X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Falgorithm.c;h=ca427a0d49549acf11e8ce099ee1072a1793853d;hb=dbb0228a4c98cbf4756ba651fda158c1565b3b55;hp=209b0b0f63cce3e3c256adf8f4ef9293ac0fdd1a;hpb=4fdeb2145d081ff1b84e3f6c99f9d1c048c0d64a;p=pspp

diff --git a/src/algorithm.c b/src/algorithm.c
index 209b0b0f63..ca427a0d49 100644
--- a/src/algorithm.c
+++ b/src/algorithm.c
@@ -393,6 +393,36 @@ remove_element (void *array, size_t count, size_t size,
   remove_range (array, count, size, idx, 1);
 }
 
+/* Moves an element in ARRAY, which consists of COUNT elements of
+   SIZE bytes each, from OLD_IDX to NEW_IDX, shifting around
+   other elements as needed.  Runs in O(abs(OLD_IDX - NEW_IDX))
+   time. */
+void
+move_element (void *array_, size_t count, size_t size,
+              size_t old_idx, size_t new_idx) 
+{
+  assert (array_ != NULL || count == 0);
+  assert (old_idx < count);
+  assert (new_idx < count);
+  
+  if (old_idx != new_idx) 
+    {
+      char *array = array_;
+      char *element = xmalloc (size);
+      char *new = array + new_idx * size;
+      char *old = array + old_idx * size;
+
+      memcpy (element, old, size);
+      if (new < old)
+        memmove (new + size, new, (old_idx - new_idx) * size);
+      else
+        memmove (old, old + size, (new_idx - old_idx) * size);
+      memcpy (new, element, size);
+
+      free (element);
+    }
+}
+
 /* A predicate and its auxiliary data. */
 struct pred_aux 
   {