Create a platform-dependent object for accessing purgeable memory.

Create a platform-dependent object for accessing purgeable memory.

Siphoned off from https://codereview.chromium.org/12433020/

Create a Skia class which can provide purgeable memory in a platform-
dependent way. Include an implementation for Ashmem and Mac/iOS.

Committed: https://code.google.com/p/skia/source/detail?r=8176

[djsollen, 2013-03-14 13:56:31]

I really like the concept so overall I'm onboard with the CL, but I did have a
few naming nits.

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
File src/lazy/SkPurgeableMemoryBlock.h (right):

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:19: static bool
PlatformSupportsPurgeableMemory();
writing SkPurgeableMemoryBlock::PlatformSupportsPurgeableMemory() seems to be a
little redundant. Could it be shortened to
SkPurgeableMemoryBlock::IsSupported();

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:27: static SkPurgeableMemoryBlock*
CreatePurgeableMemoryBlock(size_t size);
following the naming of other factories like SkBlurMaskFilter can this be
shortened to just Create(size_t size)?

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:49: int getFD() const { return fFD; }
Is this really needed? Who calls this?

[scroggo, 2013-03-14 15:36:13]

Thanks for the feedback! Your name suggestions are much better.

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
File src/lazy/SkPurgeableMemoryBlock.h (right):

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:19: static bool
PlatformSupportsPurgeableMemory();
On 2013/03/14 13:56:31, djsollen wrote:
> writing SkPurgeableMemoryBlock::PlatformSupportsPurgeableMemory() seems to be
a
> little redundant. Could it be shortened to
> SkPurgeableMemoryBlock::IsSupported();

Done.

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:27: static SkPurgeableMemoryBlock*
CreatePurgeableMemoryBlock(size_t size);
On 2013/03/14 13:56:31, djsollen wrote:
> following the naming of other factories like SkBlurMaskFilter can this be
> shortened to just Create(size_t size)?

Done.

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:49: int getFD() const { return fFD; }
On 2013/03/14 13:56:31, djsollen wrote:
> Is this really needed? Who calls this?

This is a debug only function just for debugging. It is called by
SkPurgeableImageCache::getMemoryStatus (part of my larger CL that is not
included here. The caller is on line 120 of
https://codereview.chromium.org/12433020/diff/47002/src/lazy/SkPurgeableImage...).

I wanted to have a way to test how it behaves when the system purges the memory,
but I could not find a way to do that on android (I found
ASHMEM_PURGE_ALL_CACHES, but it does not seem to be public) so I cheated and set
the file descriptor to -1, which I later use as a sign that it has been purged.
Do you know how to purge ashmem? I am not happy with this API either.

[scroggo, 2013-03-14 18:05:32]

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
File src/lazy/SkPurgeableMemoryBlock.h (right):

https://codereview.chromium.org/12645006/diff/1/src/lazy/SkPurgeableMemoryBlo...
src/lazy/SkPurgeableMemoryBlock.h:49: int getFD() const { return fFD; }
On 2013/03/14 15:36:13, scroggo wrote:
> On 2013/03/14 13:56:31, djsollen wrote:
> > Is this really needed? Who calls this?
> 
> This is a debug only function just for debugging. It is called by
> SkPurgeableImageCache::getMemoryStatus (part of my larger CL that is not
> included here. The caller is on line 120 of
>
https://codereview.chromium.org/12433020/diff/47002/src/lazy/SkPurgeableImage...).
> 
> I wanted to have a way to test how it behaves when the system purges the
memory,
> but I could not find a way to do that on android (I found
> ASHMEM_PURGE_ALL_CACHES, but it does not seem to be public) so I cheated and
set
> the file descriptor to -1, which I later use as a sign that it has been
purged.
> Do you know how to purge ashmem? I am not happy with this API either.

Removed! Thanks for adding the purge function!

[djsollen, 2013-03-15 16:54:22]

lgtm

[scroggo, 2013-03-15 18:08:15]

Committed patchset #5 manually as r8176 (presubmit successful).