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Fix alignment problems in btree and pager and allow page sizes that are

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not a multiple of 8. (CVS 2026)

FossilOrigin-Name: 0539c2d2b8e16efcbe4db3afeae9c7b426e11b05
This commit is contained in:
drh
2004-10-22 16:22:57 +00:00
parent 6138df56e7
commit 887dc4c275
5 changed files with 55 additions and 37 deletions
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49
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.192 2004/10/05 02:41:42 drh Exp $
** $Id: btree.c,v 1.193 2004/10/22 16:22:58 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -211,6 +211,11 @@
#include "os.h"
#include <assert.h>
/*
** This macro rounds values up so that if the value is an address it
** is guaranteed to be an address that is aligned to an 8-byte boundary.
*/
#define FORCE_ALIGNMENT(X) (((X)+7)&~7)
/* The following value is the maximum cell size assuming a maximum page
** size give above.
@@ -300,6 +305,7 @@ struct Btree {
u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
u8 pageSizeFixed; /* True if the page size can no longer be changed */
u16 pageSize; /* Total number of bytes on a page */
u16 psAligned; /* pageSize rounded up to a multiple of 8 */
u16 usableSize; /* Number of usable bytes on each page */
int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
int minLocal; /* Minimum local payload in non-LEAFDATA tables */
@@ -533,7 +539,7 @@ static void _pageIntegrity(MemPage *pPage){
used = sqliteMallocRaw( pPage->pBt->pageSize );
if( used==0 ) return;
usableSize = pPage->pBt->usableSize;
assert( pPage->aData==&((unsigned char*)pPage)[-pPage->pBt->pageSize] );
assert( pPage->aData==&((unsigned char*)pPage)[-pPage->pBt->psAligned] );
hdr = pPage->hdrOffset;
assert( hdr==(pPage->pgno==1 ? 100 : 0) );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
@@ -837,7 +843,7 @@ static int initPage(
assert( pBt!=0 );
assert( pParent==0 || pParent->pBt==pBt );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
assert( pPage->aData == &((unsigned char*)pPage)[-pBt->pageSize] );
assert( pPage->aData == &((unsigned char*)pPage)[-pBt->psAligned] );
if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){
/* The parent page should never change unless the file is corrupt */
return SQLITE_CORRUPT; /* bkpt-CORRUPT */
@@ -910,7 +916,7 @@ static void zeroPage(MemPage *pPage, int flags){
int first;
assert( sqlite3pager_pagenumber(data)==pPage->pgno );
assert( &data[pBt->pageSize] == (unsigned char*)pPage );
assert( &data[pBt->psAligned] == (unsigned char*)pPage );
assert( sqlite3pager_iswriteable(data) );
memset(&data[hdr], 0, pBt->usableSize - hdr);
data[hdr] = flags;
@@ -939,7 +945,7 @@ static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
MemPage *pPage;
rc = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
if( rc ) return rc;
pPage = (MemPage*)&aData[pBt->pageSize];
pPage = (MemPage*)&aData[pBt->psAligned];
pPage->aData = aData;
pPage->pBt = pBt;
pPage->pgno = pgno;
@@ -978,7 +984,7 @@ static void releasePage(MemPage *pPage){
if( pPage ){
assert( pPage->aData );
assert( pPage->pBt );
assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
assert( &pPage->aData[pPage->pBt->psAligned]==(unsigned char*)pPage );
sqlite3pager_unref(pPage->aData);
}
}
@@ -989,7 +995,7 @@ static void releasePage(MemPage *pPage){
** happens.
*/
static void pageDestructor(void *pData, int pageSize){
MemPage *pPage = (MemPage*)&((char*)pData)[pageSize];
MemPage *pPage = (MemPage*)&((char*)pData)[FORCE_ALIGNMENT(pageSize)];
if( pPage->pParent ){
MemPage *pParent = pPage->pParent;
pPage->pParent = 0;
@@ -1007,7 +1013,7 @@ static void pageDestructor(void *pData, int pageSize){
** page to agree with the restored data.
*/
static void pageReinit(void *pData, int pageSize){
MemPage *pPage = (MemPage*)&((char*)pData)[pageSize];
MemPage *pPage = (MemPage*)&((char*)pData)[FORCE_ALIGNMENT(pageSize)];
if( pPage->isInit ){
pPage->isInit = 0;
initPage(pPage, pPage->pParent);
@@ -1078,6 +1084,7 @@ int sqlite3BtreeOpen(
pBt->pageSizeFixed = 1;
}
pBt->usableSize = pBt->pageSize - nReserve;
pBt->psAligned = FORCE_ALIGNMENT(pBt->pageSize);
sqlite3pager_set_pagesize(pBt->pPager, pBt->pageSize);
*ppBtree = pBt;
return SQLITE_OK;
@@ -1148,6 +1155,7 @@ int sqlite3BtreeSetPageSize(Btree *pBt, int pageSize, int nReserve){
}
if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE ){
pBt->pageSize = pageSize;
pBt->psAligned = FORCE_ALIGNMENT(pageSize);
sqlite3pager_set_pagesize(pBt->pPager, pageSize);
}
pBt->usableSize = pBt->pageSize - nReserve;
@@ -1199,6 +1207,7 @@ static int lockBtree(Btree *pBt){
if( pBt->usableSize<500 ){
goto page1_init_failed;
}
pBt->psAligned = FORCE_ALIGNMENT(pBt->pageSize);
pBt->maxEmbedFrac = page1[21];
pBt->minEmbedFrac = page1[22];
pBt->minLeafFrac = page1[23];
@@ -1248,7 +1257,7 @@ static void unlockBtreeIfUnused(Btree *pBt){
if( pBt->inTrans==TRANS_NONE && pBt->pCursor==0 && pBt->pPage1!=0 ){
if( pBt->pPage1->aData==0 ){
MemPage *pPage = pBt->pPage1;
pPage->aData = &((char*)pPage)[-pBt->pageSize];
pPage->aData = &((char*)pPage)[-pBt->psAligned];
pPage->pBt = pBt;
pPage->pgno = 1;
}
@@ -2673,7 +2682,7 @@ static void reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
assert( pBt->pPager!=0 );
aData = sqlite3pager_lookup(pBt->pPager, pgno);
if( aData ){
pThis = (MemPage*)&aData[pBt->pageSize];
pThis = (MemPage*)&aData[pBt->psAligned];
assert( pThis->aData==aData );
if( pThis->isInit ){
if( pThis->pParent!=pNewParent ){
@@ -2960,7 +2969,7 @@ static int balance_nonroot(MemPage *pPage){
apCell = sqliteMallocRaw(
(mxCellPerPage+2)*NB*(sizeof(u8*)+sizeof(int))
+ sizeof(MemPage)*NB
+ pBt->pageSize*(5+NB)
+ pBt->psAligned*(5+NB)
);
if( apCell==0 ){
return SQLITE_NOMEM;
@@ -2968,9 +2977,9 @@ static int balance_nonroot(MemPage *pPage){
szCell = (int*)&apCell[(mxCellPerPage+2)*NB];
aCopy[0] = (u8*)&szCell[(mxCellPerPage+2)*NB];
for(i=1; i<NB; i++){
aCopy[i] = &aCopy[i-1][pBt->pageSize+sizeof(MemPage)];
aCopy[i] = &aCopy[i-1][pBt->psAligned+sizeof(MemPage)];
}
aSpace = &aCopy[NB-1][pBt->pageSize+sizeof(MemPage)];
aSpace = &aCopy[NB-1][pBt->psAligned+sizeof(MemPage)];
/*
** Find the cell in the parent page whose left child points back
@@ -3041,10 +3050,10 @@ static int balance_nonroot(MemPage *pPage){
** process of being overwritten.
*/
for(i=0; i<nOld; i++){
MemPage *p = apCopy[i] = (MemPage*)&aCopy[i][pBt->pageSize];
p->aData = &((u8*)p)[-pBt->pageSize];
memcpy(p->aData, apOld[i]->aData, pBt->pageSize + sizeof(MemPage));
p->aData = &((u8*)p)[-pBt->pageSize];
MemPage *p = apCopy[i] = (MemPage*)&aCopy[i][pBt->psAligned];
p->aData = &((u8*)p)[-pBt->psAligned];
memcpy(p->aData, apOld[i]->aData, pBt->psAligned + sizeof(MemPage));
p->aData = &((u8*)p)[-pBt->psAligned];
}
/*
@@ -3088,7 +3097,7 @@ static int balance_nonroot(MemPage *pPage){
szCell[nCell] = sz;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
assert( iSpace<=pBt->psAligned*5 );
memcpy(pTemp, apDiv[i], sz);
apCell[nCell] = pTemp+leafCorrection;
dropCell(pParent, nxDiv, sz);
@@ -3272,13 +3281,13 @@ static int balance_nonroot(MemPage *pPage){
pCell = &aSpace[iSpace];
fillInCell(pParent, pCell, 0, info.nKey, 0, 0, &sz);
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
assert( iSpace<=pBt->psAligned*5 );
pTemp = 0;
}else{
pCell -= 4;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=pBt->pageSize*5 );
assert( iSpace<=pBt->psAligned*5 );
}
insertCell(pParent, nxDiv, pCell, sz, pTemp);
put4byte(findOverflowCell(pParent,nxDiv), pNew->pgno);