1 //===- LazyRandomTypeCollection.h -------------------------------*- 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 #ifndef LLVM_DEBUGINFO_CODEVIEW_LAZYRANDOMTYPECOLLECTION_H
11 #define LLVM_DEBUGINFO_CODEVIEW_LAZYRANDOMTYPECOLLECTION_H
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/ADT/Optional.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/DebugInfo/CodeView/TypeCollection.h"
17 #include "llvm/DebugInfo/CodeView/TypeIndex.h"
18 #include "llvm/DebugInfo/CodeView/TypeRecord.h"
19 #include "llvm/Support/Allocator.h"
20 #include "llvm/Support/BinaryStreamArray.h"
21 #include "llvm/Support/Error.h"
22 #include "llvm/Support/StringSaver.h"
29 /// Provides amortized O(1) random access to a CodeView type stream.
30 /// Normally to access a type from a type stream, you must know its byte
31 /// offset into the type stream, because type records are variable-lengthed.
32 /// However, this is not the way we prefer to access them. For example, given
33 /// a symbol record one of the fields may be the TypeIndex of the symbol's
34 /// type record. Or given a type record such as an array type, there might
35 /// be a TypeIndex for the element type. Sequential access is perfect when
36 /// we're just dumping every entry, but it's very poor for real world usage.
38 /// Type streams in PDBs contain an additional field which is a list of pairs
39 /// containing indices and their corresponding offsets, roughly every ~8KB of
40 /// record data. This general idea need not be confined to PDBs though. By
41 /// supplying such an array, the producer of a type stream can allow the
42 /// consumer much better access time, because the consumer can find the nearest
43 /// index in this array, and do a linear scan forward only from there.
45 /// LazyRandomTypeCollection implements this algorithm, but additionally goes
46 /// one step further by caching offsets of every record that has been visited at
47 /// least once. This way, even repeated visits of the same record will never
48 /// require more than one linear scan. For a type stream of N elements divided
49 /// into M chunks of roughly equal size, this yields a worst case lookup time
50 /// of O(N/M) and an amortized time of O(1).
51 class LazyRandomTypeCollection : public TypeCollection {
52 using PartialOffsetArray = FixedStreamArray<TypeIndexOffset>;
61 explicit LazyRandomTypeCollection(uint32_t RecordCountHint);
62 LazyRandomTypeCollection(StringRef Data, uint32_t RecordCountHint);
63 LazyRandomTypeCollection(ArrayRef<uint8_t> Data, uint32_t RecordCountHint);
64 LazyRandomTypeCollection(const CVTypeArray &Types, uint32_t RecordCountHint,
65 PartialOffsetArray PartialOffsets);
66 LazyRandomTypeCollection(const CVTypeArray &Types, uint32_t RecordCountHint);
68 void reset(ArrayRef<uint8_t> Data, uint32_t RecordCountHint);
69 void reset(StringRef Data, uint32_t RecordCountHint);
70 void reset(BinaryStreamReader &Reader, uint32_t RecordCountHint);
72 uint32_t getOffsetOfType(TypeIndex Index);
74 Optional<CVType> tryGetType(TypeIndex Index);
76 CVType getType(TypeIndex Index) override;
77 StringRef getTypeName(TypeIndex Index) override;
78 bool contains(TypeIndex Index) override;
79 uint32_t size() override;
80 uint32_t capacity() override;
81 Optional<TypeIndex> getFirst() override;
82 Optional<TypeIndex> getNext(TypeIndex Prev) override;
85 Error ensureTypeExists(TypeIndex Index);
86 void ensureCapacityFor(TypeIndex Index);
88 Error visitRangeForType(TypeIndex TI);
89 Error fullScanForType(TypeIndex TI);
90 void visitRange(TypeIndex Begin, uint32_t BeginOffset, TypeIndex End);
92 /// Number of actual records.
95 /// The largest type index which we've visited.
96 TypeIndex LargestTypeIndex = TypeIndex::None();
98 BumpPtrAllocator Allocator;
99 StringSaver NameStorage;
101 /// The type array to allow random access visitation of.
104 std::vector<CacheEntry> Records;
106 /// An array of index offsets for the given type stream, allowing log(N)
107 /// lookups of a type record by index. Similar to KnownOffsets but only
108 /// contains offsets for some type indices, some of which may not have
109 /// ever been visited.
110 PartialOffsetArray PartialOffsets;
113 } // end namespace codeview
114 } // end namespace llvm
116 #endif // LLVM_DEBUGINFO_CODEVIEW_LAZYRANDOMTYPECOLLECTION_H