Reduce Kernel32 calls

deeprobin · Mar 16, 2022 · 8ce1a96 · 8ce1a96
1 parent f0b7773
commit 8ce1a96
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/src/libraries/Common/src/System/IO/FileSystem.Attributes.Windows.cs b/src/libraries/Common/src/System/IO/FileSystem.Attributes.Windows.cs
@@ -40,6 +40,15 @@ public static bool FileExists(string fullPath)
                 ((data.dwFileAttributes & Interop.Kernel32.FileAttributes.FILE_ATTRIBUTE_DIRECTORY) == 0);
         }
 
+        public static (int fileAttributes, int lastError) GetFileAttributes(string fullPath)
+        {
+            Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data = default;
+            int lastError = FillAttributeInfo(fullPath, ref data, returnErrorOnNotFound: true);
+            int fileAttributes = data.dwFileAttributes;
+
+            return (fileAttributes, lastError);
+        }
+
         /// <summary>
         /// Returns 0 on success, otherwise a Win32 error code.  Note that
         /// classes should use -1 as the uninitialized state for dataInitialized.

diff --git a/src/libraries/Common/src/System/IO/FileSystem.DirectoryCreation.Windows.cs b/src/libraries/Common/src/System/IO/FileSystem.DirectoryCreation.Windows.cs
@@ -106,8 +106,16 @@ public static unsafe void CreateDirectory(string fullPath, byte[]? securityDescr
                         }
                         else
                         {
+                            (int fileAttributes, int lastError) = GetFileAttributes(name);
+                            currentError = lastError;
+
+                            int directoryAttributeValue = fileAttributes &
+                                                          Interop.Kernel32.FileAttributes.FILE_ATTRIBUTE_DIRECTORY;
+                            bool fileExists = lastError == Interop.Errors.ERROR_SUCCESS && directoryAttributeValue != 0;
+                            bool directoryExists = directoryAttributeValue == 0;
+
                             // If there's a file in this directory's place, or if we have ERROR_ACCESS_DENIED when checking if the directory already exists throw.
-                            if (FileExists(name) || (!DirectoryExists(name, out currentError) && currentError == Interop.Errors.ERROR_ACCESS_DENIED))
+                            if (fileExists || !directoryExists && currentError == Interop.Errors.ERROR_ACCESS_DENIED)
                             {
                                 firstError = currentError;
                                 errorString = name;