This is a stand-alone helper class for writing properly
structured JSON to an SkWStream. It currently solves two
problems (although this CL only uses it in one context):
1) Performance. Writing out JSON this way is about 10x
faster than using JSONCPP. For the large amounts of data
generated by the tracing system, that's a big win.
2) Makes it easy to emit structured JSON from code that's
not fully centralized. We'd like to spit out JSON that
describes a GrContext, GrGpu, GrCaps, etc... Doing that
with simple string manipulation is complex, and spreads
this logic over all those functions. Using JSONCPP adds
yet another (large) third party library dependency (that
we only build into our own tools right now).
This went through several revisions. I originally planned
it as a stateful SkString wrapper, so the user could just
build their JSON as a string. That's O(N^2), though,
because SkString grows by a (small) constant amount. Even
using a better growth strategy still means needing RAM
for all the resulting text, which is usually pointless.
This version has a constant memory cost, so writing huge
amounts of JSON to disk (tracing a long DM run can emit
100's of MBs) doesn't stress resources.
Bug: skia:
Change-Id: Ia716524b246db0f97d332da60d2ce9903069e748
Reviewed-on: https://skia-review.googlesource.com/31204
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
69fd008199