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>
14 using namespace llvm;
15
16 namespace {
17
18 class RawMemoryObject : public MemoryObject {
19 public:
RawMemoryObject(const unsigned char * Start,const unsigned char * End)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
getExtent() const25 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;
isValidAddress(uint64_t address) const31 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
validAddress(uint64_t address) const41 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
readBytes(uint8_t * Buf,uint64_t Size,uint64_t Address) const49 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
getPointer(uint64_t address,uint64_t size) const65 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.
isValidAddress(uint64_t address) const74 bool StreamingMemoryObject::isValidAddress(uint64_t address) const {
75 if (ObjectSize && address < ObjectSize) return true;
76 return fetchToPos(address);
77 }
78
getExtent() const79 uint64_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
readBytes(uint8_t * Buf,uint64_t Size,uint64_t Address) const87 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
getPointer(uint64_t Address,uint64_t Size) const107 const uint8_t *StreamingMemoryObject::getPointer(uint64_t Address,
108 uint64_t Size) const {
109 fetchToPos(Address + Size - 1);
110 return &Bytes[Address + BytesSkipped];
111 }
112
dropLeadingBytes(size_t s)113 bool StreamingMemoryObject::dropLeadingBytes(size_t s) {
114 if (BytesRead < s) return true;
115 BytesSkipped = s;
116 BytesRead -= s;
117 return false;
118 }
119
setKnownObjectSize(size_t size)120 void StreamingMemoryObject::setKnownObjectSize(size_t size) {
121 ObjectSize = size;
122 Bytes.reserve(size);
123 if (ObjectSize <= BytesRead)
124 EOFReached = true;
125 }
126
getNonStreamedMemoryObject(const unsigned char * Start,const unsigned char * End)127 MemoryObject *getNonStreamedMemoryObject(const unsigned char *Start,
128 const unsigned char *End) {
129 return new RawMemoryObject(Start, End);
130 }
131
StreamingMemoryObject(std::unique_ptr<DataStreamer> Streamer)132 StreamingMemoryObject::StreamingMemoryObject(
133 std::unique_ptr<DataStreamer> Streamer)
134 : Bytes(kChunkSize), Streamer(std::move(Streamer)), BytesRead(0),
135 BytesSkipped(0), ObjectSize(0), EOFReached(false) {
136 BytesRead = this->Streamer->GetBytes(&Bytes[0], kChunkSize);
137 }
138 }
139