r201635 - Add an OverlayFileSystem class

[Ben Langmuir]

On Feb 19, 2014, at 2:03 AM, Dmitri Gribenko <gribozavr at gmail.com> wrote:

> On Wed, Feb 19, 2014 at 3:29 AM, Ben Langmuir <blangmuir at apple.com> wrote:
>> Author: benlangmuir
>> Date: Tue Feb 18 21:29:17 2014
>> New Revision: 201635
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=201635&view=rev
>> Log:
>> Add an OverlayFileSystem class
>> 
>> Provides a way to merge multiple vfs::FileSystem objects into a single
>> filesystem.
>> 
>> Added:
>>    cfe/trunk/unittests/Basic/VirtualFileSystemTest.cpp
>> Modified:
>>    cfe/trunk/include/clang/Basic/VirtualFileSystem.h
>>    cfe/trunk/lib/Basic/VirtualFileSystem.cpp
>>    cfe/trunk/unittests/Basic/CMakeLists.txt
>> 
>> Modified: cfe/trunk/include/clang/Basic/VirtualFileSystem.h
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/VirtualFileSystem.h?rev=201635&r1=201634&r2=201635&view=diff
>> ==============================================================================
>> --- cfe/trunk/include/clang/Basic/VirtualFileSystem.h (original)
>> +++ cfe/trunk/include/clang/Basic/VirtualFileSystem.h Tue Feb 18 21:29:17 2014
>> @@ -122,6 +122,42 @@ public:
>> /// the operating system.
>> llvm::IntrusiveRefCntPtr<FileSystem> getRealFileSystem();
>> 
>> +/// \brief A file system that allows overlaying one \p AbstractFileSystem on top
>> +/// of another.
>> +///
>> +/// Consists of a stack of >=1 \p FileSytem objects, which are treated as being
>> +/// one merged file system. When there is a directory that exists in more than
>> +/// one file system, the \p OverlayFileSystem contains a directory containing
>> +/// the union of their contents.  The attributes (permissions, etc.) of the
>> +/// top-most (most recently added) directory are used.  When there is a file
>> +/// that exists in more than one file system, the file in the top-most file
>> +/// system overrides the other(s).
>> +class OverlayFileSystem : public FileSystem {
>> +  typedef llvm::SmallVector<llvm::IntrusiveRefCntPtr<FileSystem>, 1>
>> +    FileSystemList;
>> +  typedef FileSystemList::reverse_iterator iterator;
>> +
>> +  /// \brief The stack of file systems, implemented as a list in order of
>> +  /// their addition.
>> +  FileSystemList FSList;
>> +
>> +  /// \brief Get an iterator pointing to the most recently added file system.
>> +  iterator overlays_begin() { return FSList.rbegin(); }
>> +
>> +  /// \brief Get an iterator pointing one-past the least recently added file
>> +  /// system.
>> +  iterator overlays_end() { return FSList.rend(); }
>> +
>> +public:
>> +  OverlayFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> Base);
>> +  /// \brief Pushes a file system on top of the stack.
>> +  void pushOverlay(llvm::IntrusiveRefCntPtr<FileSystem> FS);
>> +
>> +  llvm::ErrorOr<Status> status(const llvm::Twine &Path) LLVM_OVERRIDE;
>> +  llvm::error_code openFileForRead(const llvm::Twine &Path,
>> +                                   llvm::OwningPtr<File> &Result) LLVM_OVERRIDE;
> 
> You can drop qualifiers on SmallVector, OwningPtr, Twine and
> IntrusiveRefCntPtr if you #include "clang/Basic/LLVM.h”.

I have a patch to do exactly that :)  I should get that in this morning.

> 
>> +TEST(VirtualFileSystemTest, status_queries) {
> 
> We usually name gtest test cases in camel case as well.

Will do.  Thanks,

Ben

> 
> Dmitri
> 
> -- 
> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/