Move bundled copy of sqlite one level deeper to better separate it...

third_party/sqlite/src/backup.c

Index: third_party/sqlite/src/backup.c
===================================================================
--- third_party/sqlite/src/backup.c	(revision 56608)
+++ third_party/sqlite/src/backup.c	(working copy)
@@ -1,630 +0,0 @@
-/*
-** 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.
-**
-** $Id: backup.c,v 1.19 2009/07/06 19:03:13 drh Exp $
-*/
-#include "sqliteInt.h"
-#include "btreeInt.h"
-
-/* Macro to find the minimum of two numeric values.
-*/
-#ifndef MIN
-# define MIN(x,y) ((x)<(y)?(x):(y))
-#endif
-
-/*
-** 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 *pParse;
-    int rc = 0;
-    pParse = sqlite3StackAllocZero(pErrorDb, sizeof(*pParse));
-    if( pParse==0 ){
-      sqlite3Error(pErrorDb, SQLITE_NOMEM, "out of memory");
-      rc = SQLITE_NOMEM;
-    }else{
-      pParse->db = pDb;
-      if( sqlite3OpenTempDatabase(pParse) ){
-        sqlite3ErrorClear(pParse);
-        sqlite3Error(pErrorDb, pParse->rc, "%s", pParse->zErrMsg);
-        rc = SQLITE_ERROR;
-      }
-      sqlite3StackFree(pErrorDb, pParse);
-    }
-    if( rc ){
-      return 0;
-    }
-  }
-
-  if( i<0 ){
-    sqlite3Error(pErrorDb, SQLITE_ERROR, "unknown database %s", zDb);
-    return 0;
-  }
-
-  return pDb->aDb[i].pBt;
-}
-
-/*
-** 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 */
-
-  /* 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 */
-    p = (sqlite3_backup *)sqlite3_malloc(sizeof(sqlite3_backup));
-    if( !p ){
-      sqlite3Error(pDestDb, SQLITE_NOMEM, 0);
-    }
-  }
-
-  /* If the allocation succeeded, populate the new object. */
-  if( p ){
-    memset(p, 0, sizeof(sqlite3_backup));
-    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 ){
-      /* One (or both) of the named databases did not exist. An 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, 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;
-}
-
-/*
-** 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;
-
-  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;
-    }
-
-    /* Lock the destination database, if it is not locked already. */
-    if( SQLITE_OK==rc && p->bDestLocked==0
-     && SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2)) 
-    ){
-      p->bDestLocked = 1;
-      sqlite3BtreeGetMeta(p->pDest, BTREE_SCHEMA_VERSION, &p->iDestSchema);
-    }
-
-    /* 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);
-      bCloseTrans = 1;
-    }
-  
-    /* Now that there is a read-lock on the source database, query the
-    ** source pager for the number of pages in the database.
-    */
-    if( rc==SQLITE_OK ){
-      rc = sqlite3PagerPagecount(pSrcPager, &nSrcPage);
-    }
-    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);
-        if( rc==SQLITE_OK ){
-          rc = backupOnePage(p, iSrcPg, sqlite3PagerGetData(pSrcPg));
-          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 
-     && (rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1))==SQLITE_OK
-    ){
-      const int nSrcPagesize = sqlite3BtreeGetPageSize(p->pSrc);
-      const int nDestPagesize = sqlite3BtreeGetPageSize(p->pDest);
-      int nDestTruncate;
-  
-      if( p->pDestDb ){
-        sqlite3ResetInternalSchema(p->pDestDb, 0);
-      }
-
-      /* 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.
-      */
-      if( nSrcPagesize<nDestPagesize ){
-        int ratio = nDestPagesize/nSrcPagesize;
-        nDestTruncate = (nSrcPage+ratio-1)/ratio;
-        if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
-          nDestTruncate--;
-        }
-      }else{
-        nDestTruncate = nSrcPage * (nSrcPagesize/nDestPagesize);
-      }
-      sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
-
-      if( nSrcPagesize<nDestPagesize ){
-        /* 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)nSrcPagesize * (i64)nSrcPage;
-        sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
-
-        assert( pFile );
-        assert( (i64)nDestTruncate*(i64)nDestPagesize >= iSize || (
-              nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
-           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+nDestPagesize
-        ));
-        if( SQLITE_OK==(rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1))
-         && SQLITE_OK==(rc = backupTruncateFile(pFile, iSize))
-         && SQLITE_OK==(rc = sqlite3PagerSync(pDestPager))
-        ){
-          i64 iOff;
-          i64 iEnd = MIN(PENDING_BYTE + nDestPagesize, iSize);
-          for(
-            iOff=PENDING_BYTE+nSrcPagesize; 
-            rc==SQLITE_OK && iOff<iEnd; 
-            iOff+=nSrcPagesize
-          ){
-            PgHdr *pSrcPg = 0;
-            const Pgno iSrcPg = (Pgno)((iOff/nSrcPagesize)+1);
-            rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
-            if( rc==SQLITE_OK ){
-              u8 *zData = sqlite3PagerGetData(pSrcPg);
-              rc = sqlite3OsWrite(pFile, zData, nSrcPagesize, iOff);
-            }
-            sqlite3PagerUnref(pSrcPg);
-          }
-        }
-      }else{
-        rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 0);
-      }
-  
-      /* Finish committing the transaction to the destination database. */
-      if( SQLITE_OK==rc
-       && SQLITE_OK==(rc = sqlite3BtreeCommitPhaseTwo(p->pDest))
-      ){
-        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);
-      assert( rc2==SQLITE_OK );
-    }
-  
-    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_mutex *mutex;                /* Mutex to protect source database */
-  int rc;                              /* Value to return */
-
-  /* Enter the mutexes */
-  if( p==0 ) return SQLITE_OK;
-  sqlite3_mutex_enter(p->pSrcDb->mutex);
-  sqlite3BtreeEnter(p->pSrc);
-  mutex = p->pSrcDb->mutex;
-  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));
-    while( *pp!=p ){
-      pp = &(*pp)->pNext;
-    }
-    *pp = p->pNext;
-  }
-
-  /* If a transaction is still open on the Btree, roll it back. */
-  sqlite3BtreeRollback(p->pDest);
-
-  /* Set the error code of the destination database handle. */
-  rc = (p->rc==SQLITE_DONE) ? SQLITE_OK : p->rc;
-  sqlite3Error(p->pDestDb, rc, 0);
-
-  /* Exit the mutexes and free the backup context structure. */
-  if( p->pDestDb ){
-    sqlite3_mutex_leave(p->pDestDb->mutex);
-  }
-  sqlite3BtreeLeave(p->pSrc);
-  if( p->pDestDb ){
-    sqlite3_free(p);
-  }
-  sqlite3_mutex_leave(mutex);
-  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){
-  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){
-  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.
-*/
-void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
-  sqlite3_backup *p;                   /* Iterator variable */
-  for(p=pBackup; p; p=p->pNext){
-    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 = backupOnePage(p, iPage, aData);
-      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
-      if( rc!=SQLITE_OK ){
-        p->rc = rc;
-      }
-    }
-  }
-}
-
-/*
-** 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_backup b;
-  sqlite3BtreeEnter(pTo);
-  sqlite3BtreeEnter(pFrom);
-
-  /* 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->pageSizeFixed = 0;
-  }
-
-  sqlite3BtreeLeave(pFrom);
-  sqlite3BtreeLeave(pTo);
-  return rc;
-}
-#endif /* SQLITE_OMIT_VACUUM */