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diff --git a/gnu/llvm/include/llvm/DebugInfo/CodeView/StreamInterface.h b/gnu/llvm/include/llvm/DebugInfo/CodeView/StreamInterface.h
new file mode 100644
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+++ b/gnu/llvm/include/llvm/DebugInfo/CodeView/StreamInterface.h
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+//===- StreamInterface.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_DEBUGINFO_CODEVIEW_STREAMINTERFACE_H
+#define LLVM_DEBUGINFO_CODEVIEW_STREAMINTERFACE_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/Error.h"
+#include <cstdint>
+
+namespace llvm {
+namespace codeview {
+
+/// StreamInterface abstracts the notion of a data stream.  This way, an
+/// implementation could implement trivial reading from a contiguous memory
+/// buffer or, as in the case of PDB files, reading from a set of possibly
+/// discontiguous blocks.  The implementation is required to return references
+/// to stable memory, so if this is not possible (for example in the case of
+/// a PDB file with discontiguous blocks, it must keep its own pool of temp
+/// storage.
+class StreamInterface {
+public:
+  virtual ~StreamInterface() {}
+
+  // Given an offset into the stream and a number of bytes, attempt to read
+  // the bytes and set the output ArrayRef to point to a reference into the
+  // stream, without copying any data.
+  virtual Error readBytes(uint32_t Offset, uint32_t Size,
+                          ArrayRef<uint8_t> &Buffer) const = 0;
+
+  // 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) const = 0;
+
+  // 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) const = 0;
+
+  virtual uint32_t getLength() const = 0;
+
+  virtual Error commit() const = 0;
+};
+
+} // end namespace codeview
+} // end namespace llvm
+
+#endif // LLVM_DEBUGINFO_CODEVIEW_STREAMINTERFACE_H