Fix Build: folly/io/RecordIO.cpp under MSVC 2015u3

Summary: [Folly] Fix Build: `folly/io/RecordIO.cpp` under MSVC 2015u3, which inexplicably gives `error C2872: 'detail': ambiguous symbol`.

Reviewed By: Orvid

Differential Revision: D7875032

fbshipit-source-id: 2ff5a60c941e20ef9a05cedb2e7d8224a9e83ed2

folly/io/RecordIO-inl.h

@@ -59,7 +59,7 @@ inline auto RecordIOReader::seek(off_t pos) const -> Iterator {
 
 namespace recordio_helpers {
 
-namespace detail {
+namespace recordio_detail {
 
 FOLLY_PACK_PUSH
 struct Header {
@@ -82,9 +82,9 @@ FOLLY_PACK_POP
 static_assert(offsetof(Header, headerHash) + sizeof(Header::headerHash) ==
               sizeof(Header), "invalid header layout");
 
-} // namespace detail
+} // namespace recordio_detail
 
-constexpr size_t headerSize() { return sizeof(detail::Header); }
+constexpr size_t headerSize() { return sizeof(recordio_detail::Header); }
 
 inline RecordInfo findRecord(ByteRange range, uint32_t fileId) {
   return findRecord(range, range, fileId);

folly/io/RecordIO.cpp

@@ -106,7 +106,7 @@ void RecordIOReader::Iterator::advanceToValid() {
 
 namespace recordio_helpers {
 
-using namespace detail;
+using recordio_detail::Header;
 
 namespace {
 
@@ -160,10 +160,9 @@ size_t prependHeader(std::unique_ptr<IOBuf>& buf, uint32_t fileId) {
     b->appendChain(std::move(buf));
     buf = std::move(b);
   }
-  detail::Header* header =
-    reinterpret_cast<detail::Header*>(buf->writableData());
+  Header* header = reinterpret_cast<Header*>(buf->writableData());
   memset(header, 0, sizeof(Header));
-  header->magic = detail::Header::kMagic;
+  header->magic = Header::kMagic;
   header->fileId = fileId;
   header->dataLength = uint32_t(lengthAndHash.first);
   header->dataHash = lengthAndHash.second;

folly/io/test/RecordIOTest.cpp

@@ -168,7 +168,7 @@ TEST(RecordIOTest, ExtraMagic) {
   EXPECT_EQ(0, lseek(file.fd(), 0, SEEK_SET));
   EXPECT_EQ(sizeof(buf), read(file.fd(), buf, sizeof(buf)));
   // Append an extra magic
-  const uint32_t magic = recordio_helpers::detail::Header::kMagic;
+  const uint32_t magic = recordio_helpers::recordio_detail::Header::kMagic;
   EXPECT_EQ(sizeof(magic), write(file.fd(), &magic, sizeof(magic)));
   // and an extra record
   EXPECT_EQ(sizeof(buf), write(file.fd(), buf, sizeof(buf)));