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Diffstat (limited to 'src/backup.c')
| -rw-r--r-- | src/backup.c | 770 |
1 files changed, 770 insertions, 0 deletions
diff --git a/src/backup.c b/src/backup.c new file mode 100644 index 0000000..d967175 --- /dev/null +++ b/src/backup.c @@ -0,0 +1,770 @@ +/* +** 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 ); + + /* Catch the case where the destination is an in-memory database and the + ** page sizes of the source and destination differ. + */ + if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(pDestPager) ){ + rc = SQLITE_READONLY; + } + + /* 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 && 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 */ |