Add llvm::sys::fs::real_path.

LLVM already has real_path like functionality, but it is
cumbersome to use and involves clean up after (e.g. you have
to call openFileForRead, then close the resulting FD).

Furthermore, on Windows it doesn't work for directories since
opening a directory and opening a file require slightly
different flags.

So I add a simple function `real_path` which works for all
paths on all platforms and has a simple to use interface.

In doing so, I add the ability to opt in to resolving tilde
expressions (e.g. ~/foo), which are normally handled by
the shell.

Differential Revision: https://reviews.llvm.org/D30668

llvm-svn: 297483

1 files changed, 63 insertions, 1 deletions

diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 43549c0f564..cdc692b8f1f 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -48,6 +48,8 @@
 # endif
 #endif
 
+#include <pwd.h>
+
 #ifdef __APPLE__
 #include <mach-o/dyld.h>
 #include <sys/attr.h>
@@ -478,6 +480,45 @@ std::error_code equivalent(const Twine &A, const Twine &B, bool &result) {
   return std::error_code();
 }
 
+static void expandTildeExpr(SmallVectorImpl<char> &Path) {
+  StringRef PathStr(Path.begin(), Path.size());
+  if (PathStr.empty() || !PathStr.startswith("~"))
+    return;
+
+  PathStr = PathStr.drop_front();
+  StringRef Expr = PathStr.take_until(path::is_separator);
+  StringRef Remainder = PathStr.substr(Expr.size() + 1);
+  SmallString<128> Storage;
+  if (Expr.empty()) {
+    // This is just ~/..., resolve it to the current user's home dir.
+    if (!path::home_directory(Storage)) {
+      // For some reason we couldn't get the home directory.  Just exit.
+      return;
+    }
+
+    // Overwrite the first character and insert the rest.
+    Path[0] = Storage[0];
+    Path.insert(Path.begin() + 1, Storage.begin() + 1, Storage.end());
+    return;
+  }
+
+  // This is a string of the form ~username/, look up this user's entry in the
+  // password database.
+  struct passwd *Entry = nullptr;
+  std::string User = Expr.str();
+  Entry = ::getpwnam(User.c_str());
+
+  if (!Entry) {
+    // Unable to look up the entry, just return back the original path.
+    return;
+  }
+
+  Storage = Remainder;
+  Path.clear();
+  Path.append(Entry->pw_dir, Entry->pw_dir + strlen(Entry->pw_dir));
+  llvm::sys::path::append(Path, Storage);
+}
+
 static std::error_code fillStatus(int StatRet, const struct stat &Status,
                              file_status &Result) {
   if (StatRet != 0) {
@@ -839,6 +880,28 @@ std::error_code remove_directories(const Twine &path, bool IgnoreErrors) {
   return std::error_code();
 }
 
+std::error_code real_path(const Twine &path, SmallVectorImpl<char> &dest,
+                          bool expand_tilde) {
+  dest.clear();
+  if (path.isTriviallyEmpty())
+    return std::error_code();
+
+  if (expand_tilde) {
+    SmallString<128> Storage;
+    path.toVector(Storage);
+    expandTildeExpr(Storage);
+    return real_path(Storage, dest, false);
+  }
+
+  int fd;
+  std::error_code EC = openFileForRead(path, fd, &dest);
+
+  if (EC)
+    return EC;
+  ::close(fd);
+  return std::error_code();
+}
+
 } // end namespace fs
 
 namespace path {
@@ -849,7 +912,6 @@ bool home_directory(SmallVectorImpl<char> &result) {
     result.append(RequestedDir, RequestedDir + strlen(RequestedDir));
     return true;
   }
-
   return false;
 }