clang 19.0.0git
DeltaTree.cpp
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1//===- DeltaTree.cpp - B-Tree for Rewrite Delta tracking ------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the DeltaTree and related classes.
10//
11//===----------------------------------------------------------------------===//
12
14#include "clang/Basic/LLVM.h"
15#include "llvm/Support/Casting.h"
16#include <cassert>
17#include <cstring>
18
19using namespace clang;
20
21/// The DeltaTree class is a multiway search tree (BTree) structure with some
22/// fancy features. B-Trees are generally more memory and cache efficient
23/// than binary trees, because they store multiple keys/values in each node.
24///
25/// DeltaTree implements a key/value mapping from FileIndex to Delta, allowing
26/// fast lookup by FileIndex. However, an added (important) bonus is that it
27/// can also efficiently tell us the full accumulated delta for a specific
28/// file offset as well, without traversing the whole tree.
29///
30/// The nodes of the tree are made up of instances of two classes:
31/// DeltaTreeNode and DeltaTreeInteriorNode. The later subclasses the
32/// former and adds children pointers. Each node knows the full delta of all
33/// entries (recursively) contained inside of it, which allows us to get the
34/// full delta implied by a whole subtree in constant time.
35
36namespace {
37
38 /// SourceDelta - As code in the original input buffer is added and deleted,
39 /// SourceDelta records are used to keep track of how the input SourceLocation
40 /// object is mapped into the output buffer.
41 struct SourceDelta {
42 unsigned FileLoc;
43 int Delta;
44
45 static SourceDelta get(unsigned Loc, int D) {
46 SourceDelta Delta;
47 Delta.FileLoc = Loc;
48 Delta.Delta = D;
49 return Delta;
50 }
51 };
52
53 /// DeltaTreeNode - The common part of all nodes.
54 ///
55 class DeltaTreeNode {
56 public:
57 struct InsertResult {
58 DeltaTreeNode *LHS, *RHS;
59 SourceDelta Split;
60 };
61
62 private:
63 friend class DeltaTreeInteriorNode;
64
65 /// WidthFactor - This controls the number of K/V slots held in the BTree:
66 /// how wide it is. Each level of the BTree is guaranteed to have at least
67 /// WidthFactor-1 K/V pairs (except the root) and may have at most
68 /// 2*WidthFactor-1 K/V pairs.
69 enum { WidthFactor = 8 };
70
71 /// Values - This tracks the SourceDelta's currently in this node.
72 SourceDelta Values[2*WidthFactor-1];
73
74 /// NumValuesUsed - This tracks the number of values this node currently
75 /// holds.
76 unsigned char NumValuesUsed = 0;
77
78 /// IsLeaf - This is true if this is a leaf of the btree. If false, this is
79 /// an interior node, and is actually an instance of DeltaTreeInteriorNode.
80 bool IsLeaf;
81
82 /// FullDelta - This is the full delta of all the values in this node and
83 /// all children nodes.
84 int FullDelta = 0;
85
86 public:
87 DeltaTreeNode(bool isLeaf = true) : IsLeaf(isLeaf) {}
88
89 bool isLeaf() const { return IsLeaf; }
90 int getFullDelta() const { return FullDelta; }
91 bool isFull() const { return NumValuesUsed == 2*WidthFactor-1; }
92
93 unsigned getNumValuesUsed() const { return NumValuesUsed; }
94
95 const SourceDelta &getValue(unsigned i) const {
96 assert(i < NumValuesUsed && "Invalid value #");
97 return Values[i];
98 }
99
100 SourceDelta &getValue(unsigned i) {
101 assert(i < NumValuesUsed && "Invalid value #");
102 return Values[i];
103 }
104
105 /// DoInsertion - Do an insertion of the specified FileIndex/Delta pair into
106 /// this node. If insertion is easy, do it and return false. Otherwise,
107 /// split the node, populate InsertRes with info about the split, and return
108 /// true.
109 bool DoInsertion(unsigned FileIndex, int Delta, InsertResult *InsertRes);
110
111 void DoSplit(InsertResult &InsertRes);
112
113
114 /// RecomputeFullDeltaLocally - Recompute the FullDelta field by doing a
115 /// local walk over our contained deltas.
116 void RecomputeFullDeltaLocally();
117
118 void Destroy();
119 };
120
121 /// DeltaTreeInteriorNode - When isLeaf = false, a node has child pointers.
122 /// This class tracks them.
123 class DeltaTreeInteriorNode : public DeltaTreeNode {
124 friend class DeltaTreeNode;
125
126 DeltaTreeNode *Children[2*WidthFactor];
127
128 ~DeltaTreeInteriorNode() {
129 for (unsigned i = 0, e = NumValuesUsed+1; i != e; ++i)
130 Children[i]->Destroy();
131 }
132
133 public:
134 DeltaTreeInteriorNode() : DeltaTreeNode(false /*nonleaf*/) {}
135
136 DeltaTreeInteriorNode(const InsertResult &IR)
137 : DeltaTreeNode(false /*nonleaf*/) {
138 Children[0] = IR.LHS;
139 Children[1] = IR.RHS;
140 Values[0] = IR.Split;
141 FullDelta = IR.LHS->getFullDelta()+IR.RHS->getFullDelta()+IR.Split.Delta;
142 NumValuesUsed = 1;
143 }
144
145 const DeltaTreeNode *getChild(unsigned i) const {
146 assert(i < getNumValuesUsed()+1 && "Invalid child");
147 return Children[i];
148 }
149
150 DeltaTreeNode *getChild(unsigned i) {
151 assert(i < getNumValuesUsed()+1 && "Invalid child");
152 return Children[i];
153 }
154
155 static bool classof(const DeltaTreeNode *N) { return !N->isLeaf(); }
156 };
157
158} // namespace
159
160/// Destroy - A 'virtual' destructor.
161void DeltaTreeNode::Destroy() {
162 if (isLeaf())
163 delete this;
164 else
165 delete cast<DeltaTreeInteriorNode>(this);
166}
167
168/// RecomputeFullDeltaLocally - Recompute the FullDelta field by doing a
169/// local walk over our contained deltas.
170void DeltaTreeNode::RecomputeFullDeltaLocally() {
171 int NewFullDelta = 0;
172 for (unsigned i = 0, e = getNumValuesUsed(); i != e; ++i)
173 NewFullDelta += Values[i].Delta;
174 if (auto *IN = dyn_cast<DeltaTreeInteriorNode>(this))
175 for (unsigned i = 0, e = getNumValuesUsed()+1; i != e; ++i)
176 NewFullDelta += IN->getChild(i)->getFullDelta();
177 FullDelta = NewFullDelta;
178}
179
180/// DoInsertion - Do an insertion of the specified FileIndex/Delta pair into
181/// this node. If insertion is easy, do it and return false. Otherwise,
182/// split the node, populate InsertRes with info about the split, and return
183/// true.
184bool DeltaTreeNode::DoInsertion(unsigned FileIndex, int Delta,
185 InsertResult *InsertRes) {
186 // Maintain full delta for this node.
187 FullDelta += Delta;
188
189 // Find the insertion point, the first delta whose index is >= FileIndex.
190 unsigned i = 0, e = getNumValuesUsed();
191 while (i != e && FileIndex > getValue(i).FileLoc)
192 ++i;
193
194 // If we found an a record for exactly this file index, just merge this
195 // value into the pre-existing record and finish early.
196 if (i != e && getValue(i).FileLoc == FileIndex) {
197 // NOTE: Delta could drop to zero here. This means that the delta entry is
198 // useless and could be removed. Supporting erases is more complex than
199 // leaving an entry with Delta=0, so we just leave an entry with Delta=0 in
200 // the tree.
201 Values[i].Delta += Delta;
202 return false;
203 }
204
205 // Otherwise, we found an insertion point, and we know that the value at the
206 // specified index is > FileIndex. Handle the leaf case first.
207 if (isLeaf()) {
208 if (!isFull()) {
209 // For an insertion into a non-full leaf node, just insert the value in
210 // its sorted position. This requires moving later values over.
211 if (i != e)
212 memmove(&Values[i+1], &Values[i], sizeof(Values[0])*(e-i));
213 Values[i] = SourceDelta::get(FileIndex, Delta);
214 ++NumValuesUsed;
215 return false;
216 }
217
218 // Otherwise, if this is leaf is full, split the node at its median, insert
219 // the value into one of the children, and return the result.
220 assert(InsertRes && "No result location specified");
221 DoSplit(*InsertRes);
222
223 if (InsertRes->Split.FileLoc > FileIndex)
224 InsertRes->LHS->DoInsertion(FileIndex, Delta, nullptr /*can't fail*/);
225 else
226 InsertRes->RHS->DoInsertion(FileIndex, Delta, nullptr /*can't fail*/);
227 return true;
228 }
229
230 // Otherwise, this is an interior node. Send the request down the tree.
231 auto *IN = cast<DeltaTreeInteriorNode>(this);
232 if (!IN->Children[i]->DoInsertion(FileIndex, Delta, InsertRes))
233 return false; // If there was space in the child, just return.
234
235 // Okay, this split the subtree, producing a new value and two children to
236 // insert here. If this node is non-full, we can just insert it directly.
237 if (!isFull()) {
238 // Now that we have two nodes and a new element, insert the perclated value
239 // into ourself by moving all the later values/children down, then inserting
240 // the new one.
241 if (i != e)
242 memmove(&IN->Children[i+2], &IN->Children[i+1],
243 (e-i)*sizeof(IN->Children[0]));
244 IN->Children[i] = InsertRes->LHS;
245 IN->Children[i+1] = InsertRes->RHS;
246
247 if (e != i)
248 memmove(&Values[i+1], &Values[i], (e-i)*sizeof(Values[0]));
249 Values[i] = InsertRes->Split;
250 ++NumValuesUsed;
251 return false;
252 }
253
254 // Finally, if this interior node was full and a node is percolated up, split
255 // ourself and return that up the chain. Start by saving all our info to
256 // avoid having the split clobber it.
257 IN->Children[i] = InsertRes->LHS;
258 DeltaTreeNode *SubRHS = InsertRes->RHS;
259 SourceDelta SubSplit = InsertRes->Split;
260
261 // Do the split.
262 DoSplit(*InsertRes);
263
264 // Figure out where to insert SubRHS/NewSplit.
265 DeltaTreeInteriorNode *InsertSide;
266 if (SubSplit.FileLoc < InsertRes->Split.FileLoc)
267 InsertSide = cast<DeltaTreeInteriorNode>(InsertRes->LHS);
268 else
269 InsertSide = cast<DeltaTreeInteriorNode>(InsertRes->RHS);
270
271 // We now have a non-empty interior node 'InsertSide' to insert
272 // SubRHS/SubSplit into. Find out where to insert SubSplit.
273
274 // Find the insertion point, the first delta whose index is >SubSplit.FileLoc.
275 i = 0; e = InsertSide->getNumValuesUsed();
276 while (i != e && SubSplit.FileLoc > InsertSide->getValue(i).FileLoc)
277 ++i;
278
279 // Now we know that i is the place to insert the split value into. Insert it
280 // and the child right after it.
281 if (i != e)
282 memmove(&InsertSide->Children[i+2], &InsertSide->Children[i+1],
283 (e-i)*sizeof(IN->Children[0]));
284 InsertSide->Children[i+1] = SubRHS;
285
286 if (e != i)
287 memmove(&InsertSide->Values[i+1], &InsertSide->Values[i],
288 (e-i)*sizeof(Values[0]));
289 InsertSide->Values[i] = SubSplit;
290 ++InsertSide->NumValuesUsed;
291 InsertSide->FullDelta += SubSplit.Delta + SubRHS->getFullDelta();
292 return true;
293}
294
295/// DoSplit - Split the currently full node (which has 2*WidthFactor-1 values)
296/// into two subtrees each with "WidthFactor-1" values and a pivot value.
297/// Return the pieces in InsertRes.
298void DeltaTreeNode::DoSplit(InsertResult &InsertRes) {
299 assert(isFull() && "Why split a non-full node?");
300
301 // Since this node is full, it contains 2*WidthFactor-1 values. We move
302 // the first 'WidthFactor-1' values to the LHS child (which we leave in this
303 // node), propagate one value up, and move the last 'WidthFactor-1' values
304 // into the RHS child.
305
306 // Create the new child node.
307 DeltaTreeNode *NewNode;
308 if (auto *IN = dyn_cast<DeltaTreeInteriorNode>(this)) {
309 // If this is an interior node, also move over 'WidthFactor' children
310 // into the new node.
311 DeltaTreeInteriorNode *New = new DeltaTreeInteriorNode();
312 memcpy(&New->Children[0], &IN->Children[WidthFactor],
313 WidthFactor*sizeof(IN->Children[0]));
314 NewNode = New;
315 } else {
316 // Just create the new leaf node.
317 NewNode = new DeltaTreeNode();
318 }
319
320 // Move over the last 'WidthFactor-1' values from here to NewNode.
321 memcpy(&NewNode->Values[0], &Values[WidthFactor],
322 (WidthFactor-1)*sizeof(Values[0]));
323
324 // Decrease the number of values in the two nodes.
325 NewNode->NumValuesUsed = NumValuesUsed = WidthFactor-1;
326
327 // Recompute the two nodes' full delta.
328 NewNode->RecomputeFullDeltaLocally();
329 RecomputeFullDeltaLocally();
330
331 InsertRes.LHS = this;
332 InsertRes.RHS = NewNode;
333 InsertRes.Split = Values[WidthFactor-1];
334}
335
336//===----------------------------------------------------------------------===//
337// DeltaTree Implementation
338//===----------------------------------------------------------------------===//
339
340//#define VERIFY_TREE
341
342#ifdef VERIFY_TREE
343/// VerifyTree - Walk the btree performing assertions on various properties to
344/// verify consistency. This is useful for debugging new changes to the tree.
345static void VerifyTree(const DeltaTreeNode *N) {
346 const auto *IN = dyn_cast<DeltaTreeInteriorNode>(N);
347 if (IN == 0) {
348 // Verify leaves, just ensure that FullDelta matches up and the elements
349 // are in proper order.
350 int FullDelta = 0;
351 for (unsigned i = 0, e = N->getNumValuesUsed(); i != e; ++i) {
352 if (i)
353 assert(N->getValue(i-1).FileLoc < N->getValue(i).FileLoc);
354 FullDelta += N->getValue(i).Delta;
355 }
356 assert(FullDelta == N->getFullDelta());
357 return;
358 }
359
360 // Verify interior nodes: Ensure that FullDelta matches up and the
361 // elements are in proper order and the children are in proper order.
362 int FullDelta = 0;
363 for (unsigned i = 0, e = IN->getNumValuesUsed(); i != e; ++i) {
364 const SourceDelta &IVal = N->getValue(i);
365 const DeltaTreeNode *IChild = IN->getChild(i);
366 if (i)
367 assert(IN->getValue(i-1).FileLoc < IVal.FileLoc);
368 FullDelta += IVal.Delta;
369 FullDelta += IChild->getFullDelta();
370
371 // The largest value in child #i should be smaller than FileLoc.
372 assert(IChild->getValue(IChild->getNumValuesUsed()-1).FileLoc <
373 IVal.FileLoc);
374
375 // The smallest value in child #i+1 should be larger than FileLoc.
376 assert(IN->getChild(i+1)->getValue(0).FileLoc > IVal.FileLoc);
377 VerifyTree(IChild);
378 }
379
380 FullDelta += IN->getChild(IN->getNumValuesUsed())->getFullDelta();
381
382 assert(FullDelta == N->getFullDelta());
383}
384#endif // VERIFY_TREE
385
386static DeltaTreeNode *getRoot(void *Root) {
387 return (DeltaTreeNode*)Root;
388}
389
391 Root = new DeltaTreeNode();
392}
393
395 // Currently we only support copying when the RHS is empty.
396 assert(getRoot(RHS.Root)->getNumValuesUsed() == 0 &&
397 "Can only copy empty tree");
398 Root = new DeltaTreeNode();
399}
400
402 getRoot(Root)->Destroy();
403}
404
405/// getDeltaAt - Return the accumulated delta at the specified file offset.
406/// This includes all insertions or delections that occurred *before* the
407/// specified file index.
408int DeltaTree::getDeltaAt(unsigned FileIndex) const {
409 const DeltaTreeNode *Node = getRoot(Root);
410
411 int Result = 0;
412
413 // Walk down the tree.
414 while (true) {
415 // For all nodes, include any local deltas before the specified file
416 // index by summing them up directly. Keep track of how many were
417 // included.
418 unsigned NumValsGreater = 0;
419 for (unsigned e = Node->getNumValuesUsed(); NumValsGreater != e;
420 ++NumValsGreater) {
421 const SourceDelta &Val = Node->getValue(NumValsGreater);
422
423 if (Val.FileLoc >= FileIndex)
424 break;
425 Result += Val.Delta;
426 }
427
428 // If we have an interior node, include information about children and
429 // recurse. Otherwise, if we have a leaf, we're done.
430 const auto *IN = dyn_cast<DeltaTreeInteriorNode>(Node);
431 if (!IN) return Result;
432
433 // Include any children to the left of the values we skipped, all of
434 // their deltas should be included as well.
435 for (unsigned i = 0; i != NumValsGreater; ++i)
436 Result += IN->getChild(i)->getFullDelta();
437
438 // If we found exactly the value we were looking for, break off the
439 // search early. There is no need to search the RHS of the value for
440 // partial results.
441 if (NumValsGreater != Node->getNumValuesUsed() &&
442 Node->getValue(NumValsGreater).FileLoc == FileIndex)
443 return Result+IN->getChild(NumValsGreater)->getFullDelta();
444
445 // Otherwise, traverse down the tree. The selected subtree may be
446 // partially included in the range.
447 Node = IN->getChild(NumValsGreater);
448 }
449 // NOT REACHED.
450}
451
452/// AddDelta - When a change is made that shifts around the text buffer,
453/// this method is used to record that info. It inserts a delta of 'Delta'
454/// into the current DeltaTree at offset FileIndex.
455void DeltaTree::AddDelta(unsigned FileIndex, int Delta) {
456 assert(Delta && "Adding a noop?");
457 DeltaTreeNode *MyRoot = getRoot(Root);
458
459 DeltaTreeNode::InsertResult InsertRes;
460 if (MyRoot->DoInsertion(FileIndex, Delta, &InsertRes)) {
461 Root = new DeltaTreeInteriorNode(InsertRes);
462#ifdef VERIFY_TREE
463 MyRoot = Root;
464#endif
465 }
466
467#ifdef VERIFY_TREE
468 VerifyTree(MyRoot);
469#endif
470}
DynTypedNode Node
static DeltaTreeNode * getRoot(void *Root)
Definition: DeltaTree.cpp:386
Forward-declares and imports various common LLVM datatypes that clang wants to use unqualified.
SourceLocation Loc
Definition: SemaObjC.cpp:758
__DEVICE__ void * memcpy(void *__a, const void *__b, size_t __c)
DeltaTree - a multiway search tree (BTree) structure with some fancy features.
Definition: DeltaTree.h:25
void AddDelta(unsigned FileIndex, int Delta)
AddDelta - When a change is made that shifts around the text buffer, this method is used to record th...
Definition: DeltaTree.cpp:455
int getDeltaAt(unsigned FileIndex) const
getDeltaAt - Return the accumulated delta at the specified file offset.
Definition: DeltaTree.cpp:408
bool Destroy(InterpState &S, CodePtr OpPC, uint32_t I)
Definition: Interp.h:1938
The JSON file list parser is used to communicate input to InstallAPI.
@ Result
The result type of a method or function.
#define false
Definition: stdbool.h:26