+** CAPI3REF: Testing Interface {H11400} <S30800>
+**
+** The sqlite3_test_control() interface is used to read out internal
+** state of SQLite and to inject faults into SQLite for testing
+** purposes. The first parameter is an operation code that determines
+** the number, meaning, and operation of all subsequent parameters.
+**
+** This interface is not for use by applications. It exists solely
+** for verifying the correct operation of the SQLite library. Depending
+** on how the SQLite library is compiled, this interface might not exist.
+**
+** The details of the operation codes, their meanings, the parameters
+** they take, and what they do are all subject to change without notice.
+** Unlike most of the SQLite API, this function is not guaranteed to
+** operate consistently from one release to the next.
+*/
+int sqlite3_test_control(int op, ...);
+
+/*
+** CAPI3REF: Testing Interface Operation Codes {H11410} <H11400>
+**
+** These constants are the valid operation code parameters used
+** as the first argument to [sqlite3_test_control()].
+**
+** These parameters and their meanings are subject to change
+** without notice. These values are for testing purposes only.
+** Applications should not use any of these parameters or the
+** [sqlite3_test_control()] interface.
+*/
+#define SQLITE_TESTCTRL_PRNG_SAVE 5
+#define SQLITE_TESTCTRL_PRNG_RESTORE 6
+#define SQLITE_TESTCTRL_PRNG_RESET 7
+#define SQLITE_TESTCTRL_BITVEC_TEST 8
+#define SQLITE_TESTCTRL_FAULT_INSTALL 9
+#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS 10
+#define SQLITE_TESTCTRL_PENDING_BYTE 11
+
+/*
+** CAPI3REF: SQLite Runtime Status {H17200} <S60200>
+** EXPERIMENTAL
+**
+** This interface is used to retrieve runtime status information
+** about the preformance of SQLite, and optionally to reset various
+** highwater marks. The first argument is an integer code for
+** the specific parameter to measure. Recognized integer codes
+** are of the form [SQLITE_STATUS_MEMORY_USED | SQLITE_STATUS_...].
+** The current value of the parameter is returned into *pCurrent.
+** The highest recorded value is returned in *pHighwater. If the
+** resetFlag is true, then the highest record value is reset after
+** *pHighwater is written. Some parameters do not record the highest
+** value. For those parameters
+** nothing is written into *pHighwater and the resetFlag is ignored.
+** Other parameters record only the highwater mark and not the current
+** value. For these latter parameters nothing is written into *pCurrent.
+**
+** This routine returns SQLITE_OK on success and a non-zero
+** [error code] on failure.
+**
+** This routine is threadsafe but is not atomic. This routine can
+** called while other threads are running the same or different SQLite
+** interfaces. However the values returned in *pCurrent and
+** *pHighwater reflect the status of SQLite at different points in time
+** and it is possible that another thread might change the parameter
+** in between the times when *pCurrent and *pHighwater are written.
+**
+** See also: [sqlite3_db_status()]
+*/
+SQLITE_EXPERIMENTAL int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+
+
+/*
+** CAPI3REF: Status Parameters {H17250} <H17200>
+** EXPERIMENTAL
+**
+** These integer constants designate various run-time status parameters
+** that can be returned by [sqlite3_status()].
+**
+** <dl>
+** <dt>SQLITE_STATUS_MEMORY_USED</dt>
+** <dd>This parameter is the current amount of memory checked out
+** using [sqlite3_malloc()], either directly or indirectly. The
+** figure includes calls made to [sqlite3_malloc()] by the application
+** and internal memory usage by the SQLite library. Scratch memory
+** controlled by [SQLITE_CONFIG_SCRATCH] and auxiliary page-cache
+** memory controlled by [SQLITE_CONFIG_PAGECACHE] is not included in
+** this parameter. The amount returned is the sum of the allocation
+** sizes as reported by the xSize method in [sqlite3_mem_methods].</dd>
+**
+** <dt>SQLITE_STATUS_MALLOC_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [sqlite3_malloc()] or [sqlite3_realloc()] (or their
+** internal equivalents). Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.
+** The value written into the *pCurrent parameter is undefined.</dd>
+**
+** <dt>SQLITE_STATUS_PAGECACHE_USED</dt>
+** <dd>This parameter returns the number of pages used out of the
+** [pagecache memory allocator] that was configured using
+** [SQLITE_CONFIG_PAGECACHE]. The
+** value returned is in pages, not in bytes.</dd>
+**
+** <dt>SQLITE_STATUS_PAGECACHE_OVERFLOW</dt>
+** <dd>This parameter returns the number of bytes of page cache
+** allocation which could not be statisfied by the [SQLITE_CONFIG_PAGECACHE]
+** buffer and where forced to overflow to [sqlite3_malloc()]. The
+** returned value includes allocations that overflowed because they
+** where too large (they were larger than the "sz" parameter to
+** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
+** no space was left in the page cache.</dd>
+**
+** <dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [pagecache memory allocator]. Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.
+** The value written into the *pCurrent parameter is undefined.</dd>
+**
+** <dt>SQLITE_STATUS_SCRATCH_USED</dt>
+** <dd>This parameter returns the number of allocations used out of the
+** [scratch memory allocator] configured using
+** [SQLITE_CONFIG_SCRATCH]. The value returned is in allocations, not
+** in bytes. Since a single thread may only have one scratch allocation
+** outstanding at time, this parameter also reports the number of threads
+** using scratch memory at the same time.</dd>
+**
+** <dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>
+** <dd>This parameter returns the number of bytes of scratch memory
+** allocation which could not be statisfied by the [SQLITE_CONFIG_SCRATCH]
+** buffer and where forced to overflow to [sqlite3_malloc()]. The values
+** returned include overflows because the requested allocation was too
+** larger (that is, because the requested allocation was larger than the
+** "sz" parameter to [SQLITE_CONFIG_SCRATCH]) and because no scratch buffer
+** slots were available.
+** </dd>
+**
+** <dt>SQLITE_STATUS_SCRATCH_SIZE</dt>
+** <dd>This parameter records the largest memory allocation request
+** handed to [scratch memory allocator]. Only the value returned in the
+** *pHighwater parameter to [sqlite3_status()] is of interest.
+** The value written into the *pCurrent parameter is undefined.</dd>
+**
+** <dt>SQLITE_STATUS_PARSER_STACK</dt>
+** <dd>This parameter records the deepest parser stack. It is only
+** meaningful if SQLite is compiled with [YYTRACKMAXSTACKDEPTH].</dd>
+** </dl>
+**
+** New status parameters may be added from time to time.
+*/
+#define SQLITE_STATUS_MEMORY_USED 0
+#define SQLITE_STATUS_PAGECACHE_USED 1
+#define SQLITE_STATUS_PAGECACHE_OVERFLOW 2
+#define SQLITE_STATUS_SCRATCH_USED 3
+#define SQLITE_STATUS_SCRATCH_OVERFLOW 4
+#define SQLITE_STATUS_MALLOC_SIZE 5
+#define SQLITE_STATUS_PARSER_STACK 6
+#define SQLITE_STATUS_PAGECACHE_SIZE 7
+#define SQLITE_STATUS_SCRATCH_SIZE 8
+
+/*
+** CAPI3REF: Database Connection Status {H17500} <S60200>
+** EXPERIMENTAL
+**
+** This interface is used to retrieve runtime status information
+** about a single [database connection]. The first argument is the
+** database connection object to be interrogated. The second argument
+** is the parameter to interrogate. Currently, the only allowed value
+** for the second parameter is [SQLITE_DBSTATUS_LOOKASIDE_USED].
+** Additional options will likely appear in future releases of SQLite.
+**
+** The current value of the requested parameter is written into *pCur
+** and the highest instantaneous value is written into *pHiwtr. If
+** the resetFlg is true, then the highest instantaneous value is
+** reset back down to the current value.
+**
+** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
+*/
+SQLITE_EXPERIMENTAL int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for database connections {H17520} <H17500>
+** EXPERIMENTAL
+**
+** Status verbs for [sqlite3_db_status()].
+**
+** <dl>
+** <dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
+** <dd>This parameter returns the number of lookaside memory slots currently
+** checked out.</dd>
+** </dl>
+*/
+#define SQLITE_DBSTATUS_LOOKASIDE_USED 0
+
+
+/*
+** CAPI3REF: Prepared Statement Status {H17550} <S60200>
+** EXPERIMENTAL
+**
+** Each prepared statement maintains various
+** [SQLITE_STMTSTATUS_SORT | counters] that measure the number
+** of times it has performed specific operations. These counters can
+** be used to monitor the performance characteristics of the prepared
+** statements. For example, if the number of table steps greatly exceeds
+** the number of table searches or result rows, that would tend to indicate
+** that the prepared statement is using a full table scan rather than
+** an index.
+**
+** This interface is used to retrieve and reset counter values from
+** a [prepared statement]. The first argument is the prepared statement
+** object to be interrogated. The second argument
+** is an integer code for a specific [SQLITE_STMTSTATUS_SORT | counter]
+** to be interrogated.
+** The current value of the requested counter is returned.
+** If the resetFlg is true, then the counter is reset to zero after this
+** interface call returns.
+**
+** See also: [sqlite3_status()] and [sqlite3_db_status()].
+*/
+SQLITE_EXPERIMENTAL int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+
+/*
+** CAPI3REF: Status Parameters for prepared statements {H17570} <H17550>
+** EXPERIMENTAL
+**
+** These preprocessor macros define integer codes that name counter
+** values associated with the [sqlite3_stmt_status()] interface.
+** The meanings of the various counters are as follows:
+**
+** <dl>
+** <dt>SQLITE_STMTSTATUS_FULLSCAN_STEP</dt>
+** <dd>This is the number of times that SQLite has stepped forward in
+** a table as part of a full table scan. Large numbers for this counter
+** may indicate opportunities for performance improvement through
+** careful use of indices.</dd>
+**
+** <dt>SQLITE_STMTSTATUS_SORT</dt>
+** <dd>This is the number of sort operations that have occurred.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance through careful use of indices.</dd>
+**
+** </dl>
+*/
+#define SQLITE_STMTSTATUS_FULLSCAN_STEP 1
+#define SQLITE_STMTSTATUS_SORT 2
+
+/*
+** CAPI3REF: Custom Page Cache Object
+** EXPERIMENTAL
+**
+** The sqlite3_pcache type is opaque. It is implemented by
+** the pluggable module. The SQLite core has no knowledge of
+** its size or internal structure and never deals with the
+** sqlite3_pcache object except by holding and passing pointers
+** to the object.
+**
+** See [sqlite3_pcache_methods] for additional information.
+*/
+typedef struct sqlite3_pcache sqlite3_pcache;
+
+/*
+** CAPI3REF: Application Defined Page Cache.
+** EXPERIMENTAL
+**
+** The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
+** register an alternative page cache implementation by passing in an
+** instance of the sqlite3_pcache_methods structure. The majority of the
+** heap memory used by sqlite is used by the page cache to cache data read
+** from, or ready to be written to, the database file. By implementing a
+** custom page cache using this API, an application can control more
+** precisely the amount of memory consumed by sqlite, the way in which
+** said memory is allocated and released, and the policies used to
+** determine exactly which parts of a database file are cached and for
+** how long.
+**
+** The contents of the structure are copied to an internal buffer by sqlite
+** within the call to [sqlite3_config].
+**
+** The xInit() method is called once for each call to [sqlite3_initialize()]
+** (usually only once during the lifetime of the process). It is passed
+** a copy of the sqlite3_pcache_methods.pArg value. It can be used to set
+** up global structures and mutexes required by the custom page cache
+** implementation. The xShutdown() method is called from within
+** [sqlite3_shutdown()], if the application invokes this API. It can be used
+** to clean up any outstanding resources before process shutdown, if required.
+**
+** The xCreate() method is used to construct a new cache instance. The
+** first parameter, szPage, is the size in bytes of the pages that must
+** be allocated by the cache. szPage will not be a power of two. The
+** second argument, bPurgeable, is true if the cache being created will
+** be used to cache database pages read from a file stored on disk, or
+** false if it is used for an in-memory database. The cache implementation
+** does not have to do anything special based on the value of bPurgeable,
+** it is purely advisory.
+**
+** The xCachesize() method may be called at any time by SQLite to set the
+** suggested maximum cache-size (number of pages stored by) the cache
+** instance passed as the first argument. This is the value configured using
+** the SQLite "[PRAGMA cache_size]" command. As with the bPurgeable parameter,
+** the implementation is not required to do anything special with this
+** value, it is advisory only.
+**
+** The xPagecount() method should return the number of pages currently
+** stored in the cache supplied as an argument.
+**
+** The xFetch() method is used to fetch a page and return a pointer to it.
+** A 'page', in this context, is a buffer of szPage bytes aligned at an
+** 8-byte boundary. The page to be fetched is determined by the key. The
+** mimimum key value is 1. After it has been retrieved using xFetch, the page
+** is considered to be pinned.
+**
+** If the requested page is already in the page cache, then a pointer to
+** the cached buffer should be returned with its contents intact. If the
+** page is not already in the cache, then the expected behaviour of the
+** cache is determined by the value of the createFlag parameter passed
+** to xFetch, according to the following table:
+**
+** <table border=1 width=85% align=center>
+** <tr><th>createFlag<th>Expected Behaviour
+** <tr><td>0<td>NULL should be returned. No new cache entry is created.
+** <tr><td>1<td>If createFlag is set to 1, this indicates that
+** SQLite is holding pinned pages that can be unpinned
+** by writing their contents to the database file (a
+** relatively expensive operation). In this situation the
+** cache implementation has two choices: it can return NULL,
+** in which case SQLite will attempt to unpin one or more
+** pages before re-requesting the same page, or it can
+** allocate a new page and return a pointer to it. If a new
+** page is allocated, then the first sizeof(void*) bytes of
+** it (at least) must be zeroed before it is returned.
+** <tr><td>2<td>If createFlag is set to 2, then SQLite is not holding any
+** pinned pages associated with the specific cache passed
+** as the first argument to xFetch() that can be unpinned. The
+** cache implementation should attempt to allocate a new
+** cache entry and return a pointer to it. Again, the first
+** sizeof(void*) bytes of the page should be zeroed before
+** it is returned. If the xFetch() method returns NULL when
+** createFlag==2, SQLite assumes that a memory allocation
+** failed and returns SQLITE_NOMEM to the user.
+** </table>
+**
+** xUnpin() is called by SQLite with a pointer to a currently pinned page
+** as its second argument. If the third parameter, discard, is non-zero,
+** then the page should be evicted from the cache. In this case SQLite
+** assumes that the next time the page is retrieved from the cache using
+** the xFetch() method, it will be zeroed. If the discard parameter is
+** zero, then the page is considered to be unpinned. The cache implementation
+** may choose to reclaim (free or recycle) unpinned pages at any time.
+** SQLite assumes that next time the page is retrieved from the cache
+** it will either be zeroed, or contain the same data that it did when it
+** was unpinned.
+**
+** The cache is not required to perform any reference counting. A single
+** call to xUnpin() unpins the page regardless of the number of prior calls
+** to xFetch().
+**
+** The xRekey() method is used to change the key value associated with the
+** page passed as the second argument from oldKey to newKey. If the cache
+** previously contains an entry associated with newKey, it should be
+** discarded. Any prior cache entry associated with newKey is guaranteed not
+** to be pinned.
+**
+** When SQLite calls the xTruncate() method, the cache must discard all
+** existing cache entries with page numbers (keys) greater than or equal
+** to the value of the iLimit parameter passed to xTruncate(). If any
+** of these pages are pinned, they are implicitly unpinned, meaning that
+** they can be safely discarded.
+**
+** The xDestroy() method is used to delete a cache allocated by xCreate().
+** All resources associated with the specified cache should be freed. After
+** calling the xDestroy() method, SQLite considers the [sqlite3_pcache*]
+** handle invalid, and will not use it with any other sqlite3_pcache_methods
+** functions.
+*/
+typedef struct sqlite3_pcache_methods sqlite3_pcache_methods;
+struct sqlite3_pcache_methods {
+ void *pArg;
+ int (*xInit)(void*);
+ void (*xShutdown)(void*);
+ sqlite3_pcache *(*xCreate)(int szPage, int bPurgeable);
+ void (*xCachesize)(sqlite3_pcache*, int nCachesize);
+ int (*xPagecount)(sqlite3_pcache*);
+ 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()].
+**
+** See Also: [Using the SQLite Online Backup API]
+*/
+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.
+**
+** See Also: [Using the SQLite Online Backup API]
+**
+** Exclusive access is required to the destination database for the
+** duration of the operation. However the source database is only
+** read-locked while it is actually being read, it is not locked
+** continuously for the entire operation. Thus, the backup may be
+** performed on a live database without preventing other users from
+** writing to the database for an extended period of time.
+**
+** To perform a backup operation:
+** <ol>
+** <li><b>sqlite3_backup_init()</b> is called once to initialize the
+** backup,
+** <li><b>sqlite3_backup_step()</b> is called one or more times to transfer
+** the data between the two databases, and finally
+** <li><b>sqlite3_backup_finish()</b> is called to release all resources
+** associated with the backup operation.
+** </ol>
+** There should be exactly one call to sqlite3_backup_finish() for each
+** successful call to sqlite3_backup_init().
+**
+** <b>sqlite3_backup_init()</b>
+**
+** The first two arguments passed to [sqlite3_backup_init()] are the database
+** handle associated with the destination database and the database name
+** used to attach the destination database to the handle. The database name
+** is "main" for the main database, "temp" for the temporary database, or
+** the name specified as part of the [ATTACH] statement if the destination is
+** an attached database. The third and fourth arguments passed to
+** sqlite3_backup_init() identify the [database connection]
+** and database name used
+** to access the source database. The values passed for the source and
+** destination [database connection] 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 connection]
+** 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
+** second parameter passed to sqlite3_backup_step(). If nPage is a negative
+** value, all remaining source pages are copied. If the required pages are
+** succesfully copied, but there are still more pages to copy before the
+** backup is complete, it returns [SQLITE_OK]. If no error occured and there
+** are no more pages to copy, then [SQLITE_DONE] is returned. If an error
+** occurs, then an SQLite error code is returned. As well as [SQLITE_OK] and
+** [SQLITE_DONE], a call to sqlite3_backup_step() may return [SQLITE_READONLY],
+** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
+**
+** As well as the case where the destination database file was opened for
+** read-only access, sqlite3_backup_step() may return [SQLITE_READONLY] if
+** the destination is an in-memory database with a different page size
+** from the source database.
+**
+** If sqlite3_backup_step() cannot obtain a required file-system lock, then
+** the [sqlite3_busy_handler | busy-handler function]
+** is invoked (if one is specified). If the
+** busy-handler returns non-zero before the lock is available, then
+** [SQLITE_BUSY] is returned to the caller. In this case the call to
+** sqlite3_backup_step() can be retried later. If the source
+** [database connection]
+** is being used to write to the source database when sqlite3_backup_step()
+** is called, then [SQLITE_LOCKED] is returned immediately. Again, in this
+** case the call to sqlite3_backup_step() can be retried later on. If
+** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX], [SQLITE_NOMEM], or
+** [SQLITE_READONLY] is returned, then
+** there is no point in retrying the call to sqlite3_backup_step(). These
+** errors are considered fatal. At this point the application must accept
+** that the backup operation has failed and pass the backup operation handle
+** to the sqlite3_backup_finish() to release associated resources.
+**
+** Following the first call to sqlite3_backup_step(), an exclusive lock is
+** obtained on the destination file. It is not released until either
+** sqlite3_backup_finish() is called or the backup operation is complete
+** and sqlite3_backup_step() returns [SQLITE_DONE]. Additionally, each time
+** a call to sqlite3_backup_step() is made a [shared lock] is obtained on
+** the source database file. This lock is released before the
+** sqlite3_backup_step() call returns. Because the source database is not
+** locked between calls to sqlite3_backup_step(), it may be modified mid-way
+** through the backup procedure. If the source database is modified by an
+** external process or via a database connection other than the one being
+** used by the backup operation, then the backup will be transparently
+** restarted by the next call to sqlite3_backup_step(). If the source
+** 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
+** occurred, 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_ACCESS | SQLITE_IOERR_XXX] error code
+** is returned. In this case the error code and an error message are
+** written to the destination [database connection].
+**
+** A return of [SQLITE_BUSY] or [SQLITE_LOCKED] from sqlite3_backup_step() is
+** not a permanent 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
+** pages that need to be updated or the size of the source database file
+** changing.
+**
+** <b>Concurrent Usage of Database Handles</b>
+**
+** The source [database connection] may be used by the application for other
+** purposes while a backup operation is underway or being initialized.
+** If SQLite is compiled and configured to support threadsafe database
+** connections, then the source database connection may be used concurrently
+** from within other threads.
+**
+** However, the application must guarantee that the destination database
+** connection handle is not passed to any other API (by any thread) after
+** sqlite3_backup_init() is called and before the corresponding call to
+** sqlite3_backup_finish(). Unfortunately SQLite does not currently check
+** for this, if the application does use the destination [database connection]
+** for some other purpose during a backup operation, things may appear to
+** work correctly but in fact be subtly malfunctioning. Use of the
+** destination database connection while a backup is in progress might
+** also cause a mutex deadlock.
+**
+** 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);
+int sqlite3_backup_finish(sqlite3_backup *p);
+int sqlite3_backup_remaining(sqlite3_backup *p);
+int sqlite3_backup_pagecount(sqlite3_backup *p);
+
+/*