/**
* Defragment the page given. All Cells are moved to the end of the page and all free space is
* collected into one big FreeBlk that occurs in between the header and cell pointer array and the
* cell content area.
*
* @throws SqlJetException
*/
private void defragmentPage() throws SqlJetException {
final SqlJetMemPage pPage = this;
int i; /* Loop counter */
int pc; /* Address of a i-th cell */
int hdr; /* Offset to the page header */
int size; /* Size of a cell */
int usableSize; /* Number of usable bytes on a page */
int cellOffset; /* Offset to the cell pointer array */
int cbrk; /* Offset to the cell content area */
int nCell; /* Number of cells on the page */
ISqlJetMemoryPointer data; /* The page data */
ISqlJetMemoryPointer temp; /* Temp area for cell content */
int iCellFirst; /* First allowable cell index */
int iCellLast; /* Last possible cell index */
assert (pPage.pDbPage.isWriteable());
assert (pPage.pBt != null);
assert (pPage.pBt.usableSize <= ISqlJetLimits.SQLJET_MAX_PAGE_SIZE);
assert (pPage.nOverflow == 0);
assert (pPage.pBt.mutex.held());
temp = pPage.pBt.pPager.getTempSpace();
data = pPage.aData;
hdr = pPage.hdrOffset;
cellOffset = pPage.cellOffset;
nCell = pPage.nCell;
assert (nCell == get2byte(data, hdr + 3));
usableSize = pPage.pBt.usableSize;
cbrk = get2byte(data, hdr + 5);
memcpy(temp, cbrk, data, cbrk, usableSize - cbrk);
cbrk = usableSize;
iCellFirst = cellOffset + 2 * nCell;
iCellLast = usableSize - 4;
for (i = 0; i < nCell; i++) {
final ISqlJetMemoryPointer pAddr =
data.getBuffer().getPointer(cellOffset + i * 2); /* The i-th cell pointer */
pc = get2byte(pAddr);
if (pc < iCellFirst || pc > iCellLast) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
assert (pc >= iCellFirst && pc <= iCellLast);
size = pPage.cellSizePtr(temp.getBuffer().getPointer(pc));
cbrk -= size;
if (cbrk < iCellFirst || pc + size > usableSize) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
assert (cbrk + size <= usableSize && cbrk >= iCellFirst);
memcpy(data, cbrk, temp, pc, size);
put2byte(pAddr, cbrk);
}
assert (cbrk >= iCellFirst);
put2byte(data, hdr + 5, cbrk);
SqlJetUtility.putUnsignedByte(data, hdr + 1, (byte) 0);
SqlJetUtility.putUnsignedByte(data, hdr + 2, (byte) 0);
SqlJetUtility.putUnsignedByte(data, hdr + 7, (byte) 0);
memset(data, iCellFirst, (byte) 0, cbrk - iCellFirst);
assert (pPage.pDbPage.isWriteable());
if (cbrk - iCellFirst != pPage.nFree) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
}
/** Add a page of the database file to the freelist. unref() is NOT called for pPage. */
public void freePage() throws SqlJetException {
SqlJetMemPage pPage1 = pBt.pPage1;
int n, k;
/* Prepare the page for freeing */
assert (pBt.mutex.held());
assert (this.pgno > 1);
this.isInit = false;
/* Increment the free page count on pPage1 */
pPage1.pDbPage.write();
n = get4byte(pPage1.aData, 36);
put4byte(pPage1.aData, 36, n + 1);
if (ISqlJetConfig.SECURE_DELETE) {
/*
* If the SQLITE_SECURE_DELETE compile-time option is enabled, then
* always fully overwrite deleted information with zeros.
*/
pDbPage.write();
memset(aData, (byte) 0, pBt.pageSize);
}
/*
* If the database supports auto-vacuum, write an entry in the
* pointer-map to indicate that the page is free.
*/
if (ISAUTOVACUUM()) {
pBt.ptrmapPut(pgno, SqlJetBtreeShared.PTRMAP_FREEPAGE, 0);
}
if (n == 0) {
/* This is the first free page */
pDbPage.write();
memset(aData, (byte) 0, 8);
put4byte(pPage1.aData, 32, pgno);
TRACE("FREE-PAGE: %d first\n", this.pgno);
} else {
/*
* Other free pages already exist. Retrive the first trunk page* of
* the freelist and find out how many leaves it has.
*/
SqlJetMemPage pTrunk;
pTrunk = pBt.getPage(get4byte(pPage1.aData, 32), false);
k = get4byte(pTrunk.aData, 4);
if (k >= pBt.usableSize / 4 - 8) {
/*
* The trunk is full. Turn the page being freed into a new*
* trunk page with no leaves.** Note that the trunk page is not
* really full until it contains* usableSize/4 - 2 entries, not
* usableSize/4 - 8 entries as we have* coded. But due to a
* coding error in versions of SQLite prior to* 3.6.0, databases
* with freelist trunk pages holding more than* usableSize/4 - 8
* entries will be reported as corrupt. In order* to maintain
* backwards compatibility with older versions of SQLite,* we
* will contain to restrict the number of entries to
* usableSize/4 - 8* for now. At some point in the future (once
* everyone has upgraded* to 3.6.0 or later) we should consider
* fixing the conditional above* to read "usableSize/4-2"
* instead of "usableSize/4-8".
*/
pDbPage.write();
put4byte(aData, pTrunk.pgno);
put4byte(aData, 4, 0);
put4byte(pPage1.aData, 32, pgno);
TRACE("FREE-PAGE: %d new trunk page replacing %d\n", this.pgno, pTrunk.pgno);
} else if (k < 0) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
} else {
/* Add the newly freed page as a leaf on the current trunk */
pTrunk.pDbPage.write();
put4byte(pTrunk.aData, 4, k + 1);
put4byte(pTrunk.aData, 8 + k * 4, pgno);
if (ISqlJetConfig.SECURE_DELETE) {
pDbPage.dontWrite();
}
TRACE("FREE-PAGE: %d leaf on trunk page %d\n", this.pgno, pTrunk.pgno);
}
releasePage(pTrunk);
}
}
/*
* * Return a section of the pPage->aData to the freelist.* The first byte
* of the new free block is pPage->aDisk[start]* and the size of the block
* is "size" bytes.** Most of the effort here is involved in coalesing
* adjacent* free blocks into a single big free block.
*/
private void freeSpace(int start, int size) throws SqlJetException {
SqlJetMemPage pPage = this;
int addr, pbegin, hdr;
ISqlJetMemoryPointer data = pPage.aData;
assert (pPage.pBt != null);
assert (start >= pPage.hdrOffset + 6 + (pPage.leaf ? 0 : 4));
assert ((start + size) <= pPage.pBt.usableSize);
assert (pPage.pBt.mutex.held());
assert (size >= 0); /* Minimum cell size is 4 */
if (ISqlJetConfig.SECURE_DELETE) {
/*
* Overwrite deleted information with zeros when the SECURE_DELETE*
* option is enabled at compile-time
*/
memset(data, start, (byte) 0, size);
}
/* Add the space back into the linked list of freeblocks */
hdr = pPage.hdrOffset;
addr = hdr + 1;
while ((pbegin = get2byte(data, addr)) < start && pbegin > 0) {
assert (pbegin <= pPage.pBt.usableSize - 4);
if (pbegin <= addr) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
addr = pbegin;
}
if (pbegin > pPage.pBt.usableSize - 4) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
assert (pbegin > addr || pbegin == 0);
put2byte(data, addr, start);
put2byte(data, start, pbegin);
put2byte(data, start + 2, size);
pPage.nFree += size;
/* Coalesce adjacent free blocks */
addr = pPage.hdrOffset + 1;
while ((pbegin = get2byte(data, addr)) > 0) {
int pnext, psize, x;
assert (pbegin > addr);
assert (pbegin <= pPage.pBt.usableSize - 4);
pnext = get2byte(data, pbegin);
psize = get2byte(data, pbegin + 2);
if (pbegin + psize + 3 >= pnext && pnext > 0) {
int frag = pnext - (pbegin + psize);
if ((frag < 0) || (frag > (int) SqlJetUtility.getUnsignedByte(data, pPage.hdrOffset + 7))) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
SqlJetUtility.putUnsignedByte(
data,
pPage.hdrOffset + 7,
(byte) (SqlJetUtility.getUnsignedByte(data, pPage.hdrOffset + 7) - (byte) frag));
x = get2byte(data, pnext);
put2byte(data, pbegin, x);
x = pnext + get2byte(data, pnext + 2) - pbegin;
put2byte(data, pbegin + 2, x);
} else {
addr = pbegin;
}
}
/* If the cell content area begins with a freeblock, remove it. */
if (SqlJetUtility.getUnsignedByte(data, hdr + 1) == SqlJetUtility.getUnsignedByte(data, hdr + 5)
&& SqlJetUtility.getUnsignedByte(data, hdr + 2)
== SqlJetUtility.getUnsignedByte(data, hdr + 6)) {
int top;
pbegin = get2byte(data, hdr + 1);
memcpy(data, hdr + 1, data, pbegin, 2);
top = get2byte(data, hdr + 5) + get2byte(data, pbegin + 2);
put2byte(data, hdr + 5, top);
}
assert (pPage.pDbPage.isWriteable());
}
/**
* Create the byte sequence used to represent a cell on page pPage and write that byte sequence
* into pCell[]. Overflow pages are allocated and filled in as necessary. The calling procedure is
* responsible for making sure sufficient space has been allocated for pCell[].
*
* <p>Note that pCell does not necessary need to point to the pPage->aData area. pCell might point
* to some temporary storage. The cell will be constructed in this temporary area then copied into
* pPage->aData later.
*
* @param pCell Complete text of the cell
* @param pKey The key
* @param nKey The key
* @param pData The data
* @param nData The data
* @param nZero Extra zero bytes to append to pData
* @return cell size
* @throws SqlJetException
*/
public int fillInCell(
ISqlJetMemoryPointer pCell,
ISqlJetMemoryPointer pKey,
long nKey,
ISqlJetMemoryPointer pData,
int nData,
int nZero)
throws SqlJetException {
final SqlJetMemPage pPage = this;
int pnSize = 0;
int nPayload;
ISqlJetMemoryPointer pSrc;
int nSrc, n;
int spaceLeft;
SqlJetMemPage pOvfl = null;
SqlJetMemPage pToRelease = null;
ISqlJetMemoryPointer pPrior;
ISqlJetMemoryPointer pPayload;
SqlJetBtreeShared pBt = pPage.pBt;
int[] pgnoOvfl = {0};
int nHeader;
SqlJetBtreeCellInfo info;
assert (pPage.pBt.mutex.held());
/*
* pPage is not necessarily writeable since pCell might be auxiliary*
* buffer space that is separate from the pPage buffer area
*/
assert (pCell.getBuffer() != pPage.aData.getBuffer() || pPage.pDbPage.isWriteable());
/* Fill in the header. */
nHeader = 0;
if (!pPage.leaf) {
nHeader += 4;
}
if (pPage.hasData) {
nHeader += putVarint(pointer(pCell, nHeader), nData + nZero);
} else {
nData = nZero = 0;
}
nHeader += putVarint(pointer(pCell, nHeader), nKey);
info = pPage.parseCellPtr(pCell);
assert (info.nHeader == nHeader);
assert (info.nKey == nKey);
assert (info.nData == nData + nZero);
/* Fill in the payload */
nPayload = nData + nZero;
if (pPage.intKey) {
pSrc = pData;
nSrc = nData;
nData = 0;
} else {
/* TBD: Perhaps raise SQLITE_CORRUPT if nKey is larger than 31 bits? */
nPayload += (int) nKey;
pSrc = pKey;
nSrc = (int) nKey;
}
pnSize = info.nSize;
spaceLeft = info.nLocal;
pPayload = pointer(pCell, nHeader);
pPrior = pointer(pCell, info.iOverflow);
while (nPayload > 0) {
if (spaceLeft == 0) {
int pgnoPtrmap = pgnoOvfl[0]; /*
* Overflow page pointer-map entry
* page
*/
if (pBt.autoVacuum) {
do {
pgnoOvfl[0]++;
} while (pBt.PTRMAP_ISPAGE(pgnoOvfl[0]) || pgnoOvfl[0] == pBt.PENDING_BYTE_PAGE());
}
try {
pOvfl = pBt.allocatePage(pgnoOvfl, pgnoOvfl[0], false);
/*
* If the database supports auto-vacuum, and the second or
* subsequent* overflow page is being allocated, add an
* entry to the pointer-map* for that page now.** If this is
* the first overflow page, then write a partial entry* to
* the pointer-map. If we write nothing to this pointer-map
* slot,* then the optimistic overflow chain processing in
* clearCell()* may misinterpret the uninitialised values
* and delete the* wrong pages from the database.
*/
if (pBt.autoVacuum) {
byte eType =
(pgnoPtrmap != 0
? SqlJetBtreeShared.PTRMAP_OVERFLOW2
: SqlJetBtreeShared.PTRMAP_OVERFLOW1);
try {
pBt.ptrmapPut(pgnoOvfl[0], eType, pgnoPtrmap);
} catch (SqlJetException e) {
releasePage(pOvfl);
}
}
} catch (SqlJetException e) {
releasePage(pToRelease);
throw e;
}
/*
* If pToRelease is not zero than pPrior points into the data
* area* of pToRelease. Make sure pToRelease is still writeable.
*/
assert (pToRelease == null || pToRelease.pDbPage.isWriteable());
/*
* If pPrior is part of the data area of pPage, then make sure
* pPage* is still writeable
*/
assert (pPrior.getBuffer() != pPage.aData.getBuffer() || pPage.pDbPage.isWriteable());
put4byte(pPrior, pgnoOvfl[0]);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl.aData;
put4byte(pPrior, 0);
pPayload = pointer(pOvfl.aData, 4);
spaceLeft = pBt.usableSize - 4;
}
n = nPayload;
if (n > spaceLeft) n = spaceLeft;
/*
* If pToRelease is not zero than pPayload points into the data area
* * of pToRelease. Make sure pToRelease is still writeable.
*/
assert (pToRelease == null || pToRelease.pDbPage.isWriteable());
/*
* If pPayload is part of the data area of pPage, then make sure
* pPage* is still writeable
*/
assert (pPayload.getBuffer() != pPage.aData.getBuffer() || pPage.pDbPage.isWriteable());
if (nSrc > 0) {
if (n > nSrc) n = nSrc;
assert (pSrc != null);
memcpy(pPayload, pSrc, n);
} else {
memset(pPayload, (byte) 0, n);
}
nPayload -= n;
movePtr(pPayload, n);
pSrc = pointer(pSrc, n);
nSrc -= n;
spaceLeft -= n;
if (nSrc == 0) {
nSrc = nData;
pSrc = pData;
}
}
releasePage(pToRelease);
return pnSize;
}