Make cases simpler, faster, and easier to understand.

[pspp-builds.git] / src / data / case-map.c

diff --git a/src/data/case-map.c b/src/data/case-map.c
index a1a65cc181564e784ab4d8a7f2b230501cf0fcc1..cff621f3456df7438562aa57d79dd78c4905fb3e 100644 (file)
--- a/src/data/case-map.c
+++ b/src/data/case-map.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 1997-9, 2000, 2006, 2007 Free Software Foundation, Inc.
+   Copyright (C) 1997-9, 2000, 2006, 2007, 2009 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
@@ -19,13 +19,17 @@
 #include <data/case-map.h>
 
 #include <stdio.h>
+#include <stdlib.h>
 
+#include <data/casereader.h>
+#include <data/casewriter.h>
 #include <data/dictionary.h>
 #include <data/variable.h>
 #include <data/case.h>
-#include <libpspp/alloc.h>
 #include <libpspp/assertion.h>
 
+#include "xalloc.h"
+
 /* A case map. */
 struct case_map
   {
@@ -34,6 +38,9 @@ struct case_map
                            corresponding source index. */
   };
 
+static struct ccase *translate_case (struct ccase *, void *map_);
+static bool destroy_case_map (void *map_);
+
 /* Creates and returns an empty map. */
 static struct case_map *
 create_case_map (size_t n)
@@ -76,20 +83,30 @@ case_map_destroy (struct case_map *map)
     }
 }
 
-/* Maps from SRC to DST, applying case map MAP. */
-void
-case_map_execute (const struct case_map *map,
-                  const struct ccase *src, struct ccase *dst)
-{
-  size_t dst_idx;
+/* If MAP is nonnull, returns a new case that is the result of
+   applying case map MAP to SRC, and unrefs SRC.
 
-  case_create (dst, map->value_cnt);
-  for (dst_idx = 0; dst_idx < map->value_cnt; dst_idx++)
+   If MAP is null, returns SRC unchanged. */
+struct ccase *
+case_map_execute (const struct case_map *map, struct ccase *src)
+{
+  if (map != NULL)
     {
-      int src_idx = map->map[dst_idx];
-      if (src_idx != -1)
-        *case_data_rw_idx (dst, dst_idx) = *case_data_idx (src, src_idx);
+      struct ccase *dst;
+      size_t dst_idx;
+
+      dst = case_create (map->value_cnt);
+      for (dst_idx = 0; dst_idx < map->value_cnt; dst_idx++)
+        {
+          int src_idx = map->map[dst_idx];
+          if (src_idx != -1)
+            *case_data_rw_idx (dst, dst_idx) = *case_data_idx (src, src_idx);
+        }
+      case_unref (src);
+      return dst;
     }
+  else
+    return src;
 }
 
 /* Returns the number of `union value's in cases created by
@@ -100,6 +117,62 @@ case_map_get_value_cnt (const struct case_map *map)
   return map->value_cnt;
 }
 
+/* Creates and returns a new casereader whose cases are produced
+   by reading from SUBREADER and executing the actions of MAP.  
+   The casereader will have as many `union value's as MAP.  When
+   the new casereader is destroyed, MAP will be destroyed too.
+
+   After this function is called, SUBREADER must not ever again
+   be referenced directly.  It will be destroyed automatically
+   when the returned casereader is destroyed. */
+struct casereader *
+case_map_create_input_translator (struct case_map *map,
+                                  struct casereader *subreader) 
+{
+    return casereader_create_translator (subreader,
+                                         case_map_get_value_cnt (map),
+                                         translate_case,
+                                         destroy_case_map,
+                                         map);
+}
+
+/* Creates and returns a new casewriter.  Cases written to the
+   new casewriter will be passed through MAP and written to
+   SUBWRITER.  The casewriter will have as many `union value's as
+   MAP.  When the new casewriter is destroyed, MAP will be
+   destroyed too.
+
+   After this function is called, SUBWRITER must not ever again
+   be referenced directly.  It will be destroyed automatically
+   when the returned casewriter is destroyed. */
+struct casewriter *
+case_map_create_output_translator (struct case_map *map,
+                                   struct casewriter *subwriter) 
+{
+    return casewriter_create_translator (subwriter,
+                                         case_map_get_value_cnt (map),
+                                         translate_case,
+                                         destroy_case_map,
+                                         map);
+}
+
+/* Casereader/casewriter translation callback. */
+static struct ccase *
+translate_case (struct ccase *input, void *map_)
+{
+  struct case_map *map = map_;
+  return case_map_execute (map, input);
+}
+
+/* Casereader/casewriter destruction callback. */
+static bool
+destroy_case_map (void *map_)
+{
+  struct case_map *map = map_;
+  case_map_destroy (map);
+  return true;
+}
+
 /* Creates and returns a case_map that can be used to compact
    cases for dictionary D.