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/*
* Mach Operating System
* Copyright (c) 1991,1990,1989 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
#ifndef _VM_VM_EXTERNAL_H_
#define _VM_VM_EXTERNAL_H_
/*
* External page management hint technology
*
* The data structure exported by this module maintains
* a (potentially incomplete) map of the pages written
* to external storage for a range of virtual memory.
*/
/*
* The data structure representing the state of pages
* on external storage.
*/
typedef struct vm_external {
int existence_size; /* Size of the following bitmap */
char *existence_map; /* A bitmap of pages that have
* been written to backing
* storage.
*/
int existence_count;/* Number of bits turned on in
* existence_map.
*/
} *vm_external_t;
#define VM_EXTERNAL_NULL ((vm_external_t) 0)
#define VM_EXTERNAL_SMALL_SIZE 128
#define VM_EXTERNAL_LARGE_SIZE 8192
/*
* The states that may be recorded for a page of external storage.
*/
typedef int vm_external_state_t;
#define VM_EXTERNAL_STATE_EXISTS 1
#define VM_EXTERNAL_STATE_UNKNOWN 2
#define VM_EXTERNAL_STATE_ABSENT 3
/*
* Routines exported by this module.
*/
extern void vm_external_module_initialize();
/* Initialize the module */
extern vm_external_t vm_external_create(); /* Create a vm_external_t */
extern void vm_external_destroy(); /* Destroy one */
extern void vm_external_state_set();/* Set state of a page. */
#define vm_external_state_get(e,offset) (((e) != VM_EXTERNAL_NULL) ? \
_vm_external_state_get(e, offset) : \
VM_EXTERNAL_STATE_UNKNOWN)
/* Retrieve the state
* for a given page, if known.
*/
extern vm_external_state_t _vm_external_state_get();
/* HIDDEN routine */
#endif /* _VM_VM_EXTERNAL_H_ */
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