Subzero: Fix build problem against LLVM trunk.

pnacl-llvm/include/llvm/Support/StreamingMemoryObject.h

+//===- StreamingMemoryObject.h - Streamable data interface -----*- 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_STREAMINGMEMORYOBJECT_H
+#define LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
+
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DataStream.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MemoryObject.h"
+#include <memory>
+#include <vector>
+
+namespace llvm {
+
+/// Interface to data which is actually streamed from a DataStreamer. In
+/// addition to inherited members, it has the dropLeadingBytes and
+/// setKnownObjectSize methods which are not applicable to non-streamed objects.
+class StreamingMemoryObject : public MemoryObject {
+public:
+  StreamingMemoryObject(std::unique_ptr<DataStreamer> Streamer);
+  uint64_t getExtent() const override;
+  uint64_t readBytes(uint8_t *Buf, uint64_t Size,
+                     uint64_t Address) const override;
+  const uint8_t *getPointer(uint64_t Address, uint64_t Size) const override;
+  bool isValidAddress(uint64_t address) const override;
+
+  /// Drop s bytes from the front of the stream, pushing the positions of the
+  /// remaining bytes down by s. This is used to skip past the bitcode header,
+  /// since we don't know a priori if it's present, and we can't put bytes
+  /// back into the stream once we've read them.
+  bool dropLeadingBytes(size_t s);
+
+  /// If the data object size is known in advance, many of the operations can
+  /// be made more efficient, so this method should be called before reading
+  /// starts (although it can be called anytime).
+  void setKnownObjectSize(size_t size);
+
+  /// The number of bytes read at a time from the data streamer.
+  static const uint32_t kChunkSize = 4096 * 4;
+
+private:
+  mutable std::vector<unsigned char> Bytes;
+  std::unique_ptr<DataStreamer> Streamer;
+  mutable size_t BytesRead;   // Bytes read from stream
+  size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
+  mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
+  mutable bool EOFReached;
+
+  // Fetch enough bytes such that Pos can be read (i.e. BytesRead >
+  // Pos). Returns true if Pos can be read.  Unlike most of the
+  // functions in BitcodeReader, returns true on success.  Most of the
+  // requests will be small, but we fetch at kChunkSize bytes at a
+  // time to avoid making too many potentially expensive GetBytes
+  // calls.
+  bool fetchToPos(size_t Pos) const {
+    while (Pos >= BytesRead) {
+      if (EOFReached)
+        return false;
+      Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
+      size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
+                                        kChunkSize);
+      BytesRead += bytes;
+      if (bytes == 0) { // reached EOF/ran out of bytes
+        if (ObjectSize == 0)
+          ObjectSize = BytesRead;
+        EOFReached = true;
+      }
+    }
+    return !ObjectSize || Pos < ObjectSize;
+  }
+
+  StreamingMemoryObject(const StreamingMemoryObject&) = delete;
+  void operator=(const StreamingMemoryObject&) = delete;
+};
+
+MemoryObject *getNonStreamedMemoryObject(
+    const unsigned char *Start, const unsigned char *End);
+
+}
+#endif  // STREAMINGMEMORYOBJECT_H_