LLVM  3.7.0
StreamingMemoryObject.cpp
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1 //===- StreamingMemoryObject.cpp - Streamable data interface -------------===//
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 
11 #include <cassert>
12 #include <cstddef>
13 #include <cstring>
14 using namespace llvm;
15 
16 namespace {
17 
18 class RawMemoryObject : public MemoryObject {
19 public:
20  RawMemoryObject(const unsigned char *Start, const unsigned char *End) :
21  FirstChar(Start), LastChar(End) {
22  assert(LastChar >= FirstChar && "Invalid start/end range");
23  }
24 
25  uint64_t getExtent() const override {
26  return LastChar - FirstChar;
27  }
28  uint64_t readBytes(uint8_t *Buf, uint64_t Size,
29  uint64_t Address) const override;
30  const uint8_t *getPointer(uint64_t address, uint64_t size) const override;
31  bool isValidAddress(uint64_t address) const override {
32  return validAddress(address);
33  }
34 
35 private:
36  const uint8_t* const FirstChar;
37  const uint8_t* const LastChar;
38 
39  // These are implemented as inline functions here to avoid multiple virtual
40  // calls per public function
41  bool validAddress(uint64_t address) const {
42  return static_cast<std::ptrdiff_t>(address) < LastChar - FirstChar;
43  }
44 
45  RawMemoryObject(const RawMemoryObject&) = delete;
46  void operator=(const RawMemoryObject&) = delete;
47 };
48 
49 uint64_t RawMemoryObject::readBytes(uint8_t *Buf, uint64_t Size,
50  uint64_t Address) const {
51  uint64_t BufferSize = LastChar - FirstChar;
52  if (Address >= BufferSize)
53  return 0;
54 
55  uint64_t End = Address + Size;
56  if (End > BufferSize)
57  End = BufferSize;
58 
59  assert(static_cast<int64_t>(End - Address) >= 0);
60  Size = End - Address;
61  memcpy(Buf, Address + FirstChar, Size);
62  return Size;
63 }
64 
65 const uint8_t *RawMemoryObject::getPointer(uint64_t address,
66  uint64_t size) const {
67  return FirstChar + address;
68 }
69 } // anonymous namespace
70 
71 namespace llvm {
72 // If the bitcode has a header, then its size is known, and we don't have to
73 // block until we actually want to read it.
74 bool StreamingMemoryObject::isValidAddress(uint64_t address) const {
75  if (ObjectSize && address < ObjectSize) return true;
76  return fetchToPos(address);
77 }
78 
80  if (ObjectSize) return ObjectSize;
81  size_t pos = BytesRead + kChunkSize;
82  // keep fetching until we run out of bytes
83  while (fetchToPos(pos)) pos += kChunkSize;
84  return ObjectSize;
85 }
86 
87 uint64_t StreamingMemoryObject::readBytes(uint8_t *Buf, uint64_t Size,
88  uint64_t Address) const {
89  fetchToPos(Address + Size - 1);
90  // Note: For wrapped bitcode files will set ObjectSize after the
91  // first call to fetchToPos. In such cases, ObjectSize can be
92  // smaller than BytesRead.
93  size_t MaxAddress =
94  (ObjectSize && ObjectSize < BytesRead) ? ObjectSize : BytesRead;
95  if (Address >= MaxAddress)
96  return 0;
97 
98  uint64_t End = Address + Size;
99  if (End > MaxAddress)
100  End = MaxAddress;
101  assert(End >= Address);
102  Size = End - Address;
103  memcpy(Buf, &Bytes[Address + BytesSkipped], Size);
104  return Size;
105 }
106 
108  if (BytesRead < s) return true;
109  BytesSkipped = s;
110  BytesRead -= s;
111  return false;
112 }
113 
115  ObjectSize = size;
116  Bytes.reserve(size);
117  if (ObjectSize <= BytesRead)
118  EOFReached = true;
119 }
120 
121 MemoryObject *getNonStreamedMemoryObject(const unsigned char *Start,
122  const unsigned char *End) {
123  return new RawMemoryObject(Start, End);
124 }
125 
127  std::unique_ptr<DataStreamer> Streamer)
128  : Bytes(kChunkSize), Streamer(std::move(Streamer)), BytesRead(0),
129  BytesSkipped(0), ObjectSize(0), EOFReached(false) {
130  BytesRead = this->Streamer->GetBytes(&Bytes[0], kChunkSize);
131 }
132 }
bool isValidAddress(uint64_t address) const override
Returns true if the address is within the object (i.e.
uint64_t getExtent() const override
Returns the size of the region in bytes.
Interface to data which might be streamed.
Definition: MemoryObject.h:28
uint64_t readBytes(uint8_t *Buf, uint64_t Size, uint64_t Address) const override
Tries to read a contiguous range of bytes from the region, up to the end of the region.
#define false
Definition: ConvertUTF.c:65
void setKnownObjectSize(size_t size)
If the data object size is known in advance, many of the operations can be made more efficient...
void size_t size
StreamingMemoryObject(std::unique_ptr< DataStreamer > Streamer)
bool dropLeadingBytes(size_t s)
Drop s bytes from the front of the stream, pushing the positions of the remaining bytes down by s...
MemoryObject * getNonStreamedMemoryObject(const unsigned char *Start, const unsigned char *End)