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-rw-r--r--libshouldbeinlibc/cacheq.c142
-rw-r--r--libshouldbeinlibc/cacheq.h85
2 files changed, 227 insertions, 0 deletions
diff --git a/libshouldbeinlibc/cacheq.c b/libshouldbeinlibc/cacheq.c
new file mode 100644
index 00000000..8275dbe7
--- /dev/null
+++ b/libshouldbeinlibc/cacheq.c
@@ -0,0 +1,142 @@
+/* Helper functions for maintaining a fixed-size lru-ordered queue
+
+ Copyright (C) 1996 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 <malloc.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;
+ 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;
+ 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, *end = new_entries + esz * length;
+ 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)
+ bcopy (fh, th, esz); /* Copy the bits in a moved entry. */
+ else if (th)
+ bzero (th, esz); /* Zero the bits in a new entry. */
+
+ if (th)
+ /* Fixup headers. */
+ {
+ th->prev = prev_th;
+ th->next = next_th;
+ }
+
+ /* Call user hooks as appropiate. */
+ 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;
+}
diff --git a/libshouldbeinlibc/cacheq.h b/libshouldbeinlibc/cacheq.h
new file mode 100644
index 00000000..d3c688e8
--- /dev/null
+++ b/libshouldbeinlibc/cacheq.h
@@ -0,0 +1,85 @@
+/* Helper functions for maintaining a fixed-size lru-ordered queue
+
+ Copyright (C) 1996 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. */
+
+#ifndef __CACHEQ_H__
+#define __CACHEQ_H__
+
+#include <stddef.h>
+#include <errno.h>
+
+/* This header occurs at the start of every cacheq entry. */
+struct cacheq_hdr
+{
+ /* Next and prev entries in the cache, linked in LRU order. These are of
+ type `void *' so that it's conveient to iterate through the list using a
+ variable pointing to a structure that contains the header, by using
+ something like `VAR = VAR->hdr.next'. */
+ void *next, *prev;
+};
+
+/* A cacheq. Note that this structure is laid out to allow convenient use as
+ static initialized data. */
+struct cacheq
+{
+ /* The size of each entry, including its cacheq_hdr. */
+ size_t entry_size;
+
+ /* If non-0, then when making new entries (for instance, when the cacheq is
+ initialized, or when its size is increased), this function is called on
+ each new entry (with it's header already initialized). If this function
+ isn't defined, then each entry is simply zeroed. */
+ void (*init_entry) (void *entry);
+
+ /* When an entry is moved from one place in memory to another (for
+ instance, changing the size of the cache, new storage is used), this is
+ called for each entry, with FROM and TO the old and new locations of the
+ entry (and TO contains a bitwise copy of FROM). This is often useful
+ when the entry points to something that contains a backpointer to it. */
+ void (*move_entry) (void *from, void *to);
+
+ /* When entries are removed for some reason (for instance, when reducing
+ the size of the cacheq), this function is called on each. */
+ void (*finalize_entry) (void *entry);
+
+ /* The number of entries in the cache. This number is fixed. */
+ int length;
+
+ /* A buffer holding malloc'd memory for all the entries -- NUM_ENTRIES
+ entries of size ENTRY_SIZE. */
+ void *entries;
+
+ /* The least, and most, recently used entries in the cache. These point to
+ either end of a linked list composed of all the elements of the cache.
+ This list will always be the same length -- if an element is `removed',
+ its entry is simply marked inactive, and moved to the LRU end of the list
+ so it will be reused first. */
+ struct cacheq_hdr *lru, *mru;
+};
+
+/* Move ENTRY to the most-recently-used end of CACHEQ. */
+void cacheq_make_mru (struct cacheq *cq, void *entry);
+
+/* Move ENTRY to the least-recently-used end of CACHEQ. */
+void cacheq_make_lru (struct cacheq *cq, void *entry);
+
+/* Change CQ's size to be LENGTH entries. */
+error_t cacheq_set_length (struct cacheq *cq, int length);
+
+#endif /* __CACHEQ_H__ */
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