115 lines
2.6 KiB
C
115 lines
2.6 KiB
C
#ifndef _IPXE_REFCNT_H
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#define _IPXE_REFCNT_H
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/** @file
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*
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* Reference counting
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stddef.h>
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#include <assert.h>
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/**
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* A reference counter
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*
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* This data structure is designed to be embedded within a
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* reference-counted object.
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*
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* Reference-counted objects are freed when their reference count
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* drops below zero. This means that a freshly allocated-and-zeroed
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* reference-counted object will be freed on the first call to
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* ref_put().
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*/
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struct refcnt {
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/** Current reference count
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*
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* When this count is decremented below zero, the free()
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* method will be called.
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*/
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int count;
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/** Free containing object
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*
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* This method is called when the reference count is
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* decremented below zero.
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*
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* If this method is left NULL, the standard library free()
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* function will be called. The upshot of this is that you
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* may omit the free() method if the @c refcnt object is the
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* first element of your reference-counted struct.
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*/
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void ( * free ) ( struct refcnt *refcnt );
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};
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/**
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* Initialise a reference counter
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*
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* @v refcnt Reference counter
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* @v free Freeing function
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*/
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static inline __attribute__ (( always_inline )) void
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ref_init ( struct refcnt *refcnt,
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void ( * free ) ( struct refcnt *refcnt ) ) {
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refcnt->free = free;
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}
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/**
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* Initialise a reference counter
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*
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* @v refcnt Reference counter
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* @v free Free containing object
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*/
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#define ref_init( refcnt, free ) do { \
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if ( __builtin_constant_p ( (free) ) && ( (free) == NULL ) ) { \
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/* Skip common case of no initialisation required */ \
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} else { \
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ref_init ( (refcnt), (free) ); \
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} \
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} while ( 0 )
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/**
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* Initialise a static reference counter
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*
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* @v free_fn Free containing object
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*/
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#define REF_INIT( free_fn ) { \
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.free = free_fn, \
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}
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extern void ref_increment ( struct refcnt *refcnt );
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extern void ref_decrement ( struct refcnt *refcnt );
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/**
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* Get additional reference to object
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*
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* @v refcnt Reference counter, or NULL
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* @ret refcnt Reference counter
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*
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* If @c refcnt is NULL, no action is taken.
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*/
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#define ref_get( refcnt ) ( { \
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if ( refcnt ) \
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assert ( (refcnt)->count >= 0 ); \
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ref_increment ( refcnt ); \
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(refcnt); } )
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/**
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* Drop reference to object
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*
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* @v refcnt Reference counter, or NULL
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* @ret refcnt Reference counter
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*
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* If @c refcnt is NULL, no action is taken.
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*/
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#define ref_put( refcnt ) do { \
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if ( refcnt ) \
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assert ( (refcnt)->count >= 0 ); \
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ref_decrement ( refcnt ); \
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} while ( 0 )
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extern void ref_no_free ( struct refcnt *refcnt );
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#endif /* _IPXE_REFCNT_H */
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