diff --git a/llvm/lib/Support/BinaryStreamWriter.cpp b/llvm/lib/Support/BinaryStreamWriter.cpp
new file mode 100644
index 0000000..487bcdc
--- /dev/null
+++ b/llvm/lib/Support/BinaryStreamWriter.cpp
@@ -0,0 +1,59 @@
+//===- BinaryStreamWriter.cpp - Writes objects to a BinaryStream ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/BinaryStreamWriter.h"
+
+#include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/BinaryStreamRef.h"
+
+using namespace llvm;
+
+BinaryStreamWriter::BinaryStreamWriter(WritableBinaryStreamRef S)
+    : Stream(S), Offset(0) {}
+
+Error BinaryStreamWriter::writeBytes(ArrayRef<uint8_t> Buffer) {
+  if (auto EC = Stream.writeBytes(Offset, Buffer))
+    return EC;
+  Offset += Buffer.size();
+  return Error::success();
+}
+
+Error BinaryStreamWriter::writeCString(StringRef Str) {
+  if (auto EC = writeFixedString(Str))
+    return EC;
+  if (auto EC = writeObject('\0'))
+    return EC;
+
+  return Error::success();
+}
+
+Error BinaryStreamWriter::writeFixedString(StringRef Str) {
+  return writeBytes(ArrayRef<uint8_t>(Str.bytes_begin(), Str.bytes_end()));
+}
+
+Error BinaryStreamWriter::writeStreamRef(BinaryStreamRef Ref) {
+  return writeStreamRef(Ref, Ref.getLength());
+}
+
+Error BinaryStreamWriter::writeStreamRef(BinaryStreamRef Ref, uint32_t Length) {
+  BinaryStreamReader SrcReader(Ref.slice(0, Length));
+  // This is a bit tricky.  If we just call readBytes, we are requiring that it
+  // return us the entire stream as a contiguous buffer.  There is no guarantee
+  // this can be satisfied by returning a reference straight from the buffer, as
+  // an implementation may not store all data in a single contiguous buffer.  So
+  // we iterate over each contiguous chunk, writing each one in succession.
+  while (SrcReader.bytesRemaining() > 0) {
+    ArrayRef<uint8_t> Chunk;
+    if (auto EC = SrcReader.readLongestContiguousChunk(Chunk))
+      return EC;
+    if (auto EC = writeBytes(Chunk))
+      return EC;
+  }
+  return Error::success();
+}