Initial revision

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__ */