1//===- StreamRef.h - A copyable reference to a stream -----------*- 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_DEBUGINFO_CODEVIEW_STREAMREF_H
11#define LLVM_DEBUGINFO_CODEVIEW_STREAMREF_H
12
13#include "llvm/DebugInfo/CodeView/CodeViewError.h"
14#include "llvm/DebugInfo/CodeView/StreamInterface.h"
15
16namespace llvm {
17namespace codeview {
18
19class StreamRef {
20public:
21  StreamRef() : Stream(nullptr), ViewOffset(0), Length(0) {}
22  StreamRef(const StreamInterface &Stream)
23      : Stream(&Stream), ViewOffset(0), Length(Stream.getLength()) {}
24  StreamRef(const StreamInterface &Stream, uint32_t Offset, uint32_t Length)
25      : Stream(&Stream), ViewOffset(Offset), Length(Length) {}
26
27  // Use StreamRef.slice() instead.
28  StreamRef(const StreamRef &S, uint32_t Offset, uint32_t Length) = delete;
29
30  Error readBytes(uint32_t Offset, uint32_t Size,
31                  ArrayRef<uint8_t> &Buffer) const {
32    if (ViewOffset + Offset < Offset)
33      return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
34    if (Size + Offset > Length)
35      return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
36    return Stream->readBytes(ViewOffset + Offset, Size, Buffer);
37  }
38
39  // Given an offset into the stream, read as much as possible without copying
40  // any data.
41  Error readLongestContiguousChunk(uint32_t Offset,
42                                   ArrayRef<uint8_t> &Buffer) const {
43    if (Offset >= Length)
44      return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
45
46    if (auto EC = Stream->readLongestContiguousChunk(Offset, Buffer))
47      return EC;
48    // This StreamRef might refer to a smaller window over a larger stream.  In
49    // that case we will have read out more bytes than we should return, because
50    // we should not read past the end of the current view.
51    uint32_t MaxLength = Length - Offset;
52    if (Buffer.size() > MaxLength)
53      Buffer = Buffer.slice(0, MaxLength);
54    return Error::success();
55  }
56
57  Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) const {
58    if (Data.size() + Offset > Length)
59      return make_error<CodeViewError>(cv_error_code::insufficient_buffer);
60    return Stream->writeBytes(ViewOffset + Offset, Data);
61  }
62
63  uint32_t getLength() const { return Length; }
64
65  Error commit() const { return Stream->commit(); }
66
67  StreamRef drop_front(uint32_t N) const {
68    if (!Stream)
69      return StreamRef();
70
71    N = std::min(N, Length);
72    return StreamRef(*Stream, ViewOffset + N, Length - N);
73  }
74
75  StreamRef keep_front(uint32_t N) const {
76    if (!Stream)
77      return StreamRef();
78    N = std::min(N, Length);
79    return StreamRef(*Stream, ViewOffset, N);
80  }
81
82  StreamRef slice(uint32_t Offset, uint32_t Len) const {
83    return drop_front(Offset).keep_front(Len);
84  }
85
86  bool operator==(const StreamRef &Other) const {
87    if (Stream != Other.Stream)
88      return false;
89    if (ViewOffset != Other.ViewOffset)
90      return false;
91    if (Length != Other.Length)
92      return false;
93    return true;
94  }
95
96private:
97  const StreamInterface *Stream;
98  uint32_t ViewOffset;
99  uint32_t Length;
100};
101}
102}
103
104#endif // LLVM_DEBUGINFO_CODEVIEW_STREAMREF_H
105