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).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217625 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/FileSystem.h

@@ -352,33 +352,37 @@ std::error_code resize_file(const Twine &path, uint64_t size);
 ///          not.
 bool exists(file_status status);
 
-/// @brief Does file exist?
+/// @brief Can the file be accessed?
 ///
 /// @param path Input path.
-/// @param result Set to true if the file represented by status exists, false if
-///               it does not. Undefined otherwise.
-/// @returns errc::success if result has been successfully set, otherwise a
+/// @returns errc::success if the path can be accessed, otherwise a
 ///          platform-specific error_code.
-std::error_code exists(const Twine &path, bool &result);
+enum class AccessMode { Exist, Write, Execute };
+std::error_code access(const Twine &Path, AccessMode Mode);
 
-/// @brief Simpler version of exists for clients that don't need to
-///        differentiate between an error and false.
-inline bool exists(const Twine &path) {
-  bool result;
-  return !exists(path, result) && result;
+/// @brief Does file exist?
+///
+/// @param Path Input path.
+/// @returns True if it exists, false otherwise.
+inline bool exists(const Twine &Path) {
+  return !access(Path, AccessMode::Exist);
 }
 
 /// @brief Can we execute this file?
 ///
 /// @param Path Input path.
 /// @returns True if we can execute it, false otherwise.
-bool can_execute(const Twine &Path);
+inline bool can_execute(const Twine &Path) {
+  return !access(Path, AccessMode::Execute);
+}
 
 /// @brief Can we write this file?
 ///
 /// @param Path Input path.
 /// @returns True if we can write to it, false otherwise.
-bool can_write(const Twine &Path);
+inline bool can_write(const Twine &Path) {
+  return !access(Path, AccessMode::Write);
+}
 
 /// @brief Do file_status's represent the same thing?
 ///

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;
       }

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: {

lib/Support/Unix/Path.inc

@@ -321,40 +321,37 @@ 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);
+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");
+}
 
-  if (::access(p.begin(), F_OK) == -1) {
-    if (errno != ENOENT)
-      return std::error_code(errno, std::generic_category());
-    result = false;
-  } else
-    result = true;
+std::error_code access(const Twine &Path, AccessMode Mode) {
+  SmallString<128> PathStorage;
+  StringRef P = Path.toNullTerminatedStringRef(PathStorage);
+
+  if (::access(P.begin(), convertAccessMode(Mode)) == -1)
+    return std::error_code(errno, std::generic_category());
+
+  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 can_write(const Twine &Path) {
-  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 (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;
-}
-
 bool equivalent(file_status A, file_status B) {
   assert(status_known(A) && status_known(B));
   return A.fs_st_dev == B.fs_st_dev &&

lib/Support/Windows/Path.inc

@@ -251,51 +251,31 @@ 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 errc::no_such_file_or_directory;
+  }
+
+  if (Mode == AccessMode::Write && (Attributes & FILE_ATTRIBUTE_READONLY))
+    return errc::permission_denied;
+
   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;
-
-  if (UTF8ToUTF16(Path.toStringRef(PathStorage), PathUtf16))
-    return false;
-
-  DWORD Attr = ::GetFileAttributesW(PathUtf16.begin());
-  return Attr != INVALID_FILE_ATTRIBUTES;
-}
-
 bool equivalent(file_status A, file_status B) {
   assert(status_known(A) && status_known(B));
   return A.FileIndexHigh      == B.FileIndexHigh &&

unittests/Support/FileOutputBufferTest.cpp

@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Support/Errc.h"
 #include "llvm/Support/FileOutputBuffer.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
@@ -65,9 +66,8 @@ TEST(FileOutputBuffer, Test) {
     // Do *not* commit buffer.
   }
   // Verify file does not exist (because buffer not committed).
-  bool Exists = false;
-  ASSERT_NO_ERROR(fs::exists(Twine(File2), Exists));
-  EXPECT_FALSE(Exists);
+  ASSERT_EQ(fs::access(Twine(File2), fs::AccessMode::Exist),
+            errc::no_such_file_or_directory);
   ASSERT_NO_ERROR(fs::remove(File2.str()));
 
   // TEST 3: Verify sizing down case.

unittests/Support/Path.cpp

@@ -361,9 +361,8 @@ TEST_F(FileSystemTest, TempFiles) {
   EXPECT_EQ(B.type(), fs::file_type::file_not_found);
 
   // Make sure Temp2 doesn't exist.
-  bool TempFileExists;
-  ASSERT_NO_ERROR(fs::exists(Twine(TempPath2), TempFileExists));
-  EXPECT_FALSE(TempFileExists);
+  ASSERT_EQ(fs::access(Twine(TempPath2), sys::fs::AccessMode::Exist),
+            errc::no_such_file_or_directory);
 
   SmallString<64> TempPath3;
   ASSERT_NO_ERROR(fs::createTemporaryFile("prefix", "", TempPath3));
@@ -386,8 +385,8 @@ TEST_F(FileSystemTest, TempFiles) {
   ASSERT_NO_ERROR(fs::remove(Twine(TempPath2)));
 
   // Make sure Temp1 doesn't exist.
-  ASSERT_NO_ERROR(fs::exists(Twine(TempPath), TempFileExists));
-  EXPECT_FALSE(TempFileExists);
+  ASSERT_EQ(fs::access(Twine(TempPath), sys::fs::AccessMode::Exist),
+            errc::no_such_file_or_directory);
 
 #ifdef LLVM_ON_WIN32
   // Path name > 260 chars should get an error.