/* ** 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, Pgno iSrcPg, const u8 *zSrcData){ 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( 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(sqlite3BtreePager(p->pDest)) ){ 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)) && 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; } sqlite3PagerUnref(pDestPg); } return rc; }
/* ** 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; #ifdef SQLITE_HAS_CODEC /* Use BtreeGetReserveNoMutex() for the source b-tree, as although it is ** guaranteed that the shared-mutex is held by this thread, handle ** p->pSrc may not actually be the owner. */ int nSrcReserve = sqlite3BtreeGetReserveNoMutex(p->pSrc); int nDestReserve = sqlite3BtreeGetOptimalReserve(p->pDest); #endif 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; } #ifdef SQLITE_HAS_CODEC /* Backup is not possible if the page size of the destination is changing ** and a codec is in use. */ if( nSrcPgsz!=nDestPgsz && sqlite3PagerGetCodec(pDestPager)!=0 ){ rc = SQLITE_READONLY; } /* Backup is not possible if the number of bytes of reserve space differ ** between source and destination. If there is a difference, try to ** fix the destination to agree with the source. If that is not possible, ** then the backup cannot proceed. */ if( nSrcReserve!=nDestReserve ){ u32 newPgsz = nSrcPgsz; rc = sqlite3PagerSetPagesize(pDestPager, &newPgsz, nSrcReserve); if( rc==SQLITE_OK && newPgsz!=nSrcPgsz ) rc = SQLITE_READONLY; } #endif /* 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; }