** May you share freely, never taking more than you give.
**
*************************************************************************
-** $Id: btree.c,v 1.657 2009/07/07 17:38:39 drh Exp $
+** $Id: btree.c,v 1.658 2009/07/08 01:49:12 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
/*
** This a more complex version of findCell() that works for
-** pages that do contain overflow cells. See insert
+** pages that do contain overflow cells.
*/
static u8 *findOverflowCell(MemPage *pPage, int iCell){
int i;
}
pInfo->nPayload = nPayload;
pInfo->nHeader = n;
+ testcase( nPayload==pPage->maxLocal );
+ testcase( nPayload==pPage->maxLocal+1 );
if( likely(nPayload<=pPage->maxLocal) ){
/* This is the (easy) common case where the entire payload fits
** on the local page. No overflow is required.
minLocal = pPage->minLocal;
maxLocal = pPage->maxLocal;
surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
+ testcase( surplus==maxLocal );
+ testcase( surplus==maxLocal+1 );
if( surplus <= maxLocal ){
pInfo->nLocal = (u16)surplus;
}else{
pIter += getVarint32(pIter, nSize);
}
+ testcase( nSize==pPage->maxLocal );
+ testcase( nSize==pPage->maxLocal+1 );
if( nSize>pPage->maxLocal ){
int minLocal = pPage->minLocal;
nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
+ testcase( nSize==pPage->maxLocal );
+ testcase( nSize==pPage->maxLocal+1 );
if( nSize>pPage->maxLocal ){
nSize = minLocal;
}
u8 *pAddr; /* The i-th cell pointer */
pAddr = &data[cellOffset + i*2];
pc = get2byte(pAddr);
+ testcase( pc==iCellFirst );
+ testcase( pc==iCellLast );
#if !defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
/* These conditions have already been verified in sqlite3BtreeInitPage()
** if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined
return SQLITE_CORRUPT_BKPT;
}
#endif
- assert( cbrk+size<=usableSize && cbrk>iCellFirst );
+ assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
+ testcase( cbrk+size==usableSize );
+ testcase( cbrk==iCellFirst );
+ testcase( pc+size==usableSize );
memcpy(&data[cbrk], &temp[pc], size);
put2byte(pAddr, cbrk);
}
/*
** Allocate nByte bytes of space from within the B-Tree page passed
-** as the first argument. Return the index into pPage->aData[] of the
-** first byte of allocated space.
-**
-** The caller guarantees that the space between the end of the cell-offset
-** array and the start of the cell-content area is at least nByte bytes
-** in size. So this routine can never fail.
-**
-** If there are already 60 or more bytes of fragments within the page,
-** the page is defragmented before returning. If this were not done there
-** is a chance that the number of fragmented bytes could eventually
-** overflow the single-byte field of the page-header in which this value
-** is stored.
-*/
-static int allocateSpace(MemPage *pPage, int nByte){
+** as the first argument. Write into *pIdx the index into pPage->aData[]
+** of the first byte of allocated space. Return either SQLITE_OK or
+** an error code (usually SQLITE_CORRUPT).
+**
+** The caller guarantees that there is sufficient space to make the
+** allocation. This routine might need to defragment in order to bring
+** all the space together, however. This routine will avoid using
+** the first two bytes past the cell pointer area since presumably this
+** allocation is being made in order to insert a new cell, so we will
+** also end up needing a new cell pointer.
+*/
+static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
const int hdr = pPage->hdrOffset; /* Local cache of pPage->hdrOffset */
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int nFrag; /* Number of fragmented bytes on pPage */
- int top;
+ int top; /* First byte of cell content area */
+ int gap; /* First byte of gap between cell pointers and cell content */
+ int rc; /* Integer return code */
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( pPage->pBt );
assert( pPage->nFree>=nByte );
assert( pPage->nOverflow==0 );
- /* Assert that the space between the cell-offset array and the
- ** cell-content area is greater than nByte bytes.
- */
- assert( nByte <= (
- get2byte(&data[hdr+5])-(hdr+8+(pPage->leaf?0:4)+2*get2byte(&data[hdr+3]))
- ));
-
nFrag = data[hdr+7];
+ assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
+ gap = pPage->cellOffset + 2*pPage->nCell;
+ top = get2byte(&data[hdr+5]);
+ assert( gap<=top );
+ testcase( gap+2==top );
+ testcase( gap+1==top );
+ testcase( gap==top );
+
if( nFrag>=60 ){
- defragmentPage(pPage);
- }else{
+ /* Always defragment highly fragmented pages */
+ rc = defragmentPage(pPage);
+ if( rc ) return rc;
+ top = get2byte(&data[hdr+5]);
+ }else if( gap+2<=top ){
/* Search the freelist looking for a free slot big enough to satisfy
** the request. The allocation is made from the first free slot in
** the list that is large enough to accomadate it.
int size = get2byte(&data[pc+2]); /* Size of free slot */
if( size>=nByte ){
int x = size - nByte;
+ testcase( x==4 );
+ testcase( x==3 );
if( x<4 ){
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
** for the portion used by the new allocation. */
put2byte(&data[pc+2], x);
}
- return pc + x;
+ *pIdx = pc + x;
+ return SQLITE_OK;
}
}
}
+ /* Check to make sure there is enough space in the gap to satisfy
+ ** the allocation. If not, defragment.
+ */
+ testcase( gap+2+nByte==top );
+ if( gap+2+nByte>top ){
+ rc = defragmentPage(pPage);
+ if( rc ) return rc;
+ top = get2byte(&data[hdr+5]);
+ assert( gap+nByte<=top );
+ }
+
+
/* Allocate memory from the gap in between the cell pointer array
** and the cell content area.
*/
- top = get2byte(&data[hdr+5]) - nByte;
+ top -= nByte;
put2byte(&data[hdr+5], top);
- return top;
+ *pIdx = top;
+ return SQLITE_OK;
}
/*
*/
static int freeSpace(MemPage *pPage, int start, int size){
int addr, pbegin, hdr;
+ int iLast; /* Largest possible freeblock offset */
unsigned char *data = pPage->aData;
assert( pPage->pBt!=0 );
memset(&data[start], 0, size);
#endif
- /* Add the space back into the linked list of freeblocks */
+ /* Add the space back into the linked list of freeblocks. Note that
+ ** even though the freeblock list was checked by sqlite3BtreeInitPage(),
+ ** sqlite3BtreeInitPage() did not detect overlapping freeblocks or
+ ** freeblocks that overlapped cells. If there was overlap then
+ ** subsequent insert operations might have corrupted the freelist.
+ ** So we do need to check for corruption while scanning the freelist.
+ */
hdr = pPage->hdrOffset;
addr = hdr + 1;
+ iLast = pPage->pBt->usableSize - 4;
while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
- assert( pbegin<=pPage->pBt->usableSize-4 );
- if( pbegin<=addr ) {
+ if( pbegin>iLast || pbegin<addr+4 ){
return SQLITE_CORRUPT_BKPT;
}
addr = pbegin;
}
- if ( pbegin>pPage->pBt->usableSize-4 ) {
+ if( pbegin>iLast ){
return SQLITE_CORRUPT_BKPT;
}
assert( pbegin>addr || pbegin==0 );
pPage->nFree = pPage->nFree + (u16)size;
/* Coalesce adjacent free blocks */
- addr = pPage->hdrOffset + 1;
+ addr = hdr + 1;
while( (pbegin = get2byte(&data[addr]))>0 ){
int pnext, psize, x;
assert( pbegin>addr );
psize = get2byte(&data[pbegin+2]);
if( pbegin + psize + 3 >= pnext && pnext>0 ){
int frag = pnext - (pbegin+psize);
- if( (frag<0) || (frag>(int)data[pPage->hdrOffset+7]) ){
+ if( (frag<0) || (frag>(int)data[hdr+7]) ){
return SQLITE_CORRUPT_BKPT;
}
- data[pPage->hdrOffset+7] -= (u8)frag;
+ data[hdr+7] -= (u8)frag;
x = get2byte(&data[pnext]);
put2byte(&data[pbegin], x);
x = pnext + get2byte(&data[pnext+2]) - pbegin;
u16 cellOffset; /* Offset from start of page to first cell pointer */
u16 nFree; /* Number of unused bytes on the page */
u16 top; /* First byte of the cell content area */
+ int iCellFirst; /* First allowable cell or freeblock offset */
+ int iCellLast; /* Last possible cell or freeblock offset */
pBt = pPage->pBt;
** past the end of a page boundary and causes SQLITE_CORRUPT to be
** returned if it does.
*/
+ iCellFirst = cellOffset + 2*pPage->nCell;
+ iCellLast = usableSize - 4;
#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
{
- int iCellFirst; /* First allowable cell index */
- int iCellLast; /* Last possible cell index */
int i; /* Index into the cell pointer array */
int sz; /* Size of a cell */
- iCellFirst = cellOffset + 2*pPage->nCell;
- iCellLast = usableSize - 4;
if( !pPage->leaf ) iCellLast--;
for(i=0; i<pPage->nCell; i++){
pc = get2byte(&data[cellOffset+i*2]);
+ testcase( pc==iCellFirst );
+ testcase( pc==iCellLast );
if( pc<iCellFirst || pc>iCellLast ){
return SQLITE_CORRUPT_BKPT;
}
sz = cellSizePtr(pPage, &data[pc]);
+ testcase( pc+sz==usableSize );
if( pc+sz>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
}
+ if( !pPage->leaf ) iCellLast++;
}
#endif
nFree = data[hdr+7] + top;
while( pc>0 ){
u16 next, size;
- if( pc>usableSize-4 ){
+ if( pc<iCellFirst || pc>iCellLast ){
/* Free block is off the page */
return SQLITE_CORRUPT_BKPT;
}
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( next>0 && next<=pc+size+3 ){
- /* Free blocks must be in accending order */
+ /* Free blocks must be in ascending order */
return SQLITE_CORRUPT_BKPT;
}
nFree = nFree + size;
if( nFree>usableSize ){
return SQLITE_CORRUPT_BKPT;
}
- pPage->nFree = nFree - (cellOffset + 2*pPage->nCell);
-
-#if 0
- /* Check that all the offsets in the cell offset array are within range.
- **
- ** Omitting this consistency check and using the pPage->maskPage mask
- ** to prevent overrunning the page buffer in findCell() results in a
- ** 2.5% performance gain.
- */
- {
- u8 *pOff; /* Iterator used to check all cell offsets are in range */
- u8 *pEnd; /* Pointer to end of cell offset array */
- u8 mask; /* Mask of bits that must be zero in MSB of cell offsets */
- mask = ~(((u8)(pBt->pageSize>>8))-1);
- pEnd = &data[cellOffset + pPage->nCell*2];
- for(pOff=&data[cellOffset]; pOff!=pEnd && !((*pOff)&mask); pOff+=2);
- if( pOff!=pEnd ){
- return SQLITE_CORRUPT_BKPT;
- }
- }
-#endif
-
+ pPage->nFree = nFree - iCellFirst;
pPage->isInit = 1;
}
return SQLITE_OK;
struct KeyInfo *pKeyInfo, /* First arg to comparison function */
BtCursor *pCur /* Space for new cursor */
){
- int rc; /* Return code */
BtShared *pBt = p->pBt; /* Shared b-tree handle */
assert( sqlite3BtreeHoldsMutex(p) );
){
int idx; /* Where to write new cell content in data[] */
int j; /* Loop counter */
- int top; /* First byte of content for any cell in data[] */
int end; /* First byte past the last cell pointer in data[] */
int ins; /* Index in data[] where new cell pointer is inserted */
- int hdr; /* Offset into data[] of the page header */
int cellOffset; /* Address of first cell pointer in data[] */
u8 *data; /* The content of the whole page */
u8 *ptr; /* Used for moving information around in data[] */
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
data = pPage->aData;
- hdr = pPage->hdrOffset;
- top = get2byte(&data[hdr+5]);
cellOffset = pPage->cellOffset;
- end = cellOffset + 2*pPage->nCell + 2;
+ end = cellOffset + 2*pPage->nCell;
ins = cellOffset + 2*i;
- if( end > top - sz ){
- rc = defragmentPage(pPage);
- if( rc!=SQLITE_OK ){
- return rc;
- }
- top = get2byte(&data[hdr+5]);
- assert( end + sz <= top );
- }
- idx = allocateSpace(pPage, sz);
- assert( idx>0 );
- assert( end <= get2byte(&data[hdr+5]) );
- if (idx+sz > pPage->pBt->usableSize) {
+ rc = allocateSpace(pPage, sz, &idx);
+ if( rc ) return rc;
+ assert( idx>=end+2 );
+ if( idx+sz > pPage->pBt->usableSize ){
return SQLITE_CORRUPT_BKPT;
}
pPage->nCell++;
- pPage->nFree = pPage->nFree - (u16)(2 + sz);
+ pPage->nFree -= (u16)(2 + sz);
memcpy(&data[idx+nSkip], pCell+nSkip, sz-nSkip);
if( iChild ){
put4byte(&data[idx], iChild);
}
- for(j=end-2, ptr=&data[j]; j>ins; j-=2, ptr-=2){
+ for(j=end, ptr=&data[j]; j>ins; j-=2, ptr-=2){
ptr[0] = ptr[-2];
ptr[1] = ptr[-1];
}
put2byte(&data[ins], idx);
- put2byte(&data[hdr+3], pPage->nCell);
+ put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPage->pBt->autoVacuum ){
/* The cell may contain a pointer to an overflow page. If so, write
projects / thirdparty / sqlite.git / commitdiff
