Generisise map implementation.

1 files changed, 126 insertions, 0 deletions

diff --git a/libdimension/map.c b/libdimension/map.c
new file mode 100644
index 0000000..3ea4b0c
--- /dev/null
+++ b/libdimension/map.c
@@ -0,0 +1,126 @@
+/*************************************************************************
+ * Copyright (C) 2010 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library 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  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Generic maps.
+ */
+
+#include "dimension.h"
+#include <alloca.h>
+
+/** An [index, object] pair. */
+typedef struct dmnsn_map_entry {
+  double n;
+  char object[];
+} dmnsn_map_entry;
+
+dmnsn_map *
+dmnsn_new_map(size_t size)
+{
+  dmnsn_map *map = dmnsn_malloc(sizeof(dmnsn_map));
+  map->free_fn = NULL;
+  map->obj_size = size;
+  map->array = dmnsn_new_array(sizeof(dmnsn_map_entry) + size);
+  return map;
+}
+
+void
+dmnsn_delete_map(dmnsn_map *map)
+{
+  if (map) {
+    if (map->free_fn) {
+      for (size_t i = 0; i < dmnsn_array_size(map->array); ++i) {
+        dmnsn_map_entry *entry = dmnsn_array_at(map->array, i);
+        (*map->free_fn)(entry->object);
+      }
+    }
+
+    dmnsn_delete_array(map->array);
+    dmnsn_free(map);
+  }
+}
+
+void
+dmnsn_add_map_entry(dmnsn_map *map, double n, const void *obj)
+{
+  dmnsn_map_entry *entry = alloca(sizeof(dmnsn_map_entry) + map->obj_size);
+  entry->n = n;
+  memcpy(entry->object, obj, map->obj_size);
+
+  /* Sorted insertion */
+  size_t i;
+  for (i = dmnsn_array_size(map->array); i-- > 0;) {
+    dmnsn_map_entry *other = dmnsn_array_at(map->array, i);
+    if (other->n <= n)
+      break;
+  }
+
+  dmnsn_array_insert(map->array, i + 1, entry);
+}
+
+size_t
+dmnsn_map_size(const dmnsn_map *map)
+{
+  return dmnsn_array_size(map->array);
+}
+
+void
+dmnsn_evaluate_map(const dmnsn_map *map, double n,
+                   double *val, void *obj1, void *obj2)
+{
+  dmnsn_assert(dmnsn_array_size(map->array) > 0,
+               "Attempt to evaluate empty map.");
+
+  const dmnsn_map_entry *entry = dmnsn_array_first(map->array);
+
+  double n1, n2 = 0.0;
+  const void *o1, *o2 = entry->object;
+
+  if (n < n2) {
+    *val = 0.0;
+    memcpy(obj1, o2, map->obj_size);
+    memcpy(obj2, o2, map->obj_size);
+    return;
+  }
+
+  const dmnsn_map_entry *last = dmnsn_array_last(map->array);
+  ptrdiff_t skip = sizeof(dmnsn_map_entry) + map->obj_size;
+  for (; entry <= last;
+       entry = (const dmnsn_map_entry *)((const char *)entry + skip))
+  {
+    n1 = n2;
+    o1 = o2;
+
+    n2 = entry->n;
+    o2 = entry->object;
+
+    if (n < n2) {
+      *val = (n - n1)/(n2 - n1);
+      memcpy(obj1, o1, map->obj_size);
+      memcpy(obj2, o2, map->obj_size);
+      return;
+    }
+  }
+
+  *val = 1.0;
+  memcpy(obj1, o2, map->obj_size);
+  memcpy(obj2, o2, map->obj_size);
+}