);
					sqlite3VtabUnlock(pVTable);
					rc = SQLITE_ERROR;
				}
				else
				{
					int iCol;
					/* If everything went according to plan, link the new VTable structure
					** into the linked list headed by pTab->pVTable. Then loop through the
					** columns of the table to see if any of them contain the token "hidden".
					** If so, set the Column.isHidden flag and remove the token from
					** the type string.  */
					pVTable.pNext = pTab.pVTable;
					pTab.pVTable = pVTable;

					for (iCol = 0; iCol < pTab.nCol; iCol++)
					{
						if (String.IsNullOrEmpty(pTab.aCol[iCol].zType))
							continue;
						StringBuilder zType = new StringBuilder(pTab.aCol[iCol].zType);
						int nType;
						int i = 0;
						//if ( zType )
						//  continue;
						nType = sqlite3Strlen30(zType);
						if (sqlite3StrNICmp("hidden", 0, zType.ToString(), 6) != 0 || (zType.Length > 6 && zType[6] != ' '))
						{
							for (i = 0; i < nType; i++)
							{
								if ((0 == sqlite3StrNICmp(" hidden", zType.ToString().Substring(i), 7))
								 && (i + 7 == zType.Length || (zType[i + 7] == '\0' || zType[i + 7] == ' '))
								)
								{
									i++;
									break;
								}
							}
						}
						if (i < nType)
						{
							int j;
							int nDel = 6 + (zType.Length > i + 6 ? 1 : 0);
							for (j = i; (j + nDel) < nType; j++)
							{
								zType[j] = zType[j + nDel];
							}
							if (zType[i] == '\0' && i > 0)
							{
								Debug.Assert(zType[i - 1] == ' ');
								zType.Length = i;//[i - 1] = '\0';
							}
							pTab.aCol[iCol].isHidden = 1;
							pTab.aCol[iCol].zType = zType.ToString().Substring(0, j);
						}
					}
				}
			}

			sqlite3DbFree(db, ref zModuleName);
			return rc;
		}

		/*
		** This function is invoked by the parser to call the xConnect() method
		** of the virtual table pTab. If an error occurs, an error code is returned
		** and an error left in pParse.
		**
		** This call is a no-op if table pTab is not a virtual table.
		*/

		private static int sqlite3VtabCallConnect(Parse pParse, Table pTab)
		{
			sqlite3 db = pParse.db;
			string zMod;
			Module pMod;
			int rc;

			Debug.Assert(pTab != null);
			if ((pTab.tabFlags & TF_Virtual) == 0 || sqlite3GetVTable(db, pTab) != null)
			{
				return SQLITE_OK;
			}

			/* Locate the required virtual table module */
			zMod = pTab.azModuleArg[0];
			pMod = (Module)sqlite3HashFind(db.aModule, zMod, sqlite3Strlen30(zMod), (Module)null);

			if (null == pMod)
			{
				string zModule = pTab.azModuleArg[0];
				sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
				rc = SQLITE_ERROR;
			}
			else
			{
				string zErr = null;
				rc = vtabCallConstructor(db, pTab, pMod, pMod.pModule.xConnect, ref zErr);
				if (rc != SQLITE_OK)
				{
					sqlite3ErrorMsg(pParse, "%s", zErr);
				}
				zErr = null;//sqlite3DbFree( db, zErr );
			}

			return rc;
		}

		/*
		** Grow the db.aVTrans[] array so that there is room for at least one
		** more v-table. Return SQLITE_NOMEM if a malloc fails, or SQLITE_OK otherwise.
		*/

		private static int growVTrans(sqlite3 db)
		{
			const int ARRAY_INCR = 5;

			/* Grow the sqlite3.aVTrans array if required */
			if ((db.nVTrans % ARRAY_INCR) == 0)
			{
				//VTable** aVTrans;
				//int nBytes = sizeof( sqlite3_vtab* ) * ( db.nVTrans + ARRAY_INCR );
				//aVTrans = sqlite3DbRealloc( db, (void)db.aVTrans, nBytes );
				//if ( !aVTrans )
				//{
				//  return SQLITE_NOMEM;
				//}
				//memset( &aVTrans[db.nVTrans], 0, sizeof( sqlite3_vtab* ) * ARRAY_INCR );
				Array.Resize(ref db.aVTrans, db.nVTrans + ARRAY_INCR);
			}

			return SQLITE_OK;
		}

		/*
		** Add the virtual table pVTab to the array sqlite3.aVTrans[]. Space should
		** have already been reserved using growVTrans().
		*/

		private static void addToVTrans(sqlite3 db, VTable pVTab)
		{
			/* Add pVtab to the end of sqlite3.aVTrans */
			db.aVTrans[db.nVTrans++] = pVTab;
			sqlite3VtabLock(pVTab);
		}

		/*
		** This function is invoked by the vdbe to call the xCreate method
		** of the virtual table named zTab in database iDb.
		**
		** If an error occurs, *pzErr is set to point an an English language
		** description of the error and an SQLITE_XXX error code is returned.
		** In this case the caller must call sqlite3DbFree(db, ) on *pzErr.
		*/

		private static int sqlite3VtabCallCreate(sqlite3 db, int iDb, string zTab, ref string pzErr)
		{
			int rc = SQLITE_OK;
			Table pTab;
			Module pMod;
			string zMod;

			pTab = sqlite3FindTable(db, zTab, db.aDb[iDb].zName);
			Debug.Assert(pTab != null && (pTab.tabFlags & TF_Virtual) != 0 && null == pTab.pVTable);

			/* Locate the required virtual table module */
			zMod = pTab.azModuleArg[0];
			pMod = (Module)sqlite3HashFind(db.aModule, zMod, sqlite3Strlen30(zMod), (Module)null);

			/* If the module has been registered and includes a Create method,
			** invoke it now. If the module has not been registered, return an
			** error. Otherwise, do nothing.
			*/
			if (null == pMod)
			{
				pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
				rc = SQLITE_ERROR;
			}
			else
			{
				rc = vtabCallConstructor(db, pTab, pMod, pMod.pModule.xCreate, ref pzErr);
			}

			/* Justification of ALWAYS():  The xConstructor method is required to
			** create a valid sqlite3_vtab if it returns SQLITE_OK. */
			if (rc == SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)))
			{
				rc = growVTrans(db);
				if (rc == SQLITE_OK)
				{
					addToVTrans(db, sqlite3GetVTable(db, pTab));
				}
			}

			return rc;
		}

		/*
		** This function is used to set the schema of a virtual table.  It is only
		** valid to call this function from within the xCreate() or xConnect() of a
		** virtual table module.
		*/

		private static int sqlite3_declare_vtab(sqlite3 db, string zCreateTable)
		{
			Parse pParse;

			int rc = SQLITE_OK;
			Table pTab;
			string zErr = "";

			sqlite3_mutex_enter(db.mutex);
			if (null == db.pVtabCtx || null == (pTab = db.pVtabCtx.pTab))
			{
				sqlite3Error(db, SQLITE_MISUSE, 0);
				sqlite3_mutex_leave(db.mutex);
				return SQLITE_MISUSE_BKPT();
			}
			Debug.Assert((pTab.tabFlags & TF_Virtual) != 0);

			pParse = new Parse();//sqlite3StackAllocZero(db, sizeof(*pParse));
			//if ( pParse == null )
			//{
			//  rc = SQLITE_NOMEM;
			//}
			//else
			{
				pParse.declareVtab = 1;
				pParse.db = db;
				pParse.nQueryLoop = 1;

				if (SQLITE_OK == sqlite3RunParser(pParse, zCreateTable, ref zErr)
				 && pParse.pNewTable != null
					//&& !db.mallocFailed
				 && null == pParse.pNewTable.pSelect
				 && (pParse.pNewTable.tabFlags & TF_Virtual) == 0
				)
				{
					if (null == pTab.aCol)
					{
						pTab.aCol = pParse.pNewTable.aCol;
						pTab.nCol = pParse.pNewTable.nCol;
						pParse.pNewTable.nCol = 0;
						pParse.pNewTable.aCol = null;
					}
					db.pVtabCtx.pTab = null;
				}
				else
				{
					sqlite3Error(db, SQLITE_ERROR, (zErr != null ? "%s" : null), zErr);
					zErr = null;//sqlite3DbFree( db, zErr );
					rc = SQLITE_ERROR;
				}
				pParse.declareVtab = 0;

				if (pParse.pVdbe != null)
				{
					sqlite3VdbeFinalize(ref pParse.pVdbe);
				}
				sqlite3DeleteTable(db, ref pParse.pNewTable);
				//sqlite3StackFree( db, pParse );
			}

			Debug.Assert((rc & 0xff) == rc);
			rc = sqlite3ApiExit(db, rc);
			sqlite3_mutex_leave(db.mutex);
			return rc;
		}

		/*
		** This function is invoked by the vdbe to call the xDestroy method
		** of the virtual table named zTab in database iDb. This occurs
		** when a DROP TABLE is mentioned.
		**
		** This call is a no-op if zTab is not a virtual table.
		*/

		private static int sqlite3VtabCallDestroy(sqlite3 db, int iDb, string zTab)
		{
			int rc = SQLITE_OK;
			Table pTab;

			pTab = sqlite3FindTable(db, zTab, db.aDb[iDb].zName);
			if (ALWAYS(pTab != null && pTab.pVTable != null))
			{
				VTable p = vtabDisconnectAll(db, pTab);

				Debug.Assert(rc == SQLITE_OK);
				object obj = p.pVtab;
				rc = p.pMod.pModule.xDestroy(ref obj);
				p.pVtab = null;

				/* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
				if (rc == SQLITE_OK)
				{
					Debug.Assert(pTab.pVTable == p && p.pNext == null);
					p.pVtab = null;
					pTab.pVTable = null;
					sqlite3VtabUnlock(p);
				}
			}

			return rc;
		}

		/*
		** This function invokes either the xRollback or xCommit method
		** of each of the virtual tables in the sqlite3.aVTrans array. The method
		** called is identified by the second argument, "offset", which is
		** the offset of the method to call in the sqlite3_module structure.
		**
		** The array is cleared after invoking the callbacks.
		*/

		private static void callFinaliser(sqlite3 db, int offset)
		{
			int i;
			if (db.aVTrans != null)
			{
				for (i = 0; i < db.nVTrans; i++)
				{
					VTable pVTab = db.aVTrans[i];
					sqlite3_vtab p = pVTab.pVtab;
					if (p != null)
					{
						//int (*x)(sqlite3_vtab );
						//x = *(int (*)(sqlite3_vtab ))((char )p.pModule + offset);
						//if( x ) x(p);
						if (offset == 0)
						{
							if (p.pModule.xCommit != null)
								p.pModule.xCommit(p);
						}
						else
						{
							if (p.pModule.xRollback != null)
								p.pModule.xRollback(p);
						}
					}
					pVTab.iSavepoint = 0;
					sqlite3VtabUnlock(pVTab);
				}
				sqlite3DbFree(db, ref db.aVTrans);
				db.nVTrans = 0;
				db.aVTrans = null;
			}
		}

		/*
		** Invoke the xSync method of all virtual tables in the sqlite3.aVTrans
		** array. Return the error code for the first error that occurs, or
		** SQLITE_OK if all xSync operations are successful.
		**
		** Set *pzErrmsg to point to a buffer that should be released using
		** sqlite3DbFree() containing an error message, if one is available.
		*/

		private static int sqlite3VtabSync(sqlite3 db, ref string pzErrmsg)
		{
			int i;
			int rc = SQLITE_OK;
			VTable[] aVTrans = db.aVTrans;

			db.aVTrans = null;
			for (i = 0; rc == SQLITE_OK && i < db.nVTrans; i++)
			{
				smdxFunction x;//int (*x)(sqlite3_vtab );
				sqlite3_vtab pVtab = aVTrans[i].pVtab;
				if (pVtab != null && (x = pVtab.pModule.xSync) != null)
				{
					rc = x(pVtab);
					//sqlite3DbFree(db, ref pzErrmsg);
					pzErrmsg = pVtab.zErrMsg;// sqlite3DbStrDup( db, pVtab.zErrMsg );
					pVtab.zErrMsg = null;//sqlite3_free( ref pVtab.zErrMsg );
				}
			}
			db.aVTrans = aVTrans;
			return rc;
		}

		/*
		** Invoke the xRollback method of all virtual tables in the
		** sqlite3.aVTrans array. Then clear the array itself.
		*/

		private static int sqlite3VtabRollback(sqlite3 db)
		{
			callFinaliser(db, 1);//offsetof( sqlite3_module, xRollback ) );
			return SQLITE_OK;
		}

		/*
		** Invoke the xCommit method of all virtual tables in the
		** sqlite3.aVTrans array. Then clear the array itself.
		*/

		private static int sqlite3VtabCommit(sqlite3 db)
		{
			callFinaliser(db, 0);//offsetof( sqlite3_module, xCommit ) );
			return SQLITE_OK;
		}

		/*
		** If the virtual table pVtab supports the transaction interface
		** (xBegin/xRollback/xCommit and optionally xSync) and a transaction is
		** not currently open, invoke the xBegin method now.
		**
		** If the xBegin call is successful, place the sqlite3_vtab pointer
		** in the sqlite3.aVTrans array.
		*/

		private static int sqlite3VtabBegin(sqlite3 db, VTable pVTab)
		{
			int rc = SQLITE_OK;
			sqlite3_module pModule;

			/* Special case: If db.aVTrans is NULL and db.nVTrans is greater
			** than zero, then this function is being called from within a
			** virtual module xSync() callback. It is illegal to write to
			** virtual module tables in this case, so return SQLITE_LOCKED.
			*/
			if (sqlite3VtabInSync(db))
			{
				return SQLITE_LOCKED;
			}
			if (null == pVTab)
			{
				return SQLITE_OK;
			}
			pModule = pVTab.pVtab.pModule;

			if (pModule.xBegin != null)
			{
				int i;

				/* If pVtab is already in the aVTrans array, return early */
				for (i = 0; i < db.nVTrans; i++)
				{
					if (db.aVTrans[i] == pVTab)
					{
						return SQLITE_OK;
					}
				}

				/* Invoke the xBegin method. If successful, add the vtab to the
				** sqlite3.aVTrans[] array. */
				rc = growVTrans(db);
				if (rc == SQLITE_OK)
				{
					rc = pModule.xBegin(pVTab.pVtab);
					if (rc == SQLITE_OK)
					{
						addToVTrans(db, pVTab);
					}
				}
			}
			return rc;
		}

		/*
		** Invoke either the xSavepoint, xRollbackTo or xRelease method of all
		** virtual tables that currently have an open transaction. Pass iSavepoint
		** as the second argument to the virtual table method invoked.
		**
		** If op is SAVEPOINT_BEGIN, the xSavepoint method is invoked. If it is
		** SAVEPOINT_ROLLBACK, the xRollbackTo method. Otherwise, if op is
		** SAVEPOINT_RELEASE, then the xRelease method of each virtual table with
		** an open transaction is invoked.
		**
		** If any virtual table method returns an error code other than SQLITE_OK,
		** processing is abandoned and the error returned to the caller of this
		** function immediately. If all calls to virtual table methods are successful,
		** SQLITE_OK is returned.
		*/

		private static int sqlite3VtabSavepoint(sqlite3 db, int op, int iSavepoint)
		{
			int rc = SQLITE_OK;

			Debug.Assert(op == SAVEPOINT_RELEASE || op == SAVEPOINT_ROLLBACK || op == SAVEPOINT_BEGIN);
			Debug.Assert(iSavepoint >= 0);
			if (db.aVTrans != null)
			{
				int i;
				for (i = 0; rc == SQLITE_OK && i < db.nVTrans; i++)
				{
					VTable pVTab = db.aVTrans[i];
					sqlite3_module pMod = pVTab.pMod.pModule;
					if (pMod.iVersion >= 2)
					{
						smdxFunctionArg xMethod = null; //int (*xMethod)(sqlite3_vtab *, int);
						switch (op)
						{
							case SAVEPOINT_BEGIN:
								xMethod = pMod.xSavepoint;
								pVTab.iSavepoint = iSavepoint + 1;
								break;

							case SAVEPOINT_ROLLBACK:
								xMethod = pMod.xRollbackTo;
								break;

							default:
								xMethod = pMod.xRelease;
								break;
						}
						if (xMethod != null && pVTab.iSavepoint > iSavepoint)
						{
							rc = xMethod(db.aVTrans[i].pVtab, iSavepoint);
						}
					}
				}
			}
			return rc;
		}

		/*
		** The first parameter (pDef) is a function implementation.  The
		** second parameter (pExpr) is the first argument to this function.
		** If pExpr is a column in a virtual table, then let the virtual
		** table implementation have an opportunity to overload the function.
		**
		** This routine is used to allow virtual table implementations to
		** overload MATCH, LIKE, GLOB, and REGEXP operators.
		**
		** Return either the pDef argument (indicating no change) or a
		** new FuncDef structure that is marked as ephemeral using the
		** SQLITE_FUNC_EPHEM flag.
		*/

		private static FuncDef sqlite3VtabOverloadFunction(
		  sqlite3 db,    /* Database connection for reporting malloc problems */
		  FuncDef pDef,  /* Function to possibly overload */
		  int nArg,      /* Number of arguments to the function */
		  Expr pExpr     /* First argument to the function */
		)
		{
			Table pTab;
			sqlite3_vtab pVtab;
			sqlite3_module pMod;
			dxFunc xFunc = null;//void (*xFunc)(sqlite3_context*,int,sqlite3_value*) = 0;
			object pArg = null;
			FuncDef pNew;
			int rc = 0;
			string zLowerName;
			string z;

			/* Check to see the left operand is a column in a virtual table */
			if (NEVER(pExpr == null))
				return pDef;
			if (pExpr.op != TK_COLUMN)
				return pDef;
			pTab = pExpr.pTab;
			if (NEVER(pTab == null))
				return pDef;
			if ((pTab.tabFlags & TF_Virtual) == 0)
				return pDef;
			pVtab = sqlite3GetVTable(db, pTab).pVtab;
			Debug.Assert(pVtab != null);
			Debug.Assert(pVtab.pModule != null);
			pMod = (sqlite3_module)pVtab.pModule;
			if (pMod.xFindFunction == null)
				return pDef;

			/* Call the xFindFunction method on the virtual table implementation
			** to see if the implementation wants to overload this function
			*/
			zLowerName = pDef.zName;//sqlite3DbStrDup(db, pDef.zName);
			if (zLowerName != null)
			{
				//for(z=(unsigned char)zLowerName; *z; z++){
				//  *z = sqlite3UpperToLower[*z];
				//}
				rc = pMod.xFindFunction(pVtab, nArg, zLowerName.ToLowerInvariant(), ref xFunc, ref pArg);
				sqlite3DbFree(db, ref zLowerName);
			}
			if (rc == 0)
			{
				return pDef;
			}

			/* Create a new ephemeral function definition for the overloaded
			** function */
			//sqlite3DbMallocZero(db, sizeof(*pNew)
			//      + sqlite3Strlen30(pDef.zName) + 1);
			//if ( pNew == null )
			//{
			//  return pDef;
			//}
			pNew = pDef.Copy();
			pNew.zName = pDef.zName;
			//pNew.zName = (char )&pNew[1];
			//memcpy(pNew.zName, pDef.zName, sqlite3Strlen30(pDef.zName)+1);
			pNew.xFunc = xFunc;
			pNew.pUserData = pArg;
			pNew.flags |= SQLITE_FUNC_EPHEM;
			return pNew;
		}

		/*
		** Make sure virtual table pTab is contained in the pParse.apVirtualLock[]
		** array so that an OP_VBegin will get generated for it.  Add pTab to the
		** array if it is missing.  If pTab is already in the array, this routine
		** is a no-op.
		*/

		private static void sqlite3VtabMakeWritable(Parse pParse, Table pTab)
		{
			Parse pToplevel = sqlite3ParseToplevel(pParse);
			int i, n;
			//Table[] apVtabLock = null;

			Debug.Assert(IsVirtual(pTab));
			for (i = 0; i < pToplevel.nVtabLock; i++)
			{
				if (pTab == pToplevel.apVtabLock[i])
					return;
			}
			n = pToplevel.apVtabLock == null ? 1 : pToplevel.apVtabLock.Length + 1;//(pToplevel.nVtabLock+1)*sizeof(pToplevel.apVtabLock[0]);
			//sqlite3_realloc( pToplevel.apVtabLock, n );
			//if ( apVtabLock != null )
			{
				Array.Resize(ref pToplevel.apVtabLock, n);// pToplevel.apVtabLock= apVtabLock;
				pToplevel.apVtabLock[pToplevel.nVtabLock++] = pTab;
			}
			//else
			//{
			//  pToplevel.db.mallocFailed = 1;
			//}
		}

		private static int[] aMap = new int[] {
    SQLITE_ROLLBACK, SQLITE_ABORT, SQLITE_FAIL, SQLITE_IGNORE, SQLITE_REPLACE
  };

		/*
		** Return the ON CONFLICT resolution mode in effect for the virtual
		** table update operation currently in progress.
		**
		** The results of this routine are undefined unless it is called from
		** within an xUpdate method.
		*/

		private static int sqlite3_vtab_on_conflict(sqlite3 db)
		{
			//static const unsigned char aMap[] = {
			//  SQLITE_ROLLBACK, SQLITE_ABORT, SQLITE_FAIL, SQLITE_IGNORE, SQLITE_REPLACE
			//};
			Debug.Assert(OE_Rollback == 1 && OE_Abort == 2 && OE_Fail == 3);
			Debug.Assert(OE_Ignore == 4 && OE_Replace == 5);
			Debug.Assert(db.vtabOnConflict >= 1 && db.vtabOnConflict <= 5);
			return (int)aMap[db.vtabOnConflict - 1];
		}

		/*
		** Call from within the xCreate() or xConnect() methods to provide
		** the SQLite core with additional information about the behavior
		** of the virtual table being implemented.
		*/

		private static int sqlite3_vtab_config(sqlite3 db, int op, params object[] ap)
		{ // TODO ...){
			//va_list ap;
			int rc = SQLITE_OK;

			sqlite3_mutex_enter(db.mutex);

			va_start(ap, "op");
			switch (op)
			{
				case SQLITE_VTAB_CONSTRAINT_SUPPORT:
					{
						VtabCtx p = db.pVtabCtx;
						if (null == p)
						{
							rc = SQLITE_MISUSE_BKPT();
						}
						else
						{
							Debug.Assert(p.pTab == null || (p.pTab.tabFlags & TF_Virtual) != 0);
							p.pVTable.bConstraint = (Byte)va_arg(ap, (Int32)0);
						}
						break;
					}
				default:
					rc = SQLITE_MISUSE_BKPT();
					break;
			}
			va_end(ref ap);

			if (rc != SQLITE_OK) sqlite3Error(db, rc, 0);
			sqlite3_mutex_leave(db.mutex);
			return rc;
		}

#endif //* SQLITE_OMIT_VIRTUALTABLE */
	}
}