/**
* Remove the i-th cell from pPage. This routine effects pPage only. The cell content is not freed
* or deallocated. It is assumed that the cell content has been copied someplace else. This
* routine just removes the reference to the cell from pPage.
*
* <p>"sz" must be the number of bytes in the cell.
*
* @param idx
* @param sz
* @throws SqlJetException
*/
public void dropCell(int idx, int sz) throws SqlJetException {
final SqlJetMemPage pPage = this;
int pc; /* Offset to cell content of cell being deleted */
ISqlJetMemoryPointer data; /* pPage->aData */
ISqlJetMemoryPointer ptr; /* Used to move bytes around within data[] */
assert (idx >= 0 && idx < pPage.nCell);
assert (sz == pPage.cellSize(idx));
assert (pPage.pBt.mutex.held());
data = pPage.aData;
ptr = pointer(data, pPage.cellOffset + 2 * idx);
pc = get2byte(ptr);
if ((pc < pPage.hdrOffset + 6 + (pPage.leaf ? 0 : 4)) || (pc + sz > pPage.pBt.usableSize)) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
pPage.freeSpace(pc, sz);
final ISqlJetMemoryPointer endPtr = pointer(data, pPage.cellOffset + 2 * pPage.nCell - 2);
while (ptr.getPointer() < endPtr.getPointer()) {
put2byte(ptr, get2byte(ptr, 2));
movePtr(ptr, 2);
}
// put2byte(endPtr, 0);
pPage.nCell--;
put2byte(data, pPage.hdrOffset + 3, pPage.nCell);
pPage.nFree += 2;
}
/**
* Add a list of cells to a page. The page should be initially empty. The cells are guaranteed to
* fit on the page.
*
* @param nCell The number of cells to add to this page
* @param apCell Pointers to cell bodies
* @param aSize Sizes of the cells
* @throws SqlJetException
*/
public void assemblePage(
int nCell, ISqlJetMemoryPointer[] apCell, int apCellPos, int[] aSize, int aSizePos)
throws SqlJetException {
final SqlJetMemPage pPage = this;
int i; /* Loop counter */
int hdr = pPage.hdrOffset; /* Index of page header */
ISqlJetMemoryPointer data = pPage.aData; /* Data for the page */
int nUsable = pPage.pBt.usableSize;
assert (pPage.nOverflow == 0);
assert (pPage.pBt.mutex.held());
assert (nCell >= 0 && nCell <= pPage.pBt.MX_CELL() && pPage.pBt.MX_CELL() <= 10921);
assert (pPage.pDbPage.isWriteable());
assert (pPage.nCell == 0);
assert (get2byte(data.getMoved(hdr + 5)) == nUsable);
ISqlJetMemoryPointer pCellPtr = data.getMoved(pPage.cellOffset + nCell * 2);
int cellbody = nUsable;
for (i = nCell - 1; i >= 0; i--) {
int sz = aSize[apCellPos + i];
pCellPtr = pCellPtr.getMoved(-2);
cellbody -= sz;
put2byte(pCellPtr, cellbody);
memcpy(data.getMoved(cellbody), apCell[apCellPos + i], sz);
}
put2byte(data.getMoved(hdr + 3), nCell);
put2byte(data.getMoved(hdr + 5), cellbody);
pPage.nFree -= (2 * nCell + pPage.pBt.usableSize - cellbody);
pPage.nCell = nCell;
}
/**
* Set up a raw page so that it looks like a database page holding no entries.
*
* @param sqlJetBtree
* @param flags
* @throws SqlJetException
*/
void zeroPage(int flags) throws SqlJetException {
ISqlJetMemoryPointer data = aData;
byte hdr = hdrOffset;
int first;
assert (pDbPage.getPageNumber() == pgno);
assert (pDbPage.getExtra() == this);
assert (pDbPage.getData().getBuffer() == data.getBuffer());
assert (pBt.mutex.held());
SqlJetUtility.putUnsignedByte(data, hdr, (short) flags);
first = hdr + 8 + 4 * ((flags & SqlJetMemPage.PTF_LEAF) == 0 ? 1 : 0);
// SqlJetUtility.memset(data, hdr + 1, (byte) 0, 4);
SqlJetUtility.put4byte(data, hdr + 1, 0);
//
SqlJetUtility.putUnsignedByte(data, hdr + 7, (short) 0);
SqlJetUtility.put2byte(data, hdr + 5, pBt.usableSize);
nFree = pBt.usableSize - first;
decodeFlags(flags);
hdrOffset = hdr;
cellOffset = first;
nOverflow = 0;
assert (pBt.pageSize >= 512 && pBt.pageSize <= 32768);
maskPage = pBt.pageSize - 1;
nCell = 0;
isInit = true;
}
/**
* 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);
}
}
/**
* Allocate nByte bytes of space on a page.
*
* <p>Return the index into pPage->aData[] of the first byte of the new allocation. The caller
* guarantees that there is enough space. This routine will never fail.
*
* <p>If the page contains nBytes of free space but does not contain nBytes of contiguous free
* space, then this routine automatically calls defragementPage() to consolidate all free space
* before allocating the new chunk.
*
* @param nByte
* @return
* @throws SqlJetException
*/
private int allocateSpace(int nByte) throws SqlJetException {
final SqlJetMemPage pPage = this;
int addr, pc, hdr;
int size;
int nFrag;
ISqlJetMemoryPointer data;
data = pPage.aData;
assert (pPage.pDbPage.isWriteable());
assert (pPage.pBt != null);
assert (pPage.pBt.mutex.held());
assert (nByte >= 0); /* Minimum cell size is 4 */
assert (pPage.nFree >= nByte);
assert (pPage.nOverflow == 0);
int usableSize = pPage.pBt.usableSize;
assert (nByte < usableSize - 8);
hdr = pPage.hdrOffset;
nFrag = SqlJetUtility.getUnsignedByte(data, hdr + 7);
assert (pPage.cellOffset == hdr + 12 - 4 * (pPage.leaf ? 1 : 0));
int gap = pPage.cellOffset + 2 * pPage.nCell;
int top = get2byte(data.getMoved(hdr + 5));
if (gap > top) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
if (nFrag >= 60) {
pPage.defragmentPage();
top = get2byte(data.getMoved(hdr + 5));
} else if (gap + 2 <= top) {
addr = hdr + 1;
while ((pc = get2byte(data, addr)) > 0) {
if (pc > usableSize - 4 || pc < addr + 4) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
size = get2byte(data, pc + 2);
if (size >= nByte) {
int x = size - nByte;
if (x < 4) {
memcpy(data, addr, data, pc, 2);
SqlJetUtility.putUnsignedByte(data, hdr + 7, nFrag + x);
} else if (size + pc > usableSize) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
} else {
put2byte(data, pc + 2, x);
}
return pc + x;
}
addr = pc;
}
}
if (gap + 2 + nByte > top) {
pPage.defragmentPage();
top = get2byte(data, hdr + 5);
assert (gap + nByte <= top);
}
top -= nByte;
put2byte(data, hdr + 5, top);
assert (top + nByte <= pPage.pBt.usableSize);
return top;
}
/**
* Insert a new cell on pPage at cell index "i". pCell points to the content of the cell.
*
* <p>If the cell content will fit on the page, then put it there. If it will not fit, then make a
* copy of the cell content into pTemp if pTemp is not null. Regardless of pTemp, allocate a new
* entry in pPage->aOvfl[] and make it point to the cell content (either in pTemp or the original
* pCell) and also record its index. Allocating a new entry in pPage->aCell[] implies that
* pPage->nOverflow is incremented.
*
* <p>If nSkip is non-zero, then do not copy the first nSkip bytes of the cell. The caller will
* overwrite them after this function returns. If nSkip is non-zero, then pCell may not point to
* an invalid memory location (but pCell+nSkip is always valid).
*
* @param i New cell becomes the i-th cell of the page
* @param pCell Content of the new cell
* @param sz Bytes of content in pCell
* @param pTemp Temp storage space for pCell, if needed
* @param nSkip Do not write the first nSkip bytes of the cell
* @throws SqlJetException
*/
public void insertCell(
int i, ISqlJetMemoryPointer pCell, int sz, ISqlJetMemoryPointer pTemp, int iChild)
throws SqlJetException {
int nSkip = (iChild > 0 ? 4 : 0);
final SqlJetMemPage pPage = this;
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[] */
ISqlJetMemoryPointer data; /* The content of the whole page */
assert (i >= 0 && i <= pPage.nCell + pPage.nOverflow);
assert (pPage.nCell <= pPage.pBt.MX_CELL() && pPage.pBt.MX_CELL() <= 5460);
assert (pPage.nOverflow <= pPage.aOvfl.length);
assert (sz == pPage.cellSizePtr(pCell) || (sz == 8 && iChild > 0));
assert (pPage.pBt.mutex.held());
if (pPage.nOverflow != 0 || sz + 2 > pPage.nFree) {
if (pTemp != null) {
memcpy(pTemp, nSkip, pCell, nSkip, sz - nSkip);
pCell = pTemp;
}
if (iChild > 0) {
put4byte(pCell, iChild);
}
j = pPage.nOverflow++;
// assert( j<(int)(sizeof(pPage.aOvfl)/sizeof(pPage.aOvfl[0])) );
pPage.aOvfl[j].pCell = pCell;
pPage.aOvfl[j].idx = i;
} else {
pPage.pDbPage.write();
assert (pPage.pDbPage.isWriteable());
data = pPage.aData;
hdr = pPage.hdrOffset;
top = get2byte(data, hdr + 5);
cellOffset = pPage.cellOffset;
end = cellOffset + 2 * pPage.nCell + 2;
ins = cellOffset + 2 * i;
if (end > top - sz) {
pPage.defragmentPage();
top = get2byte(data, hdr + 5);
assert (end + sz <= top);
}
idx = pPage.allocateSpace(sz);
assert (idx > 0);
assert (end <= get2byte(data, hdr + 5));
if (idx + sz > pPage.pBt.usableSize) {
throw new SqlJetException(SqlJetErrorCode.CORRUPT);
}
pPage.nCell++;
pPage.nFree -= (2 + sz);
memcpy(data, idx + nSkip, pCell, nSkip, sz - nSkip);
if (iChild > 0) {
put4byte(data, idx, iChild);
}
for (j = end - 2; j > ins; j -= 2) {
SqlJetUtility.putUnsignedByte(data, j, SqlJetUtility.getUnsignedByte(data, j - 2));
SqlJetUtility.putUnsignedByte(data, j + 1, SqlJetUtility.getUnsignedByte(data, j - 1));
}
put2byte(data, ins, idx);
put2byte(data, hdr + 3, pPage.nCell);
if (pPage.pBt.autoVacuum) {
/*
* The cell may contain a pointer to an overflow page. If so,
* write* the entry for the overflow page into the pointer map.
*/
SqlJetBtreeCellInfo info = pPage.parseCellPtr(pCell);
assert ((info.nData + (pPage.intKey ? 0 : info.nKey)) == info.nPayload);
if ((info.nData + (pPage.intKey ? 0 : info.nKey)) > info.nLocal) {
int pgnoOvfl = get4byte(pCell, info.iOverflow);
pPage.pBt.ptrmapPut(pgnoOvfl, SqlJetBtreeShared.PTRMAP_OVERFLOW1, pPage.pgno);
}
}
}
}
/*
* * 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());
}
