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Size and performance optimization in btreeInitPage() in the freeblock

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validation step.

FossilOrigin-Name: 57deb1b412e0c328528f2b4d697e326bfd028dca
This commit is contained in:
drh
2016-12-12 01:30:01 +00:00
parent f0bc50aa3a
commit 77dc0ed621
3 changed files with 26 additions and 21 deletions
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33
src/btree.c
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@@ -1743,7 +1743,7 @@ static int btreeInitPage(MemPage *pPage){
assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
if( !pPage->isInit ){
u16 pc; /* Address of a freeblock within pPage->aData[] */
u32 pc; /* Address of a freeblock within pPage->aData[] */
u8 hdr; /* Offset to beginning of page header */
u8 *data; /* Equal to pPage->aData */
BtShared *pBt; /* The main btree structure */
@@ -1823,25 +1823,30 @@ static int btreeInitPage(MemPage *pPage){
** freeblocks. */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+7] + top; /* Init nFree to non-freeblock free space */
while( pc>0 ){
u16 next, size;
if( pc<iCellFirst || pc>iCellLast ){
if( pc>0 ){
u32 next, size;
if( pc<iCellFirst ){
/* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
** always be at least one cell before the first freeblock.
**
** Or, the freeblock is off the end of the page
*/
return SQLITE_CORRUPT_BKPT;
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
/* Free blocks must be in ascending order. And the last byte of
** the free-block must lie on the database page. */
return SQLITE_CORRUPT_BKPT;
while( 1 ){
if( pc>iCellLast ){
return SQLITE_CORRUPT_BKPT; /* Freeblock off the end of the page */
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
nFree = nFree + size;
if( next<=pc+size+3 ) break;
pc = next;
}
if( next>0 ){
return SQLITE_CORRUPT_BKPT; /* Freeblock not in ascending order */
}
if( pc+size>usableSize ){
return SQLITE_CORRUPT_BKPT; /* Last freeblock extends past page end */
}
nFree = nFree + size;
pc = next;
}
/* At this point, nFree contains the sum of the offset to the start