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Diffstat (limited to 'chromium/third_party/skia/src/core/SkLazyPtr.h')
-rw-r--r-- | chromium/third_party/skia/src/core/SkLazyPtr.h | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/chromium/third_party/skia/src/core/SkLazyPtr.h b/chromium/third_party/skia/src/core/SkLazyPtr.h new file mode 100644 index 00000000000..c25d3c81202 --- /dev/null +++ b/chromium/third_party/skia/src/core/SkLazyPtr.h @@ -0,0 +1,146 @@ +/* + * Copyright 2014 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef SkLazyPtr_DEFINED +#define SkLazyPtr_DEFINED + +/** Declare a lazily-chosen static pointer (or array of pointers) of type F. + * + * Example usage: + * + * Foo* GetSingletonFoo() { + * SK_DECLARE_STATIC_LAZY_PTR(Foo, singleton); // Created with SkNEW, destroyed with SkDELETE. + * return singleton.get(); + * } + * + * These macros take an optional T* (*Create)() and void (*Destroy)(T*) at the end. + * If not given, we'll use SkNEW and SkDELETE. + * These options are most useful when T doesn't have a public constructor or destructor. + * Create comes first, so you may use a custom Create with a default Destroy, but not vice versa. + * + * Foo* CustomCreate() { return ...; } + * void CustomDestroy(Foo* ptr) { ... } + * Foo* GetSingletonFooWithCustomCleanup() { + * SK_DECLARE_STATIC_LAZY_PTR(Foo, singleton, CustomCreate, CustomDestroy); + * return singleton.get(); + * } + * + * If you have a bunch of related static pointers of the same type, you can + * declare an array of lazy pointers together, and we'll pass the index to Create(). + * + * Foo* CreateFoo(int i) { return ...; } + * Foo* GetCachedFoo(Foo::Enum enumVal) { + * SK_DECLARE_STATIC_LAZY_PTR_ARRAY(Foo, Foo::kEnumCount, cachedFoos, CreateFoo); + * return cachedFoos[enumVal]; + * } + * + * + * You can think of SK_DECLARE_STATIC_LAZY_PTR as a cheaper specialization of + * SkOnce. There is no mutex or extra storage used past the pointer itself. + * In debug mode, each lazy pointer will be cleaned up at process exit so we + * can check that we've not leaked or freed them early. + * + * We may call Create more than once, but all threads will see the same pointer + * returned from get(). Any extra calls to Create will be cleaned up. + * + * These macros must be used in a global or function scope, not as a class member. + */ + +#define SK_DECLARE_STATIC_LAZY_PTR(T, name, ...) \ + static Private::SkLazyPtr<T, ##__VA_ARGS__> name + +#define SK_DECLARE_STATIC_LAZY_PTR_ARRAY(T, name, N, ...) \ + static Private::SkLazyPtrArray<T, N, ##__VA_ARGS__> name + + + +// Everything below here is private implementation details. Don't touch, don't even look. + +#include "SkDynamicAnnotations.h" +#include "SkThread.h" +#include "SkThreadPriv.h" + +// See FIXME below. +class SkFontConfigInterfaceDirect; + +namespace Private { + +// Set *dst to ptr if *dst is NULL. Returns value of *dst, destroying ptr if not swapped in. +// Issues the same memory barriers as sk_atomic_cas: acquire on failure, release on success. +template <typename P, void (*Destroy)(P)> +static P try_cas(void** dst, P ptr) { + P prev = (P)sk_atomic_cas(dst, NULL, ptr); + + if (prev) { + // We need an acquire barrier before returning prev, which sk_atomic_cas provided. + Destroy(ptr); + return prev; + } else { + // We need a release barrier before returning ptr, which sk_atomic_cas provided. + return ptr; + } +} + +template <typename T> T* sk_new() { return SkNEW(T); } +template <typename T> void sk_delete(T* ptr) { SkDELETE(ptr); } + +// This has no constructor and must be zero-initalized (the macro above does this). +template <typename T, T* (*Create)() = sk_new<T>, void (*Destroy)(T*) = sk_delete<T> > +class SkLazyPtr { +public: + T* get() { + // If fPtr has already been filled, we need an acquire barrier when loading it. + // If not, we need a release barrier when setting it. try_cas will do that. + T* ptr = (T*)sk_acquire_load(&fPtr); + return ptr ? ptr : try_cas<T*, Destroy>(&fPtr, Create()); + } + +#ifdef SK_DEVELOPER + // FIXME: We know we leak refs on some classes. For now, let them leak. + void cleanup(SkFontConfigInterfaceDirect*) {} + template <typename U> void cleanup(U* ptr) { Destroy(ptr); } + + ~SkLazyPtr() { + this->cleanup((T*)fPtr); + fPtr = NULL; + } +#endif + +private: + void* fPtr; +}; + +template <typename T> T* sk_new_arg(int i) { return SkNEW_ARGS(T, (i)); } + +// This has no constructor and must be zero-initalized (the macro above does this). +template <typename T, int N, T* (*Create)(int) = sk_new_arg<T>, void (*Destroy)(T*) = sk_delete<T> > +class SkLazyPtrArray { +public: + T* operator[](int i) { + SkASSERT(i >= 0 && i < N); + // If fPtr has already been filled, we need an acquire barrier when loading it. + // If not, we need a release barrier when setting it. try_cas will do that. + T* ptr = (T*)sk_acquire_load(&fArray[i]); + return ptr ? ptr : try_cas<T*, Destroy>(&fArray[i], Create(i)); + } + +#ifdef SK_DEVELOPER + ~SkLazyPtrArray() { + for (int i = 0; i < N; i++) { + Destroy((T*)fArray[i]); + fArray[i] = NULL; + } + } +#endif + +private: + void* fArray[N]; +}; + +} // namespace Private + +#endif//SkLazyPtr_DEFINED |