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diff --git a/include/llvm/Support/BinaryStream.h b/include/llvm/Support/BinaryStream.h
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+++ b/include/llvm/Support/BinaryStream.h
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+//===- 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_BINARYSTREAM_H
+#define LLVM_SUPPORT_BINARYSTREAM_H
+
+#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 {
+public:
+  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;
+
+protected:
+  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 {
+public:
+  ~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
+
+#endif // LLVM_SUPPORT_BINARYSTREAM_H