1 //===- BinaryStream.h - Base interface for a stream of data -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLVM_SUPPORT_BINARYSTREAM_H
11 #define LLVM_SUPPORT_BINARYSTREAM_H
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/Support/BinaryStreamError.h"
15 #include "llvm/Support/Endian.h"
16 #include "llvm/Support/Error.h"
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
30 virtual ~BinaryStream() = default;
32 virtual llvm::support::endianness getEndian() const = 0;
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
37 virtual Error readBytes(uint32_t Offset, uint32_t Size,
38 ArrayRef<uint8_t> &Buffer) = 0;
40 /// \brief Given an offset into the stream, read as much as possible without
42 virtual Error readLongestContiguousChunk(uint32_t Offset,
43 ArrayRef<uint8_t> &Buffer) = 0;
45 /// \brief Return the number of bytes of data in this stream.
46 virtual uint32_t getLength() = 0;
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();
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.
63 class WritableBinaryStream : public BinaryStream {
65 ~WritableBinaryStream() override = default;
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;
72 /// \brief For buffered streams, commits changes to the backing store.
73 virtual Error commit() = 0;
76 } // end namespace llvm
78 #endif // LLVM_SUPPORT_BINARYSTREAM_H