Unsafe.{get,put}-X-Unaligned; Efficient array comparison intrinsics (original) (raw)

Remi Forax forax at univ-mlv.fr
Sat Mar 7 19:24:34 UTC 2015

On 03/07/2015 07:48 PM, Andrew Haley wrote:

On 03/07/2015 05:57 PM, Remi Forax wrote:

Hi Andrew, I've just read carefully the JDK part and I'm mostly ok with it.

in Unsafe, all private methods should be static You're going to have to explain that. Firstly, why? There's no real performance advantage, and secondly, how is a static method supposed to invoke the virtual methods in Unsafe? I suppose it could use theUnsafe.blah() but that would be worse than a simple virtual call.

I mean all private methods that doesn't starts with "put*", convEndian, toUnsignedInt/toUnsignedLong, pick, make*, pickPos.

and I think that isBigEndian() and unalignedAccess() native methods should be called once in a static block and their results cached/stored as static final fields. That's not unreasonable. In that case the public version of isBigEndian() and unalignedAccess() should just return the value of the static final fields. OK. Also I'm wondering if this method are really unsafe, exporting the endianess or the support of unaligned access doesn't seem unsafe too me; It's not, but the we have a public API to get the endianness of this machine in java.nio,ByteOrder.nativeOrder() and I really don't want to create another one. With regard to unalignedAccess() I don't really mind making it public static but it's of marginal use in that form IMO. Maybe some user code could make use of this information, in which case it shouldn't be in Unsafe at all. maybe there is a security issue ?; if not, the static final fields should be public and the public methods removed. Sorry, I don't want to do that. Accessor methods for such things should stay as methods, not public fields.

OK.

Andrew.

Rémi

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