SQLite

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.424 2009/02/03 18:25:13 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++.

  void *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
  void (*xUnpin)(sqlite3_pcache*, void*, int discard);
  void (*xRekey)(sqlite3_pcache*, void*, unsigned oldKey, unsigned newKey);
  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
  void (*xDestroy)(sqlite3_pcache*);
};

/*
** CAPI3REF: Online Backup Object
** EXPERIMENTAL
**
** The sqlite3_backup object records state information about an ongoing
** online backup operation.  The sqlite3_backup object is created by
** a call to [sqlite3_backup_init()] and is destroyed by a call to
** [sqlite3_backup_finish()].
*/
typedef struct sqlite3_backup sqlite3_backup;

/*
** CAPI3REF: Online Backup API.
** EXPERIMENTAL
**
** This API is used to overwrite the contents of one database with that
** of another. It is useful either for creating backups of databases or
** for copying in-memory databases to or from persistent files. 

** to access the source database. The values passed for the source and 
** destination database handle parameters must not be the same.
**
** If an error occurs within sqlite3_backup_init(), then NULL is returned
** and an error code and error message written into the database handle 
** passed as the first argument. They may be retrieved using the
** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16() functions.
** Otherwise, if successful, a pointer to an [sqlite3_backup] object is
** returned. This pointer may be used with the sqlite3_backup_step() and
** sqlite3_backup_finish() functions to perform the specified backup 
** operation.
**
** <b>sqlite3_backup_step()</b>
**
** Function [sqlite3_backup_step()] is used to copy up to nPage pages between 
** the source and destination databases, where nPage is the value of the 

** database is modified by the using the same database connection as is used
** by the backup operation, then the backup database is transparently 
** updated at the same time.
**
** <b>sqlite3_backup_finish()</b>
**
** Once sqlite3_backup_step() has returned SQLITE_DONE, or when the 
** application wishes to abandon the backup operation, the [sqlite3_backup]
** object should be passed to sqlite3_backup_finish(). This releases all
** resources associated with the backup operation. If sqlite3_backup_step()
** has not yet returned SQLITE_DONE, then any active write-transaction on the
** destination database is rolled back. The [sqlite3_backup] object is invalid
** and may not be used following a call to sqlite3_backup_finish().
**
** The value returned by sqlite3_backup_finish is SQLITE_OK if no error
** occured, regardless or whether or not sqlite3_backup_step() was called
** a sufficient number of times to complete the backup operation. Or, if
** an out-of-memory condition or IO error occured during a call to
** sqlite3_backup_step() then SQLITE_NOMEM or an SQLITE_IOERR_XXX error code
** is returned. In this case the error code and an error message are
** written to the destination database handle.
**
** A return of SQLITE_BUSY or SQLITE_LOCKED from sqlite3_backup_step() is
** not considered an error and does not affect the return value of
** sqlite3_backup_finish().
**
** <b>sqlite3_backup_remaining(), sqlite3_backup_pagecount()</b>
**
** Each call to sqlite3_backup_step() sets two values stored internally
** by an [sqlite3_backup] object. The number of pages still to be backed
** up, which may be queried by sqlite3_backup_remaining(), and the total
** number of pages in the source database file, which may be queried by
** sqlite3_backup_pagecount().
**
** The values returned by these functions are only updated by
** sqlite3_backup_step(). If the source database is modified during a backup
** operation, then the values are not updated to account for any extra

** Furthermore, if running in shared cache mode, the application must
** guarantee that the shared cache used by the destination database
** is not accessed while the backup is running. In practice this means
** that the application must guarantee that the file-system file being 
** backed up to is not accessed by any connection within the process,
** not just the specific connection that was passed to sqlite3_backup_init().
**
** The [sqlite3_backup] object itself is partially threadsafe. Multiple 
** threads may safely make multiple concurrent calls to sqlite3_backup_step().
** However, the sqlite3_backup_remaining() and sqlite3_backup_pagecount()
** APIs are not strictly speaking threadsafe. If they are invoked at the
** same time as another thread is invoking sqlite3_backup_step() it is
** possible that they return invalid values.
*/

sqlite3_backup *sqlite3_backup_init(
  sqlite3 *pDest,                        /* Destination database handle */
  const char *zDestName,                 /* Destination database name */
  sqlite3 *pSource,                      /* Source database handle */
  const char *zSourceName                /* Source database name */
);
int sqlite3_backup_step(sqlite3_backup *p, int nPage);