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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.
- */
- #if 0
- /* XXX: Currently, existence_count is not used. I guess it
- could be useful to get rid of the map if the count drops to
- zero. */
- int existence_count;/* Number of bits turned on in
- * existence_map.
- */
- #endif
- } *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.
- */
- /* Initialize the module */
- extern void vm_external_module_initialize(void);
- /* Create a vm_external_t */
- extern vm_external_t vm_external_create(vm_offset_t);
- /* Destroy one */
- extern void vm_external_destroy(vm_external_t);
- /* Set state of a page. */
- extern void vm_external_state_set(vm_external_t, vm_offset_t,
- vm_external_state_t);
- /* Retrieve the state for a given page, if known. */
- #define vm_external_state_get(e,offset) (((e) != VM_EXTERNAL_NULL) ? \
- _vm_external_state_get(e, offset) : \
- VM_EXTERNAL_STATE_UNKNOWN)
- /* HIDDEN routine */
- extern vm_external_state_t _vm_external_state_get(vm_external_t, vm_offset_t);
- #endif /* _VM_VM_EXTERNAL_H_ */
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