/*
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* Copyright 2012 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkTLS_DEFINED
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#define SkTLS_DEFINED
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#include "SkTypes.h"
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/**
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* Maintains a per-thread cache, using a CreateProc as the key into that cache.
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*/
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class SkTLS {
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public:
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typedef void* (*CreateProc)();
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typedef void (*DeleteProc)(void*);
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/**
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* If Get() has previously been called with this CreateProc, then this
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* returns its cached data, otherwise it returns nullptr. The CreateProc is
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* never invoked in Find, it is only used as a key for searching the
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* cache.
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*/
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static void* Find(CreateProc);
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/**
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* Return the cached data that was returned by the CreateProc. This proc
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* is only called the first time Get is called, and there after it is
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* cached (per-thread), using the CreateProc as a key to look it up.
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*
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* When this thread, or Delete is called, the cached data is removed, and
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* if a DeleteProc was specified, it is passed the pointer to the cached
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* data.
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*/
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static void* Get(CreateProc, DeleteProc);
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/**
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* Remove (optionally calling the DeleteProc if it was specificed in Get)
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* the cached data associated with this CreateProc. If no associated cached
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* data is found, do nothing.
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*/
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static void Delete(CreateProc);
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private:
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// Our implementation requires only 1 TLS slot, as we manage multiple values
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// ourselves in a list, with the platform specific value as our head.
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/**
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* Implemented by the platform, to return the value of our (one) slot per-thread
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*
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* If forceCreateTheSlot is true, then we must have created the "slot" for
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* our TLS, even though we know that the return value will be nullptr in that
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* case (i.e. no-slot and first-time-slot both return nullptr). This ensures
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* that after calling GetSpecific, we know that we can legally call
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* SetSpecific.
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*
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* If forceCreateTheSlot is false, then the impl can either create the
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* slot or not.
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*/
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static void* PlatformGetSpecific(bool forceCreateTheSlot);
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/**
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* Implemented by the platform, to set the value for our (one) slot per-thread
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*
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* The implementation can rely on GetSpecific(true) having been previously
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* called before SetSpecific is called.
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*/
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static void PlatformSetSpecific(void*);
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public:
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/**
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* Will delete our internal list. To be called by the platform if/when its
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* TLS slot is deleted (often at thread shutdown).
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*
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* Public *only* for the platform's use, not to be called by a client.
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*/
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static void Destructor(void* ptr);
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};
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#endif
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