[clang] Split ObjectFilePCHContainerReader from ObjectFilePCHContainerWriter (#99599)

Close https://github.com/llvm/llvm-project/issues/99479

See https://github.com/llvm/llvm-project/issues/99479 for details

1 files changed, 56 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ObjectFilePCHContainerReader.cpp b/clang/lib/Serialization/ObjectFilePCHContainerReader.cpp
new file mode 100644
index 0000000..59fc469
--- /dev/null
+++ b/clang/lib/Serialization/ObjectFilePCHContainerReader.cpp
@@ -0,0 +1,56 @@
+//===--- ObjectFilePCHContainerReader.cpp ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Serialization/ObjectFilePCHContainerReader.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/Object/ObjectFile.h"
+
+using namespace clang;
+
+ArrayRef<StringRef> ObjectFilePCHContainerReader::getFormats() const {
+  static StringRef Formats[] = {"obj", "raw"};
+  return Formats;
+}
+
+StringRef
+ObjectFilePCHContainerReader::ExtractPCH(llvm::MemoryBufferRef Buffer) const {
+  StringRef PCH;
+  auto OFOrErr = llvm::object::ObjectFile::createObjectFile(Buffer);
+  if (OFOrErr) {
+    auto &OF = OFOrErr.get();
+    bool IsCOFF = isa<llvm::object::COFFObjectFile>(*OF);
+    // Find the clang AST section in the container.
+    for (auto &Section : OF->sections()) {
+      StringRef Name;
+      if (Expected<StringRef> NameOrErr = Section.getName())
+        Name = *NameOrErr;
+      else
+        consumeError(NameOrErr.takeError());
+
+      if ((!IsCOFF && Name == "__clangast") || (IsCOFF && Name == "clangast")) {
+        if (Expected<StringRef> E = Section.getContents())
+          return *E;
+        else {
+          handleAllErrors(E.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
+            EIB.log(llvm::errs());
+          });
+          return "";
+        }
+      }
+    }
+  }
+  handleAllErrors(OFOrErr.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
+    if (EIB.convertToErrorCode() ==
+        llvm::object::object_error::invalid_file_type)
+      // As a fallback, treat the buffer as a raw AST.
+      PCH = Buffer.getBuffer();
+    else
+      EIB.log(llvm::errs());
+  });
+  return PCH;
+}