Misc cleanups to the FileSytem api.

The main difference is the removal of

std::error_code exists(const Twine &path, bool &result);

It was an horribly redundant interface since a file not existing is also a valid
error_code. Now we have an access function that returns just an error_code. This
is the only function that has to be implemented for Unix and Windows. The
functions can_write, exists and can_execute an now just wrappers.

One still has to be very careful using these function to avoid introducing
race conditions (Time of check to time of use).

llvm-svn: 217625

1 files changed, 23 insertions, 26 deletions

diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 2e0519b..634d404 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -321,38 +321,35 @@ std::error_code resize_file(const Twine &path, uint64_t size) {
   return std::error_code();
 }
 
-std::error_code exists(const Twine &path, bool &result) {
-  SmallString<128> path_storage;
-  StringRef p = path.toNullTerminatedStringRef(path_storage);
-
-  if (::access(p.begin(), F_OK) == -1) {
-    if (errno != ENOENT)
-      return std::error_code(errno, std::generic_category());
-    result = false;
-  } else
-    result = true;
-
-  return std::error_code();
+static int convertAccessMode(AccessMode Mode) {
+  switch (Mode) {
+  case AccessMode::Exist:
+    return F_OK;
+  case AccessMode::Write:
+    return W_OK;
+  case AccessMode::Execute:
+    return R_OK | X_OK; // scripts also need R_OK.
+  }
+  llvm_unreachable("invalid enum");
 }
 
-bool can_write(const Twine &Path) {
+std::error_code access(const Twine &Path, AccessMode Mode) {
   SmallString<128> PathStorage;
   StringRef P = Path.toNullTerminatedStringRef(PathStorage);
-  return 0 == access(P.begin(), W_OK);
-}
 
-bool can_execute(const Twine &Path) {
-  SmallString<128> PathStorage;
-  StringRef P = Path.toNullTerminatedStringRef(PathStorage);
+  if (::access(P.begin(), convertAccessMode(Mode)) == -1)
+    return std::error_code(errno, std::generic_category());
 
-  if (0 != access(P.begin(), R_OK | X_OK))
-    return false;
-  struct stat buf;
-  if (0 != stat(P.begin(), &buf))
-    return false;
-  if (!S_ISREG(buf.st_mode))
-    return false;
-  return true;
+  if (Mode == AccessMode::Execute) {
+    // Don't say that directories are executable.
+    struct stat buf;
+    if (0 != stat(P.begin(), &buf))
+      return errc::permission_denied;
+    if (!S_ISREG(buf.st_mode))
+      return errc::permission_denied;
+  }
+
+  return std::error_code();
 }
 
 bool equivalent(file_status A, file_status B) {