8278356: Improve file creation

Reviewed-by: bpb

src/java.base/share/classes/java/io/File.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -175,8 +175,9 @@ public class File
 
     /**
      * Check if the file has an invalid path. Currently, the inspection of
-     * a file path is very limited, and it only covers Nul character check.
-     * Returning true means the path is definitely invalid/garbage. But
+     * a file path is very limited, and it only covers Nul character check
+     * unless further checking is explicitly enabled by a system property.
+     * Returning true means the path is definitely invalid/garbage, but
      * returning false does not guarantee that the path is valid.
      *
      * @return true if the file path is invalid.
@@ -184,8 +185,7 @@ public class File
     final boolean isInvalid() {
         PathStatus s = status;
         if (s == null) {
-            s = (this.path.indexOf('\u0000') < 0) ? PathStatus.CHECKED
-                                                  : PathStatus.INVALID;
+            s = fs.isInvalid(this) ? PathStatus.INVALID : PathStatus.CHECKED;
             status = s;
         }
         return s == PathStatus.INVALID;

src/java.base/share/classes/java/io/FileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -87,6 +87,11 @@ abstract class FileSystem {
      */
     public abstract boolean isAbsolute(File f);
 
+    /**
+     * Tell whether the given abstract pathname is invalid.
+     */
+    public abstract boolean isInvalid(File f);
+
     /**
      * Resolve the given abstract pathname into absolute form.  Invoked by the
      * getAbsolutePath and getCanonicalPath methods in the File class.

src/java.base/unix/classes/java/io/UnixFileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -141,6 +141,11 @@ class UnixFileSystem extends FileSystem {
         return (f.getPrefixLength() != 0);
     }
 
+    @Override
+    public boolean isInvalid(File f) {
+        return f.getPath().indexOf('\u0000') < 0 ? false : true;
+    }
+
     @Override
     public String resolve(File f) {
         if (isAbsolute(f)) return f.getPath();

src/java.base/windows/classes/java/io/WinNTFileSystem.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,7 @@
 package java.io;
 
 import java.io.File;
+import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
 import java.util.BitSet;
 import java.util.Locale;
@@ -45,6 +46,21 @@ class WinNTFileSystem extends FileSystem {
     private final char semicolon;
     private final String userDir;
 
+    // Whether to enable alternative data streams (ADS) by suppressing
+    // checking the path for invalid characters, in particular ":".
+    // ADS support will be enabled if and only if the property is set and
+    // is the empty string or is equal, ignoring case, to the string "true".
+    // By default ADS support is disabled.
+    private static final boolean ENABLE_ADS;
+    static {
+        String enableADS = GetPropertyAction.privilegedGetProperty("jdk.io.File.enableADS");
+        if (enableADS != null) {
+            ENABLE_ADS = "".equals(enableADS) || Boolean.parseBoolean(enableADS);
+        } else {
+            ENABLE_ADS = false;
+        }
+    }
+
     public WinNTFileSystem() {
         Properties props = GetPropertyAction.privilegedGetProperties();
         slash = props.getProperty("file.separator").charAt(0);
@@ -305,6 +321,33 @@ class WinNTFileSystem extends FileSystem {
                 || (pl == 3));
     }
 
+    @Override
+    public boolean isInvalid(File f) {
+        if (f.getPath().indexOf('\u0000') >= 0)
+            return true;
+
+        if (ENABLE_ADS)
+            return false;
+
+        // Invalid if there is a ":" at a position greater than 1, or if there
+        // is a ":" at position 1 and the first character is not a letter
+        String pathname = f.getPath();
+        int lastColon = pathname.lastIndexOf(":");
+        if (lastColon > 1 ||
+            (lastColon == 1 && !isLetter(pathname.charAt(0))))
+            return true;
+
+        // Invalid if path creation fails
+        Path path = null;
+        try {
+            path = sun.nio.fs.DefaultFileSystemProvider.theFileSystem().getPath(pathname);
+            return false;
+        } catch (InvalidPathException ignored) {
+        }
+
+        return true;
+    }
+
     @Override
     public String resolve(File f) {
         String path = f.getPath();