1 //===--- RewriteRope.cpp - Rope specialized for rewriter --------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the RewriteRope class, which is a powerful string.
12 //===----------------------------------------------------------------------===//
14 #include "clang/Rewrite/RewriteRope.h"
15 #include "llvm/Support/Casting.h"
17 using namespace clang;
21 /// RewriteRope is a "strong" string class, designed to make insertions and
22 /// deletions in the middle of the string nearly constant time (really, they are
23 /// O(log N), but with a very low constant factor).
25 /// The implementation of this datastructure is a conceptual linear sequence of
26 /// RopePiece elements. Each RopePiece represents a view on a separately
27 /// allocated and reference counted string. This means that splitting a very
28 /// long string can be done in constant time by splitting a RopePiece that
29 /// references the whole string into two rope pieces that reference each half.
30 /// Once split, another string can be inserted in between the two halves by
31 /// inserting a RopePiece in between the two others. All of this is very
32 /// inexpensive: it takes time proportional to the number of RopePieces, not the
33 /// length of the strings they represent.
35 /// While a linear sequences of RopePieces is the conceptual model, the actual
36 /// implementation captures them in an adapted B+ Tree. Using a B+ tree (which
37 /// is a tree that keeps the values in the leaves and has where each node
38 /// contains a reasonable number of pointers to children/values) allows us to
39 /// maintain efficient operation when the RewriteRope contains a *huge* number
40 /// of RopePieces. The basic idea of the B+ Tree is that it allows us to find
41 /// the RopePiece corresponding to some offset very efficiently, and it
42 /// automatically balances itself on insertions of RopePieces (which can happen
43 /// for both insertions and erases of string ranges).
45 /// The one wrinkle on the theory is that we don't attempt to keep the tree
46 /// properly balanced when erases happen. Erases of string data can both insert
47 /// new RopePieces (e.g. when the middle of some other rope piece is deleted,
48 /// which results in two rope pieces, which is just like an insert) or it can
49 /// reduce the number of RopePieces maintained by the B+Tree. In the case when
50 /// the number of RopePieces is reduced, we don't attempt to maintain the
51 /// standard 'invariant' that each node in the tree contains at least
52 /// 'WidthFactor' children/values. For our use cases, this doesn't seem to
55 /// The implementation below is primarily implemented in terms of three classes:
56 /// RopePieceBTreeNode - Common base class for:
58 /// RopePieceBTreeLeaf - Directly manages up to '2*WidthFactor' RopePiece
59 /// nodes. This directly represents a chunk of the string with those
60 /// RopePieces contatenated.
61 /// RopePieceBTreeInterior - An interior node in the B+ Tree, which manages
62 /// up to '2*WidthFactor' other nodes in the tree.
65 //===----------------------------------------------------------------------===//
66 // RopePieceBTreeNode Class
67 //===----------------------------------------------------------------------===//
70 /// RopePieceBTreeNode - Common base class of RopePieceBTreeLeaf and
71 /// RopePieceBTreeInterior. This provides some 'virtual' dispatching methods
72 /// and a flag that determines which subclass the instance is. Also
73 /// important, this node knows the full extend of the node, including any
74 /// children that it has. This allows efficient skipping over entire subtrees
75 /// when looking for an offset in the BTree.
76 class RopePieceBTreeNode {
78 /// WidthFactor - This controls the number of K/V slots held in the BTree:
79 /// how wide it is. Each level of the BTree is guaranteed to have at least
80 /// 'WidthFactor' elements in it (either ropepieces or children), (except
81 /// the root, which may have less) and may have at most 2*WidthFactor
83 enum { WidthFactor = 8 };
85 /// Size - This is the number of bytes of file this node (including any
86 /// potential children) covers.
89 /// IsLeaf - True if this is an instance of RopePieceBTreeLeaf, false if it
90 /// is an instance of RopePieceBTreeInterior.
93 RopePieceBTreeNode(bool isLeaf) : Size(0), IsLeaf(isLeaf) {}
94 ~RopePieceBTreeNode() {}
97 bool isLeaf() const { return IsLeaf; }
98 unsigned size() const { return Size; }
102 /// split - Split the range containing the specified offset so that we are
103 /// guaranteed that there is a place to do an insertion at the specified
104 /// offset. The offset is relative, so "0" is the start of the node.
106 /// If there is no space in this subtree for the extra piece, the extra tree
107 /// node is returned and must be inserted into a parent.
108 RopePieceBTreeNode *split(unsigned Offset);
110 /// insert - Insert the specified ropepiece into this tree node at the
111 /// specified offset. The offset is relative, so "0" is the start of the
114 /// If there is no space in this subtree for the extra piece, the extra tree
115 /// node is returned and must be inserted into a parent.
116 RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R);
118 /// erase - Remove NumBytes from this node at the specified offset. We are
119 /// guaranteed that there is a split at Offset.
120 void erase(unsigned Offset, unsigned NumBytes);
122 static inline bool classof(const RopePieceBTreeNode *) { return true; }
125 } // end anonymous namespace
127 //===----------------------------------------------------------------------===//
128 // RopePieceBTreeLeaf Class
129 //===----------------------------------------------------------------------===//
132 /// RopePieceBTreeLeaf - Directly manages up to '2*WidthFactor' RopePiece
133 /// nodes. This directly represents a chunk of the string with those
134 /// RopePieces contatenated. Since this is a B+Tree, all values (in this case
135 /// instances of RopePiece) are stored in leaves like this. To make iteration
136 /// over the leaves efficient, they maintain a singly linked list through the
137 /// NextLeaf field. This allows the B+Tree forward iterator to be constant
138 /// time for all increments.
139 class RopePieceBTreeLeaf : public RopePieceBTreeNode {
140 /// NumPieces - This holds the number of rope pieces currently active in the
142 unsigned char NumPieces;
144 /// Pieces - This tracks the file chunks currently in this leaf.
146 RopePiece Pieces[2*WidthFactor];
148 /// NextLeaf - This is a pointer to the next leaf in the tree, allowing
149 /// efficient in-order forward iteration of the tree without traversal.
150 RopePieceBTreeLeaf **PrevLeaf, *NextLeaf;
152 RopePieceBTreeLeaf() : RopePieceBTreeNode(true), NumPieces(0),
153 PrevLeaf(0), NextLeaf(0) {}
154 ~RopePieceBTreeLeaf() {
155 if (PrevLeaf || NextLeaf)
156 removeFromLeafInOrder();
159 bool isFull() const { return NumPieces == 2*WidthFactor; }
161 /// clear - Remove all rope pieces from this leaf.
164 Pieces[--NumPieces] = RopePiece();
168 unsigned getNumPieces() const { return NumPieces; }
170 const RopePiece &getPiece(unsigned i) const {
171 assert(i < getNumPieces() && "Invalid piece ID");
175 const RopePieceBTreeLeaf *getNextLeafInOrder() const { return NextLeaf; }
176 void insertAfterLeafInOrder(RopePieceBTreeLeaf *Node) {
177 assert(PrevLeaf == 0 && NextLeaf == 0 && "Already in ordering");
179 NextLeaf = Node->NextLeaf;
181 NextLeaf->PrevLeaf = &NextLeaf;
182 PrevLeaf = &Node->NextLeaf;
183 Node->NextLeaf = this;
186 void removeFromLeafInOrder() {
188 *PrevLeaf = NextLeaf;
190 NextLeaf->PrevLeaf = PrevLeaf;
191 } else if (NextLeaf) {
192 NextLeaf->PrevLeaf = 0;
196 /// FullRecomputeSizeLocally - This method recomputes the 'Size' field by
197 /// summing the size of all RopePieces.
198 void FullRecomputeSizeLocally() {
200 for (unsigned i = 0, e = getNumPieces(); i != e; ++i)
201 Size += getPiece(i).size();
204 /// split - Split the range containing the specified offset so that we are
205 /// guaranteed that there is a place to do an insertion at the specified
206 /// offset. The offset is relative, so "0" is the start of the node.
208 /// If there is no space in this subtree for the extra piece, the extra tree
209 /// node is returned and must be inserted into a parent.
210 RopePieceBTreeNode *split(unsigned Offset);
212 /// insert - Insert the specified ropepiece into this tree node at the
213 /// specified offset. The offset is relative, so "0" is the start of the
216 /// If there is no space in this subtree for the extra piece, the extra tree
217 /// node is returned and must be inserted into a parent.
218 RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R);
221 /// erase - Remove NumBytes from this node at the specified offset. We are
222 /// guaranteed that there is a split at Offset.
223 void erase(unsigned Offset, unsigned NumBytes);
225 static inline bool classof(const RopePieceBTreeLeaf *) { return true; }
226 static inline bool classof(const RopePieceBTreeNode *N) {
230 } // end anonymous namespace
232 /// split - Split the range containing the specified offset so that we are
233 /// guaranteed that there is a place to do an insertion at the specified
234 /// offset. The offset is relative, so "0" is the start of the node.
236 /// If there is no space in this subtree for the extra piece, the extra tree
237 /// node is returned and must be inserted into a parent.
238 RopePieceBTreeNode *RopePieceBTreeLeaf::split(unsigned Offset) {
239 // Find the insertion point. We are guaranteed that there is a split at the
240 // specified offset so find it.
241 if (Offset == 0 || Offset == size()) {
242 // Fastpath for a common case. There is already a splitpoint at the end.
246 // Find the piece that this offset lands in.
247 unsigned PieceOffs = 0;
249 while (Offset >= PieceOffs+Pieces[i].size()) {
250 PieceOffs += Pieces[i].size();
254 // If there is already a split point at the specified offset, just return
256 if (PieceOffs == Offset)
259 // Otherwise, we need to split piece 'i' at Offset-PieceOffs. Convert Offset
260 // to being Piece relative.
261 unsigned IntraPieceOffset = Offset-PieceOffs;
263 // We do this by shrinking the RopePiece and then doing an insert of the tail.
264 RopePiece Tail(Pieces[i].StrData, Pieces[i].StartOffs+IntraPieceOffset,
266 Size -= Pieces[i].size();
267 Pieces[i].EndOffs = Pieces[i].StartOffs+IntraPieceOffset;
268 Size += Pieces[i].size();
270 return insert(Offset, Tail);
274 /// insert - Insert the specified RopePiece into this tree node at the
275 /// specified offset. The offset is relative, so "0" is the start of the node.
277 /// If there is no space in this subtree for the extra piece, the extra tree
278 /// node is returned and must be inserted into a parent.
279 RopePieceBTreeNode *RopePieceBTreeLeaf::insert(unsigned Offset,
280 const RopePiece &R) {
281 // If this node is not full, insert the piece.
283 // Find the insertion point. We are guaranteed that there is a split at the
284 // specified offset so find it.
285 unsigned i = 0, e = getNumPieces();
286 if (Offset == size()) {
287 // Fastpath for a common case.
290 unsigned SlotOffs = 0;
291 for (; Offset > SlotOffs; ++i)
292 SlotOffs += getPiece(i).size();
293 assert(SlotOffs == Offset && "Split didn't occur before insertion!");
296 // For an insertion into a non-full leaf node, just insert the value in
297 // its sorted position. This requires moving later values over.
299 Pieces[e] = Pieces[e-1];
306 // Otherwise, if this is leaf is full, split it in two halves. Since this
307 // node is full, it contains 2*WidthFactor values. We move the first
308 // 'WidthFactor' values to the LHS child (which we leave in this node) and
309 // move the last 'WidthFactor' values into the RHS child.
311 // Create the new node.
312 RopePieceBTreeLeaf *NewNode = new RopePieceBTreeLeaf();
314 // Move over the last 'WidthFactor' values from here to NewNode.
315 std::copy(&Pieces[WidthFactor], &Pieces[2*WidthFactor],
316 &NewNode->Pieces[0]);
317 // Replace old pieces with null RopePieces to drop refcounts.
318 std::fill(&Pieces[WidthFactor], &Pieces[2*WidthFactor], RopePiece());
320 // Decrease the number of values in the two nodes.
321 NewNode->NumPieces = NumPieces = WidthFactor;
323 // Recompute the two nodes' size.
324 NewNode->FullRecomputeSizeLocally();
325 FullRecomputeSizeLocally();
327 // Update the list of leaves.
328 NewNode->insertAfterLeafInOrder(this);
330 // These insertions can't fail.
331 if (this->size() >= Offset)
332 this->insert(Offset, R);
334 NewNode->insert(Offset - this->size(), R);
338 /// erase - Remove NumBytes from this node at the specified offset. We are
339 /// guaranteed that there is a split at Offset.
340 void RopePieceBTreeLeaf::erase(unsigned Offset, unsigned NumBytes) {
341 // Since we are guaranteed that there is a split at Offset, we start by
342 // finding the Piece that starts there.
343 unsigned PieceOffs = 0;
345 for (; Offset > PieceOffs; ++i)
346 PieceOffs += getPiece(i).size();
347 assert(PieceOffs == Offset && "Split didn't occur before erase!");
349 unsigned StartPiece = i;
351 // Figure out how many pieces completely cover 'NumBytes'. We want to remove
353 for (; Offset+NumBytes > PieceOffs+getPiece(i).size(); ++i)
354 PieceOffs += getPiece(i).size();
356 // If we exactly include the last one, include it in the region to delete.
357 if (Offset+NumBytes == PieceOffs+getPiece(i).size())
358 PieceOffs += getPiece(i).size(), ++i;
360 // If we completely cover some RopePieces, erase them now.
361 if (i != StartPiece) {
362 unsigned NumDeleted = i-StartPiece;
363 for (; i != getNumPieces(); ++i)
364 Pieces[i-NumDeleted] = Pieces[i];
366 // Drop references to dead rope pieces.
367 std::fill(&Pieces[getNumPieces()-NumDeleted], &Pieces[getNumPieces()],
369 NumPieces -= NumDeleted;
371 unsigned CoverBytes = PieceOffs-Offset;
372 NumBytes -= CoverBytes;
376 // If we completely removed some stuff, we could be done.
377 if (NumBytes == 0) return;
379 // Okay, now might be erasing part of some Piece. If this is the case, then
380 // move the start point of the piece.
381 assert(getPiece(StartPiece).size() > NumBytes);
382 Pieces[StartPiece].StartOffs += NumBytes;
384 // The size of this node just shrunk by NumBytes.
388 //===----------------------------------------------------------------------===//
389 // RopePieceBTreeInterior Class
390 //===----------------------------------------------------------------------===//
393 /// RopePieceBTreeInterior - This represents an interior node in the B+Tree,
394 /// which holds up to 2*WidthFactor pointers to child nodes.
395 class RopePieceBTreeInterior : public RopePieceBTreeNode {
396 /// NumChildren - This holds the number of children currently active in the
398 unsigned char NumChildren;
399 RopePieceBTreeNode *Children[2*WidthFactor];
401 RopePieceBTreeInterior() : RopePieceBTreeNode(false), NumChildren(0) {}
403 RopePieceBTreeInterior(RopePieceBTreeNode *LHS, RopePieceBTreeNode *RHS)
404 : RopePieceBTreeNode(false) {
408 Size = LHS->size() + RHS->size();
411 bool isFull() const { return NumChildren == 2*WidthFactor; }
413 unsigned getNumChildren() const { return NumChildren; }
414 const RopePieceBTreeNode *getChild(unsigned i) const {
415 assert(i < NumChildren && "invalid child #");
418 RopePieceBTreeNode *getChild(unsigned i) {
419 assert(i < NumChildren && "invalid child #");
423 /// FullRecomputeSizeLocally - Recompute the Size field of this node by
424 /// summing up the sizes of the child nodes.
425 void FullRecomputeSizeLocally() {
427 for (unsigned i = 0, e = getNumChildren(); i != e; ++i)
428 Size += getChild(i)->size();
432 /// split - Split the range containing the specified offset so that we are
433 /// guaranteed that there is a place to do an insertion at the specified
434 /// offset. The offset is relative, so "0" is the start of the node.
436 /// If there is no space in this subtree for the extra piece, the extra tree
437 /// node is returned and must be inserted into a parent.
438 RopePieceBTreeNode *split(unsigned Offset);
441 /// insert - Insert the specified ropepiece into this tree node at the
442 /// specified offset. The offset is relative, so "0" is the start of the
445 /// If there is no space in this subtree for the extra piece, the extra tree
446 /// node is returned and must be inserted into a parent.
447 RopePieceBTreeNode *insert(unsigned Offset, const RopePiece &R);
449 /// HandleChildPiece - A child propagated an insertion result up to us.
450 /// Insert the new child, and/or propagate the result further up the tree.
451 RopePieceBTreeNode *HandleChildPiece(unsigned i, RopePieceBTreeNode *RHS);
453 /// erase - Remove NumBytes from this node at the specified offset. We are
454 /// guaranteed that there is a split at Offset.
455 void erase(unsigned Offset, unsigned NumBytes);
457 static inline bool classof(const RopePieceBTreeInterior *) { return true; }
458 static inline bool classof(const RopePieceBTreeNode *N) {
462 } // end anonymous namespace
464 /// split - Split the range containing the specified offset so that we are
465 /// guaranteed that there is a place to do an insertion at the specified
466 /// offset. The offset is relative, so "0" is the start of the node.
468 /// If there is no space in this subtree for the extra piece, the extra tree
469 /// node is returned and must be inserted into a parent.
470 RopePieceBTreeNode *RopePieceBTreeInterior::split(unsigned Offset) {
471 // Figure out which child to split.
472 if (Offset == 0 || Offset == size())
473 return 0; // If we have an exact offset, we're already split.
475 unsigned ChildOffset = 0;
477 for (; Offset >= ChildOffset+getChild(i)->size(); ++i)
478 ChildOffset += getChild(i)->size();
480 // If already split there, we're done.
481 if (ChildOffset == Offset)
484 // Otherwise, recursively split the child.
485 if (RopePieceBTreeNode *RHS = getChild(i)->split(Offset-ChildOffset))
486 return HandleChildPiece(i, RHS);
490 /// insert - Insert the specified ropepiece into this tree node at the
491 /// specified offset. The offset is relative, so "0" is the start of the
494 /// If there is no space in this subtree for the extra piece, the extra tree
495 /// node is returned and must be inserted into a parent.
496 RopePieceBTreeNode *RopePieceBTreeInterior::insert(unsigned Offset,
497 const RopePiece &R) {
498 // Find the insertion point. We are guaranteed that there is a split at the
499 // specified offset so find it.
500 unsigned i = 0, e = getNumChildren();
502 unsigned ChildOffs = 0;
503 if (Offset == size()) {
504 // Fastpath for a common case. Insert at end of last child.
506 ChildOffs = size()-getChild(i)->size();
508 for (; Offset > ChildOffs+getChild(i)->size(); ++i)
509 ChildOffs += getChild(i)->size();
514 // Insert at the end of this child.
515 if (RopePieceBTreeNode *RHS = getChild(i)->insert(Offset-ChildOffs, R))
516 return HandleChildPiece(i, RHS);
521 /// HandleChildPiece - A child propagated an insertion result up to us.
522 /// Insert the new child, and/or propagate the result further up the tree.
524 RopePieceBTreeInterior::HandleChildPiece(unsigned i, RopePieceBTreeNode *RHS) {
525 // Otherwise the child propagated a subtree up to us as a new child. See if
526 // we have space for it here.
528 // Insert RHS after child 'i'.
529 if (i + 1 != getNumChildren())
530 memmove(&Children[i+2], &Children[i+1],
531 (getNumChildren()-i-1)*sizeof(Children[0]));
537 // Okay, this node is full. Split it in half, moving WidthFactor children to
538 // a newly allocated interior node.
540 // Create the new node.
541 RopePieceBTreeInterior *NewNode = new RopePieceBTreeInterior();
543 // Move over the last 'WidthFactor' values from here to NewNode.
544 memcpy(&NewNode->Children[0], &Children[WidthFactor],
545 WidthFactor*sizeof(Children[0]));
547 // Decrease the number of values in the two nodes.
548 NewNode->NumChildren = NumChildren = WidthFactor;
550 // Finally, insert the two new children in the side the can (now) hold them.
551 // These insertions can't fail.
553 this->HandleChildPiece(i, RHS);
555 NewNode->HandleChildPiece(i-WidthFactor, RHS);
557 // Recompute the two nodes' size.
558 NewNode->FullRecomputeSizeLocally();
559 FullRecomputeSizeLocally();
563 /// erase - Remove NumBytes from this node at the specified offset. We are
564 /// guaranteed that there is a split at Offset.
565 void RopePieceBTreeInterior::erase(unsigned Offset, unsigned NumBytes) {
566 // This will shrink this node by NumBytes.
569 // Find the first child that overlaps with Offset.
571 for (; Offset >= getChild(i)->size(); ++i)
572 Offset -= getChild(i)->size();
574 // Propagate the delete request into overlapping children, or completely
575 // delete the children as appropriate.
577 RopePieceBTreeNode *CurChild = getChild(i);
579 // If we are deleting something contained entirely in the child, pass on the
581 if (Offset+NumBytes < CurChild->size()) {
582 CurChild->erase(Offset, NumBytes);
586 // If this deletion request starts somewhere in the middle of the child, it
587 // must be deleting to the end of the child.
589 unsigned BytesFromChild = CurChild->size()-Offset;
590 CurChild->erase(Offset, BytesFromChild);
591 NumBytes -= BytesFromChild;
592 // Start at the beginning of the next child.
598 // If the deletion request completely covers the child, delete it and move
600 NumBytes -= CurChild->size();
603 if (i != getNumChildren())
604 memmove(&Children[i], &Children[i+1],
605 (getNumChildren()-i)*sizeof(Children[0]));
609 //===----------------------------------------------------------------------===//
610 // RopePieceBTreeNode Implementation
611 //===----------------------------------------------------------------------===//
613 void RopePieceBTreeNode::Destroy() {
614 if (RopePieceBTreeLeaf *Leaf = dyn_cast<RopePieceBTreeLeaf>(this))
617 delete cast<RopePieceBTreeInterior>(this);
620 /// split - Split the range containing the specified offset so that we are
621 /// guaranteed that there is a place to do an insertion at the specified
622 /// offset. The offset is relative, so "0" is the start of the node.
624 /// If there is no space in this subtree for the extra piece, the extra tree
625 /// node is returned and must be inserted into a parent.
626 RopePieceBTreeNode *RopePieceBTreeNode::split(unsigned Offset) {
627 assert(Offset <= size() && "Invalid offset to split!");
628 if (RopePieceBTreeLeaf *Leaf = dyn_cast<RopePieceBTreeLeaf>(this))
629 return Leaf->split(Offset);
630 return cast<RopePieceBTreeInterior>(this)->split(Offset);
633 /// insert - Insert the specified ropepiece into this tree node at the
634 /// specified offset. The offset is relative, so "0" is the start of the
637 /// If there is no space in this subtree for the extra piece, the extra tree
638 /// node is returned and must be inserted into a parent.
639 RopePieceBTreeNode *RopePieceBTreeNode::insert(unsigned Offset,
640 const RopePiece &R) {
641 assert(Offset <= size() && "Invalid offset to insert!");
642 if (RopePieceBTreeLeaf *Leaf = dyn_cast<RopePieceBTreeLeaf>(this))
643 return Leaf->insert(Offset, R);
644 return cast<RopePieceBTreeInterior>(this)->insert(Offset, R);
647 /// erase - Remove NumBytes from this node at the specified offset. We are
648 /// guaranteed that there is a split at Offset.
649 void RopePieceBTreeNode::erase(unsigned Offset, unsigned NumBytes) {
650 assert(Offset+NumBytes <= size() && "Invalid offset to erase!");
651 if (RopePieceBTreeLeaf *Leaf = dyn_cast<RopePieceBTreeLeaf>(this))
652 return Leaf->erase(Offset, NumBytes);
653 return cast<RopePieceBTreeInterior>(this)->erase(Offset, NumBytes);
657 //===----------------------------------------------------------------------===//
658 // RopePieceBTreeIterator Implementation
659 //===----------------------------------------------------------------------===//
661 static const RopePieceBTreeLeaf *getCN(const void *P) {
662 return static_cast<const RopePieceBTreeLeaf*>(P);
666 RopePieceBTreeIterator::RopePieceBTreeIterator(const void *n) {
667 const RopePieceBTreeNode *N = static_cast<const RopePieceBTreeNode*>(n);
669 // Walk down the left side of the tree until we get to a leaf.
670 while (const RopePieceBTreeInterior *IN = dyn_cast<RopePieceBTreeInterior>(N))
673 // We must have at least one leaf.
674 CurNode = cast<RopePieceBTreeLeaf>(N);
676 // If we found a leaf that happens to be empty, skip over it until we get
677 // to something full.
678 while (CurNode && getCN(CurNode)->getNumPieces() == 0)
679 CurNode = getCN(CurNode)->getNextLeafInOrder();
682 CurPiece = &getCN(CurNode)->getPiece(0);
683 else // Empty tree, this is an end() iterator.
688 void RopePieceBTreeIterator::MoveToNextPiece() {
689 if (CurPiece != &getCN(CurNode)->getPiece(getCN(CurNode)->getNumPieces()-1)) {
695 // Find the next non-empty leaf node.
697 CurNode = getCN(CurNode)->getNextLeafInOrder();
698 while (CurNode && getCN(CurNode)->getNumPieces() == 0);
701 CurPiece = &getCN(CurNode)->getPiece(0);
707 //===----------------------------------------------------------------------===//
708 // RopePieceBTree Implementation
709 //===----------------------------------------------------------------------===//
711 static RopePieceBTreeNode *getRoot(void *P) {
712 return static_cast<RopePieceBTreeNode*>(P);
715 RopePieceBTree::RopePieceBTree() {
716 Root = new RopePieceBTreeLeaf();
718 RopePieceBTree::RopePieceBTree(const RopePieceBTree &RHS) {
719 assert(RHS.empty() && "Can't copy non-empty tree yet");
720 Root = new RopePieceBTreeLeaf();
722 RopePieceBTree::~RopePieceBTree() {
723 getRoot(Root)->Destroy();
726 unsigned RopePieceBTree::size() const {
727 return getRoot(Root)->size();
730 void RopePieceBTree::clear() {
731 if (RopePieceBTreeLeaf *Leaf = dyn_cast<RopePieceBTreeLeaf>(getRoot(Root)))
734 getRoot(Root)->Destroy();
735 Root = new RopePieceBTreeLeaf();
739 void RopePieceBTree::insert(unsigned Offset, const RopePiece &R) {
740 // #1. Split at Offset.
741 if (RopePieceBTreeNode *RHS = getRoot(Root)->split(Offset))
742 Root = new RopePieceBTreeInterior(getRoot(Root), RHS);
744 // #2. Do the insertion.
745 if (RopePieceBTreeNode *RHS = getRoot(Root)->insert(Offset, R))
746 Root = new RopePieceBTreeInterior(getRoot(Root), RHS);
749 void RopePieceBTree::erase(unsigned Offset, unsigned NumBytes) {
750 // #1. Split at Offset.
751 if (RopePieceBTreeNode *RHS = getRoot(Root)->split(Offset))
752 Root = new RopePieceBTreeInterior(getRoot(Root), RHS);
754 // #2. Do the erasing.
755 getRoot(Root)->erase(Offset, NumBytes);
758 //===----------------------------------------------------------------------===//
759 // RewriteRope Implementation
760 //===----------------------------------------------------------------------===//
762 /// MakeRopeString - This copies the specified byte range into some instance of
763 /// RopeRefCountString, and return a RopePiece that represents it. This uses
764 /// the AllocBuffer object to aggregate requests for small strings into one
765 /// allocation instead of doing tons of tiny allocations.
766 RopePiece RewriteRope::MakeRopeString(const char *Start, const char *End) {
767 unsigned Len = End-Start;
768 assert(Len && "Zero length RopePiece is invalid!");
770 // If we have space for this string in the current alloc buffer, use it.
771 if (AllocOffs+Len <= AllocChunkSize) {
772 memcpy(AllocBuffer->Data+AllocOffs, Start, Len);
774 return RopePiece(AllocBuffer, AllocOffs-Len, AllocOffs);
777 // If we don't have enough room because this specific allocation is huge,
778 // just allocate a new rope piece for it alone.
779 if (Len > AllocChunkSize) {
780 unsigned Size = End-Start+sizeof(RopeRefCountString)-1;
781 RopeRefCountString *Res =
782 reinterpret_cast<RopeRefCountString *>(new char[Size]);
784 memcpy(Res->Data, Start, End-Start);
785 return RopePiece(Res, 0, End-Start);
788 // Otherwise, this was a small request but we just don't have space for it
789 // Make a new chunk and share it with later allocations.
791 // If we had an old allocation, drop our reference to it.
792 if (AllocBuffer && --AllocBuffer->RefCount == 0)
793 delete [] (char*)AllocBuffer;
795 unsigned AllocSize = offsetof(RopeRefCountString, Data) + AllocChunkSize;
796 AllocBuffer = reinterpret_cast<RopeRefCountString *>(new char[AllocSize]);
797 AllocBuffer->RefCount = 0;
798 memcpy(AllocBuffer->Data, Start, Len);
801 // Start out the new allocation with a refcount of 1, since we have an
802 // internal reference to it.
803 AllocBuffer->addRef();
804 return RopePiece(AllocBuffer, 0, Len);