tree 945e5cc6d699513e5c2f1070c76fe1f4096e34a4
parent 98f3fd97f45e022e74405220670d2292f6b15733
author Nigel Tao <nigeltao@google.com> 1574213330 +1100
committer Skia Commit-Bot <skia-commit-bot@chromium.org> 1574434173 +0000

Optimize SkWuffsCodec's sk_bzero calls

The *previous* SkWuffsCodec.cpp commit, 39da10b5 "Optimize SkWuffsCodec
pixbuf zero-initialization", removed the need to *explicitly*
zero-initialize the fPixelBuffer on the first frame decode. Subsequent
frames, including the first frame of the animation again if the
animation is looped, still need to call sk_bzero.

Prior to *this* commit, each row of the pixel buffer was zeroed
separately. When it is necessary to memset to zero, it can be faster to
issue one big call instead of many small calls.

For example, the single-frame droids.gif file mentioned in the previous
commit (39da10b5) now skips the explicit sk_bzero calls, due to the
optimization in exactly that previous commit. But if it was a looped
animation, decoding subsequent (repeated) frames would need to memset
the re-used buffer to zero. The time taken for those sk_bzero calls
would be affected by this commit: from 2.900ms to 2.454ms (out of a
total decode time of 33.342ms as per 39da10b5's commit message).

Bug: skia:8235
Change-Id: I72ec3dc4230f06f358b5e8fee1b2799607d86615
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255358
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>