RFR: 8265699: (bf) Scopes passed to ScopedMemoryAccess.copy[Swap]Memory in incorrect order

[Brian Burkhalter]

On Wed, 21 Apr 2021 20:10:17 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Please consider this request to correct what appear to be `jdk.internal.misc.ScopedMemoryAccess$Scope`s passed in incorrect order to the `copyMemory()` and `copySwapMemory()` methods of `jdk.internal.misc.ScopedMemoryAccess` in some of the `java.nio.Buffer` bulk transfer methods.
>
> src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template line 551:
> 
>> 549:         int rem = (pos <= lim ? lim - pos : 0);
>> 550:         try {
>> 551:             SCOPED_MEMORY_ACCESS.copyMemory(scope(), scope(), null,
> 
> Is this deliberate? same strange to use same scope for both address and target?

Yes, it is. In this case the buffer is copying to itself, moving the data down to the beginning of the buffer, position zero.

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PR: https://git.openjdk.java.net/jdk/pull/3607