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Unified Diff: src/once.h

Issue 9666052: Landing for pliard@chromium.org: Remove static initializers in v8. (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: Created 8 years, 9 months ago
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Index: src/once.h
===================================================================
--- src/once.h (revision 0)
+++ src/once.h (revision 0)
@@ -0,0 +1,123 @@
+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following
+// disclaimer in the documentation and/or other materials provided
+// with the distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived
+// from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// emulates google3/base/once.h
+//
+// This header is intended to be included only by v8's internal code. Users
+// should not use this directly.
+//
+// This is basically a portable version of pthread_once().
+//
+// This header declares:
+// * A type called OnceType.
+// * A macro V8_DECLARE_ONCE() which declares a (global) variable of type
+// OnceType.
+// * A function CallOnce(OnceType* once, void (*init_func)()).
+// This function, when invoked multiple times given the same OnceType object,
+// will invoke init_func on the first call only, and will make sure none of
+// the calls return before that first call to init_func has finished.
+//
+// Additionally, the following features are supported:
+// * A macro V8_ONCE_INIT which is expanded into the expression used to
+// initialize a OnceType. This is only useful when clients embed a OnceType
+// into a structure of their own and want to initialize it statically.
+// * The user can provide a parameter which CallOnce() forwards to the
+// user-provided function when it is called. Usage example:
+// CallOnce(&my_once, &MyFunctionExpectingIntArgument, 10);
+// * This implementation guarantees that OnceType is a POD (i.e. no static
+// initializer generated).
+//
+// This implements a way to perform lazy initialization. It's more efficient
+// than using mutexes as no lock is needed if initialization has already
+// happened.
+//
+// Example usage:
+// void Init();
+// V8_DECLARE_ONCE(once_init);
+//
+// // Calls Init() exactly once.
+// void InitOnce() {
+// CallOnce(&once_init, &Init);
+// }
+//
+// Note that if CallOnce() is called before main() has begun, it must
+// only be called by the thread that will eventually call main() -- that is,
+// the thread that performs dynamic initialization. In general this is a safe
+// assumption since people don't usually construct threads before main() starts,
+// but it is technically not guaranteed. Unfortunately, Win32 provides no way
+// whatsoever to statically-initialize its synchronization primitives, so our
+// only choice is to assume that dynamic initialization is single-threaded.
+
+#ifndef V8_ONCE_H_
+#define V8_ONCE_H_
+
+#include "atomicops.h"
+
+namespace v8 {
+namespace internal {
+
+typedef AtomicWord OnceType;
+
+#define V8_ONCE_INIT 0
+
+#define V8_DECLARE_ONCE(NAME) ::v8::internal::OnceType NAME
+
+enum {
+ ONCE_STATE_UNINITIALIZED = 0,
+ ONCE_STATE_EXECUTING_FUNCTION = 1,
+ ONCE_STATE_DONE = 2
+};
+
+typedef void (*NoArgFunction)();
+typedef void (*PointerArgFunction)(void* arg);
+
+template <typename T>
+struct OneArgFunction {
+ typedef void (*type)(T);
+};
+
+void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg);
+
+inline void CallOnce(OnceType* once, NoArgFunction init_func) {
+ if (Acquire_Load(once) != ONCE_STATE_DONE) {
+ CallOnceImpl(once, reinterpret_cast<PointerArgFunction>(init_func), NULL);
+ }
+}
+
+
+template <typename Arg>
+inline void CallOnce(OnceType* once,
+ typename OneArgFunction<Arg*>::type init_func, Arg* arg) {
+ if (Acquire_Load(once) != ONCE_STATE_DONE) {
+ CallOnceImpl(once, reinterpret_cast<PointerArgFunction>(init_func),
+ static_cast<void*>(arg));
+ }
+}
+
+} } // namespace v8::internal
+
+#endif // V8_ONCE_H_
Property changes on: src/once.h
___________________________________________________________________
Added: svn:eol-style
+ LF
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