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allocator(3m)		     MBA Library Functions		 allocator(3m)

       allocator - Allocate and	free memory.

       #include	<mba/allocator.h>

       struct allocator	*stdlib_allocator;

       typedef int (*reclaim_fn)(struct	allocator *al, void *arg, int attempt);
       typedef void *(*new_fn)(void *context, size_t size, int flags);
       typedef int (*del_fn)(void *context, void *object);

       void *allocator_alloc(struct allocator *al, size_t size,	int flags);
       int allocator_free(struct allocator *al,	void *obj);
       void *allocator_realloc(struct allocator	*al, void *obj,	size_t size);
       void allocator_set_reclaim(struct allocator *al,	reclaim_fn recl, void *arg);

       The  allocator(3m) module defines an interface for allocating and free-
       ing memory without defining the implementation. Modules that  implement
       this  interface	such as	suba(3m) provide a struct allocator * that can
       be used with these functions. Modules that utilize this interface  such
       as  varray(3m)  accept the specification	of an allocator. This abstrac-
       tion permits changing the memory	management behavior of	a  program  by
       switching allocators.

       alloc  The allocator_alloc function allocates and returns at least size
	      bytes of memory from the	allocator  al.	 The  memory  will  be
	      aligned appropriately for	the platform. The flags	parameter per-
	      mits additional allocator	specific information to	be  specified.
	      The  stdlib_allocator and	suba(3m) allocator support the value 1
	      for this flag to indicate	that the memory	should be set to  zero
	      (like  calloc).	If  al	is  NULL  memory is allocated from the

       free   The allocator_free function releases the memory  pointed	to  by
	      obj back to the allocator	al.

	      The  allocator_realloc function resizes the memory pointed to by
	      ptr using	the allocator al.  The old portion of the memory  will
	      be  unchanged  up	 to  size bytes. If obj	is NULL, size bytes of
	      memory will be allocated.	If size	is 0, obj will be  freed.  The
	      pointer  to obj must have	been allocated previously from the al-
	      locator al.

	      The allocator_set_reclaim	function sets the function  that  will
	      be  called to reclaim memory when	it becomes scarce. The reclaim
	      function will be called with the provided	arg parameter and  may
	      be  called more than once	indicating memory should be freed more
	      agressively with each call. The attempt parameter	indicates  how
	      may  times the reclaim function has been called without satisfy-
	      ing the allocators current need. The reclaim function should re-
	      turn  a positive value to	indicate that progress in freeing mem-
	      ory has occured. If the reclaim function returns 0 it  will  not
	      be called	again and the allocation that created the memory pres-
	      sure will	return failure.	Currently  only	 the  suba(3m)	module
	      will  take  advantage  of	 this feedback mechanism. See also the
	      clean functions of other modules in this package.

       alloc  The allocator_alloc function returns  the	 allocated  memory  or
	      NULL  if an error	occured	in which case errno will be set	appro-
	      priately.	If al is NULL  the  memory  will  be  freed  from  the

       free   The  allocator_free  function returns zero upon success or -1 if
	      an error occured in which	case errno is set appropriately.

	      The allocator_realloc function returns a pointer to the  resized
	      memory which may not equal obj.  If an error occurs, NULL	is re-
	      turned and errno is set appropriately.

libmba-0.9.1			 Apr 29, 2005			 allocator(3m)


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