michael@0: //
michael@0: //  SkTLS.h
michael@0: //
michael@0: //
michael@0: //  Created by Mike Reed on 4/21/12.
michael@0: //  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
michael@0: //
michael@0: 
michael@0: #ifndef SkTLS_DEFINED
michael@0: #define SkTLS_DEFINED
michael@0: 
michael@0: #include "SkTypes.h"
michael@0: 
michael@0: /**
michael@0:  *  Maintains a per-thread cache, using a CreateProc as the key into that cache.
michael@0:  */
michael@0: class SkTLS {
michael@0: public:
michael@0:     typedef void* (*CreateProc)();
michael@0:     typedef void  (*DeleteProc)(void*);
michael@0: 
michael@0:     /**
michael@0:      *  If Get() has previously been called with this CreateProc, then this
michael@0:      *  returns its cached data, otherwise it returns NULL. The CreateProc is
michael@0:      *  never invoked in Find, it is only used as a key for searching the
michael@0:      *  cache.
michael@0:      */
michael@0:     static void* Find(CreateProc);
michael@0: 
michael@0:     /**
michael@0:      *  Return the cached data that was returned by the CreateProc. This proc
michael@0:      *  is only called the first time Get is called, and there after it is
michael@0:      *  cached (per-thread), using the CreateProc as a key to look it up.
michael@0:      *
michael@0:      *  When this thread, or Delete is called, the cached data is removed, and
michael@0:      *  if a DeleteProc was specified, it is passed the pointer to the cached
michael@0:      *  data.
michael@0:      */
michael@0:     static void* Get(CreateProc, DeleteProc);
michael@0: 
michael@0:     /**
michael@0:      *  Remove (optionally calling the DeleteProc if it was specificed in Get)
michael@0:      *  the cached data associated with this CreateProc. If no associated cached
michael@0:      *  data is found, do nothing.
michael@0:      */
michael@0:     static void Delete(CreateProc);
michael@0: 
michael@0: private:
michael@0:     // Our implementation requires only 1 TLS slot, as we manage multiple values
michael@0:     // ourselves in a list, with the platform specific value as our head.
michael@0: 
michael@0:     /**
michael@0:      *  Implemented by the platform, to return the value of our (one) slot per-thread
michael@0:      *
michael@0:      *  If forceCreateTheSlot is true, then we must have created the "slot" for
michael@0:      *  our TLS, even though we know that the return value will be NULL in that
michael@0:      *  case (i.e. no-slot and first-time-slot both return NULL). This ensures
michael@0:      *  that after calling GetSpecific, we know that we can legally call
michael@0:      *  SetSpecific.
michael@0:      *
michael@0:      *  If forceCreateTheSlot is false, then the impl can either create the
michael@0:      *  slot or not.
michael@0:      */
michael@0:     static void* PlatformGetSpecific(bool forceCreateTheSlot);
michael@0: 
michael@0:     /**
michael@0:      *  Implemented by the platform, to set the value for our (one) slot per-thread
michael@0:      *
michael@0:      *  The implementation can rely on GetSpecific(true) having been previously
michael@0:      *  called before SetSpecific is called.
michael@0:      */
michael@0:     static void  PlatformSetSpecific(void*);
michael@0: 
michael@0: public:
michael@0:     /**
michael@0:      *  Will delete our internal list. To be called by the platform if/when its
michael@0:      *  TLS slot is deleted (often at thread shutdown).
michael@0:      *
michael@0:      *  Public *only* for the platform's use, not to be called by a client.
michael@0:      */
michael@0:     static void Destructor(void* ptr);
michael@0: };
michael@0: 
michael@0: #endif