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+/*
+** 2009 January 28
+**
+** 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 the implementation of the sqlite3_backup_XXX()
+** API functions and the related features.
+*/
+#include "sqliteInt.h"
+#include "btreeInt.h"
+
+/*
+** Structure allocated for each backup operation.
+*/
+struct sqlite3_backup {
+ sqlite3* pDestDb; /* Destination database handle */
+ Btree *pDest; /* Destination b-tree file */
+ u32 iDestSchema; /* Original schema cookie in destination */
+ int bDestLocked; /* True once a write-transaction is open on pDest */
+
+ Pgno iNext; /* Page number of the next source page to copy */
+ sqlite3* pSrcDb; /* Source database handle */
+ Btree *pSrc; /* Source b-tree file */
+
+ int rc; /* Backup process error code */
+
+ /* These two variables are set by every call to backup_step(). They are
+ ** read by calls to backup_remaining() and backup_pagecount().
+ */
+ Pgno nRemaining; /* Number of pages left to copy */
+ Pgno nPagecount; /* Total number of pages to copy */
+
+ int isAttached; /* True once backup has been registered with pager */
+ sqlite3_backup *pNext; /* Next backup associated with source pager */
+};
+
+/*
+** THREAD SAFETY NOTES:
+**
+** Once it has been created using backup_init(), a single sqlite3_backup
+** structure may be accessed via two groups of thread-safe entry points:
+**
+** * Via the sqlite3_backup_XXX() API function backup_step() and
+** backup_finish(). Both these functions obtain the source database
+** handle mutex and the mutex associated with the source BtShared
+** structure, in that order.
+**
+** * Via the BackupUpdate() and BackupRestart() functions, which are
+** invoked by the pager layer to report various state changes in
+** the page cache associated with the source database. The mutex
+** associated with the source database BtShared structure will always
+** be held when either of these functions are invoked.
+**
+** The other sqlite3_backup_XXX() API functions, backup_remaining() and
+** backup_pagecount() are not thread-safe functions. If they are called
+** while some other thread is calling backup_step() or backup_finish(),
+** the values returned may be invalid. There is no way for a call to
+** BackupUpdate() or BackupRestart() to interfere with backup_remaining()
+** or backup_pagecount().
+**
+** Depending on the SQLite configuration, the database handles and/or
+** the Btree objects may have their own mutexes that require locking.
+** Non-sharable Btrees (in-memory databases for example), do not have
+** associated mutexes.
+*/
+
+/*
+** Return a pointer corresponding to database zDb (i.e. "main", "temp")
+** in connection handle pDb. If such a database cannot be found, return
+** a NULL pointer and write an error message to pErrorDb.
+**
+** If the "temp" database is requested, it may need to be opened by this
+** function. If an error occurs while doing so, return 0 and write an
+** error message to pErrorDb.
+*/
+static Btree *findBtree(sqlite3 *pErrorDb, sqlite3 *pDb, const char *zDb){
+ int i = sqlite3FindDbName(pDb, zDb);
+
+ if( i==1 ){
+ Parse sParse;
+ int rc = 0;
+ sqlite3ParseObjectInit(&sParse,pDb);
+ if( sqlite3OpenTempDatabase(&sParse) ){
+ sqlite3ErrorWithMsg(pErrorDb, sParse.rc, "%s", sParse.zErrMsg);
+ rc = SQLITE_ERROR;
+ }
+ sqlite3DbFree(pErrorDb, sParse.zErrMsg);
+ sqlite3ParseObjectReset(&sParse);
+ if( rc ){
+ return 0;
+ }
+ }
+
+ if( i<0 ){
+ sqlite3ErrorWithMsg(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
+ return 0;
+ }
+
+ return pDb->aDb[i].pBt;
+}
+
+/*
+** Attempt to set the page size of the destination to match the page size
+** of the source.
+*/
+static int setDestPgsz(sqlite3_backup *p){
+ int rc;
+ rc = sqlite3BtreeSetPageSize(p->pDest,sqlite3BtreeGetPageSize(p->pSrc),0,0);
+ return rc;
+}
+
+/*
+** Check that there is no open read-transaction on the b-tree passed as the
+** second argument. If there is not, return SQLITE_OK. Otherwise, if there
+** is an open read-transaction, return SQLITE_ERROR and leave an error
+** message in database handle db.
+*/
+static int checkReadTransaction(sqlite3 *db, Btree *p){
+ if( sqlite3BtreeTxnState(p)!=SQLITE_TXN_NONE ){
+ sqlite3ErrorWithMsg(db, SQLITE_ERROR, "destination database is in use");
+ return SQLITE_ERROR;
+ }
+ return SQLITE_OK;
+}
+
+/*
+** Create an sqlite3_backup process to copy the contents of zSrcDb from
+** connection handle pSrcDb to zDestDb in pDestDb. If successful, return
+** a pointer to the new sqlite3_backup object.
+**
+** If an error occurs, NULL is returned and an error code and error message
+** stored in database handle pDestDb.
+*/
+sqlite3_backup *sqlite3_backup_init(
+ sqlite3* pDestDb, /* Database to write to */
+ const char *zDestDb, /* Name of database within pDestDb */
+ sqlite3* pSrcDb, /* Database connection to read from */
+ const char *zSrcDb /* Name of database within pSrcDb */
+){
+ sqlite3_backup *p; /* Value to return */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+ if( !sqlite3SafetyCheckOk(pSrcDb)||!sqlite3SafetyCheckOk(pDestDb) ){
+ (void)SQLITE_MISUSE_BKPT;
+ return 0;
+ }
+#endif
+
+ /* Lock the source database handle. The destination database
+ ** handle is not locked in this routine, but it is locked in
+ ** sqlite3_backup_step(). The user is required to ensure that no
+ ** other thread accesses the destination handle for the duration
+ ** of the backup operation. Any attempt to use the destination
+ ** database connection while a backup is in progress may cause
+ ** a malfunction or a deadlock.
+ */
+ sqlite3_mutex_enter(pSrcDb->mutex);
+ sqlite3_mutex_enter(pDestDb->mutex);
+
+ if( pSrcDb==pDestDb ){
+ sqlite3ErrorWithMsg(
+ pDestDb, SQLITE_ERROR, "source and destination must be distinct"
+ );
+ p = 0;
+ }else {
+ /* Allocate space for a new sqlite3_backup object...
+ ** EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+ ** call to sqlite3_backup_init() and is destroyed by a call to
+ ** sqlite3_backup_finish(). */
+ p = (sqlite3_backup *)sqlite3MallocZero(sizeof(sqlite3_backup));
+ if( !p ){
+ sqlite3Error(pDestDb, SQLITE_NOMEM_BKPT);
+ }
+ }
+
+ /* If the allocation succeeded, populate the new object. */
+ if( p ){
+ p->pSrc = findBtree(pDestDb, pSrcDb, zSrcDb);
+ p->pDest = findBtree(pDestDb, pDestDb, zDestDb);
+ p->pDestDb = pDestDb;
+ p->pSrcDb = pSrcDb;
+ p->iNext = 1;
+ p->isAttached = 0;
+
+ if( 0==p->pSrc || 0==p->pDest
+ || checkReadTransaction(pDestDb, p->pDest)!=SQLITE_OK
+ ){
+ /* One (or both) of the named databases did not exist or an OOM
+ ** error was hit. Or there is a transaction open on the destination
+ ** database. The error has already been written into the pDestDb
+ ** handle. All that is left to do here is free the sqlite3_backup
+ ** structure. */
+ sqlite3_free(p);
+ p = 0;
+ }
+ }
+ if( p ){
+ p->pSrc->nBackup++;
+ }
+
+ sqlite3_mutex_leave(pDestDb->mutex);
+ sqlite3_mutex_leave(pSrcDb->mutex);
+ return p;
+}
+
+/*
+** Argument rc is an SQLite error code. Return true if this error is
+** considered fatal if encountered during a backup operation. All errors
+** are considered fatal except for SQLITE_BUSY and SQLITE_LOCKED.
+*/
+static int isFatalError(int rc){
+ return (rc!=SQLITE_OK && rc!=SQLITE_BUSY && ALWAYS(rc!=SQLITE_LOCKED));
+}
+
+/*
+** Parameter zSrcData points to a buffer containing the data for
+** page iSrcPg from the source database. Copy this data into the
+** destination database.
+*/
+static int backupOnePage(
+ sqlite3_backup *p, /* Backup handle */
+ Pgno iSrcPg, /* Source database page to backup */
+ const u8 *zSrcData, /* Source database page data */
+ int bUpdate /* True for an update, false otherwise */
+){
+ Pager * const pDestPager = sqlite3BtreePager(p->pDest);
+ const int nSrcPgsz = sqlite3BtreeGetPageSize(p->pSrc);
+ int nDestPgsz = sqlite3BtreeGetPageSize(p->pDest);
+ const int nCopy = MIN(nSrcPgsz, nDestPgsz);
+ const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
+ int rc = SQLITE_OK;
+ i64 iOff;
+
+ assert( sqlite3BtreeGetReserveNoMutex(p->pSrc)>=0 );
+ assert( p->bDestLocked );
+ assert( !isFatalError(p->rc) );
+ assert( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) );
+ assert( zSrcData );
+ assert( nSrcPgsz==nDestPgsz || sqlite3PagerIsMemdb(pDestPager)==0 );
+
+ /* This loop runs once for each destination page spanned by the source
+ ** page. For each iteration, variable iOff is set to the byte offset
+ ** of the destination page.
+ */
+ for(iOff=iEnd-(i64)nSrcPgsz; rc==SQLITE_OK && iOff<iEnd; iOff+=nDestPgsz){
+ DbPage *pDestPg = 0;
+ Pgno iDest = (Pgno)(iOff/nDestPgsz)+1;
+ if( iDest==PENDING_BYTE_PAGE(p->pDest->pBt) ) continue;
+ if( SQLITE_OK==(rc = sqlite3PagerGet(pDestPager, iDest, &pDestPg, 0))
+ && SQLITE_OK==(rc = sqlite3PagerWrite(pDestPg))
+ ){
+ const u8 *zIn = &zSrcData[iOff%nSrcPgsz];
+ u8 *zDestData = sqlite3PagerGetData(pDestPg);
+ u8 *zOut = &zDestData[iOff%nDestPgsz];
+
+ /* Copy the data from the source page into the destination page.
+ ** Then clear the Btree layer MemPage.isInit flag. Both this module
+ ** and the pager code use this trick (clearing the first byte
+ ** of the page 'extra' space to invalidate the Btree layers
+ ** cached parse of the page). MemPage.isInit is marked
+ ** "MUST BE FIRST" for this purpose.
+ */
+ memcpy(zOut, zIn, nCopy);
+ ((u8 *)sqlite3PagerGetExtra(pDestPg))[0] = 0;
+ if( iOff==0 && bUpdate==0 ){
+ sqlite3Put4byte(&zOut[28], sqlite3BtreeLastPage(p->pSrc));
+ }
+ }
+ sqlite3PagerUnref(pDestPg);
+ }
+
+ return rc;
+}
+
+/*
+** If pFile is currently larger than iSize bytes, then truncate it to
+** exactly iSize bytes. If pFile is not larger than iSize bytes, then
+** this function is a no-op.
+**
+** Return SQLITE_OK if everything is successful, or an SQLite error
+** code if an error occurs.
+*/
+static int backupTruncateFile(sqlite3_file *pFile, i64 iSize){
+ i64 iCurrent;
+ int rc = sqlite3OsFileSize(pFile, &iCurrent);
+ if( rc==SQLITE_OK && iCurrent>iSize ){
+ rc = sqlite3OsTruncate(pFile, iSize);
+ }
+ return rc;
+}
+
+/*
+** Register this backup object with the associated source pager for
+** callbacks when pages are changed or the cache invalidated.
+*/
+static void attachBackupObject(sqlite3_backup *p){
+ sqlite3_backup **pp;
+ assert( sqlite3BtreeHoldsMutex(p->pSrc) );
+ pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+ p->pNext = *pp;
+ *pp = p;
+ p->isAttached = 1;
+}
+
+/*
+** Copy nPage pages from the source b-tree to the destination.
+*/
+int sqlite3_backup_step(sqlite3_backup *p, int nPage){
+ int rc;
+ int destMode; /* Destination journal mode */
+ int pgszSrc = 0; /* Source page size */
+ int pgszDest = 0; /* Destination page size */
+
+#ifdef SQLITE_ENABLE_API_ARMOR
+ if( p==0 ) return SQLITE_MISUSE_BKPT;
+#endif
+ sqlite3_mutex_enter(p->pSrcDb->mutex);
+ sqlite3BtreeEnter(p->pSrc);
+ if( p->pDestDb ){
+ sqlite3_mutex_enter(p->pDestDb->mutex);
+ }
+
+ rc = p->rc;
+ if( !isFatalError(rc) ){
+ Pager * const pSrcPager = sqlite3BtreePager(p->pSrc); /* Source pager */
+ Pager * const pDestPager = sqlite3BtreePager(p->pDest); /* Dest pager */
+ int ii; /* Iterator variable */
+ int nSrcPage = -1; /* Size of source db in pages */
+ int bCloseTrans = 0; /* True if src db requires unlocking */
+
+ /* If the source pager is currently in a write-transaction, return
+ ** SQLITE_BUSY immediately.
+ */
+ if( p->pDestDb && p->pSrc->pBt->inTransaction==TRANS_WRITE ){
+ rc = SQLITE_BUSY;
+ }else{
+ rc = SQLITE_OK;
+ }
+
+ /* If there is no open read-transaction on the source database, open
+ ** one now. If a transaction is opened here, then it will be closed
+ ** before this function exits.
+ */
+ if( rc==SQLITE_OK && SQLITE_TXN_NONE==sqlite3BtreeTxnState(p->pSrc) ){
+ rc = sqlite3BtreeBeginTrans(p->pSrc, 0, 0);
+ bCloseTrans = 1;
+ }
+
+ /* If the destination database has not yet been locked (i.e. if this
+ ** is the first call to backup_step() for the current backup operation),
+ ** try to set its page size to the same as the source database. This
+ ** is especially important on ZipVFS systems, as in that case it is
+ ** not possible to create a database file that uses one page size by
+ ** writing to it with another. */
+ if( p->bDestLocked==0 && rc==SQLITE_OK && setDestPgsz(p)==SQLITE_NOMEM ){
+ rc = SQLITE_NOMEM;
+ }
+
+ /* Lock the destination database, if it is not locked already. */
+ if( SQLITE_OK==rc && p->bDestLocked==0
+ && SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2,
+ (int*)&p->iDestSchema))
+ ){
+ p->bDestLocked = 1;
+ }
+
+ /* Do not allow backup if the destination database is in WAL mode
+ ** and the page sizes are different between source and destination */
+ pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+ pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+ destMode = sqlite3PagerGetJournalMode(sqlite3BtreePager(p->pDest));
+ if( SQLITE_OK==rc
+ && (destMode==PAGER_JOURNALMODE_WAL || sqlite3PagerIsMemdb(pDestPager))
+ && pgszSrc!=pgszDest
+ ){
+ rc = SQLITE_READONLY;
+ }
+
+ /* Now that there is a read-lock on the source database, query the
+ ** source pager for the number of pages in the database.
+ */
+ nSrcPage = (int)sqlite3BtreeLastPage(p->pSrc);
+ assert( nSrcPage>=0 );
+ for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
+ const Pgno iSrcPg = p->iNext; /* Source page number */
+ if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
+ DbPage *pSrcPg; /* Source page object */
+ rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg,PAGER_GET_READONLY);
+ if( rc==SQLITE_OK ){
+ rc = backupOnePage(p, iSrcPg, sqlite3PagerGetData(pSrcPg), 0);
+ sqlite3PagerUnref(pSrcPg);
+ }
+ }
+ p->iNext++;
+ }
+ if( rc==SQLITE_OK ){
+ p->nPagecount = nSrcPage;
+ p->nRemaining = nSrcPage+1-p->iNext;
+ if( p->iNext>(Pgno)nSrcPage ){
+ rc = SQLITE_DONE;
+ }else if( !p->isAttached ){
+ attachBackupObject(p);
+ }
+ }
+
+ /* Update the schema version field in the destination database. This
+ ** is to make sure that the schema-version really does change in
+ ** the case where the source and destination databases have the
+ ** same schema version.
+ */
+ if( rc==SQLITE_DONE ){
+ if( nSrcPage==0 ){
+ rc = sqlite3BtreeNewDb(p->pDest);
+ nSrcPage = 1;
+ }
+ if( rc==SQLITE_OK || rc==SQLITE_DONE ){
+ rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1);
+ }
+ if( rc==SQLITE_OK ){
+ if( p->pDestDb ){
+ sqlite3ResetAllSchemasOfConnection(p->pDestDb);
+ }
+ if( destMode==PAGER_JOURNALMODE_WAL ){
+ rc = sqlite3BtreeSetVersion(p->pDest, 2);
+ }
+ }
+ if( rc==SQLITE_OK ){
+ int nDestTruncate;
+ /* Set nDestTruncate to the final number of pages in the destination
+ ** database. The complication here is that the destination page
+ ** size may be different to the source page size.
+ **
+ ** If the source page size is smaller than the destination page size,
+ ** round up. In this case the call to sqlite3OsTruncate() below will
+ ** fix the size of the file. However it is important to call
+ ** sqlite3PagerTruncateImage() here so that any pages in the
+ ** destination file that lie beyond the nDestTruncate page mark are
+ ** journalled by PagerCommitPhaseOne() before they are destroyed
+ ** by the file truncation.
+ */
+ assert( pgszSrc==sqlite3BtreeGetPageSize(p->pSrc) );
+ assert( pgszDest==sqlite3BtreeGetPageSize(p->pDest) );
+ if( pgszSrc<pgszDest ){
+ int ratio = pgszDest/pgszSrc;
+ nDestTruncate = (nSrcPage+ratio-1)/ratio;
+ if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
+ nDestTruncate--;
+ }
+ }else{
+ nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
+ }
+ assert( nDestTruncate>0 );
+
+ if( pgszSrc<pgszDest ){
+ /* If the source page-size is smaller than the destination page-size,
+ ** two extra things may need to happen:
+ **
+ ** * The destination may need to be truncated, and
+ **
+ ** * Data stored on the pages immediately following the
+ ** pending-byte page in the source database may need to be
+ ** copied into the destination database.
+ */
+ const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
+ sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
+ Pgno iPg;
+ int nDstPage;
+ i64 iOff;
+ i64 iEnd;
+
+ assert( pFile );
+ assert( nDestTruncate==0
+ || (i64)nDestTruncate*(i64)pgszDest >= iSize || (
+ nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
+ && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
+ ));
+
+ /* This block ensures that all data required to recreate the original
+ ** database has been stored in the journal for pDestPager and the
+ ** journal synced to disk. So at this point we may safely modify
+ ** the database file in any way, knowing that if a power failure
+ ** occurs, the original database will be reconstructed from the
+ ** journal file. */
+ sqlite3PagerPagecount(pDestPager, &nDstPage);
+ for(iPg=nDestTruncate; rc==SQLITE_OK && iPg<=(Pgno)nDstPage; iPg++){
+ if( iPg!=PENDING_BYTE_PAGE(p->pDest->pBt) ){
+ DbPage *pPg;
+ rc = sqlite3PagerGet(pDestPager, iPg, &pPg, 0);
+ if( rc==SQLITE_OK ){
+ rc = sqlite3PagerWrite(pPg);
+ sqlite3PagerUnref(pPg);
+ }
+ }
+ }
+ if( rc==SQLITE_OK ){
+ rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1);
+ }
+
+ /* Write the extra pages and truncate the database file as required */
+ iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
+ for(
+ iOff=PENDING_BYTE+pgszSrc;
+ rc==SQLITE_OK && iOff<iEnd;
+ iOff+=pgszSrc
+ ){
+ PgHdr *pSrcPg = 0;
+ const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
+ rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg, 0);
+ if( rc==SQLITE_OK ){
+ u8 *zData = sqlite3PagerGetData(pSrcPg);
+ rc = sqlite3OsWrite(pFile, zData, pgszSrc, iOff);
+ }
+ sqlite3PagerUnref(pSrcPg);
+ }
+ if( rc==SQLITE_OK ){
+ rc = backupTruncateFile(pFile, iSize);
+ }
+
+ /* Sync the database file to disk. */
+ if( rc==SQLITE_OK ){
+ rc = sqlite3PagerSync(pDestPager, 0);
+ }
+ }else{
+ sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
+ rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
+ }
+
+ /* Finish committing the transaction to the destination database. */
+ if( SQLITE_OK==rc
+ && SQLITE_OK==(rc = sqlite3BtreeCommitPhaseTwo(p->pDest, 0))
+ ){
+ rc = SQLITE_DONE;
+ }
+ }
+ }
+
+ /* If bCloseTrans is true, then this function opened a read transaction
+ ** on the source database. Close the read transaction here. There is
+ ** no need to check the return values of the btree methods here, as
+ ** "committing" a read-only transaction cannot fail.
+ */
+ if( bCloseTrans ){
+ TESTONLY( int rc2 );
+ TESTONLY( rc2 = ) sqlite3BtreeCommitPhaseOne(p->pSrc, 0);
+ TESTONLY( rc2 |= ) sqlite3BtreeCommitPhaseTwo(p->pSrc, 0);
+ assert( rc2==SQLITE_OK );
+ }
+
+ if( rc==SQLITE_IOERR_NOMEM ){
+ rc = SQLITE_NOMEM_BKPT;
+ }
+ p->rc = rc;
+ }
+ if( p->pDestDb ){
+ sqlite3_mutex_leave(p->pDestDb->mutex);
+ }
+ sqlite3BtreeLeave(p->pSrc);
+ sqlite3_mutex_leave(p->pSrcDb->mutex);
+ return rc;
+}
+
+/*
+** Release all resources associated with an sqlite3_backup* handle.
+*/
+int sqlite3_backup_finish(sqlite3_backup *p){
+ sqlite3_backup **pp; /* Ptr to head of pagers backup list */
+ sqlite3 *pSrcDb; /* Source database connection */
+ int rc; /* Value to return */
+
+ /* Enter the mutexes */
+ if( p==0 ) return SQLITE_OK;
+ pSrcDb = p->pSrcDb;
+ sqlite3_mutex_enter(pSrcDb->mutex);
+ sqlite3BtreeEnter(p->pSrc);
+ if( p->pDestDb ){
+ sqlite3_mutex_enter(p->pDestDb->mutex);
+ }
+
+ /* Detach this backup from the source pager. */
+ if( p->pDestDb ){
+ p->pSrc->nBackup--;
+ }
+ if( p->isAttached ){
+ pp = sqlite3PagerBackupPtr(sqlite3BtreePager(p->pSrc));
+ assert( pp!=0 );
+ while( *pp!=p ){
+ pp = &(*pp)->pNext;
+ assert( pp!=0 );
+ }
+ *pp = p->pNext;
+ }
+
+ /* If a transaction is still open on the Btree, roll it back. */
+ sqlite3BtreeRollback(p->pDest, SQLITE_OK, 0);
+
+ /* Set the error code of the destination database handle. */
+ rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
+ if( p->pDestDb ){
+ sqlite3Error(p->pDestDb, rc);
+
+ /* Exit the mutexes and free the backup context structure. */
+ sqlite3LeaveMutexAndCloseZombie(p->pDestDb);
+ }
+ sqlite3BtreeLeave(p->pSrc);
+ if( p->pDestDb ){
+ /* EVIDENCE-OF: R-64852-21591 The sqlite3_backup object is created by a
+ ** call to sqlite3_backup_init() and is destroyed by a call to
+ ** sqlite3_backup_finish(). */
+ sqlite3_free(p);
+ }
+ sqlite3LeaveMutexAndCloseZombie(pSrcDb);
+ return rc;
+}
+
+/*
+** Return the number of pages still to be backed up as of the most recent
+** call to sqlite3_backup_step().
+*/
+int sqlite3_backup_remaining(sqlite3_backup *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+ if( p==0 ){
+ (void)SQLITE_MISUSE_BKPT;
+ return 0;
+ }
+#endif
+ return p->nRemaining;
+}
+
+/*
+** Return the total number of pages in the source database as of the most
+** recent call to sqlite3_backup_step().
+*/
+int sqlite3_backup_pagecount(sqlite3_backup *p){
+#ifdef SQLITE_ENABLE_API_ARMOR
+ if( p==0 ){
+ (void)SQLITE_MISUSE_BKPT;
+ return 0;
+ }
+#endif
+ return p->nPagecount;
+}
+
+/*
+** This function is called after the contents of page iPage of the
+** source database have been modified. If page iPage has already been
+** copied into the destination database, then the data written to the
+** destination is now invalidated. The destination copy of iPage needs
+** to be updated with the new data before the backup operation is
+** complete.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+static SQLITE_NOINLINE void backupUpdate(
+ sqlite3_backup *p,
+ Pgno iPage,
+ const u8 *aData
+){
+ assert( p!=0 );
+ do{
+ assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+ if( !isFatalError(p->rc) && iPage<p->iNext ){
+ /* The backup process p has already copied page iPage. But now it
+ ** has been modified by a transaction on the source pager. Copy
+ ** the new data into the backup.
+ */
+ int rc;
+ assert( p->pDestDb );
+ sqlite3_mutex_enter(p->pDestDb->mutex);
+ rc = backupOnePage(p, iPage, aData, 1);
+ sqlite3_mutex_leave(p->pDestDb->mutex);
+ assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
+ if( rc!=SQLITE_OK ){
+ p->rc = rc;
+ }
+ }
+ }while( (p = p->pNext)!=0 );
+}
+void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
+ if( pBackup ) backupUpdate(pBackup, iPage, aData);
+}
+
+/*
+** Restart the backup process. This is called when the pager layer
+** detects that the database has been modified by an external database
+** connection. In this case there is no way of knowing which of the
+** pages that have been copied into the destination database are still
+** valid and which are not, so the entire process needs to be restarted.
+**
+** It is assumed that the mutex associated with the BtShared object
+** corresponding to the source database is held when this function is
+** called.
+*/
+void sqlite3BackupRestart(sqlite3_backup *pBackup){
+ sqlite3_backup *p; /* Iterator variable */
+ for(p=pBackup; p; p=p->pNext){
+ assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
+ p->iNext = 1;
+ }
+}
+
+#ifndef SQLITE_OMIT_VACUUM
+/*
+** Copy the complete content of pBtFrom into pBtTo. A transaction
+** must be active for both files.
+**
+** The size of file pTo may be reduced by this operation. If anything
+** goes wrong, the transaction on pTo is rolled back. If successful, the
+** transaction is committed before returning.
+*/
+int sqlite3BtreeCopyFile(Btree *pTo, Btree *pFrom){
+ int rc;
+ sqlite3_file *pFd; /* File descriptor for database pTo */
+ sqlite3_backup b;
+ sqlite3BtreeEnter(pTo);
+ sqlite3BtreeEnter(pFrom);
+
+ assert( sqlite3BtreeTxnState(pTo)==SQLITE_TXN_WRITE );
+ pFd = sqlite3PagerFile(sqlite3BtreePager(pTo));
+ if( pFd->pMethods ){
+ i64 nByte = sqlite3BtreeGetPageSize(pFrom)*(i64)sqlite3BtreeLastPage(pFrom);
+ rc = sqlite3OsFileControl(pFd, SQLITE_FCNTL_OVERWRITE, &nByte);
+ if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+ if( rc ) goto copy_finished;
+ }
+
+ /* Set up an sqlite3_backup object. sqlite3_backup.pDestDb must be set
+ ** to 0. This is used by the implementations of sqlite3_backup_step()
+ ** and sqlite3_backup_finish() to detect that they are being called
+ ** from this function, not directly by the user.
+ */
+ memset(&b, 0, sizeof(b));
+ b.pSrcDb = pFrom->db;
+ b.pSrc = pFrom;
+ b.pDest = pTo;
+ b.iNext = 1;
+
+ /* 0x7FFFFFFF is the hard limit for the number of pages in a database
+ ** file. By passing this as the number of pages to copy to
+ ** sqlite3_backup_step(), we can guarantee that the copy finishes
+ ** within a single call (unless an error occurs). The assert() statement
+ ** checks this assumption - (p->rc) should be set to either SQLITE_DONE
+ ** or an error code. */
+ sqlite3_backup_step(&b, 0x7FFFFFFF);
+ assert( b.rc!=SQLITE_OK );
+
+ rc = sqlite3_backup_finish(&b);
+ if( rc==SQLITE_OK ){
+ pTo->pBt->btsFlags &= ~BTS_PAGESIZE_FIXED;
+ }else{
+ sqlite3PagerClearCache(sqlite3BtreePager(b.pDest));
+ }
+
+ assert( sqlite3BtreeTxnState(pTo)!=SQLITE_TXN_WRITE );
+copy_finished:
+ sqlite3BtreeLeave(pFrom);
+ sqlite3BtreeLeave(pTo);
+ return rc;
+}
+#endif /* SQLITE_OMIT_VACUUM */