RFR: 8274112: (fc) Tune FileChannel.transferTo() [v6]

[Roger Riggs]

On Thu, 28 Apr 2022 00:08:18 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Please consider this patch which would improve the performance of
>> `FileChannel.transferTo()` on macOS and Windows.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8274112: Revert all changes except mapped transfer threshold

test/jdk/java/nio/channels/FileChannel/TransferToChannel.java line 126:

> 124:                 for (int i=0; i<size; i++)
> 125:                     if (incoming[i] != expected[i])
> 126:                         throw new RuntimeException("Data corrupted");

Perhaps `if (!Arrays.equals(incoming, 0, size, expected, 0, size))...`

test/jdk/java/nio/channels/FileChannel/TransferToChannel.java line 157:

> 155:     private static void transferFileDirectly() throws Exception {
> 156:         outFile.delete();
> 157:         FileOutputStream fos = new FileOutputStream(outFile);

Can try-with-resources be used here for both fos and out?

test/jdk/java/nio/channels/FileChannel/TransferToChannel.java line 169:

> 167:                 pos += bytesTransferred;
> 168:             else
> 169:                 throw new Exception("transfer failed");

Including some position information in the exception would help diagnose, especially with intermittent failures, if they happen.

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PR: https://git.openjdk.java.net/jdk/pull/5623