LLVM  6.0.0svn
BinaryStream.h
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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"
15 #include "llvm/Support/Endian.h"
16 #include "llvm/Support/Error.h"
17 #include <cstdint>
18 
19 namespace llvm {
20 
21 /// \brief An interface for accessing data in a stream-like format, but which
22 /// discourages copying. Instead of specifying a buffer in which to copy
23 /// data on a read, the API returns an ArrayRef to data owned by the stream's
24 /// implementation. Since implementations may not necessarily store data in a
25 /// single contiguous buffer (or even in memory at all), in such cases a it may
26 /// be necessary for an implementation to cache such a buffer so that it can
27 /// return it.
28 class BinaryStream {
29 public:
30  virtual ~BinaryStream() = default;
31 
32  virtual llvm::support::endianness getEndian() const = 0;
33 
34  /// \brief Given an offset into the stream and a number of bytes, attempt to
35  /// read the bytes and set the output ArrayRef to point to data owned by the
36  /// stream.
38  ArrayRef<uint8_t> &Buffer) = 0;
39 
40  /// \brief Given an offset into the stream, read as much as possible without
41  /// copying any data.
43  ArrayRef<uint8_t> &Buffer) = 0;
44 
45  /// \brief Return the number of bytes of data in this stream.
46  virtual uint32_t getLength() = 0;
47 
48 protected:
49  Error checkOffset(uint32_t Offset, uint32_t DataSize) {
50  if (Offset > getLength())
51  return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
52  if (getLength() < DataSize + Offset)
53  return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
54  return Error::success();
55  }
56 };
57 
58 /// \brief A BinaryStream which can be read from as well as written to. Note
59 /// that writing to a BinaryStream always necessitates copying from the input
60 /// buffer to the stream's backing store. Streams are assumed to be buffered
61 /// so that to be portable it is necessary to call commit() on the stream when
62 /// all data has been written.
64 public:
65  ~WritableBinaryStream() override = default;
66 
67  /// \brief Attempt to write the given bytes into the stream at the desired
68  /// offset. This will always necessitate a copy. Cannot shrink or grow the
69  /// stream, only writes into existing allocated space.
70  virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0;
71 
72  /// \brief For buffered streams, commits changes to the backing store.
73  virtual Error commit() = 0;
74 };
75 
76 } // end namespace llvm
77 
78 #endif // LLVM_SUPPORT_BINARYSTREAM_H
Error checkOffset(uint32_t Offset, uint32_t DataSize)
Definition: BinaryStream.h:49
Compute iterated dominance frontiers using a linear time algorithm.
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...
virtual ~BinaryStream()=default
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:28
static ErrorSuccess success()
Create a success value.
Definition: Error.h:313
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
Lightweight error class with error context and mandatory checking.
Definition: Error.h:156
A BinaryStream which can be read from as well as written to.
Definition: BinaryStream.h:63