llvm.org GIT mirror llvm / release_50 include / llvm / Support / BinaryStream.h

Tree @release_50 (Download .tar.gz)

BinaryStream.h @release_50raw · history · blame

//===- BinaryStream.h - Base interface for a stream of data -----*- C++ -*-===//
//                     The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.


#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/BinaryStreamError.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Error.h"
#include <cstdint>

namespace llvm {

/// \brief An interface for accessing data in a stream-like format, but which
/// discourages copying.  Instead of specifying a buffer in which to copy
/// data on a read, the API returns an ArrayRef to data owned by the stream's
/// implementation.  Since implementations may not necessarily store data in a
/// single contiguous buffer (or even in memory at all), in such cases a it may
/// be necessary for an implementation to cache such a buffer so that it can
/// return it.
class BinaryStream {
  virtual ~BinaryStream() = default;

  virtual llvm::support::endianness getEndian() const = 0;

  /// \brief Given an offset into the stream and a number of bytes, attempt to
  /// read the bytes and set the output ArrayRef to point to data owned by the
  /// stream.
  virtual Error readBytes(uint32_t Offset, uint32_t Size,
                          ArrayRef<uint8_t> &Buffer) = 0;

  /// \brief Given an offset into the stream, read as much as possible without
  /// copying any data.
  virtual Error readLongestContiguousChunk(uint32_t Offset,
                                           ArrayRef<uint8_t> &Buffer) = 0;

  /// \brief Return the number of bytes of data in this stream.
  virtual uint32_t getLength() = 0;

  Error checkOffset(uint32_t Offset, uint32_t DataSize) {
    if (Offset > getLength())
      return make_error<BinaryStreamError>(stream_error_code::invalid_offset);
    if (getLength() < DataSize + Offset)
      return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
    return Error::success();

/// \brief A BinaryStream which can be read from as well as written to.  Note
/// that writing to a BinaryStream always necessitates copying from the input
/// buffer to the stream's backing store.  Streams are assumed to be buffered
/// so that to be portable it is necessary to call commit() on the stream when
/// all data has been written.
class WritableBinaryStream : public BinaryStream {
  ~WritableBinaryStream() override = default;

  /// \brief Attempt to write the given bytes into the stream at the desired
  /// offset. This will always necessitate a copy.  Cannot shrink or grow the
  /// stream, only writes into existing allocated space.
  virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0;

  /// \brief For buffered streams, commits changes to the backing store.
  virtual Error commit() = 0;

} // end namespace llvm