[Support] Extend sys::path with user_cache_directory function.

Summary:
The new function sys::path::user_cache_directory tries to discover
a directory suitable for cache storage for current system user.

On Windows and Darwin it returns a path to system-specific user cache directory.

On Linux it follows XDG Base Directory Specification, what is:
- use non-empty $XDG_CACHE_HOME env var,
- use $HOME/.cache.

Reviewers: chapuni, aaron.ballman, rafael

Subscribers: rafael, aaron.ballman, llvm-commits

Differential Revision: http://reviews.llvm.org/D13801

llvm-svn: 251784

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/include/llvm/Support/Path.h b/llvm/include/llvm/Support/Path.h
index 0853f916b58..1e56be4a5fc 100644
--- a/llvm/include/llvm/Support/Path.h
+++ b/llvm/include/llvm/Support/Path.h
@@ -325,6 +325,22 @@ void system_temp_directory(bool erasedOnReboot, SmallVectorImpl<char> &result);
 /// @result True if a home directory is set, false otherwise.
 bool home_directory(SmallVectorImpl<char> &result);
 
+/// @brief Get the user's cache directory.
+///
+/// Expect the resulting path to be a directory shared with other
+/// applications/services used by the user. Params \p Path1 to \p Path3 can be
+/// used to append additional directory names to the resulting path. Recommended
+/// pattern is <user_cache_directory>/<vendor>/<application>.
+///
+/// @param Result Holds the resulting path.
+/// @param Path1 Additional path to be appended to the user's cache directory
+/// path. "" can be used to append nothing.
+/// @param Path2 Second additional path to be appended.
+/// @param Path3 Third additional path to be appended.
+/// @result True if a cache directory path is set, false otherwise.
+bool user_cache_directory(SmallVectorImpl<char> &Result, const Twine &Path1,
+                          const Twine &Path2 = "", const Twine &Path3 = "");
+
 /// @brief Has root name?
 ///
 /// root_name != ""