internal void btreeParseCellPtr(byte[] cell, int cellID, ref CellInfo info)
{
var nPayload = (uint)0; // Number of bytes of cell payload
Debug.Assert(MutexEx.Held(Shared.Mutex));
if (info.Cells != cell)
{
info.Cells = cell;
}
info.CellID = cellID;
Debug.Assert(Leaf == 0 || Leaf == 1);
var n = (ushort)ChildPtrSize; // Number bytes in cell content header
Debug.Assert(n == 4 - 4 * Leaf);
if (HasIntKey)
{
if (HasData != 0)
{
n += (ushort)ConvertEx.GetVariant4(cell, (uint)(cellID + n), out nPayload);
}
else
{
nPayload = 0;
}
n += (ushort)ConvertEx.GetVariant9L(cell, (uint)(cellID + n), out info.nKey);
info.nData = nPayload;
}
else
{
info.nData = 0;
n += (ushort)ConvertEx.GetVariant4(cell, (uint)(cellID + n), out nPayload);
info.nKey = nPayload;
}
info.nPayload = nPayload;
info.nHeader = n;
if (Check.LIKELY(nPayload <= this.MaxLocal))
{
// This is the (easy) common case where the entire payload fits on the local page. No overflow is required.
if ((info.nSize = (ushort)(n + nPayload)) < 4)
{
info.nSize = 4;
}
info.nLocal = (ushort)nPayload;
info.iOverflow = 0;
}
else
{
// If the payload will not fit completely on the local page, we have to decide how much to store locally and how much to spill onto
// overflow pages. The strategy is to minimize the amount of unused space on overflow pages while keeping the amount of local storage
// in between minLocal and maxLocal.
// Warning: changing the way overflow payload is distributed in any way will result in an incompatible file format.
var minLocal = (int)MinLocal; // Minimum amount of payload held locally
var maxLocal = (int)MaxLocal; // Maximum amount of payload held locally
var surplus = (int)(minLocal + (nPayload - minLocal) % (Shared.UsableSize - 4)); // Overflow payload available for local storage
info.nLocal = (surplus <= maxLocal ? (ushort)surplus : (ushort)minLocal);
info.iOverflow = (ushort)(info.nLocal + n);
info.nSize = (ushort)(info.iOverflow + 4);
}
}
// was:sqlite3BtreeMovetoUnpacked
public RC MoveToUnpacked(Btree.UnpackedRecord idxKey, long intKey, bool biasRight, ref int pRes)
{
Debug.Assert(HoldsMutex());
Debug.Assert(MutexEx.Held(Tree.DB.Mutex));
Debug.Assert((idxKey == null) == (KeyInfo == null));
// If the cursor is already positioned at the point we are trying to move to, then just return without doing any work
if (State == CursorState.VALID && ValidNKey && Pages[0].HasIntKey)
{
if (Info.nKey == intKey)
{
pRes = 0;
return(RC.OK);
}
if (AtLast && Info.nKey < intKey)
{
pRes = -1;
return(RC.OK);
}
}
var rc = MoveToRoot();
if (rc != RC.OK)
{
return(rc);
}
Debug.Assert(Pages[PageID] != null);
Debug.Assert(Pages[PageID].HasInit);
Debug.Assert(Pages[PageID].Cells > 0 || State == CursorState.INVALID);
if (State == CursorState.INVALID)
{
pRes = -1;
Debug.Assert(Pages[PageID].Cells == 0);
return(RC.OK);
}
Debug.Assert(Pages[0].HasIntKey || idxKey != null);
for (; ;)
{
var page = Pages[PageID];
// pPage.nCell must be greater than zero. If this is the root-page the cursor would have been INVALID above and this for(;;) loop
// not run. If this is not the root-page, then the moveToChild() routine would have already detected db corruption. Similarly, pPage must
// be the right kind (index or table) of b-tree page. Otherwise a moveToChild() or moveToRoot() call would have detected corruption.
Debug.Assert(page.Cells > 0);
Debug.Assert(page.HasIntKey == (idxKey == null));
var lwr = 0;
var upr = page.Cells - 1;
int idx;
PagesIndexs[PageID] = (ushort)(biasRight ? (idx = upr) : (idx = (upr + lwr) / 2));
int c;
for (; ;)
{
Debug.Assert(idx == PagesIndexs[PageID]);
Info.nSize = 0;
var cell = page.FindCell(idx) + page.ChildPtrSize; // Pointer to current cell in pPage
if (page.HasIntKey)
{
var nCellKey = 0L;
if (page.HasData != 0)
{
uint dummy0;
cell += ConvertEx.GetVariant4(page.Data, (uint)cell, out dummy0);
}
ConvertEx.GetVariant9L(page.Data, (uint)cell, out nCellKey);
if (nCellKey == intKey)
{
c = 0;
}
else if (nCellKey < intKey)
{
c = -1;
}
else
{
Debug.Assert(nCellKey > intKey);
c = 1;
}
ValidNKey = true;
Info.nKey = nCellKey;
}
else
{
// The maximum supported page-size is 65536 bytes. This means that the maximum number of record bytes stored on an index B-Tree
// page is less than 16384 bytes and may be stored as a 2-byte varint. This information is used to attempt to avoid parsing
// the entire cell by checking for the cases where the record is stored entirely within the b-tree page by inspecting the first
// 2 bytes of the cell.
var nCell = (int)page.Data[cell + 0];
if (0 == (nCell & 0x80) && nCell <= page.MaxLocal)
{
// This branch runs if the record-size field of the cell is a single byte varint and the record fits entirely on the main b-tree page.
c = Btree._vdbe.sqlite3VdbeRecordCompare(nCell, page.Data, cell + 1, idxKey);
}
else if (0 == (page.Data[cell + 1] & 0x80) && (nCell = ((nCell & 0x7f) << 7) + page.Data[cell + 1]) <= page.MaxLocal)
{
// The record-size field is a 2 byte varint and the record fits entirely on the main b-tree page.
c = Btree._vdbe.sqlite3VdbeRecordCompare(nCell, page.Data, cell + 2, idxKey);
}
else
{
// The record flows over onto one or more overflow pages. In this case the whole cell needs to be parsed, a buffer allocated
// and accessPayload() used to retrieve the record into the buffer before VdbeRecordCompare() can be called.
var pCellBody = new byte[page.Data.Length - cell + page.ChildPtrSize];
Buffer.BlockCopy(page.Data, cell - page.ChildPtrSize, pCellBody, 0, pCellBody.Length);
page.btreeParseCellPtr(pCellBody, ref Info);
nCell = (int)Info.nKey;
var pCellKey = MallocEx.sqlite3Malloc(nCell);
rc = AccessPayload(0, (uint)nCell, pCellKey, false);
if (rc != RC.OK)
{
pCellKey = null;
goto moveto_finish;
}
c = Btree._vdbe.sqlite3VdbeRecordCompare(nCell, pCellKey, idxKey);
pCellKey = null;
}
}
if (c == 0)
{
if (page.HasIntKey && 0 == page.Leaf)
{
lwr = idx;
upr = lwr - 1;
break;
}
else
{
pRes = 0;
rc = RC.OK;
goto moveto_finish;
}
}
if (c < 0)
{
lwr = idx + 1;
}
else
{
upr = idx - 1;
}
if (lwr > upr)
{
break;
}
PagesIndexs[PageID] = (ushort)(idx = (lwr + upr) / 2);
}
Debug.Assert(lwr == upr + 1);
Debug.Assert(page.HasInit);
Pgno chldPg;
if (page.Leaf != 0)
{
chldPg = 0;
}
else if (lwr >= page.Cells)
{
chldPg = ConvertEx.Get4(page.Data, page.HeaderOffset + 8);
}
else
{
chldPg = ConvertEx.Get4(page.Data, page.FindCell(lwr));
}
if (chldPg == 0)
{
Debug.Assert(PagesIndexs[PageID] < Pages[PageID].Cells);
pRes = c;
rc = RC.OK;
goto moveto_finish;
}
PagesIndexs[PageID] = (ushort)lwr;
Info.nSize = 0;
ValidNKey = false;
rc = MoveToChild(chldPg);
if (rc != RC.OK)
{
goto moveto_finish;
}
}
moveto_finish:
return(rc);
}