Make VFS and FileManager match the current MemoryBuffer API.

This eliminates converting back and forth between the 3 formats and
gives us a more homogeneous interface.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220657 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 65 insertions, 100 deletions

diff --git a/lib/Basic/FileManager.cpp b/lib/Basic/FileManager.cpp
index 87844864a8..91681edcc5 100644
--- a/lib/Basic/FileManager.cpp
+++ b/lib/Basic/FileManager.cpp
@@ -399,12 +399,9 @@ void FileManager::FixupRelativePath(SmallVectorImpl<char> &path) const {
   path = NewPath;
 }
 
-std::unique_ptr<llvm::MemoryBuffer>
-FileManager::getBufferForFile(const FileEntry *Entry, std::string *ErrorStr,
-                              bool isVolatile, bool ShouldCloseOpenFile) {
-  std::unique_ptr<llvm::MemoryBuffer> Result;
-  std::error_code ec;
-
+llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+FileManager::getBufferForFile(const FileEntry *Entry, bool isVolatile,
+                              bool ShouldCloseOpenFile) {
   uint64_t FileSize = Entry->getSize();
   // If there's a high enough chance that the file have changed since we
   // got its size, force a stat before opening it.
@@ -414,10 +411,9 @@ FileManager::getBufferForFile(const FileEntry *Entry, std::string *ErrorStr,
   const char *Filename = Entry->getName();
   // If the file is already open, use the open file descriptor.
   if (Entry->File) {
-    ec = Entry->File->getBuffer(Filename, Result, FileSize,
-                                /*RequiresNullTerminator=*/true, isVolatile);
-    if (ErrorStr)
-      *ErrorStr = ec.message();
+    auto Result =
+        Entry->File->getBuffer(Filename, FileSize,
+                               /*RequiresNullTerminator=*/true, isVolatile);
     // FIXME: we need a set of APIs that can make guarantees about whether a
     // FileEntry is open or not.
     if (ShouldCloseOpenFile)
@@ -427,40 +423,24 @@ FileManager::getBufferForFile(const FileEntry *Entry, std::string *ErrorStr,
 
   // Otherwise, open the file.
 
-  if (FileSystemOpts.WorkingDir.empty()) {
-    ec = FS->getBufferForFile(Filename, Result, FileSize,
-                              /*RequiresNullTerminator=*/true, isVolatile);
-    if (ec && ErrorStr)
-      *ErrorStr = ec.message();
-    return Result;
-  }
+  if (FileSystemOpts.WorkingDir.empty())
+    return FS->getBufferForFile(Filename, FileSize,
+                                /*RequiresNullTerminator=*/true, isVolatile);
 
   SmallString<128> FilePath(Entry->getName());
   FixupRelativePath(FilePath);
-  ec = FS->getBufferForFile(FilePath.str(), Result, FileSize,
-                            /*RequiresNullTerminator=*/true, isVolatile);
-  if (ec && ErrorStr)
-    *ErrorStr = ec.message();
-  return Result;
+  return FS->getBufferForFile(FilePath.str(), FileSize,
+                              /*RequiresNullTerminator=*/true, isVolatile);
 }
 
-std::unique_ptr<llvm::MemoryBuffer>
-FileManager::getBufferForFile(StringRef Filename, std::string *ErrorStr) {
-  std::unique_ptr<llvm::MemoryBuffer> Result;
-  std::error_code ec;
-  if (FileSystemOpts.WorkingDir.empty()) {
-    ec = FS->getBufferForFile(Filename, Result);
-    if (ec && ErrorStr)
-      *ErrorStr = ec.message();
-    return Result;
-  }
+llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+FileManager::getBufferForFile(StringRef Filename) {
+  if (FileSystemOpts.WorkingDir.empty())
+    return FS->getBufferForFile(Filename);
 
   SmallString<128> FilePath(Filename);
   FixupRelativePath(FilePath);
-  ec = FS->getBufferForFile(FilePath.c_str(), Result);
-  if (ec && ErrorStr)
-    *ErrorStr = ec.message();
-  return Result;
+  return FS->getBufferForFile(FilePath.c_str());
 }
 
 /// getStatValue - Get the 'stat' information for the specified path,
diff --git a/lib/Basic/FileSystemStatCache.cpp b/lib/Basic/FileSystemStatCache.cpp
index 7515cfb440..83e42bdb84 100644
--- a/lib/Basic/FileSystemStatCache.cpp
+++ b/lib/Basic/FileSystemStatCache.cpp
@@ -78,21 +78,20 @@ bool FileSystemStatCache::get(const char *Path, FileData &Data, bool isFile,
     //
     // Because of this, check to see if the file exists with 'open'.  If the
     // open succeeds, use fstat to get the stat info.
-    std::unique_ptr<vfs::File> OwnedFile;
-    std::error_code EC = FS.openFileForRead(Path, OwnedFile);
+    auto OwnedFile = FS.openFileForRead(Path);
 
-    if (EC) {
+    if (!OwnedFile) {
       // If the open fails, our "stat" fails.
       R = CacheMissing;
     } else {
       // Otherwise, the open succeeded.  Do an fstat to get the information
       // about the file.  We'll end up returning the open file descriptor to the
       // client to do what they please with it.
-      llvm::ErrorOr<vfs::Status> Status = OwnedFile->status();
+      llvm::ErrorOr<vfs::Status> Status = (*OwnedFile)->status();
       if (Status) {
         R = CacheExists;
         copyStatusToFileData(*Status, Data);
-        *F = std::move(OwnedFile);
+        *F = std::move(*OwnedFile);
       } else {
         // fstat rarely fails.  If it does, claim the initial open didn't
         // succeed.
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 6450406453..6991783056 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -94,11 +94,9 @@ llvm::MemoryBuffer *ContentCache::getBuffer(DiagnosticsEngine &Diag,
     return Buffer.getPointer();
   }    
 
-  std::string ErrorStr;
   bool isVolatile = SM.userFilesAreVolatile() && !IsSystemFile;
-  Buffer.setPointer(SM.getFileManager()
-                        .getBufferForFile(ContentsEntry, &ErrorStr, isVolatile)
-                        .release());
+  auto BufferOrError =
+      SM.getFileManager().getBufferForFile(ContentsEntry, isVolatile);
 
   // If we were unable to open the file, then we are in an inconsistent
   // situation where the content cache referenced a file which no longer
@@ -110,7 +108,7 @@ llvm::MemoryBuffer *ContentCache::getBuffer(DiagnosticsEngine &Diag,
   // currently handle returning a null entry here. Ideally we should detect
   // that we are in an inconsistent situation and error out as quickly as
   // possible.
-  if (!Buffer.getPointer()) {
+  if (!BufferOrError) {
     StringRef FillStr("<<<MISSING SOURCE FILE>>>\n");
     Buffer.setPointer(MemoryBuffer::getNewMemBuffer(ContentsEntry->getSize(),
                                                     "<invalid>").release());
@@ -119,18 +117,21 @@ llvm::MemoryBuffer *ContentCache::getBuffer(DiagnosticsEngine &Diag,
       Ptr[i] = FillStr[i % FillStr.size()];
 
     if (Diag.isDiagnosticInFlight())
-      Diag.SetDelayedDiagnostic(diag::err_cannot_open_file, 
-                                ContentsEntry->getName(), ErrorStr);
-    else 
+      Diag.SetDelayedDiagnostic(diag::err_cannot_open_file,
+                                ContentsEntry->getName(),
+                                BufferOrError.getError().message());
+    else
       Diag.Report(Loc, diag::err_cannot_open_file)
-        << ContentsEntry->getName() << ErrorStr;
+          << ContentsEntry->getName() << BufferOrError.getError().message();
 
     Buffer.setInt(Buffer.getInt() | InvalidFlag);
     
     if (Invalid) *Invalid = true;
     return Buffer.getPointer();
   }
-  
+
+  Buffer.setPointer(BufferOrError->release());
+
   // Check that the file's size is the same as in the file entry (which may
   // have come from a stat cache).
   if (getRawBuffer()->getBufferSize() != (size_t)ContentsEntry->getSize()) {
diff --git a/lib/Basic/VirtualFileSystem.cpp b/lib/Basic/VirtualFileSystem.cpp
index df446bbcd5..8dc7006f2d 100644
--- a/lib/Basic/VirtualFileSystem.cpp
+++ b/lib/Basic/VirtualFileSystem.cpp
@@ -67,16 +67,14 @@ File::~File() {}
 
 FileSystem::~FileSystem() {}
 
-std::error_code FileSystem::getBufferForFile(
-    const llvm::Twine &Name, std::unique_ptr<MemoryBuffer> &Result,
-    int64_t FileSize, bool RequiresNullTerminator, bool IsVolatile) {
-  std::unique_ptr<File> F;
-  if (std::error_code EC = openFileForRead(Name, F))
-    return EC;
-
-  std::error_code EC =
-      F->getBuffer(Name, Result, FileSize, RequiresNullTerminator, IsVolatile);
-  return EC;
+ErrorOr<std::unique_ptr<MemoryBuffer>>
+FileSystem::getBufferForFile(const llvm::Twine &Name, int64_t FileSize,
+                             bool RequiresNullTerminator, bool IsVolatile) {
+  auto F = openFileForRead(Name);
+  if (!F)
+    return F.getError();
+
+  return (*F)->getBuffer(Name, FileSize, RequiresNullTerminator, IsVolatile);
 }
 
 //===-----------------------------------------------------------------------===/
@@ -96,11 +94,10 @@ class RealFile : public File {
 public:
   ~RealFile();
   ErrorOr<Status> status() override;
-  std::error_code getBuffer(const Twine &Name,
-                            std::unique_ptr<MemoryBuffer> &Result,
-                            int64_t FileSize = -1,
-                            bool RequiresNullTerminator = true,
-                            bool IsVolatile = false) override;
+  ErrorOr<std::unique_ptr<MemoryBuffer>>
+  getBuffer(const Twine &Name, int64_t FileSize = -1,
+            bool RequiresNullTerminator = true,
+            bool IsVolatile = false) override;
   std::error_code close() override;
   void setName(StringRef Name) override;
 };
@@ -120,19 +117,12 @@ ErrorOr<Status> RealFile::status() {
   return S;
 }
 
-std::error_code RealFile::getBuffer(const Twine &Name,
-                                    std::unique_ptr<MemoryBuffer> &Result,
-                                    int64_t FileSize,
-                                    bool RequiresNullTerminator,
-                                    bool IsVolatile) {
+ErrorOr<std::unique_ptr<MemoryBuffer>>
+RealFile::getBuffer(const Twine &Name, int64_t FileSize,
+                    bool RequiresNullTerminator, bool IsVolatile) {
   assert(FD != -1 && "cannot get buffer for closed file");
-  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
-      MemoryBuffer::getOpenFile(FD, Name.str().c_str(), FileSize,
-                                RequiresNullTerminator, IsVolatile);
-  if (std::error_code EC = BufferOrErr.getError())
-    return EC;
-  Result = std::move(BufferOrErr.get());
-  return std::error_code();
+  return MemoryBuffer::getOpenFile(FD, Name, FileSize, RequiresNullTerminator,
+                                   IsVolatile);
 }
 
 // FIXME: This is terrible, we need this for ::close.
@@ -161,8 +151,7 @@ namespace {
 class RealFileSystem : public FileSystem {
 public:
   ErrorOr<Status> status(const Twine &Path) override;
-  std::error_code openFileForRead(const Twine &Path,
-                                  std::unique_ptr<File> &Result) override;
+  ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
 };
 } // end anonymous namespace
@@ -176,14 +165,14 @@ ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
   return Result;
 }
 
-std::error_code RealFileSystem::openFileForRead(const Twine &Name,
-                                                std::unique_ptr<File> &Result) {
+ErrorOr<std::unique_ptr<File>>
+RealFileSystem::openFileForRead(const Twine &Name) {
   int FD;
   if (std::error_code EC = sys::fs::openFileForRead(Name, FD))
     return EC;
-  Result.reset(new RealFile(FD));
+  std::unique_ptr<File> Result(new RealFile(FD));
   Result->setName(Name.str());
-  return std::error_code();
+  return std::move(Result);
 }
 
 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
@@ -252,14 +241,13 @@ ErrorOr<Status> OverlayFileSystem::status(const Twine &Path) {
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
 
-std::error_code
-OverlayFileSystem::openFileForRead(const llvm::Twine &Path,
-                                   std::unique_ptr<File> &Result) {
+ErrorOr<std::unique_ptr<File>>
+OverlayFileSystem::openFileForRead(const llvm::Twine &Path) {
   // FIXME: handle symlinks that cross file systems
   for (iterator I = overlays_begin(), E = overlays_end(); I != E; ++I) {
-    std::error_code EC = (*I)->openFileForRead(Path, Result);
-    if (!EC || EC != llvm::errc::no_such_file_or_directory)
-      return EC;
+    auto Result = (*I)->openFileForRead(Path);
+    if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
+      return Result;
   }
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
@@ -520,8 +508,7 @@ public:
                              IntrusiveRefCntPtr<FileSystem> ExternalFS);
 
   ErrorOr<Status> status(const Twine &Path) override;
-  std::error_code openFileForRead(const Twine &Path,
-                                  std::unique_ptr<File> &Result) override;
+  ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
 
   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override{
     ErrorOr<Entry *> E = lookupPath(Dir);
@@ -969,9 +956,7 @@ ErrorOr<Status> VFSFromYAML::status(const Twine &Path) {
   return status(Path, *Result);
 }
 
-std::error_code
-VFSFromYAML::openFileForRead(const Twine &Path,
-                             std::unique_ptr<vfs::File> &Result) {
+ErrorOr<std::unique_ptr<File>> VFSFromYAML::openFileForRead(const Twine &Path) {
   ErrorOr<Entry *> E = lookupPath(Path);
   if (!E)
     return E.getError();
@@ -980,14 +965,14 @@ VFSFromYAML::openFileForRead(const Twine &Path,
   if (!F) // FIXME: errc::not_a_file?
     return make_error_code(llvm::errc::invalid_argument);
 
-  if (std::error_code EC =
-          ExternalFS->openFileForRead(F->getExternalContentsPath(), Result))
-    return EC;
+  auto Result = ExternalFS->openFileForRead(F->getExternalContentsPath());
+  if (!Result)
+    return Result;
 
   if (!F->useExternalName(UseExternalNames))
-    Result->setName(Path.str());
+    (*Result)->setName(Path.str());
 
-  return std::error_code();
+  return Result;
 }
 
 IntrusiveRefCntPtr<FileSystem>