Enable streaming of bitcode

This CL delays reading of function bodies from initial parse until
materialization, allowing overlap of compilation with bitcode download.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149918 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/DataStream.h

@@ -0,0 +1,38 @@
+//===---- llvm/Support/DataStream.h - Lazy bitcode streaming -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines DataStreamer, which fetches bytes of data from
+// a stream source. It provides support for streaming (lazy reading) of
+// data, e.g. bitcode
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef LLVM_SUPPORT_DATASTREAM_H_
+#define LLVM_SUPPORT_DATASTREAM_H_
+
+#include <string>
+
+namespace llvm {
+
+class DataStreamer {
+public:
+  /// Fetch bytes [start-end) from the stream, and write them to the
+  /// buffer pointed to by buf. Returns the number of bytes actually written.
+  virtual size_t GetBytes(unsigned char *buf, size_t len) = 0;
+
+  virtual ~DataStreamer();
+};
+
+DataStreamer *getDataFileStreamer(const std::string &Filename,
+                                  std::string *Err);
+
+}
+
+#endif  // LLVM_SUPPORT_DATASTREAM_H_