trivial patch to reduce allocations in nio open* methods

[Roger Riggs]

Hi Michael,

To track the request:JDK-8199124 
<https://bugs.openjdk.java.net/browse/JDK-8199124> Reduce allocations in 
nio open* methods

Regards, Roger

On 3/6/2018 3:17 AM, Michael Skells wrote:
> Hi,
> below is a trivial patch to reduce allocation on the file open call 
> path, when no OpenOption is specified( which is a common case in my 
> test code at least)
>
> There is some duplication of empty set  handling, but I could not see 
> a suitable utility class to provide this and didnt want to create a 
> public method
>
> Regards
> Mike
> ---
> Index: 
> src/java.base/share/classes/java/nio/channels/AsynchronousFileChannel.java
> IDEA additional info:
> Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
> <+>UTF-8
> ===================================================================
> --- 
> src/java.base/share/classes/java/nio/channels/AsynchronousFileChannel.java(revision 
> 49129:fb9f590b9eeecae202277c0606ed12b4d3f674c3)
> +++ 
> src/java.base/share/classes/java/nio/channels/AsynchronousFileChannel.java(revision 
> 49129+:fb9f590b9eee+)
> @@ -301,8 +301,13 @@
>      public static AsynchronousFileChannel open(Path file, 
> OpenOption... options)
>          throws IOException
>      {
> -        Set<OpenOption> set = new HashSet<>(options.length);
> -        Collections.addAll(set, options);
> +        Set<OpenOption> set;
> +        if (options.length == 0) {
> +            set = Collections.emptySet();
> +        } else {
> +            set = new HashSet<>(options.length);
> +            Collections.addAll(set, options);
> +        }
>          return open(file, set, null, NO_ATTRIBUTES);
>      }
> Index: src/java.base/share/classes/java/nio/channels/FileChannel.java
> IDEA additional info:
> Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
> <+>UTF-8
> ===================================================================
> --- 
> src/java.base/share/classes/java/nio/channels/FileChannel.java(revision 
> 49129:fb9f590b9eeecae202277c0606ed12b4d3f674c3)
> +++ 
> src/java.base/share/classes/java/nio/channels/FileChannel.java(revision 
> 49129+:fb9f590b9eee+)
> @@ -335,8 +335,11 @@
>      public static FileChannel open(Path path, OpenOption... options)
>          throws IOException
>      {
> -        Set<OpenOption> set = new HashSet<>(options.length);
> -        Collections.addAll(set, options);
> +        Set<OpenOption> set;
> +        if (options.length > 0) {
> +            set = new HashSet<>(options.length);
> +            Collections.addAll(set, options);
> +        } else set = Collections.emptySet();
>          return open(path, set, NO_ATTRIBUTES);
>      }
> Index: 
> src/java.base/share/classes/java/nio/file/spi/FileSystemProvider.java
> IDEA additional info:
> Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
> <+>UTF-8
> ===================================================================
> --- 
> src/java.base/share/classes/java/nio/file/spi/FileSystemProvider.java(revision 
> 49129:fb9f590b9eeecae202277c0606ed12b4d3f674c3)
> +++ 
> src/java.base/share/classes/java/nio/file/spi/FileSystemProvider.java(revision 
> 49129+:fb9f590b9eee+)
> @@ -419,20 +419,22 @@
>          throws IOException
>      {
>          int len = options.length;
> -        Set<OpenOption> opts = new HashSet<>(len + 3);
> +        Set<OpenOption> opts ;
>          if (len == 0) {
> -            opts.add(StandardOpenOption.CREATE);
> - opts.add(StandardOpenOption.TRUNCATE_EXISTING);
> +            opts = DEFAULT_OPEN_OPTIONS;
>          } else {
> +            opts = new HashSet<>(len + 1);
>              for (OpenOption opt: options) {
>                  if (opt == StandardOpenOption.READ)
>                      throw new IllegalArgumentException("READ not 
> allowed");
>                  opts.add(opt);
>              }
> -        }
> -        opts.add(StandardOpenOption.WRITE);
> +            opts.add(StandardOpenOption.WRITE);
> +        }
>          return Channels.newOutputStream(newByteChannel(path, opts));
>      }
> +    private final static Set<OpenOption> DEFAULT_OPEN_OPTIONS = 
> Collections.unmodifiableSet(
> + 
> EnumSet.of(StandardOpenOption.CREATE,StandardOpenOption.TRUNCATE_EXISTING,StandardOpenOption.WRITE));
>      /**
>       * Opens or creates a file for reading and/or writing, returning 
> a file
> Index: src/java.base/share/classes/java/nio/file/Files.java
> IDEA additional info:
> Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
> <+>UTF-8
> ===================================================================
> --- src/java.base/share/classes/java/nio/file/Files.java(revision 
> 49129:fb9f590b9eeecae202277c0606ed12b4d3f674c3)
> +++ src/java.base/share/classes/java/nio/file/Files.java(revision 
> 49129+:fb9f590b9eee+)
> @@ -410,8 +410,11 @@
>      public static SeekableByteChannel newByteChannel(Path path, 
> OpenOption... options)
>          throws IOException
>      {
> -        Set<OpenOption> set = new HashSet<>(options.length);
> -        Collections.addAll(set, options);
> +        Set<OpenOption> set;
> +        if (options.length > 0) {
> +          set = new HashSet<>(options.length);
> +          Collections.addAll(set, options);
> +        } else set = Collections.emptySet();
>          return newByteChannel(path, set);
>      }
> @@ -635,11 +638,12 @@
>      public static Path createFile(Path path, FileAttribute<?>... attrs)
>          throws IOException
>      {
> -        EnumSet<StandardOpenOption> options =
> - EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, 
> StandardOpenOption.WRITE);
> -        newByteChannel(path, options, attrs).close();
> +        newByteChannel(path, DEFAULT_CREATE_OPTIONS, attrs).close();
>          return path;
>      }
> +    private final static Set<StandardOpenOption> 
> DEFAULT_CREATE_OPTIONS = Collections.unmodifiableSet(
> + EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, 
> StandardOpenOption.WRITE)
> +    );
>      /**
>       * Creates a new directory. The check for the existence of the 
> file and the
> ---
>
> On Tue, 6 Mar 2018 at 01:12 Brian Burkhalter 
> <brian.burkhalter at oracle.com <mailto:brian.burkhalter at oracle.com>> wrote:
>
>     Hello,
>
>     Redirecting to nio-dev. Please reply omitting core-libs-dev.
>
>     If the patch is small you can include it in e-mail to the mailing
>     list as attachments are generally scrubbed.
>
>     Thanks,
>
>     Brian
>
>     On Mar 5, 2018, at 4:35 PM, Michael Skells <mike.skells1 at gmail.com
>     <mailto:mike.skells1 at gmail.com>> wrote:
>
>>     I have a trivial patch to reduce allocation of OpenOption sets
>>     where no
>>     args are supplied
>>
>>     Spotted this while working on scala compiler, trying to reduce
>>     allocations
>>
>>     I cannot build JDK due to visual studio issues
>>
>>     Can someone progress the patch for me? Dont want to send a patch
>>     to this
>>     mailgroup!
>>
>>     I have previously signed OCA and contributed (although it has
>>     been a while)
>