X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Flibpspp%2Ftower.c;h=02447d76237d335170dbbf877f099b41e20d8d8e;hb=c1e75ee809efd2f4bfd9ebcc1c2b0689c1da0e4c;hp=ead91e61a7093beda05e3708256be0ed9222b7d0;hpb=93b4335785430ab6de290b7978e2d506106a8ba5;p=pspp

diff --git a/src/libpspp/tower.c b/src/libpspp/tower.c
index ead91e61a7..02447d7623 100644
--- a/src/libpspp/tower.c
+++ b/src/libpspp/tower.c
@@ -1,32 +1,35 @@
-/* PSPP - computes sample statistics.
+/* PSPP - a program for statistical analysis.
    Copyright (C) 2007 Free Software Foundation, Inc.
 
-   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 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 3 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.
+   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., 51 Franklin Street, Fifth Floor, Boston, MA
-   02110-1301, USA. */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
 #include <config.h>
 
 #include <libpspp/tower.h>
 
+#include <limits.h>
+
 #include <libpspp/assertion.h>
 #include <libpspp/compiler.h>
 
 static struct tower_node *abt_to_tower_node (const struct abt_node *);
 static struct tower_node *first_node (const struct tower *);
+static struct tower_node *last_node (const struct tower *);
 static struct tower_node *next_node (const struct tower *,
                                      const struct tower_node *);
+static struct tower_node *prev_node (const struct tower *,
+                                     const struct tower_node *);
 static unsigned long int get_subtree_height (const struct abt_node *);
 static void reaugment_tower_node (struct abt_node *,
                                   const struct abt_node *,
@@ -35,21 +38,22 @@ static void reaugment_tower_node (struct abt_node *,
 
 /* Initializes T as an empty tower. */
 void
-tower_init (struct tower *t) 
+tower_init (struct tower *t)
 {
   abt_init (&t->abt, NULL, reaugment_tower_node, NULL);
+  t->cache_bottom = ULONG_MAX;
 }
 
 /* Returns true if T contains no nodes, false otherwise. */
 bool
-tower_is_empty (const struct tower *t) 
+tower_is_empty (const struct tower *t)
 {
   return t->abt.root == NULL;
 }
 
 /* Returns the total height of tower T. */
 unsigned long
-tower_height (const struct tower *t) 
+tower_height (const struct tower *t)
 {
   return get_subtree_height (t->abt.root);
 }
@@ -58,20 +62,22 @@ tower_height (const struct tower *t)
    node UNDER, or at the top of T if UNDER is a null pointer. */
 void
 tower_insert (struct tower *t, unsigned long height, struct tower_node *new,
-              struct tower_node *under) 
+              struct tower_node *under)
 {
   assert (height > 0);
   new->height = height;
   abt_insert_before (&t->abt, under ? &under->abt_node : NULL,
                      &new->abt_node);
+  t->cache_bottom = ULONG_MAX;
 }
 
 /* Deletes NODE from tower T. */
 struct tower_node *
-tower_delete (struct tower *t, struct tower_node *node) 
+tower_delete (struct tower *t, struct tower_node *node)
 {
   struct tower_node *next = next_node (t, node);
   abt_delete (&t->abt, &node->abt_node);
+  t->cache_bottom = ULONG_MAX;
   return next;
 }
 
@@ -83,6 +89,7 @@ tower_resize (struct tower *t, struct tower_node *node,
   assert (new_height > 0);
   node->height = new_height;
   abt_reaugmented (&t->abt, &node->abt_node);
+  t->cache_bottom = ULONG_MAX;
 }
 
 /* Removes nodes FIRST through LAST (exclusive) from tower SRC
@@ -95,10 +102,10 @@ tower_resize (struct tower *t, struct tower_node *node,
 void
 tower_splice (struct tower *dst, struct tower_node *under,
               struct tower *src,
-              struct tower_node *first, struct tower_node *last) 
+              struct tower_node *first, struct tower_node *last)
 {
   struct tower_node *next;
-  
+
   /* Conceptually, DST == SRC is valid.
      Practically, it's more difficult to get it right, and our
      client code doesn't need it. */
@@ -110,6 +117,7 @@ tower_splice (struct tower *dst, struct tower_node *under,
       abt_insert_before (&dst->abt, under ? &under->abt_node : NULL,
                          &first->abt_node);
     }
+  dst->cache_bottom = src->cache_bottom = ULONG_MAX;
 }
 
 /* Returns the node at the given HEIGHT from the bottom of tower
@@ -118,25 +126,32 @@ tower_splice (struct tower *dst, struct tower_node *under,
    of the returned node, which may be less than HEIGHT if HEIGHT
    refers to the middle of a node instead of its bottom. */
 struct tower_node *
-tower_lookup (const struct tower *t,
+tower_lookup (const struct tower *t_,
               unsigned long height,
-              unsigned long *node_start) 
+              unsigned long *node_start)
 {
+  struct tower *t = (struct tower *) t_;
   struct abt_node *p;
 
   assert (height < tower_height (t));
 
+  if (height >= t->cache_bottom && height - t->cache_bottom < t->cache->height)
+    {
+      *node_start = t->cache_bottom;
+      return t->cache;
+    }
+
   *node_start = 0;
   p = t->abt.root;
   for (;;)
     {
       unsigned long left_height = get_subtree_height (p->down[0]);
-      if (height < left_height) 
+      if (height < left_height)
         {
           /* Our goal height must lie within the left subtree. */
           p = p->down[0];
         }
-      else 
+      else
         {
           /* Our goal height cannot be in the left subtree. */
           struct tower_node *node = abt_to_tower_node (p);
@@ -144,17 +159,19 @@ tower_lookup (const struct tower *t,
 
           height -= left_height;
           *node_start += left_height;
-          if (height < node_height) 
+          if (height < node_height)
             {
               /* Our goal height is in P. */
-              return node; 
+              t->cache = node;
+              t->cache_bottom = *node_start;
+              return node;
             }
-          else 
+          else
             {
               /* Our goal height is in the right subtree. */
               p = p->down[1];
               height -= node_height;
-              *node_start += node_height; 
+              *node_start += node_height;
             }
         }
     }
@@ -163,47 +180,83 @@ tower_lookup (const struct tower *t,
 /* Returns the node at height 0 in tower T, or a null pointer if
    T is empty. */
 struct tower_node *
-tower_first (const struct tower *t) 
+tower_first (const struct tower *t)
 {
   return first_node (t);
 }
 
+/* Returns the node at the top of tower T, or a null pointer if T
+   is empty. */
+struct tower_node *
+tower_last (const struct tower *t)
+{
+  return last_node (t);
+}
+
 /* If NODE is nonnull, returns the node just above NODE in tower
    T, or a null pointer if NODE is the topmost node in T.
    If NODE is null, acts like tower_first. */
 struct tower_node *
-tower_next (const struct tower *t, const struct tower_node *node) 
+tower_next (const struct tower *t, const struct tower_node *node)
 {
   return node != NULL ? next_node (t, node) : first_node (t);
 }
+
+/* If NODE is nonnull, returns the node just below NODE in tower
+   T, or a null pointer if NODE is the bottommost node in T.
+   If NODE is null, acts like tower_last. */
+struct tower_node *
+tower_prev (const struct tower *t, const struct tower_node *node)
+{
+  return node != NULL ? prev_node (t, node) : last_node (t);
+}
 
 /* Returns the tower node corresponding to the given ABT_NODE. */
 static struct tower_node *
-abt_to_tower_node (const struct abt_node *abt_node) 
+abt_to_tower_node (const struct abt_node *abt_node)
 {
   return abt_data (abt_node, struct tower_node, abt_node);
 }
 
-/* Returns the first node in TOWER. */
+/* Returns the tower node corresponding to the given ABT_NODE. */
 static struct tower_node *
-first_node (const struct tower *t) 
+abt_to_tower_node_null (const struct abt_node *abt_node)
 {
-  struct abt_node *abt_node = abt_first (&t->abt);
   return abt_node != NULL ? abt_to_tower_node (abt_node) : NULL;
 }
 
+/* Returns the first node in TOWER. */
+static struct tower_node *
+first_node (const struct tower *t)
+{
+  return abt_to_tower_node_null (abt_first (&t->abt));
+}
+
+/* Returns the first node in TOWER. */
+static struct tower_node *
+last_node (const struct tower *t)
+{
+  return abt_to_tower_node_null (abt_last (&t->abt));
+}
+
 /* Returns the next node in TOWER after NODE. */
 static struct tower_node *
-next_node (const struct tower *t, const struct tower_node *node) 
+next_node (const struct tower *t, const struct tower_node *node)
 {
-  struct abt_node *abt_node = abt_next (&t->abt, &node->abt_node);
-  return abt_node != NULL ? abt_to_tower_node (abt_node) : NULL;
+  return abt_to_tower_node_null (abt_next (&t->abt, &node->abt_node));
+}
+
+/* Returns the previous node in TOWER before NODE. */
+static struct tower_node *
+prev_node (const struct tower *t, const struct tower_node *node)
+{
+  return abt_to_tower_node_null (abt_prev (&t->abt, &node->abt_node));
 }
 
 /* Returns the total height of the nodes in the subtree rooted at
    P, or 0 if P is null. */
 static unsigned long int
-get_subtree_height (const struct abt_node *p) 
+get_subtree_height (const struct abt_node *p)
 {
   return p != NULL ? abt_to_tower_node (p)->subtree_height : 0;
 }