forked from OSchip/llvm-project
469 lines
16 KiB
C++
469 lines
16 KiB
C++
//===- DeltaTree.cpp - B-Tree for Rewrite Delta tracking ------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the DeltaTree and related classes.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Rewrite/Core/DeltaTree.h"
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#include "clang/Basic/LLVM.h"
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#include "llvm/Support/Casting.h"
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#include <cassert>
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#include <cstring>
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using namespace clang;
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/// The DeltaTree class is a multiway search tree (BTree) structure with some
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/// fancy features. B-Trees are generally more memory and cache efficient
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/// than binary trees, because they store multiple keys/values in each node.
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///
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/// DeltaTree implements a key/value mapping from FileIndex to Delta, allowing
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/// fast lookup by FileIndex. However, an added (important) bonus is that it
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/// can also efficiently tell us the full accumulated delta for a specific
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/// file offset as well, without traversing the whole tree.
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///
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/// The nodes of the tree are made up of instances of two classes:
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/// DeltaTreeNode and DeltaTreeInteriorNode. The later subclasses the
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/// former and adds children pointers. Each node knows the full delta of all
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/// entries (recursively) contained inside of it, which allows us to get the
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/// full delta implied by a whole subtree in constant time.
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namespace {
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/// SourceDelta - As code in the original input buffer is added and deleted,
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/// SourceDelta records are used to keep track of how the input SourceLocation
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/// object is mapped into the output buffer.
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struct SourceDelta {
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unsigned FileLoc;
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int Delta;
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static SourceDelta get(unsigned Loc, int D) {
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SourceDelta Delta;
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Delta.FileLoc = Loc;
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Delta.Delta = D;
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return Delta;
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}
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};
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/// DeltaTreeNode - The common part of all nodes.
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///
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class DeltaTreeNode {
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public:
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struct InsertResult {
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DeltaTreeNode *LHS, *RHS;
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SourceDelta Split;
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};
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private:
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friend class DeltaTreeInteriorNode;
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/// WidthFactor - This controls the number of K/V slots held in the BTree:
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/// how wide it is. Each level of the BTree is guaranteed to have at least
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/// WidthFactor-1 K/V pairs (except the root) and may have at most
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/// 2*WidthFactor-1 K/V pairs.
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enum { WidthFactor = 8 };
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/// Values - This tracks the SourceDelta's currently in this node.
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SourceDelta Values[2*WidthFactor-1];
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/// NumValuesUsed - This tracks the number of values this node currently
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/// holds.
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unsigned char NumValuesUsed = 0;
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/// IsLeaf - This is true if this is a leaf of the btree. If false, this is
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/// an interior node, and is actually an instance of DeltaTreeInteriorNode.
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bool IsLeaf;
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/// FullDelta - This is the full delta of all the values in this node and
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/// all children nodes.
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int FullDelta = 0;
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public:
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DeltaTreeNode(bool isLeaf = true) : IsLeaf(isLeaf) {}
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bool isLeaf() const { return IsLeaf; }
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int getFullDelta() const { return FullDelta; }
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bool isFull() const { return NumValuesUsed == 2*WidthFactor-1; }
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unsigned getNumValuesUsed() const { return NumValuesUsed; }
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const SourceDelta &getValue(unsigned i) const {
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assert(i < NumValuesUsed && "Invalid value #");
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return Values[i];
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}
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SourceDelta &getValue(unsigned i) {
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assert(i < NumValuesUsed && "Invalid value #");
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return Values[i];
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}
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/// DoInsertion - Do an insertion of the specified FileIndex/Delta pair into
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/// this node. If insertion is easy, do it and return false. Otherwise,
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/// split the node, populate InsertRes with info about the split, and return
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/// true.
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bool DoInsertion(unsigned FileIndex, int Delta, InsertResult *InsertRes);
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void DoSplit(InsertResult &InsertRes);
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/// RecomputeFullDeltaLocally - Recompute the FullDelta field by doing a
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/// local walk over our contained deltas.
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void RecomputeFullDeltaLocally();
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void Destroy();
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};
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/// DeltaTreeInteriorNode - When isLeaf = false, a node has child pointers.
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/// This class tracks them.
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class DeltaTreeInteriorNode : public DeltaTreeNode {
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friend class DeltaTreeNode;
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DeltaTreeNode *Children[2*WidthFactor];
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~DeltaTreeInteriorNode() {
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for (unsigned i = 0, e = NumValuesUsed+1; i != e; ++i)
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Children[i]->Destroy();
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}
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public:
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DeltaTreeInteriorNode() : DeltaTreeNode(false /*nonleaf*/) {}
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DeltaTreeInteriorNode(const InsertResult &IR)
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: DeltaTreeNode(false /*nonleaf*/) {
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Children[0] = IR.LHS;
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Children[1] = IR.RHS;
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Values[0] = IR.Split;
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FullDelta = IR.LHS->getFullDelta()+IR.RHS->getFullDelta()+IR.Split.Delta;
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NumValuesUsed = 1;
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}
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const DeltaTreeNode *getChild(unsigned i) const {
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assert(i < getNumValuesUsed()+1 && "Invalid child");
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return Children[i];
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}
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DeltaTreeNode *getChild(unsigned i) {
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assert(i < getNumValuesUsed()+1 && "Invalid child");
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return Children[i];
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}
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static bool classof(const DeltaTreeNode *N) { return !N->isLeaf(); }
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};
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} // namespace
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/// Destroy - A 'virtual' destructor.
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void DeltaTreeNode::Destroy() {
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if (isLeaf())
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delete this;
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else
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delete cast<DeltaTreeInteriorNode>(this);
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}
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/// RecomputeFullDeltaLocally - Recompute the FullDelta field by doing a
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/// local walk over our contained deltas.
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void DeltaTreeNode::RecomputeFullDeltaLocally() {
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int NewFullDelta = 0;
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for (unsigned i = 0, e = getNumValuesUsed(); i != e; ++i)
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NewFullDelta += Values[i].Delta;
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if (auto *IN = dyn_cast<DeltaTreeInteriorNode>(this))
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for (unsigned i = 0, e = getNumValuesUsed()+1; i != e; ++i)
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NewFullDelta += IN->getChild(i)->getFullDelta();
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FullDelta = NewFullDelta;
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}
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/// DoInsertion - Do an insertion of the specified FileIndex/Delta pair into
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/// this node. If insertion is easy, do it and return false. Otherwise,
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/// split the node, populate InsertRes with info about the split, and return
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/// true.
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bool DeltaTreeNode::DoInsertion(unsigned FileIndex, int Delta,
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InsertResult *InsertRes) {
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// Maintain full delta for this node.
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FullDelta += Delta;
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// Find the insertion point, the first delta whose index is >= FileIndex.
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unsigned i = 0, e = getNumValuesUsed();
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while (i != e && FileIndex > getValue(i).FileLoc)
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++i;
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// If we found an a record for exactly this file index, just merge this
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// value into the pre-existing record and finish early.
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if (i != e && getValue(i).FileLoc == FileIndex) {
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// NOTE: Delta could drop to zero here. This means that the delta entry is
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// useless and could be removed. Supporting erases is more complex than
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// leaving an entry with Delta=0, so we just leave an entry with Delta=0 in
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// the tree.
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Values[i].Delta += Delta;
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return false;
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}
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// Otherwise, we found an insertion point, and we know that the value at the
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// specified index is > FileIndex. Handle the leaf case first.
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if (isLeaf()) {
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if (!isFull()) {
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// For an insertion into a non-full leaf node, just insert the value in
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// its sorted position. This requires moving later values over.
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if (i != e)
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memmove(&Values[i+1], &Values[i], sizeof(Values[0])*(e-i));
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Values[i] = SourceDelta::get(FileIndex, Delta);
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++NumValuesUsed;
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return false;
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}
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// Otherwise, if this is leaf is full, split the node at its median, insert
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// the value into one of the children, and return the result.
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assert(InsertRes && "No result location specified");
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DoSplit(*InsertRes);
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if (InsertRes->Split.FileLoc > FileIndex)
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InsertRes->LHS->DoInsertion(FileIndex, Delta, nullptr /*can't fail*/);
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else
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InsertRes->RHS->DoInsertion(FileIndex, Delta, nullptr /*can't fail*/);
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return true;
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}
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// Otherwise, this is an interior node. Send the request down the tree.
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auto *IN = cast<DeltaTreeInteriorNode>(this);
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if (!IN->Children[i]->DoInsertion(FileIndex, Delta, InsertRes))
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return false; // If there was space in the child, just return.
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// Okay, this split the subtree, producing a new value and two children to
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// insert here. If this node is non-full, we can just insert it directly.
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if (!isFull()) {
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// Now that we have two nodes and a new element, insert the perclated value
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// into ourself by moving all the later values/children down, then inserting
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// the new one.
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if (i != e)
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memmove(&IN->Children[i+2], &IN->Children[i+1],
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(e-i)*sizeof(IN->Children[0]));
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IN->Children[i] = InsertRes->LHS;
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IN->Children[i+1] = InsertRes->RHS;
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if (e != i)
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memmove(&Values[i+1], &Values[i], (e-i)*sizeof(Values[0]));
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Values[i] = InsertRes->Split;
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++NumValuesUsed;
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return false;
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}
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// Finally, if this interior node was full and a node is percolated up, split
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// ourself and return that up the chain. Start by saving all our info to
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// avoid having the split clobber it.
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IN->Children[i] = InsertRes->LHS;
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DeltaTreeNode *SubRHS = InsertRes->RHS;
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SourceDelta SubSplit = InsertRes->Split;
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// Do the split.
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DoSplit(*InsertRes);
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// Figure out where to insert SubRHS/NewSplit.
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DeltaTreeInteriorNode *InsertSide;
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if (SubSplit.FileLoc < InsertRes->Split.FileLoc)
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InsertSide = cast<DeltaTreeInteriorNode>(InsertRes->LHS);
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else
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InsertSide = cast<DeltaTreeInteriorNode>(InsertRes->RHS);
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// We now have a non-empty interior node 'InsertSide' to insert
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// SubRHS/SubSplit into. Find out where to insert SubSplit.
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// Find the insertion point, the first delta whose index is >SubSplit.FileLoc.
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i = 0; e = InsertSide->getNumValuesUsed();
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while (i != e && SubSplit.FileLoc > InsertSide->getValue(i).FileLoc)
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++i;
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// Now we know that i is the place to insert the split value into. Insert it
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// and the child right after it.
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if (i != e)
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memmove(&InsertSide->Children[i+2], &InsertSide->Children[i+1],
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(e-i)*sizeof(IN->Children[0]));
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InsertSide->Children[i+1] = SubRHS;
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if (e != i)
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memmove(&InsertSide->Values[i+1], &InsertSide->Values[i],
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(e-i)*sizeof(Values[0]));
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InsertSide->Values[i] = SubSplit;
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++InsertSide->NumValuesUsed;
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InsertSide->FullDelta += SubSplit.Delta + SubRHS->getFullDelta();
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return true;
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}
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/// DoSplit - Split the currently full node (which has 2*WidthFactor-1 values)
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/// into two subtrees each with "WidthFactor-1" values and a pivot value.
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/// Return the pieces in InsertRes.
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void DeltaTreeNode::DoSplit(InsertResult &InsertRes) {
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assert(isFull() && "Why split a non-full node?");
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// Since this node is full, it contains 2*WidthFactor-1 values. We move
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// the first 'WidthFactor-1' values to the LHS child (which we leave in this
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// node), propagate one value up, and move the last 'WidthFactor-1' values
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// into the RHS child.
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// Create the new child node.
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DeltaTreeNode *NewNode;
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if (auto *IN = dyn_cast<DeltaTreeInteriorNode>(this)) {
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// If this is an interior node, also move over 'WidthFactor' children
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// into the new node.
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DeltaTreeInteriorNode *New = new DeltaTreeInteriorNode();
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memcpy(&New->Children[0], &IN->Children[WidthFactor],
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WidthFactor*sizeof(IN->Children[0]));
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NewNode = New;
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} else {
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// Just create the new leaf node.
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NewNode = new DeltaTreeNode();
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}
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// Move over the last 'WidthFactor-1' values from here to NewNode.
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memcpy(&NewNode->Values[0], &Values[WidthFactor],
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(WidthFactor-1)*sizeof(Values[0]));
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// Decrease the number of values in the two nodes.
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NewNode->NumValuesUsed = NumValuesUsed = WidthFactor-1;
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// Recompute the two nodes' full delta.
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NewNode->RecomputeFullDeltaLocally();
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RecomputeFullDeltaLocally();
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InsertRes.LHS = this;
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InsertRes.RHS = NewNode;
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InsertRes.Split = Values[WidthFactor-1];
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}
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//===----------------------------------------------------------------------===//
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// DeltaTree Implementation
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//===----------------------------------------------------------------------===//
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//#define VERIFY_TREE
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#ifdef VERIFY_TREE
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/// VerifyTree - Walk the btree performing assertions on various properties to
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/// verify consistency. This is useful for debugging new changes to the tree.
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static void VerifyTree(const DeltaTreeNode *N) {
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const auto *IN = dyn_cast<DeltaTreeInteriorNode>(N);
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if (IN == 0) {
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// Verify leaves, just ensure that FullDelta matches up and the elements
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// are in proper order.
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int FullDelta = 0;
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for (unsigned i = 0, e = N->getNumValuesUsed(); i != e; ++i) {
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if (i)
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assert(N->getValue(i-1).FileLoc < N->getValue(i).FileLoc);
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FullDelta += N->getValue(i).Delta;
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}
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assert(FullDelta == N->getFullDelta());
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return;
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}
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// Verify interior nodes: Ensure that FullDelta matches up and the
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// elements are in proper order and the children are in proper order.
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int FullDelta = 0;
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for (unsigned i = 0, e = IN->getNumValuesUsed(); i != e; ++i) {
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const SourceDelta &IVal = N->getValue(i);
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const DeltaTreeNode *IChild = IN->getChild(i);
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if (i)
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assert(IN->getValue(i-1).FileLoc < IVal.FileLoc);
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FullDelta += IVal.Delta;
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FullDelta += IChild->getFullDelta();
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// The largest value in child #i should be smaller than FileLoc.
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assert(IChild->getValue(IChild->getNumValuesUsed()-1).FileLoc <
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IVal.FileLoc);
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// The smallest value in child #i+1 should be larger than FileLoc.
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assert(IN->getChild(i+1)->getValue(0).FileLoc > IVal.FileLoc);
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VerifyTree(IChild);
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}
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FullDelta += IN->getChild(IN->getNumValuesUsed())->getFullDelta();
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assert(FullDelta == N->getFullDelta());
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}
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#endif // VERIFY_TREE
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static DeltaTreeNode *getRoot(void *Root) {
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return (DeltaTreeNode*)Root;
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}
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DeltaTree::DeltaTree() {
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Root = new DeltaTreeNode();
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}
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DeltaTree::DeltaTree(const DeltaTree &RHS) {
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// Currently we only support copying when the RHS is empty.
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assert(getRoot(RHS.Root)->getNumValuesUsed() == 0 &&
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"Can only copy empty tree");
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Root = new DeltaTreeNode();
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}
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DeltaTree::~DeltaTree() {
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getRoot(Root)->Destroy();
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}
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/// getDeltaAt - Return the accumulated delta at the specified file offset.
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/// This includes all insertions or delections that occurred *before* the
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/// specified file index.
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int DeltaTree::getDeltaAt(unsigned FileIndex) const {
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const DeltaTreeNode *Node = getRoot(Root);
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int Result = 0;
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// Walk down the tree.
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while (true) {
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// For all nodes, include any local deltas before the specified file
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// index by summing them up directly. Keep track of how many were
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// included.
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unsigned NumValsGreater = 0;
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for (unsigned e = Node->getNumValuesUsed(); NumValsGreater != e;
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++NumValsGreater) {
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const SourceDelta &Val = Node->getValue(NumValsGreater);
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if (Val.FileLoc >= FileIndex)
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break;
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Result += Val.Delta;
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}
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// If we have an interior node, include information about children and
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// recurse. Otherwise, if we have a leaf, we're done.
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const auto *IN = dyn_cast<DeltaTreeInteriorNode>(Node);
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if (!IN) return Result;
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// Include any children to the left of the values we skipped, all of
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// their deltas should be included as well.
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for (unsigned i = 0; i != NumValsGreater; ++i)
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Result += IN->getChild(i)->getFullDelta();
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// If we found exactly the value we were looking for, break off the
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// search early. There is no need to search the RHS of the value for
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// partial results.
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if (NumValsGreater != Node->getNumValuesUsed() &&
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Node->getValue(NumValsGreater).FileLoc == FileIndex)
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return Result+IN->getChild(NumValsGreater)->getFullDelta();
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// Otherwise, traverse down the tree. The selected subtree may be
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// partially included in the range.
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Node = IN->getChild(NumValsGreater);
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}
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// NOT REACHED.
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}
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/// AddDelta - When a change is made that shifts around the text buffer,
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/// this method is used to record that info. It inserts a delta of 'Delta'
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/// into the current DeltaTree at offset FileIndex.
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void DeltaTree::AddDelta(unsigned FileIndex, int Delta) {
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assert(Delta && "Adding a noop?");
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DeltaTreeNode *MyRoot = getRoot(Root);
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DeltaTreeNode::InsertResult InsertRes;
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if (MyRoot->DoInsertion(FileIndex, Delta, &InsertRes)) {
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Root = MyRoot = new DeltaTreeInteriorNode(InsertRes);
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}
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#ifdef VERIFY_TREE
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VerifyTree(MyRoot);
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#endif
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}
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