/* ** 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 && 0==sqlite3BtreeIsInReadTrans(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 && 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; }
/* ** 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. */ SQLITE_API 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 */ /* 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 ) { sqlite3Error( 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, 0); } } /* 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 || setDestPgsz(p)==SQLITE_NOMEM ) { /* One (or both) of the named databases did not exist or an OOM ** error was hit. 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; }