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
10#include "llvm/Support/StreamingMemoryObject.h"
11#include <cassert>
12#include <cstddef>
13#include <cstring>
14using namespace llvm;
15
16namespace {
17
18class RawMemoryObject : public MemoryObject {
19public:
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
35private:
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
49uint64_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
65const uint8_t *RawMemoryObject::getPointer(uint64_t address,
66                                           uint64_t size) const {
67  return FirstChar + address;
68}
69} // anonymous namespace
70
71namespace 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.
74bool StreamingMemoryObject::isValidAddress(uint64_t address) const {
75  if (ObjectSize && address < ObjectSize) return true;
76  return fetchToPos(address);
77}
78
79uint64_t StreamingMemoryObject::getExtent() const {
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
87uint64_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
107bool StreamingMemoryObject::dropLeadingBytes(size_t s) {
108  if (BytesRead < s) return true;
109  BytesSkipped = s;
110  BytesRead -= s;
111  return false;
112}
113
114void StreamingMemoryObject::setKnownObjectSize(size_t size) {
115  ObjectSize = size;
116  Bytes.reserve(size);
117  if (ObjectSize <= BytesRead)
118    EOFReached = true;
119}
120
121MemoryObject *getNonStreamedMemoryObject(const unsigned char *Start,
122                                         const unsigned char *End) {
123  return new RawMemoryObject(Start, End);
124}
125
126StreamingMemoryObject::StreamingMemoryObject(
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}
133