Modernize and trim down SkOnce.

The API and implementation are very much simplified.
You may not want to bother reading the diff.

As is our trend, SkOnce now uses <atomic> directly.

Member initialization means we don't need SK_DECLARE_STATIC_ONCE.
SkSpinlock already works this same way.

All uses of the old API taking an external bool* and Lock* were pessimal,
so I have not carried this sort of API forward.  It's simpler, faster,
and more space-efficient to always use this single SkOnce class interface.

SkOnce weighs 2 bytes: a done bool and an SkSpinlock, also a bool internally.
This API refactoring opens up the opportunity to fuse those into a single
three-state byte if we'd like.

No public API changes.
TBR=reed@google.com

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1894893002

Review URL: https://codereview.chromium.org/1894893002

1 files changed, 13 insertions, 13 deletions

diff --git a/tests/OnceTest.cpp b/tests/OnceTest.cpp
index 83ee66b6c8..ef8d3d9225 100644
--- a/tests/OnceTest.cpp
+++ b/tests/OnceTest.cpp
@@ -13,27 +13,27 @@ static void add_five(int* x) {
     *x += 5;
 }
 
-SK_DECLARE_STATIC_ONCE(st_once);
 DEF_TEST(SkOnce_Singlethreaded, r) {
     int x = 0;
 
     // No matter how many times we do this, x will be 5.
-    SkOnce(&st_once, add_five, &x);
-    SkOnce(&st_once, add_five, &x);
-    SkOnce(&st_once, add_five, &x);
-    SkOnce(&st_once, add_five, &x);
-    SkOnce(&st_once, add_five, &x);
+    SkOnce once;
+    once(add_five, &x);
+    once(add_five, &x);
+    once(add_five, &x);
+    once(add_five, &x);
+    once(add_five, &x);
 
     REPORTER_ASSERT(r, 5 == x);
 }
 
-SK_DECLARE_STATIC_ONCE(mt_once);
 DEF_TEST(SkOnce_Multithreaded, r) {
     int x = 0;
+
     // Run a bunch of tasks to be the first to add six to x.
+    SkOnce once;
     SkTaskGroup().batch(1021, [&](int) {
-        void(*add_six)(int*) = [](int* p) { *p += 6; };
-        SkOnce(&mt_once, add_six, &x);
+        once([&] { x += 6; });
     });
 
     // Only one should have done the +=.
@@ -43,10 +43,10 @@ DEF_TEST(SkOnce_Multithreaded, r) {
 static int gX = 0;
 static void inc_gX() { gX++; }
 
-SK_DECLARE_STATIC_ONCE(noarg_once);
 DEF_TEST(SkOnce_NoArg, r) {
-    SkOnce(&noarg_once, inc_gX);
-    SkOnce(&noarg_once, inc_gX);
-    SkOnce(&noarg_once, inc_gX);
+    SkOnce once;
+    once(inc_gX);
+    once(inc_gX);
+    once(inc_gX);
     REPORTER_ASSERT(r, 1 == gX);
 }