internal void dropCell(int idx, int sz, ref RC pRC) { if (pRC != RC.OK) { return; } Debug.Assert(idx >= 0 && idx < this.Cells); #if DEBUG Debug.Assert(sz == cellSize(idx)); #endif Debug.Assert(Pager.IsPageWriteable(this.DbPage)); Debug.Assert(MutexEx.Held(this.Shared.Mutex)); var data = this.Data; var ptr = this.CellOffset + 2 * idx; // Used to move bytes around within data[] var pc = (uint)ConvertEx.Get2(data, ptr); // Offset to cell content of cell being deleted var hdr = this.HeaderOffset; // Beginning of the header. 0 most pages. 100 page 1 if (pc < (uint)ConvertEx.Get2(data, hdr + 5) || pc + sz > this.Shared.UsableSize) { pRC = SysEx.SQLITE_CORRUPT_BKPT(); return; } var rc = freeSpace(pc, sz); if (rc != RC.OK) { pRC = rc; return; } Buffer.BlockCopy(data, ptr + 2, data, ptr, (this.Cells - 1 - idx) * 2); this.Cells--; data[this.HeaderOffset + 3] = (byte)(this.Cells >> 8); data[this.HeaderOffset + 4] = (byte)(this.Cells); this.FreeBytes += 2; }
internal void assemblePage(int nCell, byte[] apCell, ushort[] aSize) { Debug.Assert(this.NOverflows == 0); Debug.Assert(MutexEx.Held(this.Shared.Mutex)); Debug.Assert(nCell >= 0 && nCell <= Btree.MX_CELL(this.Shared) && Btree.MX_CELL(this.Shared) <= 5460); 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 var hdr = this.HeaderOffset; // Offset of header on pPage var nUsable = (int)this.Shared.UsableSize; // Usable size of page Debug.Assert(ConvertEx.Get2(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--) { pCellptr -= 2; cellbody -= aSize[i]; ConvertEx.Put2(data, pCellptr, cellbody); Buffer.BlockCopy(apCell, 0, data, cellbody, aSize[i]); } ConvertEx.Put2(data, hdr + 3, nCell); ConvertEx.Put2(data, hdr + 5, cellbody); this.FreeBytes -= (ushort)(nCell * 2 + nUsable - cellbody); this.Cells = (ushort)nCell; }
internal RC defragmentPage() { Debug.Assert(Pager.IsPageWriteable(this.DbPage)); Debug.Assert(this.Shared != null); Debug.Assert(this.Shared.UsableSize <= Pager.SQLITE_MAX_PAGE_SIZE); Debug.Assert(this.NOverflows == 0); Debug.Assert(MutexEx.Held(this.Shared.Mutex)); var temp = this.Shared.Pager.sqlite3PagerTempSpace(); // Temp area for cell content var data = this.Data; // The page data var hdr = this.HeaderOffset; // Offset to the page header var cellOffset = this.CellOffset; // Offset to the cell pointer array var nCell = this.Cells; // Number of cells on the page Debug.Assert(nCell == ConvertEx.Get2(data, hdr + 3)); var usableSize = (int)this.Shared.UsableSize; // Number of usable bytes on a page var cbrk = (int)ConvertEx.Get2(data, hdr + 5); // Offset to the cell content area Buffer.BlockCopy(data, cbrk, temp, cbrk, usableSize - cbrk); cbrk = usableSize; var iCellFirst = cellOffset + 2 * nCell; // First allowable cell index var iCellLast = usableSize - 4; // Last possible cell index for (var i = 0; i < nCell; i++) { var pAddr = cellOffset + i * 2; // The i-th cell pointer var pc = ConvertEx.Get2(data, pAddr); // Address of a i-th cell #if !SQLITE_ENABLE_OVERSIZE_CELL_CHECK // These conditions have already been verified in btreeInitPage() if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined if (pc < iCellFirst || pc > iCellLast) { return(SysEx.SQLITE_CORRUPT_BKPT()); } #endif Debug.Assert(pc >= iCellFirst && pc <= iCellLast); var size = cellSizePtr(temp, pc); // Size of a cell cbrk -= size; if (cbrk < iCellFirst || pc + size > usableSize) { return(SysEx.SQLITE_CORRUPT_BKPT()); } Debug.Assert(cbrk + size <= usableSize && cbrk >= iCellFirst); Buffer.BlockCopy(temp, pc, data, cbrk, size); ConvertEx.Put2(data, pAddr, cbrk); } Debug.Assert(cbrk >= iCellFirst); ConvertEx.Put2(data, hdr + 5, cbrk); data[hdr + 1] = 0; data[hdr + 2] = 0; data[hdr + 7] = 0; var addr = cellOffset + 2 * nCell; // Offset of first byte after cell pointer array Array.Clear(data, addr, cbrk - addr); Debug.Assert(Pager.IsPageWriteable(this.DbPage)); return(cbrk - iCellFirst != this.FreeBytes ? SysEx.SQLITE_CORRUPT_BKPT() : RC.OK); }
internal static void copyNodeContent(MemPage pFrom, MemPage pTo, ref RC pRC) { if (pRC != RC.OK) { return; } var pBt = pFrom.Shared; var aFrom = pFrom.Data; var aTo = pTo.Data; var iFromHdr = pFrom.HeaderOffset; var iToHdr = (pTo.ID == 1 ? 100 : 0); Debug.Assert(pFrom.HasInit); Debug.Assert(pFrom.FreeBytes >= iToHdr); Debug.Assert(ConvertEx.Get2(aFrom, iFromHdr + 5) <= (int)pBt.UsableSize); // Copy the b-tree node content from page pFrom to page pTo. var iData = (int)ConvertEx.Get2(aFrom, iFromHdr + 5); Buffer.BlockCopy(aFrom, iData, aTo, iData, (int)pBt.UsableSize - iData); Buffer.BlockCopy(aFrom, iFromHdr, aTo, iToHdr, pFrom.CellOffset + 2 * pFrom.Cells); // Reinitialize page pTo so that the contents of the MemPage structure match the new data. The initialization of pTo can actually fail under // fairly obscure circumstances, even though it is a copy of initialized page pFrom. pTo.HasInit = false; var rc = pTo.btreeInitPage(); if (rc != RC.OK) { pRC = rc; return; } // If this is an auto-vacuum database, update the pointer-map entries for any b-tree or overflow pages that pTo now contains the pointers to. #if !SQLITE_OMIT_AUTOVACUUM if (pBt.AutoVacuum) #else if (false) #endif { pRC = pTo.setChildPtrmaps(); } }
internal static RC balance_nonroot(MemPage pParent, int iParentIdx, byte[] aOvflSpace, int isRoot) { var apOld = new MemPage[NB]; // pPage and up to two siblings var apCopy = new MemPage[NB]; // Private copies of apOld[] pages var apNew = new MemPage[NB + 2]; // pPage and up to NB siblings after balancing var apDiv = new int[NB - 1]; // Divider cells in pParent var cntNew = new int[NB + 2]; // Index in aCell[] of cell after i-th page var szNew = new int[NB + 2]; // Combined size of cells place on i-th page var szCell = new ushort[1]; // Local size of all cells in apCell[] BtShared pBt; // The whole database int nCell = 0; // Number of cells in apCell[] int nMaxCells = 0; // Allocated size of apCell, szCell, aFrom. int nNew = 0; // Number of pages in apNew[] ushort leafCorrection; // 4 if pPage is a leaf. 0 if not int leafData; // True if pPage is a leaf of a LEAFDATA tree int usableSpace; // Bytes in pPage beyond the header int pageFlags; // Value of pPage.aData[0] int subtotal; // Subtotal of bytes in cells on one page int iOvflSpace = 0; // First unused byte of aOvflSpace[] //int szScratch; // Size of scratch memory requested byte[][] apCell = null; // All cells begin balanced // pBt = pParent.Shared; Debug.Assert(MutexEx.Held(pBt.Mutex)); Debug.Assert(Pager.IsPageWriteable(pParent.DbPage)); #if false Btree.TRACE("BALANCE: begin page %d child of %d\n", pPage.pgno, pParent.pgno); #endif // At this point pParent may have at most one overflow cell. And if this overflow cell is present, it must be the cell with // index iParentIdx. This scenario comes about when this function is called (indirectly) from sqlite3BtreeDelete(). Debug.Assert(pParent.NOverflows == 0 || pParent.NOverflows == 1); Debug.Assert(pParent.NOverflows == 0 || pParent.Overflows[0].Index == iParentIdx); // Find the sibling pages to balance. Also locate the cells in pParent that divide the siblings. An attempt is made to find NN siblings on // either side of pPage. More siblings are taken from one side, however, if there are fewer than NN siblings on the other side. If pParent // has NB or fewer children then all children of pParent are taken. // This loop also drops the divider cells from the parent page. This way, the remainder of the function does not have to deal with any // overflow cells in the parent page, since if any existed they will have already been removed. int nOld; // Number of pages in apOld[] int nxDiv; // Next divider slot in pParent.aCell[] var i = pParent.NOverflows + pParent.Cells; if (i < 2) { nxDiv = 0; nOld = i + 1; } else { nOld = 3; if (iParentIdx == 0) { nxDiv = 0; } else if (iParentIdx == i) { nxDiv = i - 2; } else { nxDiv = iParentIdx - 1; } i = 2; } var pRight = ((i + nxDiv - pParent.NOverflows) == pParent.Cells ? pParent.HeaderOffset + 8 : pParent.FindCell(i + nxDiv - pParent.NOverflows)); // Location in parent of right-sibling pointer var pgno = (Pgno)ConvertEx.Get4(pParent.Data, pRight); var rc = RC.OK; while (true) { rc = pBt.getAndInitPage(pgno, ref apOld[i]); if (rc != RC.OK) { goto balance_cleanup; } nMaxCells += 1 + apOld[i].Cells + apOld[i].NOverflows; if (i-- == 0) { break; } if (i + nxDiv == pParent.Overflows[0].Index && pParent.NOverflows != 0) { apDiv[i] = 0; pgno = ConvertEx.Get4(pParent.Overflows[0].Cell, apDiv[i]); szNew[i] = pParent.cellSizePtr(apDiv[i]); pParent.NOverflows = 0; } else { apDiv[i] = pParent.FindCell(i + nxDiv - pParent.NOverflows); pgno = ConvertEx.Get4(pParent.Data, apDiv[i]); szNew[i] = pParent.cellSizePtr(apDiv[i]); // Drop the cell from the parent page. apDiv[i] still points to the cell within the parent, even though it has been dropped. // This is safe because dropping a cell only overwrites the first four bytes of it, and this function does not need the first // four bytes of the divider cell. So the pointer is safe to use later on. // // Unless SQLite is compiled in secure-delete mode. In this case, the dropCell() routine will overwrite the entire cell with zeroes. // In this case, temporarily copy the cell into the aOvflSpace[] buffer. It will be copied out again as soon as the aSpace[] buffer // is allocated. //if (pBt.secureDelete) //{ // int iOff = (int)(apDiv[i]) - (int)(pParent.aData); //SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent.aData); // if( (iOff+szNew[i])>(int)pBt->usableSize ) // { // rc = SQLITE_CORRUPT_BKPT(); // Array.Clear(apOld[0].aData,0,apOld[0].aData.Length); //memset(apOld, 0, (i + 1) * sizeof(MemPage*)); // goto balance_cleanup; // } // else // { // memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]); // apDiv[i] = &aOvflSpace[apDiv[i] - pParent.aData]; // } //} pParent.dropCell(i + nxDiv - pParent.NOverflows, szNew[i], ref rc); } } // Make nMaxCells a multiple of 4 in order to preserve 8-byte alignment nMaxCells = (nMaxCells + 3) & ~3; // Allocate space for memory structures apCell = MallocEx.sqlite3ScratchMalloc(apCell, nMaxCells); if (szCell.Length < nMaxCells) { Array.Resize(ref szCell, nMaxCells); } // Load pointers to all cells on sibling pages and the divider cells into the local apCell[] array. Make copies of the divider cells // into space obtained from aSpace1[] and remove the the divider Cells from pParent. // If the siblings are on leaf pages, then the child pointers of the divider cells are stripped from the cells before they are copied // into aSpace1[]. In this way, all cells in apCell[] are without child pointers. If siblings are not leaves, then all cell in // apCell[] include child pointers. Either way, all cells in apCell[] are alike. // leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf. // leafData: 1 if pPage holds key+data and pParent holds only keys. leafCorrection = (ushort)(apOld[0].Leaf * 4); leafData = apOld[0].HasData; int j; for (i = 0; i < nOld; i++) { // Before doing anything else, take a copy of the i'th original sibling The rest of this function will use data from the copies rather // that the original pages since the original pages will be in the process of being overwritten. var pOld = apCopy[i] = apOld[i].Clone(); var limit = pOld.Cells + pOld.NOverflows; if (pOld.NOverflows > 0 || true) { for (j = 0; j < limit; j++) { Debug.Assert(nCell < nMaxCells); var iFOFC = pOld.FindOverflowCell(j); szCell[nCell] = pOld.cellSizePtr(iFOFC); // Copy the Data Locally if (apCell[nCell] == null) { apCell[nCell] = new byte[szCell[nCell]]; } else if (apCell[nCell].Length < szCell[nCell]) { Array.Resize(ref apCell[nCell], szCell[nCell]); } if (iFOFC < 0) // Overflow Cell { Buffer.BlockCopy(pOld.Overflows[-(iFOFC + 1)].Cell, 0, apCell[nCell], 0, szCell[nCell]); } else { Buffer.BlockCopy(pOld.Data, iFOFC, apCell[nCell], 0, szCell[nCell]); } nCell++; } } else { var aData = pOld.Data; var maskPage = pOld.MaskPage; var cellOffset = pOld.CellOffset; for (j = 0; j < limit; j++) { Debugger.Break(); Debug.Assert(nCell < nMaxCells); apCell[nCell] = FindCellv2(aData, maskPage, cellOffset, j); szCell[nCell] = pOld.cellSizePtr(apCell[nCell]); nCell++; } } if (i < nOld - 1 && 0 == leafData) { var sz = (ushort)szNew[i]; var pTemp = MallocEx.sqlite3Malloc(sz + leafCorrection); Debug.Assert(nCell < nMaxCells); szCell[nCell] = sz; Debug.Assert(sz <= pBt.MaxLocal + 23); Buffer.BlockCopy(pParent.Data, apDiv[i], pTemp, 0, sz); if (apCell[nCell] == null || apCell[nCell].Length < sz) { Array.Resize(ref apCell[nCell], sz); } Buffer.BlockCopy(pTemp, leafCorrection, apCell[nCell], 0, sz); Debug.Assert(leafCorrection == 0 || leafCorrection == 4); szCell[nCell] = (ushort)(szCell[nCell] - leafCorrection); if (0 == pOld.Leaf) { Debug.Assert(leafCorrection == 0); Debug.Assert(pOld.HeaderOffset == 0); // The right pointer of the child page pOld becomes the left pointer of the divider cell Buffer.BlockCopy(pOld.Data, 8, apCell[nCell], 0, 4);//memcpy( apCell[nCell], ref pOld.aData[8], 4 ); } else { Debug.Assert(leafCorrection == 4); if (szCell[nCell] < 4) { // Do not allow any cells smaller than 4 bytes. szCell[nCell] = 4; } } nCell++; } } // Figure out the number of pages needed to hold all nCell cells. Store this number in "k". Also compute szNew[] which is the total // size of all cells on the i-th page and cntNew[] which is the index in apCell[] of the cell that divides page i from page i+1. // cntNew[k] should equal nCell. // Values computed by this block: // k: The total number of sibling pages // szNew[i]: Spaced used on the i-th sibling page. // cntNew[i]: Index in apCell[] and szCell[] for the first cell to // the right of the i-th sibling page. // usableSpace: Number of bytes of space available on each sibling. usableSpace = (int)pBt.UsableSize - 12 + leafCorrection; int k; for (subtotal = k = i = 0; i < nCell; i++) { Debug.Assert(i < nMaxCells); subtotal += szCell[i] + 2; if (subtotal > usableSpace) { szNew[k] = subtotal - szCell[i]; cntNew[k] = i; if (leafData != 0) { i--; } subtotal = 0; k++; if (k > NB + 1) { rc = SysEx.SQLITE_CORRUPT_BKPT(); goto balance_cleanup; } } } szNew[k] = subtotal; cntNew[k] = nCell; k++; // The packing computed by the previous block is biased toward the siblings on the left side. The left siblings are always nearly full, while the // right-most sibling might be nearly empty. This block of code attempts to adjust the packing of siblings to get a better balance. // // This adjustment is more than an optimization. The packing above might be so out of balance as to be illegal. For example, the right-most // sibling might be completely empty. This adjustment is not optional. for (i = k - 1; i > 0; i--) { var szRight = szNew[i]; // Size of sibling on the right var szLeft = szNew[i - 1]; // Size of sibling on the left var r = cntNew[i - 1] - 1; // Index of right-most cell in left sibling var d = r + 1 - leafData; // Index of first cell to the left of right sibling Debug.Assert(d < nMaxCells); Debug.Assert(r < nMaxCells); while (szRight == 0 || szRight + szCell[d] + 2 <= szLeft - (szCell[r] + 2)) { szRight += szCell[d] + 2; szLeft -= szCell[r] + 2; cntNew[i - 1]--; r = cntNew[i - 1] - 1; d = r + 1 - leafData; } szNew[i] = szRight; szNew[i - 1] = szLeft; } // Either we found one or more cells (cntnew[0])>0) or pPage is a virtual root page. A virtual root page is when the real root // page is page 1 and we are the only child of that page. Debug.Assert(cntNew[0] > 0 || (pParent.ID == 1 && pParent.Cells == 0)); Btree.TRACE("BALANCE: old: %d %d %d ", apOld[0].ID, (nOld >= 2 ? apOld[1].ID : 0), (nOld >= 3 ? apOld[2].ID : 0)); // Allocate k new pages. Reuse old pages where possible. if (apOld[0].ID <= 1) { rc = SysEx.SQLITE_CORRUPT_BKPT(); goto balance_cleanup; } pageFlags = apOld[0].Data[0]; for (i = 0; i < k; i++) { var pNew = new MemPage(); if (i < nOld) { pNew = apNew[i] = apOld[i]; apOld[i] = null; rc = Pager.Write(pNew.DbPage); nNew++; if (rc != RC.OK) { goto balance_cleanup; } } else { Debug.Assert(i > 0); rc = pBt.allocateBtreePage(ref pNew, ref pgno, pgno, 0); if (rc != 0) { goto balance_cleanup; } apNew[i] = pNew; nNew++; // Set the pointer-map entry for the new sibling page. #if !SQLITE_OMIT_AUTOVACUUM if (pBt.AutoVacuum) #else if (false) #endif { pBt.ptrmapPut(pNew.ID, PTRMAP.BTREE, pParent.ID, ref rc); if (rc != RC.OK) { goto balance_cleanup; } } } } // Free any old pages that were not reused as new pages. while (i < nOld) { apOld[i].freePage(ref rc); if (rc != RC.OK) { goto balance_cleanup; } apOld[i].releasePage(); apOld[i] = null; i++; } // Put the new pages in accending order. This helps to keep entries in the disk file in order so that a scan // of the table is a linear scan through the file. That in turn helps the operating system to deliver pages // from the disk more rapidly. // An O(n^2) insertion sort algorithm is used, but since n is never more than NB (a small constant), that should // not be a problem. // When NB==3, this one optimization makes the database about 25% faster for large insertions and deletions. for (i = 0; i < k - 1; i++) { var minV = (int)apNew[i].ID; var minI = i; for (j = i + 1; j < k; j++) { if (apNew[j].ID < (uint)minV) { minI = j; minV = (int)apNew[j].ID; } } if (minI > i) { var pT = apNew[i]; apNew[i] = apNew[minI]; apNew[minI] = pT; } } Btree.TRACE("new: %d(%d) %d(%d) %d(%d) %d(%d) %d(%d)\n", apNew[0].ID, szNew[0], (nNew >= 2 ? apNew[1].ID : 0), (nNew >= 2 ? szNew[1] : 0), (nNew >= 3 ? apNew[2].ID : 0), (nNew >= 3 ? szNew[2] : 0), (nNew >= 4 ? apNew[3].ID : 0), (nNew >= 4 ? szNew[3] : 0), (nNew >= 5 ? apNew[4].ID : 0), (nNew >= 5 ? szNew[4] : 0)); Debug.Assert(Pager.IsPageWriteable(pParent.DbPage)); ConvertEx.Put4L(pParent.Data, pRight, apNew[nNew - 1].ID); // Evenly distribute the data in apCell[] across the new pages. Insert divider cells into pParent as necessary. j = 0; for (i = 0; i < nNew; i++) { // Assemble the new sibling page. MemPage pNew = apNew[i]; Debug.Assert(j < nMaxCells); pNew.zeroPage(pageFlags); pNew.assemblePage(cntNew[i] - j, apCell, szCell, j); Debug.Assert(pNew.Cells > 0 || (nNew == 1 && cntNew[0] == 0)); Debug.Assert(pNew.NOverflows == 0); j = cntNew[i]; // If the sibling page assembled above was not the right-most sibling, insert a divider cell into the parent page. Debug.Assert(i < nNew - 1 || j == nCell); if (j < nCell) { Debug.Assert(j < nMaxCells); var pCell = apCell[j]; var sz = szCell[j] + leafCorrection; var pTemp = MallocEx.sqlite3Malloc(sz); if (pNew.Leaf == 0) { Buffer.BlockCopy(pCell, 0, pNew.Data, 8, 4); } else if (leafData != 0) { // If the tree is a leaf-data tree, and the siblings are leaves, then there is no divider cell in apCell[]. Instead, the divider // cell consists of the integer key for the right-most cell of the sibling-page assembled above only. var info = new CellInfo(); j--; pNew.btreeParseCellPtr(apCell[j], ref info); pCell = pTemp; sz = 4 + ConvertEx.PutVarint9L(pCell, 4, (ulong)info.nKey); pTemp = null; } else { //------------ pCell -= 4; var _pCell_4 = MallocEx.sqlite3Malloc(pCell.Length + 4); Buffer.BlockCopy(pCell, 0, _pCell_4, 4, pCell.Length); pCell = _pCell_4; // Obscure case for non-leaf-data trees: If the cell at pCell was previously stored on a leaf node, and its reported size was 4 // bytes, then it may actually be smaller than this (see btreeParseCellPtr(), 4 bytes is the minimum size of // any cell). But it is important to pass the correct size to insertCell(), so reparse the cell now. // Note that this can never happen in an SQLite data file, as all cells are at least 4 bytes. It only happens in b-trees used // to evaluate "IN (SELECT ...)" and similar clauses. if (szCell[j] == 4) { Debug.Assert(leafCorrection == 4); sz = pParent.cellSizePtr(pCell); } } iOvflSpace += sz; Debug.Assert(sz <= pBt.MaxLocal + 23); Debug.Assert(iOvflSpace <= (int)pBt.PageSize); pParent.insertCell(nxDiv, pCell, sz, pTemp, pNew.ID, ref rc); if (rc != RC.OK) { goto balance_cleanup; } Debug.Assert(Pager.IsPageWriteable(pParent.DbPage)); j++; nxDiv++; } } Debug.Assert(j == nCell); Debug.Assert(nOld > 0); Debug.Assert(nNew > 0); if ((pageFlags & Btree.PTF_LEAF) == 0) { Buffer.BlockCopy(apCopy[nOld - 1].Data, 8, apNew[nNew - 1].Data, 8, 4); } if (isRoot != 0 && pParent.Cells == 0 && pParent.HeaderOffset <= apNew[0].FreeBytes) { // The root page of the b-tree now contains no cells. The only sibling page is the right-child of the parent. Copy the contents of the // child page into the parent, decreasing the overall height of the b-tree structure by one. This is described as the "balance-shallower" // sub-algorithm in some documentation. // If this is an auto-vacuum database, the call to copyNodeContent() sets all pointer-map entries corresponding to database image pages // for which the pointer is stored within the content being copied. // The second Debug.Assert below verifies that the child page is defragmented (it must be, as it was just reconstructed using assemblePage()). This // is important if the parent page happens to be page 1 of the database image. */ Debug.Assert(nNew == 1); Debug.Assert(apNew[0].FreeBytes == (ConvertEx.Get2(apNew[0].Data, 5) - apNew[0].CellOffset - apNew[0].Cells * 2)); copyNodeContent(apNew[0], pParent, ref rc); apNew[0].freePage(ref rc); } else #if !SQLITE_OMIT_AUTOVACUUM if (pBt.AutoVacuum) #else if (false) #endif { // Fix the pointer-map entries for all the cells that were shifted around. There are several different types of pointer-map entries that need to // be dealt with by this routine. Some of these have been set already, but many have not. The following is a summary: // 1) The entries associated with new sibling pages that were not siblings when this function was called. These have already // been set. We don't need to worry about old siblings that were moved to the free-list - the freePage() code has taken care // of those. // 2) The pointer-map entries associated with the first overflow page in any overflow chains used by new divider cells. These // have also already been taken care of by the insertCell() code. // 3) If the sibling pages are not leaves, then the child pages of cells stored on the sibling pages may need to be updated. // 4) If the sibling pages are not internal intkey nodes, then any overflow pages used by these cells may need to be updated // (internal intkey nodes never contain pointers to overflow pages). // 5) If the sibling pages are not leaves, then the pointer-map entries for the right-child pages of each sibling may need // to be updated. // Cases 1 and 2 are dealt with above by other code. The next block deals with cases 3 and 4 and the one after that, case 5. Since // setting a pointer map entry is a relatively expensive operation, this code only sets pointer map entries for child or overflow pages that have // actually moved between pages. var pNew = apNew[0]; var pOld = apCopy[0]; var nOverflow = pOld.NOverflows; var iNextOld = pOld.Cells + nOverflow; var iOverflow = (nOverflow != 0 ? pOld.Overflows[0].Index : -1); j = 0; // Current 'old' sibling page k = 0; // Current 'new' sibling page for (i = 0; i < nCell; i++) { var isDivider = 0; while (i == iNextOld) { // Cell i is the cell immediately following the last cell on old sibling page j. If the siblings are not leaf pages of an // intkey b-tree, then cell i was a divider cell. pOld = apCopy[++j]; iNextOld = i + (0 == leafData ? 1 : 0) + pOld.Cells + pOld.NOverflows; if (pOld.NOverflows != 0) { nOverflow = pOld.NOverflows; iOverflow = i + (0 == leafData ? 1 : 0) + pOld.Overflows[0].Index; } isDivider = 0 == leafData ? 1 : 0; } Debug.Assert(nOverflow > 0 || iOverflow < i); Debug.Assert(nOverflow < 2 || pOld.Overflows[0].Index == pOld.Overflows[1].Index - 1); Debug.Assert(nOverflow < 3 || pOld.Overflows[1].Index == pOld.Overflows[2].Index - 1); if (i == iOverflow) { isDivider = 1; if (--nOverflow > 0) { iOverflow++; } } if (i == cntNew[k]) { // Cell i is the cell immediately following the last cell on new sibling page k. If the siblings are not leaf pages of an // intkey b-tree, then cell i is a divider cell. pNew = apNew[++k]; if (leafData == 0) { continue; } } Debug.Assert(j < nOld); Debug.Assert(k < nNew); // If the cell was originally divider cell (and is not now) or an overflow cell, or if the cell was located on a different sibling // page before the balancing, then the pointer map entries associated with any child or overflow pages need to be updated. if (isDivider != 0 || pOld.ID != pNew.ID) { if (leafCorrection == 0) { pBt.ptrmapPut(ConvertEx.Get4(apCell[i]), PTRMAP.BTREE, pNew.ID, ref rc); } if (szCell[i] > pNew.MinLocal) { pNew.ptrmapPutOvflPtr(apCell[i], ref rc); } } } if (leafCorrection == 0) { for (i = 0; i < nNew; i++) { var key = ConvertEx.Get4(apNew[i].Data, 8); pBt.ptrmapPut(key, PTRMAP.BTREE, apNew[i].ID, ref rc); } } #if false // The ptrmapCheckPages() contains Debug.Assert() statements that verify that all pointer map pages are set correctly. This is helpful while // debugging. This is usually disabled because a corrupt database may cause an Debug.Assert() statement to fail. ptrmapCheckPages(apNew, nNew); ptrmapCheckPages(pParent, 1); #endif } Debug.Assert(pParent.HasInit); Btree.TRACE("BALANCE: finished: old=%d new=%d cells=%d\n", nOld, nNew, nCell); // Cleanup before returning. balance_cleanup: MallocEx.sqlite3ScratchFree(apCell); for (i = 0; i < nOld; i++) { apOld[i].releasePage(); } for (i = 0; i < nNew; i++) { apNew[i].releasePage(); } return(rc); }
// was:findCell internal int FindCell(int cellID) { return(ConvertEx.Get2(Data, CellOffset + (2 * cellID))); }
internal RC allocateSpace(int nByte, ref int pIdx) { var hdr = this.HeaderOffset; var data = this.Data; Debug.Assert(Pager.IsPageWriteable(this.DbPage)); Debug.Assert(this.Shared != null); Debug.Assert(MutexEx.Held(this.Shared.Mutex)); Debug.Assert(nByte >= 0); // Minimum cell size is 4 Debug.Assert(this.FreeBytes >= nByte); Debug.Assert(this.NOverflows == 0); var usableSize = this.Shared.UsableSize; // Usable size of the page Debug.Assert(nByte < usableSize - 8); var nFrag = data[hdr + 7]; // Number of fragmented bytes on pPage Debug.Assert(this.CellOffset == hdr + 12 - 4 * this.Leaf); var gap = this.CellOffset + 2 * this.Cells; // First byte of gap between cell pointers and cell content var top = ConvertEx.Get2nz(data, hdr + 5); // First byte of cell content area if (gap > top) { return(SysEx.SQLITE_CORRUPT_BKPT()); } if (nFrag >= 60) { // Always defragment highly fragmented pages var rc = defragmentPage(); if (rc != RC.OK) { return(rc); } top = ConvertEx.Get2nz(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 pc; for (var addr = hdr + 1; (pc = ConvertEx.Get2(data, addr)) > 0; addr = pc) { if (pc > usableSize - 4 || pc < addr + 4) { return(SysEx.SQLITE_CORRUPT_BKPT()); } var size = ConvertEx.Get2(data, pc + 2); // Size of free slot if (size >= nByte) { var x = size - nByte; if (x < 4) { // Remove the slot from the free-list. Update the number of fragmented bytes within the page. data[addr + 0] = data[pc + 0]; data[addr + 1] = data[pc + 1]; data[hdr + 7] = (byte)(nFrag + x); } else if (size + pc > usableSize) { return(SysEx.SQLITE_CORRUPT_BKPT()); } else { // The slot remains on the free-list. Reduce its size to account for the portion used by the new allocation. ConvertEx.Put2(data, pc + 2, x); } pIdx = pc + x; return(RC.OK); } } } // Check to make sure there is enough space in the gap to satisfy the allocation. If not, defragment. if (gap + 2 + nByte > top) { var rc = defragmentPage(); if (rc != RC.OK) { return(rc); } top = ConvertEx.Get2nz(data, hdr + 5); Debug.Assert(gap + nByte <= top); } // Allocate memory from the gap in between the cell pointer array and the cell content area. The btreeInitPage() call has already // validated the freelist. Given that the freelist is valid, there is no way that the allocation can extend off the end of the page. // The Debug.Assert() below verifies the previous sentence. top -= nByte; ConvertEx.Put2(data, hdr + 5, top); Debug.Assert(top + nByte <= (int)this.Shared.UsableSize); pIdx = top; return(RC.OK); }
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); }
internal RC freeSpace(int start, int size) { var data = this.Data; Debug.Assert(this.Shared != null); Debug.Assert(Pager.IsPageWriteable(this.DbPage)); Debug.Assert(start >= this.HeaderOffset + 6 + this.ChildPtrSize); Debug.Assert((start + size) <= (int)this.Shared.UsableSize); Debug.Assert(MutexEx.Held(this.Shared.Mutex)); Debug.Assert(size >= 0); // Minimum cell size is 4 if (this.Shared.SecureDelete) { // Overwrite deleted information with zeros when the secure_delete option is enabled Array.Clear(data, start, size); } // Add the space back into the linked list of freeblocks. Note that even though the freeblock list was checked by btreeInitPage(), // btreeInitPage() did not detect overlapping cells or freeblocks that overlapped cells. Nor does it detect when the // cell content area exceeds the value in the page header. If these situations arise, then subsequent insert operations might corrupt // the freelist. So we do need to check for corruption while scanning the freelist. var hdr = this.HeaderOffset; var addr = hdr + 1; var iLast = (int)this.Shared.UsableSize - 4; // Largest possible freeblock offset Debug.Assert(start <= iLast); int pbegin; while ((pbegin = ConvertEx.Get2(data, addr)) < start && pbegin > 0) { if (pbegin < addr + 4) { return(SysEx.SQLITE_CORRUPT_BKPT()); } addr = pbegin; } if (pbegin > iLast) { return(SysEx.SQLITE_CORRUPT_BKPT()); } Debug.Assert(pbegin > addr || pbegin == 0); ConvertEx.Put2(data, addr, start); ConvertEx.Put2(data, start, pbegin); ConvertEx.Put2(data, start + 2, size); this.FreeBytes = (ushort)(this.FreeBytes + size); // Coalesce adjacent free blocks addr = hdr + 1; while ((pbegin = ConvertEx.Get2(data, addr)) > 0) { Debug.Assert(pbegin > addr); Debug.Assert(pbegin <= (int)this.Shared.UsableSize - 4); var pnext = ConvertEx.Get2(data, pbegin); var psize = ConvertEx.Get2(data, pbegin + 2); if (pbegin + psize + 3 >= pnext && pnext > 0) { var frag = pnext - (pbegin + psize); if ((frag < 0) || (frag > (int)data[hdr + 7])) { return(SysEx.SQLITE_CORRUPT_BKPT()); } data[hdr + 7] -= (byte)frag; var x = ConvertEx.Get2(data, pnext); ConvertEx.Put2(data, pbegin, x); x = pnext + ConvertEx.Get2(data, pnext + 2) - pbegin; ConvertEx.Put2(data, pbegin + 2, x); } else { addr = pbegin; } } // If the cell content area begins with a freeblock, remove it. if (data[hdr + 1] == data[hdr + 5] && data[hdr + 2] == data[hdr + 6]) { pbegin = ConvertEx.Get2(data, hdr + 1); ConvertEx.Put2(data, hdr + 1, ConvertEx.Get2(data, pbegin)); var top = ConvertEx.Get2(data, hdr + 5) + ConvertEx.Get2(data, pbegin + 2); ConvertEx.Put2(data, hdr + 5, top); } Debug.Assert(Pager.IsPageWriteable(this.DbPage)); return(RC.OK); }