Index: include/core/SkOnce.h |
diff --git a/include/core/SkOnce.h b/include/core/SkOnce.h |
deleted file mode 100644 |
index 43e7353d4dd9240fde565a8a115a1344318672da..0000000000000000000000000000000000000000 |
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-/* |
- * Copyright 2013 Google Inc. |
- * |
- * Use of this source code is governed by a BSD-style license that can be |
- * found in the LICENSE file. |
- */ |
- |
-#ifndef SkOnce_DEFINED |
-#define SkOnce_DEFINED |
- |
-// Before trying SkOnce, see if SkLazyPtr or SkLazyFnPtr will work for you. |
-// They're smaller and faster, if slightly less versatile. |
- |
- |
-// SkOnce.h defines SK_DECLARE_STATIC_ONCE and SkOnce(), which you can use |
-// together to create a threadsafe way to call a function just once. E.g. |
-// |
-// static void register_my_stuff(GlobalRegistry* registry) { |
-// registry->register(...); |
-// } |
-// ... |
-// void EnsureRegistered() { |
-// SK_DECLARE_STATIC_ONCE(once); |
-// SkOnce(&once, register_my_stuff, GetGlobalRegistry()); |
-// } |
-// |
-// No matter how many times you call EnsureRegistered(), register_my_stuff will be called just once. |
-// OnceTest.cpp also should serve as a few other simple examples. |
- |
-#include "../private/SkAtomics.h" |
-#include "SkSpinlock.h" |
- |
-// This must be used in a global scope, not in function scope or as a class member. |
-#define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name |
- |
-class SkOnceFlag; |
- |
-inline void SkOnce(SkOnceFlag* once, void (*f)()); |
- |
-template <typename Arg> |
-inline void SkOnce(SkOnceFlag* once, void (*f)(Arg), Arg arg); |
- |
-// If you've already got a lock and a flag to use, this variant lets you avoid an extra SkOnceFlag. |
-template <typename Lock> |
-inline void SkOnce(bool* done, Lock* lock, void (*f)()); |
- |
-template <typename Lock, typename Arg> |
-inline void SkOnce(bool* done, Lock* lock, void (*f)(Arg), Arg arg); |
- |
-// ---------------------- Implementation details below here. ----------------------------- |
- |
-// This class has no constructor and must be zero-initialized (the macro above does this). |
-class SkOnceFlag { |
-public: |
- bool* mutableDone() { return &fDone; } |
- |
- void acquire() { fSpinlock.acquire(); } |
- void release() { fSpinlock.release(); } |
- |
-private: |
- bool fDone; |
- SkPODSpinlock fSpinlock; |
-}; |
- |
-// We've pulled a pretty standard double-checked locking implementation apart |
-// into its main fast path and a slow path that's called when we suspect the |
-// one-time code hasn't run yet. |
- |
-// This is the guts of the code, called when we suspect the one-time code hasn't been run yet. |
-// This should be rarely called, so we separate it from SkOnce and don't mark it as inline. |
-// (We don't mind if this is an actual function call, but odds are it'll be inlined anyway.) |
-template <typename Lock, typename Arg> |
-static void sk_once_slow(bool* done, Lock* lock, void (*f)(Arg), Arg arg) { |
- lock->acquire(); |
- if (!sk_atomic_load(done, sk_memory_order_relaxed)) { |
- f(arg); |
- // Also known as a store-store/load-store barrier, this makes sure that the writes |
- // done before here---in particular, those done by calling f(arg)---are observable |
- // before the writes after the line, *done = true. |
- // |
- // In version control terms this is like saying, "check in the work up |
- // to and including f(arg), then check in *done=true as a subsequent change". |
- // |
- // We'll use this in the fast path to make sure f(arg)'s effects are |
- // observable whenever we observe *done == true. |
- sk_release_store(done, true); |
- } |
- lock->release(); |
-} |
- |
-// This is our fast path, called all the time. We do really want it to be inlined. |
-template <typename Lock, typename Arg> |
-inline void SkOnce(bool* done, Lock* lock, void (*f)(Arg), Arg arg) { |
- // When *done == true: |
- // Also known as a load-load/load-store barrier, this acquire barrier makes |
- // sure that anything we read from memory---in particular, memory written by |
- // calling f(arg)---is at least as current as the value we read from done. |
- // |
- // In version control terms, this is a lot like saying "sync up to the |
- // commit where we wrote done = true". |
- // |
- // The release barrier in sk_once_slow guaranteed that done = true |
- // happens after f(arg), so by syncing to done = true here we're |
- // forcing ourselves to also wait until the effects of f(arg) are readble. |
- // |
- // When *done == false: |
- // We'll try to call f(arg) in sk_once_slow. |
- // If we get the lock, great, we call f(arg), release true into done, and drop the lock. |
- // If we race and don't get the lock first, we'll wait for the first guy to finish. |
- // Then lock acquire() will give us at least an acquire memory barrier to get the same |
- // effect as the acquire load in the *done == true fast case. We'll see *done is true, |
- // then just drop the lock and return. |
- if (!sk_atomic_load(done, sk_memory_order_acquire)) { |
- sk_once_slow(done, lock, f, arg); |
- } |
-} |
- |
-template <typename Arg> |
-inline void SkOnce(SkOnceFlag* once, void (*f)(Arg), Arg arg) { |
- return SkOnce(once->mutableDone(), once, f, arg); |
-} |
- |
-// Calls its argument. |
-// This lets us use functions that take no arguments with SkOnce methods above. |
-// (We pass _this_ as the function and the no-arg function as its argument. Cute eh?) |
-static void sk_once_no_arg_adaptor(void (*f)()) { |
- f(); |
-} |
- |
-inline void SkOnce(SkOnceFlag* once, void (*func)()) { |
- return SkOnce(once, sk_once_no_arg_adaptor, func); |
-} |
- |
-template <typename Lock> |
-inline void SkOnce(bool* done, Lock* lock, void (*func)()) { |
- return SkOnce(done, lock, sk_once_no_arg_adaptor, func); |
-} |
- |
-#endif // SkOnce_DEFINED |