LLVM  6.0.0svn
BinaryItemStream.h
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1 //===- BinaryItemStream.h ---------------------------------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef LLVM_SUPPORT_BINARYITEMSTREAM_H
11 #define LLVM_SUPPORT_BINARYITEMSTREAM_H
12 
13 #include "llvm/ADT/ArrayRef.h"
16 #include "llvm/Support/Error.h"
17 #include <cstddef>
18 #include <cstdint>
19 
20 namespace llvm {
21 
22 template <typename T> struct BinaryItemTraits {
23  static size_t length(const T &Item) = delete;
24  static ArrayRef<uint8_t> bytes(const T &Item) = delete;
25 };
26 
27 /// BinaryItemStream represents a sequence of objects stored in some kind of
28 /// external container but for which it is useful to view as a stream of
29 /// contiguous bytes. An example of this might be if you have a collection of
30 /// records and you serialize each one into a buffer, and store these serialized
31 /// records in a container. The pointers themselves are not laid out
32 /// contiguously in memory, but we may wish to read from or write to these
33 /// records as if they were.
34 template <typename T, typename Traits = BinaryItemTraits<T>>
36 public:
38  : Endian(Endian) {}
39 
40  llvm::support::endianness getEndian() const override { return Endian; }
41 
43  ArrayRef<uint8_t> &Buffer) override {
44  auto ExpectedIndex = translateOffsetIndex(Offset);
45  if (!ExpectedIndex)
46  return ExpectedIndex.takeError();
47  const auto &Item = Items[*ExpectedIndex];
48  if (auto EC = checkOffset(Offset, Size))
49  return EC;
50  if (Size > Traits::length(Item))
51  return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
52  Buffer = Traits::bytes(Item).take_front(Size);
53  return Error::success();
54  }
55 
57  ArrayRef<uint8_t> &Buffer) override {
58  auto ExpectedIndex = translateOffsetIndex(Offset);
59  if (!ExpectedIndex)
60  return ExpectedIndex.takeError();
61  Buffer = Traits::bytes(Items[*ExpectedIndex]);
62  return Error::success();
63  }
64 
65  void setItems(ArrayRef<T> ItemArray) {
66  Items = ItemArray;
67  computeItemOffsets();
68  }
69 
70  uint32_t getLength() override {
71  return ItemEndOffsets.empty() ? 0 : ItemEndOffsets.back();
72  }
73 
74 private:
75  void computeItemOffsets() {
76  ItemEndOffsets.clear();
77  ItemEndOffsets.reserve(Items.size());
78  uint32_t CurrentOffset = 0;
79  for (const auto &Item : Items) {
80  uint32_t Len = Traits::length(Item);
81  assert(Len > 0 && "no empty items");
82  CurrentOffset += Len;
83  ItemEndOffsets.push_back(CurrentOffset);
84  }
85  }
86 
87  Expected<uint32_t> translateOffsetIndex(uint32_t Offset) {
88  // Make sure the offset is somewhere in our items array.
89  if (Offset >= getLength())
90  return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
91  ++Offset;
92  auto Iter =
93  std::lower_bound(ItemEndOffsets.begin(), ItemEndOffsets.end(), Offset);
94  size_t Idx = std::distance(ItemEndOffsets.begin(), Iter);
95  assert(Idx < Items.size() && "binary search for offset failed");
96  return Idx;
97  }
98 
100  ArrayRef<T> Items;
101 
102  // Sorted vector of offsets to accelerate lookup.
103  std::vector<uint32_t> ItemEndOffsets;
104 };
105 
106 } // end namespace llvm
107 
108 #endif // LLVM_SUPPORT_BINARYITEMSTREAM_H
ArrayRef< T > take_front(size_t N=1) const
Return a copy of *this with only the first N elements.
Definition: ArrayRef.h:212
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
static ArrayRef< uint8_t > bytes(const T &Item)=delete
Error readLongestContiguousChunk(uint32_t Offset, ArrayRef< uint8_t > &Buffer) override
Given an offset into the stream, read as much as possible without copying any data.
Tagged union holding either a T or a Error.
Definition: CachePruning.h:23
An interface for accessing data in a stream-like format, but which discourages copying.
Definition: BinaryStream.h:28
llvm::support::endianness getEndian() const override
BinaryItemStream(llvm::support::endianness Endian)
Error readBytes(uint32_t Offset, uint32_t Size, ArrayRef< uint8_t > &Buffer) override
Given an offset into the stream and a number of bytes, attempt to read the bytes and set the output A...
static ErrorSuccess success()
Create a success value.
Definition: Error.h:313
auto lower_bound(R &&Range, ForwardIt I) -> decltype(std::begin(Range))
Provide wrappers to std::lower_bound which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:859
static size_t length(const T &Item)=delete
uint32_t getLength() override
Return the number of bytes of data in this stream.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
BinaryItemStream represents a sequence of objects stored in some kind of external container but for w...
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
Lightweight error class with error context and mandatory checking.
Definition: Error.h:156
void setItems(ArrayRef< T > ItemArray)