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

4 files changed, 43 insertions, 66 deletions

diff --git a/llvm/lib/Support/LockFileManager.cpp b/llvm/lib/Support/LockFileManager.cpp
index 8fc58017cb0..5b82c367c0a 100644
--- a/llvm/lib/Support/LockFileManager.cpp
+++ b/llvm/lib/Support/LockFileManager.cpp
@@ -204,8 +204,8 @@ LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
     // If the lock file is still expected to be there, check whether it still
     // is.
     if (!LockFileGone) {
-      bool Exists;
-      if (!sys::fs::exists(LockFileName.str(), Exists) && !Exists) {
+      if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
+          errc::no_such_file_or_directory) {
         LockFileGone = true;
         LockFileJustDisappeared = true;
       }
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index bdaa12820b8..ef75fc1cd83 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -210,13 +210,13 @@ retry_random_path:
   }
 
   case FS_Name: {
-    bool Exists;
-    std::error_code EC = sys::fs::exists(ResultPath.begin(), Exists);
+    std::error_code EC =
+        sys::fs::access(ResultPath.begin(), sys::fs::AccessMode::Exist);
+    if (EC == errc::no_such_file_or_directory)
+      return std::error_code();
     if (EC)
       return EC;
-    if (Exists)
-      goto retry_random_path;
-    return std::error_code();
+    goto retry_random_path;
   }
 
   case FS_Dir: {
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 2e0519b3ca6..634d4049d7d 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) {
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index bff82141b34..d90d408e661 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -251,49 +251,29 @@ std::error_code resize_file(const Twine &path, uint64_t size) {
   return std::error_code(error, std::generic_category());
 }
 
-std::error_code exists(const Twine &path, bool &result) {
-  SmallString<128> path_storage;
-  SmallVector<wchar_t, 128> path_utf16;
+std::error_code access(const Twine &Path, AccessMode Mode) {
+  SmallString<128> PathStorage;
+  SmallVector<wchar_t, 128> PathUtf16;
 
-  if (std::error_code ec =
-          UTF8ToUTF16(path.toStringRef(path_storage), path_utf16))
-    return ec;
+  if (std::error_code EC =
+          UTF8ToUTF16(Path.toStringRef(PathStorage), PathUtf16))
+    return EC;
 
-  DWORD attributes = ::GetFileAttributesW(path_utf16.begin());
+  DWORD Attributes = ::GetFileAttributesW(PathUtf16.begin());
 
-  if (attributes == INVALID_FILE_ATTRIBUTES) {
+  if (Attributes == INVALID_FILE_ATTRIBUTES) {
     // See if the file didn't actually exist.
     DWORD LastError = ::GetLastError();
     if (LastError != ERROR_FILE_NOT_FOUND &&
         LastError != ERROR_PATH_NOT_FOUND)
       return windows_error(LastError);
-    result = false;
-  } else
-    result = true;
-  return std::error_code();
-}
-
-bool can_write(const Twine &Path) {
-  // FIXME: take security attributes into account.
-  SmallString<128> PathStorage;
-  SmallVector<wchar_t, 128> PathUtf16;
-
-  if (UTF8ToUTF16(Path.toStringRef(PathStorage), PathUtf16))
-    return false;
-
-  DWORD Attr = ::GetFileAttributesW(PathUtf16.begin());
-  return (Attr != INVALID_FILE_ATTRIBUTES) && !(Attr & FILE_ATTRIBUTE_READONLY);
-}
-
-bool can_execute(const Twine &Path) {
-  SmallString<128> PathStorage;
-  SmallVector<wchar_t, 128> PathUtf16;
+    return errc::no_such_file_or_directory;
+  }
 
-  if (UTF8ToUTF16(Path.toStringRef(PathStorage), PathUtf16))
-    return false;
+  if (Mode == AccessMode::Write && (Attributes & FILE_ATTRIBUTE_READONLY))
+    return errc::permission_denied;
 
-  DWORD Attr = ::GetFileAttributesW(PathUtf16.begin());
-  return Attr != INVALID_FILE_ATTRIBUTES;
+  return std::error_code();
 }
 
 bool equivalent(file_status A, file_status B) {