Refactor Subzero initialization and add a browser callback handler.

src/IceBrowserCompileServer.h

+//===- subzero/src/IceBrowserCompileServer.h - Compile server ---*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the compile server. Given a compiler implementation,
+// it dispatches compile requests to the implementation. Each request is paired
+// with an abstraction of the input and output streams, which the compiler
+// will acquire.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICEBROWSERCOMPILESERVER_H
+#define SUBZERO_SRC_ICEBROWSERCOMPILESERVER_H
+
+#include <thread>
+
+#include "IceCompileServer.h"
+#include "IceDefs.h"
+
+namespace llvm {
+class DataStreamer;
+class QueueStreamer;
+class raw_fd_ostream;
+};
+
+namespace Ice {
+
+// Browser variant of the compile server.
+class BrowserCompileServer : public CompileServer {
+  BrowserCompileServer() = delete;
+  BrowserCompileServer(const BrowserCompileServer &) = delete;
+  BrowserCompileServer &operator=(const BrowserCompileServer &) = delete;
+
+public:
+  BrowserCompileServer(Compiler &Comp)
+      : CompileServer(Comp), OutputFD(-1), InputStream(nullptr), argc(-1),
+        argv(nullptr) {}
+
+  ~BrowserCompileServer() final;
+
+  void run() final;
+
+  std::unique_ptr<llvm::DataStreamer>
+  getInputStream(const IceString &InputFilename,
+                 std::string &ErrorString) final;
+
+  std::unique_ptr<llvm::raw_fd_ostream>
+  getOutputStream(const IceString &OutputFilename, std::error_code &EC) final;
+
+  void takeArgs(int argc_, char **argv_) {
+    argc = argc_;
+    argv = argv_;
+  }
+
+  // Call to push more bytes to the current input stream.
+  // Returns false on success and true on error.
+  bool pushInputBytes(unsigned char *Data, size_t NumBytes);
+
+  // Notify the input stream of EOF.
+  void endInputStream();
+
+  // Set the output file descriptor to use for the current compile
+  // request. Must be called before getOutputStream().
+  void setOutputFD(int fd) { OutputFD = fd; }
+
+  // Start the compile thread.
+  void startCompileThread();
+
+  // Wait for the compile thread to complete.
+  void waitForCompileThread() {
+    CompileThread.join();
+    InputStream = nullptr;
+  }
+
+private:
+  // This currently only handles a single compile request, hence one copy
+  // of the state.
+  int OutputFD;
+  // A borrowed reference to the current InputStream. The compiler owns
+  // the actual reference so the server must be careful not to access
+  // after the compiler is done.
+  llvm::QueueStreamer *InputStream;
+  std::thread CompileThread;
+  int argc;
+  char **argv;
+};
+
+} // end of namespace Ice
+
+#endif // SUBZERO_SRC_ICEBROWSERCOMPILESERVER_H