1 files changed, 131 insertions, 0 deletions
diff --git a/sql/hash_filo.h b/sql/hash_filo.h
new file mode 100644
index 00000000000..7d659f706a3
--- /dev/null
+++ b/sql/hash_filo.h
@@ -0,0 +1,131 @@
+/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+   
+   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 of the License, 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+
+/*
+** A class for static sized hash tables where old entries are deleted in
+** first-in-last-out to usage.
+*/
+
+#ifndef  HASH_FILO_H
+#define  HASH_FILO_H
+
+#ifdef __GNUC__
+#pragma interface			/* gcc class implementation */
+#endif
+
+class hash_filo_element
+{
+  hash_filo_element *next_used,*prev_used;
+ public:
+  hash_filo_element() {}
+  friend class hash_filo;
+};
+
+
+class hash_filo
+{
+  const uint size, key_offset, key_length;
+  const hash_get_key get_key;
+  void (*free_element)(void*);
+  bool init;
+
+  hash_filo_element *first_link,*last_link;
+public:
+  pthread_mutex_t lock;
+  HASH cache;
+
+  hash_filo(uint size_arg, uint key_offset_arg , uint key_length_arg,
+	    hash_get_key get_key_arg,void (*free_element_arg)(void*))
+    :size(size_arg), key_offset(key_offset_arg), key_length(key_length_arg),
+    get_key(get_key_arg), free_element(free_element_arg),init(0)
+  {
+    bzero((char*) &cache,sizeof(cache));
+  }
+
+  ~hash_filo()
+  {
+    if (init)
+    {
+      if (cache.array.buffer)	/* Avoid problems with thread library */
+	(void) hash_free(&cache);
+      pthread_mutex_destroy(&lock);
+    }
+  }
+  void clear(bool locked=0)
+  {
+    if (!init)
+    {
+      init=1;
+      (void) pthread_mutex_init(&lock,NULL);
+    }
+    if (!locked)
+      (void) pthread_mutex_lock(&lock);
+    (void) hash_free(&cache);
+    (void) hash_init(&cache,size,key_offset, key_length, get_key, free_element,
+		     0);
+    if (!locked)
+      (void) pthread_mutex_unlock(&lock);
+    first_link=last_link=0;
+  }
+
+  hash_filo_element *search(gptr key,uint length)
+  {
+    hash_filo_element *entry=(hash_filo_element*)
+      hash_search(&cache,(byte*) key,length);
+    if (entry)
+    {						// Found; link it first
+      if (entry != first_link)
+      {						// Relink used-chain
+	if (entry == last_link)
+	  last_link=entry->prev_used;
+	else
+	{
+	  entry->next_used->prev_used = entry->prev_used;
+	  entry->prev_used->next_used = entry->next_used;
+	}
+	if ((entry->next_used= first_link))
+	  first_link->prev_used=entry;
+	first_link=entry;
+      }
+    }
+    return entry;
+  }
+
+  my_bool add(hash_filo_element *entry)
+  {
+    if (cache.records == size)
+    {
+      hash_filo_element *tmp=last_link;
+      last_link=last_link->prev_used;
+      hash_delete(&cache,(byte*) tmp);
+    }
+    if (hash_insert(&cache,(byte*) entry))
+    {
+      if (free_element)
+	(*free_element)(entry);		// This should never happen
+      return 1;
+    }
+    if ((entry->next_used=first_link))
+      first_link->prev_used=entry;
+    else
+      last_link=entry;
+    first_link=entry;
+    return 0;
+  }
+};
+
+#endif