/**
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* \file
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* Lazy initialization and cleanup utilities
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*
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* Authors: Ludovic Henry <ludovic@xamarin.com>
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*
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* Copyright 2015 Xamarin, Inc. (www.xamarin.com)
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* Licensed under the MIT license. See LICENSE file in the project root for full license information.
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*/
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#ifndef __MONO_LAZY_INIT_H__
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#define __MONO_LAZY_INIT_H__
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#include <glib.h>
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#include <config.h>
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#include "atomic.h"
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#include "mono-threads.h"
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#include "mono-memory-model.h"
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/*
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* These functions should be used if you want some form of lazy initialization. You can have a look at the
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* threadpool for a more detailed example.
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*
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* The idea is that a module can be in 5 different states:
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* - not initialized: it is the first state it starts in
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* - initializing/initialized: whenever we need this module for the first time, we need to initialize it: allocate
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* memory, launch background thread, etc. To achieve this, we have a module specific function (let's call it
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* initialize)
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* - cleaning/cleaned: when we want to clean this module specific data up, then we need to clean it up: deallocate
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* memory, wait for background threads to finish, etc. As for the initialization process, we need a module specific
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* function (let's call it cleanup)
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*
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* The switch from one state to the other can only happen in the following ways:
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* - not initialized
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* - not initialized -> initializing -> initialized
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* - not initialized -> cleaned
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* - not initialized -> initializing -> initialized -> cleaning -> cleaned
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*
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* The initialize and cleanup functions are guaranteed to:
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* - be each called once and only once
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* - not be called concurrently (either 2+ initialize or 2+ cleanup, either initialize and cleanup)
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*/
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typedef gint32 mono_lazy_init_t;
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enum {
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MONO_LAZY_INIT_STATUS_NOT_INITIALIZED,
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MONO_LAZY_INIT_STATUS_INITIALIZING,
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MONO_LAZY_INIT_STATUS_INITIALIZED,
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MONO_LAZY_INIT_STATUS_CLEANING,
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MONO_LAZY_INIT_STATUS_CLEANED,
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};
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static inline gboolean
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mono_lazy_initialize (mono_lazy_init_t *lazy_init, void (*initialize) (void))
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{
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gint32 status;
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g_assert (lazy_init);
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status = *lazy_init;
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if (status >= MONO_LAZY_INIT_STATUS_INITIALIZED)
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return status == MONO_LAZY_INIT_STATUS_INITIALIZED;
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if (status == MONO_LAZY_INIT_STATUS_INITIALIZING
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|| mono_atomic_cas_i32 (lazy_init, MONO_LAZY_INIT_STATUS_INITIALIZING, MONO_LAZY_INIT_STATUS_NOT_INITIALIZED)
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!= MONO_LAZY_INIT_STATUS_NOT_INITIALIZED
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) {
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while (*lazy_init == MONO_LAZY_INIT_STATUS_INITIALIZING)
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mono_thread_info_yield ();
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g_assert (mono_atomic_load_i32 (lazy_init) >= MONO_LAZY_INIT_STATUS_INITIALIZED);
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return status == MONO_LAZY_INIT_STATUS_INITIALIZED;
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}
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initialize ();
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mono_atomic_store_release (lazy_init, MONO_LAZY_INIT_STATUS_INITIALIZED);
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return TRUE;
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}
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static inline void
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mono_lazy_cleanup (mono_lazy_init_t *lazy_init, void (*cleanup) (void))
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{
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gint32 status;
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g_assert (lazy_init);
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status = *lazy_init;
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if (status == MONO_LAZY_INIT_STATUS_NOT_INITIALIZED
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&& mono_atomic_cas_i32 (lazy_init, MONO_LAZY_INIT_STATUS_CLEANED, MONO_LAZY_INIT_STATUS_NOT_INITIALIZED)
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== MONO_LAZY_INIT_STATUS_NOT_INITIALIZED
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) {
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return;
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}
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if (status == MONO_LAZY_INIT_STATUS_INITIALIZING) {
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while ((status = *lazy_init) == MONO_LAZY_INIT_STATUS_INITIALIZING)
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mono_thread_info_yield ();
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}
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if (status == MONO_LAZY_INIT_STATUS_CLEANED)
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return;
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if (status == MONO_LAZY_INIT_STATUS_CLEANING
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|| mono_atomic_cas_i32 (lazy_init, MONO_LAZY_INIT_STATUS_CLEANING, MONO_LAZY_INIT_STATUS_INITIALIZED)
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!= MONO_LAZY_INIT_STATUS_INITIALIZED
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) {
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while (*lazy_init == MONO_LAZY_INIT_STATUS_CLEANING)
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mono_thread_info_yield ();
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g_assert (mono_atomic_load_i32 (lazy_init) == MONO_LAZY_INIT_STATUS_CLEANED);
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return;
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}
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cleanup ();
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mono_atomic_store_release (lazy_init, MONO_LAZY_INIT_STATUS_CLEANED);
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}
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static inline gboolean
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mono_lazy_is_initialized (mono_lazy_init_t *lazy_init)
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{
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g_assert (lazy_init);
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return mono_atomic_load_i32 (lazy_init) == MONO_LAZY_INIT_STATUS_INITIALIZED;
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}
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#endif
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