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Diffstat (limited to 'clang/lib/Rewrite/RewriteRope.cpp')
| -rw-r--r-- | clang/lib/Rewrite/RewriteRope.cpp | 806 |
1 files changed, 806 insertions, 0 deletions
diff --git a/clang/lib/Rewrite/RewriteRope.cpp b/clang/lib/Rewrite/RewriteRope.cpp new file mode 100644 index 0000000000000..980d0f01e277c --- /dev/null +++ b/clang/lib/Rewrite/RewriteRope.cpp @@ -0,0 +1,806 @@ +//===- RewriteRope.cpp - Rope specialized for rewriter --------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements the RewriteRope class, which is a powerful string. +// +//===----------------------------------------------------------------------===// + +#include "clang/Rewrite/Core/RewriteRope.h" +#include "clang/Basic/LLVM.h" +#include "llvm/Support/Casting.h" +#include <algorithm> +#include <cassert> +#include <cstring> + +using namespace clang; + +/// RewriteRope is a "strong" string class, designed to make insertions and +/// deletions in the middle of the string nearly constant time (really, they are +/// O(log N), but with a very low constant factor). +/// +/// The implementation of this datastructure is a conceptual linear sequence of +/// RopePiece elements. Each RopePiece represents a view on a separately +/// allocated and reference counted string. This means that splitting a very +/// long string can be done in constant time by splitting a RopePiece that +/// references the whole string into two rope pieces that reference each half. +/// Once split, another string can be inserted in between the two halves by +/// inserting a RopePiece in between the two others. All of this is very +/// inexpensive: it takes time proportional to the number of RopePieces, not the +/// length of the strings they represent. +/// +/// While a linear sequences of RopePieces is the conceptual model, the actual +/// implementation captures them in an adapted B+ Tree. Using a B+ tree (which +/// is a tree that keeps the values in the leaves and has where each node +/// contains a reasonable number of pointers to children/values) allows us to +/// maintain efficient operation when the RewriteRope contains a *huge* number +/// of RopePieces. The basic idea of the B+ Tree is that it allows us to find +/// the RopePiece corresponding to some offset very efficiently, and it +/// automatically balances itself on insertions of RopePieces (which can happen +/// for both insertions and erases of string ranges). +/// +/// The one wrinkle on the theory is that we don't attempt to keep the tree +/// properly balanced when erases happen. Erases of string data can both insert +/// new RopePieces (e.g. when the middle of some other rope piece is deleted, +/// which results in two rope pieces, which is just like an insert) or it can +/// reduce the number of RopePieces maintained by the B+Tree. In the case when +/// the number of RopePieces is reduced, we don't attempt to maintain the +/// standard 'invariant' that each node in the tree contains at least +/// 'WidthFactor' children/values. For our use cases, this doesn't seem to +/// matter. +/// +/// The implementation below is primarily implemented in terms of three classes: +/// RopePieceBTreeNode - Common base class for: +/// +/// RopePieceBTreeLeaf - Directly manages up to '2*WidthFactor' RopePiece +/// nodes. This directly represents a chunk of the string with those +/// RopePieces concatenated. +/// RopePieceBTreeInterior - An interior node in the B+ Tree, which manages +/// up to '2*WidthFactor' other nodes in the tree. + +namespace { + +//===----------------------------------------------------------------------===// +// RopePieceBTreeNode Class +//===----------------------------------------------------------------------===// + + /// RopePieceBTreeNode - Common base class of RopePieceBTreeLeaf and + /// RopePieceBTreeInterior. This provides some 'virtual' dispatching methods + /// and a flag that determines which subclass the instance is. Also + /// important, this node knows the full extend of the node, including any + /// children that it has. This allows efficient skipping over entire subtrees + /// when looking for an offset in the BTree. + class RopePieceBTreeNode { + protected: + /// WidthFactor - This controls the number of K/V slots held in the BTree: + /// how wide it is. Each level of the BTree is guaranteed to have at least + /// 'WidthFactor' elements in it (either ropepieces or children), (except + /// the root, which may have less) and may have at most 2*WidthFactor + /// elements. + enum { WidthFactor = 8 }; + + /// Size - This is the number of bytes of file this node (including any + /// potential children) covers. + unsigned Size = 0; + + /// IsLeaf - True if this is an instance of RopePieceBTreeLeaf, false if it + /// is an instance of RopePieceBTreeInterior. + bool IsLeaf; + + RopePieceBTreeNode(bool isLeaf) : IsLeaf(isLeaf) {} + ~RopePieceBTreeNode() = default; + + public: + bool isLeaf() const { return IsLeaf; } + unsigned size() const { return Size; } + + void Destroy(); + + /// split - Split the range containing the specified offset so that we are + /// guaranteed that there is a place to do an insertion at the specified + /// offset. The offset is relative, so "0" is the start of the node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *split(unsigned Offset); + + /// insert - Insert the specified ropepiece into this tree node at the + /// specified offset. The offset is relative, so "0" is the start of the + /// node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R); + + /// erase - Remove NumBytes from this node at the specified offset. We are + /// guaranteed that there is a split at Offset. + void erase(unsigned Offset, unsigned NumBytes); + }; + +//===----------------------------------------------------------------------===// +// RopePieceBTreeLeaf Class +//===----------------------------------------------------------------------===// + + /// RopePieceBTreeLeaf - Directly manages up to '2*WidthFactor' RopePiece + /// nodes. This directly represents a chunk of the string with those + /// RopePieces concatenated. Since this is a B+Tree, all values (in this case + /// instances of RopePiece) are stored in leaves like this. To make iteration + /// over the leaves efficient, they maintain a singly linked list through the + /// NextLeaf field. This allows the B+Tree forward iterator to be constant + /// time for all increments. + class RopePieceBTreeLeaf : public RopePieceBTreeNode { + /// NumPieces - This holds the number of rope pieces currently active in the + /// Pieces array. + unsigned char NumPieces = 0; + + /// Pieces - This tracks the file chunks currently in this leaf. + RopePiece Pieces[2*WidthFactor]; + + /// NextLeaf - This is a pointer to the next leaf in the tree, allowing + /// efficient in-order forward iteration of the tree without traversal. + RopePieceBTreeLeaf **PrevLeaf = nullptr; + RopePieceBTreeLeaf *NextLeaf = nullptr; + + public: + RopePieceBTreeLeaf() : RopePieceBTreeNode(true) {} + + ~RopePieceBTreeLeaf() { + if (PrevLeaf || NextLeaf) + removeFromLeafInOrder(); + clear(); + } + + bool isFull() const { return NumPieces == 2*WidthFactor; } + + /// clear - Remove all rope pieces from this leaf. + void clear() { + while (NumPieces) + Pieces[--NumPieces] = RopePiece(); + Size = 0; + } + + unsigned getNumPieces() const { return NumPieces; } + + const RopePiece &getPiece(unsigned i) const { + assert(i < getNumPieces() && "Invalid piece ID"); + return Pieces[i]; + } + + const RopePieceBTreeLeaf *getNextLeafInOrder() const { return NextLeaf; } + + void insertAfterLeafInOrder(RopePieceBTreeLeaf *Node) { + assert(!PrevLeaf && !NextLeaf && "Already in ordering"); + + NextLeaf = Node->NextLeaf; + if (NextLeaf) + NextLeaf->PrevLeaf = &NextLeaf; + PrevLeaf = &Node->NextLeaf; + Node->NextLeaf = this; + } + + void removeFromLeafInOrder() { + if (PrevLeaf) { + *PrevLeaf = NextLeaf; + if (NextLeaf) + NextLeaf->PrevLeaf = PrevLeaf; + } else if (NextLeaf) { + NextLeaf->PrevLeaf = nullptr; + } + } + + /// FullRecomputeSizeLocally - This method recomputes the 'Size' field by + /// summing the size of all RopePieces. + void FullRecomputeSizeLocally() { + Size = 0; + for (unsigned i = 0, e = getNumPieces(); i != e; ++i) + Size += getPiece(i).size(); + } + + /// split - Split the range containing the specified offset so that we are + /// guaranteed that there is a place to do an insertion at the specified + /// offset. The offset is relative, so "0" is the start of the node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *split(unsigned Offset); + + /// insert - Insert the specified ropepiece into this tree node at the + /// specified offset. The offset is relative, so "0" is the start of the + /// node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R); + + /// erase - Remove NumBytes from this node at the specified offset. We are + /// guaranteed that there is a split at Offset. + void erase(unsigned Offset, unsigned NumBytes); + + static bool classof(const RopePieceBTreeNode *N) { + return N->isLeaf(); + } + }; + +} // namespace + +/// split - Split the range containing the specified offset so that we are +/// guaranteed that there is a place to do an insertion at the specified +/// offset. The offset is relative, so "0" is the start of the node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeLeaf::split(unsigned Offset) { + // Find the insertion point. We are guaranteed that there is a split at the + // specified offset so find it. + if (Offset == 0 || Offset == size()) { + // Fastpath for a common case. There is already a splitpoint at the end. + return nullptr; + } + + // Find the piece that this offset lands in. + unsigned PieceOffs = 0; + unsigned i = 0; + while (Offset >= PieceOffs+Pieces[i].size()) { + PieceOffs += Pieces[i].size(); + ++i; + } + + // If there is already a split point at the specified offset, just return + // success. + if (PieceOffs == Offset) + return nullptr; + + // Otherwise, we need to split piece 'i' at Offset-PieceOffs. Convert Offset + // to being Piece relative. + unsigned IntraPieceOffset = Offset-PieceOffs; + + // We do this by shrinking the RopePiece and then doing an insert of the tail. + RopePiece Tail(Pieces[i].StrData, Pieces[i].StartOffs+IntraPieceOffset, + Pieces[i].EndOffs); + Size -= Pieces[i].size(); + Pieces[i].EndOffs = Pieces[i].StartOffs+IntraPieceOffset; + Size += Pieces[i].size(); + + return insert(Offset, Tail); +} + +/// insert - Insert the specified RopePiece into this tree node at the +/// specified offset. The offset is relative, so "0" is the start of the node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeLeaf::insert(unsigned Offset, + const RopePiece &R) { + // If this node is not full, insert the piece. + if (!isFull()) { + // Find the insertion point. We are guaranteed that there is a split at the + // specified offset so find it. + unsigned i = 0, e = getNumPieces(); + if (Offset == size()) { + // Fastpath for a common case. + i = e; + } else { + unsigned SlotOffs = 0; + for (; Offset > SlotOffs; ++i) + SlotOffs += getPiece(i).size(); + assert(SlotOffs == Offset && "Split didn't occur before insertion!"); + } + + // For an insertion into a non-full leaf node, just insert the value in + // its sorted position. This requires moving later values over. + for (; i != e; --e) + Pieces[e] = Pieces[e-1]; + Pieces[i] = R; + ++NumPieces; + Size += R.size(); + return nullptr; + } + + // Otherwise, if this is leaf is full, split it in two halves. Since this + // node is full, it contains 2*WidthFactor values. We move the first + // 'WidthFactor' values to the LHS child (which we leave in this node) and + // move the last 'WidthFactor' values into the RHS child. + + // Create the new node. + RopePieceBTreeLeaf *NewNode = new RopePieceBTreeLeaf(); + + // Move over the last 'WidthFactor' values from here to NewNode. + std::copy(&Pieces[WidthFactor], &Pieces[2*WidthFactor], + &NewNode->Pieces[0]); + // Replace old pieces with null RopePieces to drop refcounts. + std::fill(&Pieces[WidthFactor], &Pieces[2*WidthFactor], RopePiece()); + + // Decrease the number of values in the two nodes. + NewNode->NumPieces = NumPieces = WidthFactor; + + // Recompute the two nodes' size. + NewNode->FullRecomputeSizeLocally(); + FullRecomputeSizeLocally(); + + // Update the list of leaves. + NewNode->insertAfterLeafInOrder(this); + + // These insertions can't fail. + if (this->size() >= Offset) + this->insert(Offset, R); + else + NewNode->insert(Offset - this->size(), R); + return NewNode; +} + +/// erase - Remove NumBytes from this node at the specified offset. We are +/// guaranteed that there is a split at Offset. +void RopePieceBTreeLeaf::erase(unsigned Offset, unsigned NumBytes) { + // Since we are guaranteed that there is a split at Offset, we start by + // finding the Piece that starts there. + unsigned PieceOffs = 0; + unsigned i = 0; + for (; Offset > PieceOffs; ++i) + PieceOffs += getPiece(i).size(); + assert(PieceOffs == Offset && "Split didn't occur before erase!"); + + unsigned StartPiece = i; + + // Figure out how many pieces completely cover 'NumBytes'. We want to remove + // all of them. + for (; Offset+NumBytes > PieceOffs+getPiece(i).size(); ++i) + PieceOffs += getPiece(i).size(); + + // If we exactly include the last one, include it in the region to delete. + if (Offset+NumBytes == PieceOffs+getPiece(i).size()) { + PieceOffs += getPiece(i).size(); + ++i; + } + + // If we completely cover some RopePieces, erase them now. + if (i != StartPiece) { + unsigned NumDeleted = i-StartPiece; + for (; i != getNumPieces(); ++i) + Pieces[i-NumDeleted] = Pieces[i]; + + // Drop references to dead rope pieces. + std::fill(&Pieces[getNumPieces()-NumDeleted], &Pieces[getNumPieces()], + RopePiece()); + NumPieces -= NumDeleted; + + unsigned CoverBytes = PieceOffs-Offset; + NumBytes -= CoverBytes; + Size -= CoverBytes; + } + + // If we completely removed some stuff, we could be done. + if (NumBytes == 0) return; + + // Okay, now might be erasing part of some Piece. If this is the case, then + // move the start point of the piece. + assert(getPiece(StartPiece).size() > NumBytes); + Pieces[StartPiece].StartOffs += NumBytes; + + // The size of this node just shrunk by NumBytes. + Size -= NumBytes; +} + +//===----------------------------------------------------------------------===// +// RopePieceBTreeInterior Class +//===----------------------------------------------------------------------===// + +namespace { + + /// RopePieceBTreeInterior - This represents an interior node in the B+Tree, + /// which holds up to 2*WidthFactor pointers to child nodes. + class RopePieceBTreeInterior : public RopePieceBTreeNode { + /// NumChildren - This holds the number of children currently active in the + /// Children array. + unsigned char NumChildren = 0; + + RopePieceBTreeNode *Children[2*WidthFactor]; + + public: + RopePieceBTreeInterior() : RopePieceBTreeNode(false) {} + + RopePieceBTreeInterior(RopePieceBTreeNode *LHS, RopePieceBTreeNode *RHS) + : RopePieceBTreeNode(false) { + Children[0] = LHS; + Children[1] = RHS; + NumChildren = 2; + Size = LHS->size() + RHS->size(); + } + + ~RopePieceBTreeInterior() { + for (unsigned i = 0, e = getNumChildren(); i != e; ++i) + Children[i]->Destroy(); + } + + bool isFull() const { return NumChildren == 2*WidthFactor; } + + unsigned getNumChildren() const { return NumChildren; } + + const RopePieceBTreeNode *getChild(unsigned i) const { + assert(i < NumChildren && "invalid child #"); + return Children[i]; + } + + RopePieceBTreeNode *getChild(unsigned i) { + assert(i < NumChildren && "invalid child #"); + return Children[i]; + } + + /// FullRecomputeSizeLocally - Recompute the Size field of this node by + /// summing up the sizes of the child nodes. + void FullRecomputeSizeLocally() { + Size = 0; + for (unsigned i = 0, e = getNumChildren(); i != e; ++i) + Size += getChild(i)->size(); + } + + /// split - Split the range containing the specified offset so that we are + /// guaranteed that there is a place to do an insertion at the specified + /// offset. The offset is relative, so "0" is the start of the node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *split(unsigned Offset); + + /// insert - Insert the specified ropepiece into this tree node at the + /// specified offset. The offset is relative, so "0" is the start of the + /// node. + /// + /// If there is no space in this subtree for the extra piece, the extra tree + /// node is returned and must be inserted into a parent. + RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R); + + /// HandleChildPiece - A child propagated an insertion result up to us. + /// Insert the new child, and/or propagate the result further up the tree. + RopePieceBTreeNode *HandleChildPiece(unsigned i, RopePieceBTreeNode *RHS); + + /// erase - Remove NumBytes from this node at the specified offset. We are + /// guaranteed that there is a split at Offset. + void erase(unsigned Offset, unsigned NumBytes); + + static bool classof(const RopePieceBTreeNode *N) { + return !N->isLeaf(); + } + }; + +} // namespace + +/// split - Split the range containing the specified offset so that we are +/// guaranteed that there is a place to do an insertion at the specified +/// offset. The offset is relative, so "0" is the start of the node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeInterior::split(unsigned Offset) { + // Figure out which child to split. + if (Offset == 0 || Offset == size()) + return nullptr; // If we have an exact offset, we're already split. + + unsigned ChildOffset = 0; + unsigned i = 0; + for (; Offset >= ChildOffset+getChild(i)->size(); ++i) + ChildOffset += getChild(i)->size(); + + // If already split there, we're done. + if (ChildOffset == Offset) + return nullptr; + + // Otherwise, recursively split the child. + if (RopePieceBTreeNode *RHS = getChild(i)->split(Offset-ChildOffset)) + return HandleChildPiece(i, RHS); + return nullptr; // Done! +} + +/// insert - Insert the specified ropepiece into this tree node at the +/// specified offset. The offset is relative, so "0" is the start of the +/// node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeInterior::insert(unsigned Offset, + const RopePiece &R) { + // Find the insertion point. We are guaranteed that there is a split at the + // specified offset so find it. + unsigned i = 0, e = getNumChildren(); + + unsigned ChildOffs = 0; + if (Offset == size()) { + // Fastpath for a common case. Insert at end of last child. + i = e-1; + ChildOffs = size()-getChild(i)->size(); + } else { + for (; Offset > ChildOffs+getChild(i)->size(); ++i) + ChildOffs += getChild(i)->size(); + } + + Size += R.size(); + + // Insert at the end of this child. + if (RopePieceBTreeNode *RHS = getChild(i)->insert(Offset-ChildOffs, R)) + return HandleChildPiece(i, RHS); + + return nullptr; +} + +/// HandleChildPiece - A child propagated an insertion result up to us. +/// Insert the new child, and/or propagate the result further up the tree. +RopePieceBTreeNode * +RopePieceBTreeInterior::HandleChildPiece(unsigned i, RopePieceBTreeNode *RHS) { + // Otherwise the child propagated a subtree up to us as a new child. See if + // we have space for it here. + if (!isFull()) { + // Insert RHS after child 'i'. + if (i + 1 != getNumChildren()) + memmove(&Children[i+2], &Children[i+1], + (getNumChildren()-i-1)*sizeof(Children[0])); + Children[i+1] = RHS; + ++NumChildren; + return nullptr; + } + + // Okay, this node is full. Split it in half, moving WidthFactor children to + // a newly allocated interior node. + + // Create the new node. + RopePieceBTreeInterior *NewNode = new RopePieceBTreeInterior(); + + // Move over the last 'WidthFactor' values from here to NewNode. + memcpy(&NewNode->Children[0], &Children[WidthFactor], + WidthFactor*sizeof(Children[0])); + + // Decrease the number of values in the two nodes. + NewNode->NumChildren = NumChildren = WidthFactor; + + // Finally, insert the two new children in the side the can (now) hold them. + // These insertions can't fail. + if (i < WidthFactor) + this->HandleChildPiece(i, RHS); + else + NewNode->HandleChildPiece(i-WidthFactor, RHS); + + // Recompute the two nodes' size. + NewNode->FullRecomputeSizeLocally(); + FullRecomputeSizeLocally(); + return NewNode; +} + +/// erase - Remove NumBytes from this node at the specified offset. We are +/// guaranteed that there is a split at Offset. +void RopePieceBTreeInterior::erase(unsigned Offset, unsigned NumBytes) { + // This will shrink this node by NumBytes. + Size -= NumBytes; + + // Find the first child that overlaps with Offset. + unsigned i = 0; + for (; Offset >= getChild(i)->size(); ++i) + Offset -= getChild(i)->size(); + + // Propagate the delete request into overlapping children, or completely + // delete the children as appropriate. + while (NumBytes) { + RopePieceBTreeNode *CurChild = getChild(i); + + // If we are deleting something contained entirely in the child, pass on the + // request. + if (Offset+NumBytes < CurChild->size()) { + CurChild->erase(Offset, NumBytes); + return; + } + + // If this deletion request starts somewhere in the middle of the child, it + // must be deleting to the end of the child. + if (Offset) { + unsigned BytesFromChild = CurChild->size()-Offset; + CurChild->erase(Offset, BytesFromChild); + NumBytes -= BytesFromChild; + // Start at the beginning of the next child. + Offset = 0; + ++i; + continue; + } + + // If the deletion request completely covers the child, delete it and move + // the rest down. + NumBytes -= CurChild->size(); + CurChild->Destroy(); + --NumChildren; + if (i != getNumChildren()) + memmove(&Children[i], &Children[i+1], + (getNumChildren()-i)*sizeof(Children[0])); + } +} + +//===----------------------------------------------------------------------===// +// RopePieceBTreeNode Implementation +//===----------------------------------------------------------------------===// + +void RopePieceBTreeNode::Destroy() { + if (auto *Leaf = dyn_cast<RopePieceBTreeLeaf>(this)) + delete Leaf; + else + delete cast<RopePieceBTreeInterior>(this); +} + +/// split - Split the range containing the specified offset so that we are +/// guaranteed that there is a place to do an insertion at the specified +/// offset. The offset is relative, so "0" is the start of the node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeNode::split(unsigned Offset) { + assert(Offset <= size() && "Invalid offset to split!"); + if (auto *Leaf = dyn_cast<RopePieceBTreeLeaf>(this)) + return Leaf->split(Offset); + return cast<RopePieceBTreeInterior>(this)->split(Offset); +} + +/// insert - Insert the specified ropepiece into this tree node at the +/// specified offset. The offset is relative, so "0" is the start of the +/// node. +/// +/// If there is no space in this subtree for the extra piece, the extra tree +/// node is returned and must be inserted into a parent. +RopePieceBTreeNode *RopePieceBTreeNode::insert(unsigned Offset, + const RopePiece &R) { + assert(Offset <= size() && "Invalid offset to insert!"); + if (auto *Leaf = dyn_cast<RopePieceBTreeLeaf>(this)) + return Leaf->insert(Offset, R); + return cast<RopePieceBTreeInterior>(this)->insert(Offset, R); +} + +/// erase - Remove NumBytes from this node at the specified offset. We are +/// guaranteed that there is a split at Offset. +void RopePieceBTreeNode::erase(unsigned Offset, unsigned NumBytes) { + assert(Offset+NumBytes <= size() && "Invalid offset to erase!"); + if (auto *Leaf = dyn_cast<RopePieceBTreeLeaf>(this)) + return Leaf->erase(Offset, NumBytes); + return cast<RopePieceBTreeInterior>(this)->erase(Offset, NumBytes); +} + +//===----------------------------------------------------------------------===// +// RopePieceBTreeIterator Implementation +//===----------------------------------------------------------------------===// + +static const RopePieceBTreeLeaf *getCN(const void *P) { + return static_cast<const RopePieceBTreeLeaf*>(P); +} + +// begin iterator. +RopePieceBTreeIterator::RopePieceBTreeIterator(const void *n) { + const auto *N = static_cast<const RopePieceBTreeNode *>(n); + + // Walk down the left side of the tree until we get to a leaf. + while (const auto *IN = dyn_cast<RopePieceBTreeInterior>(N)) + N = IN->getChild(0); + + // We must have at least one leaf. + CurNode = cast<RopePieceBTreeLeaf>(N); + + // If we found a leaf that happens to be empty, skip over it until we get + // to something full. + while (CurNode && getCN(CurNode)->getNumPieces() == 0) + CurNode = getCN(CurNode)->getNextLeafInOrder(); + + if (CurNode) + CurPiece = &getCN(CurNode)->getPiece(0); + else // Empty tree, this is an end() iterator. + CurPiece = nullptr; + CurChar = 0; +} + +void RopePieceBTreeIterator::MoveToNextPiece() { + if (CurPiece != &getCN(CurNode)->getPiece(getCN(CurNode)->getNumPieces()-1)) { + CurChar = 0; + ++CurPiece; + return; + } + + // Find the next non-empty leaf node. + do + CurNode = getCN(CurNode)->getNextLeafInOrder(); + while (CurNode && getCN(CurNode)->getNumPieces() == 0); + + if (CurNode) + CurPiece = &getCN(CurNode)->getPiece(0); + else // Hit end(). + CurPiece = nullptr; + CurChar = 0; +} + +//===----------------------------------------------------------------------===// +// RopePieceBTree Implementation +//===----------------------------------------------------------------------===// + +static RopePieceBTreeNode *getRoot(void *P) { + return static_cast<RopePieceBTreeNode*>(P); +} + +RopePieceBTree::RopePieceBTree() { + Root = new RopePieceBTreeLeaf(); +} + +RopePieceBTree::RopePieceBTree(const RopePieceBTree &RHS) { + assert(RHS.empty() && "Can't copy non-empty tree yet"); + Root = new RopePieceBTreeLeaf(); +} + +RopePieceBTree::~RopePieceBTree() { + getRoot(Root)->Destroy(); +} + +unsigned RopePieceBTree::size() const { + return getRoot(Root)->size(); +} + +void RopePieceBTree::clear() { + if (auto *Leaf = dyn_cast<RopePieceBTreeLeaf>(getRoot(Root))) + Leaf->clear(); + else { + getRoot(Root)->Destroy(); + Root = new RopePieceBTreeLeaf(); + } +} + +void RopePieceBTree::insert(unsigned Offset, const RopePiece &R) { + // #1. Split at Offset. + if (RopePieceBTreeNode *RHS = getRoot(Root)->split(Offset)) + Root = new RopePieceBTreeInterior(getRoot(Root), RHS); + + // #2. Do the insertion. + if (RopePieceBTreeNode *RHS = getRoot(Root)->insert(Offset, R)) + Root = new RopePieceBTreeInterior(getRoot(Root), RHS); +} + +void RopePieceBTree::erase(unsigned Offset, unsigned NumBytes) { + // #1. Split at Offset. + if (RopePieceBTreeNode *RHS = getRoot(Root)->split(Offset)) + Root = new RopePieceBTreeInterior(getRoot(Root), RHS); + + // #2. Do the erasing. + getRoot(Root)->erase(Offset, NumBytes); +} + +//===----------------------------------------------------------------------===// +// RewriteRope Implementation +//===----------------------------------------------------------------------===// + +/// MakeRopeString - This copies the specified byte range into some instance of +/// RopeRefCountString, and return a RopePiece that represents it. This uses +/// the AllocBuffer object to aggregate requests for small strings into one +/// allocation instead of doing tons of tiny allocations. +RopePiece RewriteRope::MakeRopeString(const char *Start, const char *End) { + unsigned Len = End-Start; + assert(Len && "Zero length RopePiece is invalid!"); + + // If we have space for this string in the current alloc buffer, use it. + if (AllocOffs+Len <= AllocChunkSize) { + memcpy(AllocBuffer->Data+AllocOffs, Start, Len); + AllocOffs += Len; + return RopePiece(AllocBuffer, AllocOffs-Len, AllocOffs); + } + + // If we don't have enough room because this specific allocation is huge, + // just allocate a new rope piece for it alone. + if (Len > AllocChunkSize) { + unsigned Size = End-Start+sizeof(RopeRefCountString)-1; + auto *Res = reinterpret_cast<RopeRefCountString *>(new char[Size]); + Res->RefCount = 0; + memcpy(Res->Data, Start, End-Start); + return RopePiece(Res, 0, End-Start); + } + + // Otherwise, this was a small request but we just don't have space for it + // Make a new chunk and share it with later allocations. + + unsigned AllocSize = offsetof(RopeRefCountString, Data) + AllocChunkSize; + auto *Res = reinterpret_cast<RopeRefCountString *>(new char[AllocSize]); + Res->RefCount = 0; + memcpy(Res->Data, Start, Len); + AllocBuffer = Res; + AllocOffs = Len; + + return RopePiece(AllocBuffer, 0, Len); +} |