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/* Helper functions for maintaining a fixed-size lru-ordered queue
Copyright (C) 1996, 1998 Free Software Foundation, Inc.
Written by Miles Bader <miles@gnu.ai.mit.edu>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <string.h>
#include <stdlib.h>
#include "cacheq.h"
/* Move ENTRY to the most-recently-used end of CACHEQ. */
void
cacheq_make_mru (struct cacheq *cq, void *entry)
{
struct cacheq_hdr *h = entry;
if (h != cq->mru)
{
/* First remove it. We known H->prev isn't 0 because H wasn't
previously == MRU. */
((struct cacheq_hdr *)h->prev)->next = h->next;
if (h->next)
((struct cacheq_hdr *)h->next)->prev = h->prev;
else
cq->lru = h->prev;
/* Now make it MRU. */
h->next = cq->mru;
h->prev = 0;
((struct cacheq_hdr *)cq->mru)->prev = h;
cq->mru = h;
}
}
/* Move ENTRY to the least-recently-used end of CACHEQ. */
void
cacheq_make_lru (struct cacheq *cq, void *entry)
{
struct cacheq_hdr *h = entry;
if (h != cq->lru)
{
/* First remove it. We known H->next isn't 0 because H wasn't
previously == LRU. */
((struct cacheq_hdr *)h->next)->prev = h->prev;
if (h->prev)
((struct cacheq_hdr *)h->prev)->next = h->next;
else
cq->mru = h->next;
/* Now make it LRU. */
h->prev = cq->lru;
h->next = 0;
((struct cacheq_hdr *)cq->lru)->next = h;
cq->lru = h;
}
}
/* Change CQ's size to be LENGTH entries. */
error_t
cacheq_set_length (struct cacheq *cq, int length)
{
if (length != cq->length)
{
size_t esz = cq->entry_size;
void *new_entries = malloc (esz * length);
/* Source entries. */
struct cacheq_hdr *fh = cq->mru;
/* Destination entries (and limit). */
struct cacheq_hdr *th = new_entries;
struct cacheq_hdr *end = new_entries + esz * (length - 1);
struct cacheq_hdr *prev_th = 0;
if (! new_entries)
return ENOMEM;
while (fh || th)
{
struct cacheq_hdr *next_th =
(!th || th >= end) ? 0 : (void *)th + esz;
if (fh && th)
memcpy (th, fh, esz); /* Copy the bits in a moved entry. */
else if (th)
memset (th, 0, esz); /* Zero the bits in a new entry. */
if (th)
/* Fixup headers. */
{
th->prev = prev_th;
th->next = next_th;
}
/* Call user hooks as appropriate. */
if (fh && th)
{
if (cq->move_entry)
(*cq->move_entry) (fh, th);
}
else if (th)
{
if (cq->init_entry)
(*cq->init_entry) (th);
}
else
{
if (cq->finalize_entry)
(*cq->finalize_entry) (fh);
}
if (fh)
fh = fh->next;
if (th)
{
prev_th = th;
th = next_th;
}
}
free (cq->entries);
cq->entries = new_entries;
cq->mru = new_entries;
cq->lru = prev_th;
cq->length = length;
}
return 0;
}
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