internal void assemblePage(int nCell, byte[] apCell, int[] aSize)
{
Debug.Assert(this.NOverflows == 0);
Debug.Assert(MutexEx.Held(this.Shared.Mutex));
Debug.Assert(nCell >= 0 && nCell <= (int)Btree.MX_CELL(this.Shared) && (int)Btree.MX_CELL(this.Shared) <= 10921);
Debug.Assert(Pager.IsPageWriteable(this.DbPage));
// Check that the page has just been zeroed by zeroPage()
Debug.Assert(this.Cells == 0);
//
var data = this.Data; // Pointer to data for pPage
int hdr = this.HeaderOffset; // Offset of header on pPage
var nUsable = (int)this.Shared.UsableSize; // Usable size of page
Debug.Assert(ConvertEx.Get2nz(data, hdr + 5) == nUsable);
var pCellptr = this.CellOffset + nCell * 2; // Address of next cell pointer
var cellbody = nUsable; // Address of next cell body
for (var i = nCell - 1; i >= 0; i--)
{
var sz = (ushort)aSize[i];
pCellptr -= 2;
cellbody -= sz;
ConvertEx.Put2(data, pCellptr, cellbody);
Buffer.BlockCopy(apCell, 0, data, cellbody, sz);
}
ConvertEx.Put2(data, hdr + 3, nCell);
ConvertEx.Put2(data, hdr + 5, cellbody);
this.FreeBytes -= (ushort)(nCell * 2 + nUsable - cellbody);
this.Cells = (ushort)nCell;
}
internal void insertCell(int i, byte[] pCell, int sz, byte[] pTemp, Pgno iChild, ref RC pRC)
{
var nSkip = (iChild != 0 ? 4 : 0);
if (pRC != RC.OK)
{
return;
}
Debug.Assert(i >= 0 && i <= this.Cells + this.NOverflows);
Debug.Assert(this.Cells <= Btree.MX_CELL(this.Shared) && Btree.MX_CELL(this.Shared) <= 10921);
Debug.Assert(this.NOverflows <= this.Overflows.Length);
Debug.Assert(MutexEx.Held(this.Shared.Mutex));
// The cell should normally be sized correctly. However, when moving a malformed cell from a leaf page to an interior page, if the cell size
// wanted to be less than 4 but got rounded up to 4 on the leaf, then size might be less than 8 (leaf-size + pointer) on the interior node. Hence
// the term after the || in the following assert().
Debug.Assert(sz == cellSizePtr(pCell) || (sz == 8 && iChild > 0));
if (this.NOverflows != 0 || sz + 2 > this.FreeBytes)
{
if (pTemp != null)
{
Buffer.BlockCopy(pCell, nSkip, pTemp, nSkip, sz - nSkip);
pCell = pTemp;
}
if (iChild != 0)
{
ConvertEx.Put4L(pCell, iChild);
}
var j = this.NOverflows++;
Debug.Assert(j < this.Overflows.Length);
this.Overflows[j].Cell = pCell;
this.Overflows[j].Index = (ushort)i;
}
else
{
var rc = Pager.Write(this.DbPage);
if (rc != RC.OK)
{
pRC = rc;
return;
}
Debug.Assert(Pager.IsPageWriteable(this.DbPage));
var data = this.Data; // The content of the whole page
var cellOffset = (int)this.CellOffset; // Address of first cell pointer in data[]
var end = cellOffset + 2 * this.Cells; // First byte past the last cell pointer in data[]
var ins = cellOffset + 2 * i; // Index in data[] where new cell pointer is inserted
int idx = 0; // Where to write new cell content in data[]
rc = allocateSpace(sz, ref idx);
if (rc != RC.OK)
{
pRC = rc;
return;
}
// The allocateSpace() routine guarantees the following two properties if it returns success
Debug.Assert(idx >= end + 2);
Debug.Assert(idx + sz <= (int)this.Shared.UsableSize);
this.Cells++;
this.FreeBytes -= (ushort)(2 + sz);
Buffer.BlockCopy(pCell, nSkip, data, idx + nSkip, sz - nSkip);
if (iChild != 0)
{
ConvertEx.Put4L(data, (uint)idx, iChild);
}
for (var j = end; j > ins; j -= 2)
{
data[j + 0] = data[j - 2];
data[j + 1] = data[j - 1];
}
ConvertEx.Put2(data, ins, idx);
ConvertEx.Put2(data, this.HeaderOffset + 3, this.Cells);
#if !SQLITE_OMIT_AUTOVACUUM
if (this.Shared.AutoVacuum)
{
// The cell may contain a pointer to an overflow page. If so, write the entry for the overflow page into the pointer map.
ptrmapPutOvflPtr(pCell, ref pRC);
}
#endif
}
}
internal RC btreeInitPage()
{
Debug.Assert(this.Shared != null);
Debug.Assert(MutexEx.Held(this.Shared.Mutex));
Debug.Assert(this.ID == Pager.GetPageID(this.DbPage));
Debug.Assert(this == Pager.sqlite3PagerGetExtra <MemPage>(this.DbPage));
Debug.Assert(this.Data == Pager.sqlite3PagerGetData(this.DbPage));
if (!this.HasInit)
{
var pBt = this.Shared; // The main btree structure
var hdr = this.HeaderOffset; // Offset to beginning of page header
var data = this.Data;
if (decodeFlags(data[hdr]) != 0)
{
return(SysEx.SQLITE_CORRUPT_BKPT());
}
Debug.Assert(pBt.PageSize >= 512 && pBt.PageSize <= 65536);
this.MaskPage = (ushort)(pBt.PageSize - 1);
this.NOverflows = 0;
var usableSize = (int)pBt.UsableSize; // Amount of usable space on each page
ushort cellOffset; // Offset from start of page to first cell pointer
this.CellOffset = (cellOffset = (ushort)(hdr + 12 - 4 * this.Leaf));
var top = ConvertEx.Get2nz(data, hdr + 5); // First byte of the cell content area
this.Cells = (ushort)(ConvertEx.Get2(data, hdr + 3));
if (this.Cells > Btree.MX_CELL(pBt))
{
// To many cells for a single page. The page must be corrupt
return(SysEx.SQLITE_CORRUPT_BKPT());
}
// A malformed database page might cause us to read past the end of page when parsing a cell.
// The following block of code checks early to see if a cell extends past the end of a page boundary and causes SQLITE_CORRUPT to be
// returned if it does.
var iCellFirst = cellOffset + 2 * this.Cells; // First allowable cell or freeblock offset
var iCellLast = usableSize - 4; // Last possible cell or freeblock offset
#if SQLITE_ENABLE_OVERSIZE_CELL_CHECK
if (pPage.leaf == 0)
{
iCellLast--;
}
for (var i = 0; i < pPage.nCell; i++)
{
pc = (ushort)ConvertEx.get2byte(data, cellOffset + i * 2);
if (pc < iCellFirst || pc > iCellLast)
{
return(SysEx.SQLITE_CORRUPT_BKPT());
}
var sz = cellSizePtr(pPage, data, pc);
if (pc + sz > usableSize)
{
return(SysEx.SQLITE_CORRUPT_BKPT());
}
}
if (pPage.leaf == 0)
{
iCellLast++;
}
#endif
// Compute the total free space on the page
var pc = (ushort)ConvertEx.Get2(data, hdr + 1); // Address of a freeblock within pPage.aData[]
var nFree = (ushort)(data[hdr + 7] + top); // Number of unused bytes on the page
while (pc > 0)
{
if (pc < iCellFirst || pc > iCellLast)
{
// Start of free block is off the page
return(SysEx.SQLITE_CORRUPT_BKPT());
}
var next = (ushort)ConvertEx.Get2(data, pc);
var size = (ushort)ConvertEx.Get2(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(SysEx.SQLITE_CORRUPT_BKPT());
}
nFree = (ushort)(nFree + size);
pc = next;
}
// At this point, nFree contains the sum of the offset to the start of the cell-content area plus the number of free bytes within
// the cell-content area. If this is greater than the usable-size of the page, then the page must be corrupted. This check also
// serves to verify that the offset to the start of the cell-content area, according to the page header, lies within the page.
if (nFree > usableSize)
{
return(SysEx.SQLITE_CORRUPT_BKPT());
}
this.FreeBytes = (ushort)(nFree - iCellFirst);
this.HasInit = true;
}
return(RC.OK);
}
