LLVM  8.0.0svn
BinaryStream.h
Go to the documentation of this file.
1 //===- BinaryStream.h - Base interface for a stream of data -----*- 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_BINARYSTREAM_H
11 #define LLVM_SUPPORT_BINARYSTREAM_H
12 
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/ADT/BitmaskEnum.h"
16 #include "llvm/Support/Endian.h"
17 #include "llvm/Support/Error.h"
18 #include <cstdint>
19 
20 namespace llvm {
21 
23  BSF_None = 0,
24  BSF_Write = 1, // Stream supports writing.
25  BSF_Append = 2, // Writing can occur at offset == length.
26  LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append)
27 };
28 
29 /// An interface for accessing data in a stream-like format, but which
30 /// discourages copying. Instead of specifying a buffer in which to copy
31 /// data on a read, the API returns an ArrayRef to data owned by the stream's
32 /// implementation. Since implementations may not necessarily store data in a
33 /// single contiguous buffer (or even in memory at all), in such cases a it may
34 /// be necessary for an implementation to cache such a buffer so that it can
35 /// return it.
36 class BinaryStream {
37 public:
38  virtual ~BinaryStream() = default;
39 
40  virtual llvm::support::endianness getEndian() const = 0;
41 
42  /// Given an offset into the stream and a number of bytes, attempt to
43  /// read the bytes and set the output ArrayRef to point to data owned by the
44  /// stream.
46  ArrayRef<uint8_t> &Buffer) = 0;
47 
48  /// Given an offset into the stream, read as much as possible without
49  /// copying any data.
51  ArrayRef<uint8_t> &Buffer) = 0;
52 
53  /// Return the number of bytes of data in this stream.
54  virtual uint32_t getLength() = 0;
55 
56  /// Return the properties of this stream.
57  virtual BinaryStreamFlags getFlags() const { return BSF_None; }
58 
59 protected:
61  if (Offset > getLength())
62  return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
63  if (getLength() < DataSize + Offset)
64  return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
65  return Error::success();
66  }
67 };
68 
69 /// A BinaryStream which can be read from as well as written to. Note
70 /// that writing to a BinaryStream always necessitates copying from the input
71 /// buffer to the stream's backing store. Streams are assumed to be buffered
72 /// so that to be portable it is necessary to call commit() on the stream when
73 /// all data has been written.
75 public:
76  ~WritableBinaryStream() override = default;
77 
78  /// Attempt to write the given bytes into the stream at the desired
79  /// offset. This will always necessitate a copy. Cannot shrink or grow the
80  /// stream, only writes into existing allocated space.
81  virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0;
82 
83  /// For buffered streams, commits changes to the backing store.
84  virtual Error commit() = 0;
85 
86  /// Return the properties of this stream.
87  BinaryStreamFlags getFlags() const override { return BSF_Write; }
88 
89 protected:
91  if (!(getFlags() & BSF_Append))
92  return checkOffsetForRead(Offset, DataSize);
93 
94  if (Offset > getLength())
95  return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
96  return Error::success();
97  }
98 };
99 
100 } // end namespace llvm
101 
102 #endif // LLVM_SUPPORT_BINARYSTREAM_H
#define LLVM_MARK_AS_BITMASK_ENUM(LargestValue)
LLVM_MARK_AS_BITMASK_ENUM lets you opt in an individual enum type so you can perform bitwise operatio...
Definition: BitmaskEnum.h:42
This class represents lattice values for constants.
Definition: AllocatorList.h:24
virtual Error readBytes(uint32_t Offset, uint32_t Size, ArrayRef< uint8_t > &Buffer)=0
Given an offset into the stream and a number of bytes, attempt to read the bytes and set the output A...
Error checkOffsetForWrite(uint32_t Offset, uint32_t DataSize)
Definition: BinaryStream.h:90
virtual ~BinaryStream()=default
Error checkOffsetForRead(uint32_t Offset, uint32_t DataSize)
Definition: BinaryStream.h:60
virtual uint32_t getLength()=0
Return the number of bytes of data in this stream.
virtual llvm::support::endianness getEndian() const =0
virtual Error readLongestContiguousChunk(uint32_t Offset, ArrayRef< uint8_t > &Buffer)=0
Given an offset into the stream, read as much as possible without copying any data.
An interface for accessing data in a stream-like format, but which discourages copying.
Definition: BinaryStream.h:36
BinaryStreamFlags getFlags() const override
Return the properties of this stream.
Definition: BinaryStream.h:87
static ErrorSuccess success()
Create a success value.
Definition: Error.h:327
virtual BinaryStreamFlags getFlags() const
Return the properties of this stream.
Definition: BinaryStream.h:57
BinaryStreamFlags
Definition: BinaryStream.h:22
uint32_t Size
Definition: Profile.cpp:47
Lightweight error class with error context and mandatory checking.
Definition: Error.h:158
A BinaryStream which can be read from as well as written to.
Definition: BinaryStream.h:74