Introduce a PCHContainerOperations interface (NFC).

A PCHContainerOperations abstract interface provides operations for
creating and unwrapping containers for serialized ASTs (precompiled
headers and clang modules). The default implementation is
RawPCHContainerOperations, which uses a flat file for the output.

The main application for this interface will be an
ObjectFilePCHContainerOperations implementation that uses LLVM to
wrap the module in an ELF/Mach-O/COFF container to store debug info
alongside the AST.

rdar://problem/20091852

llvm-svn: 240225

clang/lib/Frontend/PCHContainerOperations.cpp

@@ -0,0 +1,70 @@
+//===--- Frontend/PCHContainerOperations.cpp - PCH Containers ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines PCHContainerOperations and RawPCHContainerOperation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/PCHContainerOperations.h"
+#include "clang/AST/ASTConsumer.h"
+#include "llvm/Bitcode/BitstreamReader.h"
+#include "llvm/Support/raw_ostream.h"
+#include "clang/Lex/ModuleLoader.h"
+using namespace clang;
+
+PCHContainerOperations::~PCHContainerOperations() {}
+
+namespace {
+
+/// \brief A PCHContainerGenerator that writes out the PCH to a flat file.
+class PCHContainerGenerator : public ASTConsumer {
+  std::shared_ptr<PCHBuffer> Buffer;
+  raw_pwrite_stream *OS;
+
+public:
+  PCHContainerGenerator(DiagnosticsEngine &Diags,
+                        const HeaderSearchOptions &HSO,
+                        const PreprocessorOptions &PPO, const TargetOptions &TO,
+                        const LangOptions &LO, const std::string &MainFileName,
+                        const std::string &OutputFileName,
+                        llvm::raw_pwrite_stream *OS,
+                        std::shared_ptr<PCHBuffer> Buffer)
+      : Buffer(Buffer), OS(OS) {}
+
+  virtual ~PCHContainerGenerator() {}
+
+  void HandleTranslationUnit(ASTContext &Ctx) override {
+    if (Buffer->IsComplete) {
+      // Make sure it hits disk now.
+      *OS << Buffer->Data;
+      OS->flush();
+    }
+    // Free the space of the temporary buffer.
+    llvm::SmallVector<char, 0> Empty;
+    Buffer->Data = std::move(Empty);
+  }
+};
+}
+
+std::unique_ptr<ASTConsumer>
+RawPCHContainerOperations::CreatePCHContainerGenerator(
+    DiagnosticsEngine &Diags, const HeaderSearchOptions &HSO,
+    const PreprocessorOptions &PPO, const TargetOptions &TO,
+    const LangOptions &LO, const std::string &MainFileName,
+    const std::string &OutputFileName, llvm::raw_pwrite_stream *OS,
+    std::shared_ptr<PCHBuffer> Buffer) const {
+  return llvm::make_unique<PCHContainerGenerator>(
+      Diags, HSO, PPO, TO, LO, MainFileName, OutputFileName, OS, Buffer);
+}
+
+void RawPCHContainerOperations::ExtractPCH(
+    llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
+  StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
+                  (const unsigned char *)Buffer.getBufferEnd());
+}