X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdata%2Fcasereader-translator.c;h=f0411d1fa1430a75903e8e4e3f4317cb6b5ad3fa;hb=6abd8f3ba67ec3751fc47487c1e09cf8e8de144a;hp=feffa15c4510ba97e57cd95705cd9afd290c1e04;hpb=bd17d2af982332ee1791998361b1ac6731fe14fa;p=pspp

diff --git a/src/data/casereader-translator.c b/src/data/casereader-translator.c
index feffa15c45..f0411d1fa1 100644
--- a/src/data/casereader-translator.c
+++ b/src/data/casereader-translator.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2007, 2009 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009, 2011 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
@@ -15,15 +15,16 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
 #include <config.h>
-#include <data/val-type.h>
-#include <data/casereader.h>
+
 #include <stdlib.h>
 
-#include <data/variable.h>
-#include <data/casereader-provider.h>
-#include <libpspp/taint.h>
+#include "data/casereader-provider.h"
+#include "data/casereader.h"
+#include "data/val-type.h"
+#include "data/variable.h"
+#include "libpspp/taint.h"
 
-#include "xalloc.h"
+#include "gl/xalloc.h"
 
 /* Casereader that applies a user-supplied function to translate
    each case into another in an arbitrary fashion. */
@@ -46,6 +47,11 @@ static const struct casereader_class casereader_translator_class;
    INPUT and auxiliary data AUX.  TRANSLATE must destroy its
    input case.
 
+   TRANSLATE may be stateful, that is, the output for a given
+   case may depend on previous cases.  If TRANSLATE is stateless,
+   then you may want to use casereader_translate_stateless
+   instead, since it sometimes performs better.
+
    The cases returned by TRANSLATE must match OUTPUT_PROTO.
 
    When the translating casereader is destroyed, DESTROY will be
@@ -106,7 +112,110 @@ static const struct casereader_class casereader_translator_class =
     NULL,
     NULL,
   };
+
+/* Casereader that applies a user-supplied function to translate
+   each case into another in a stateless fashion. */
+
+/* A statelessly translating casereader. */
+struct casereader_stateless_translator
+  {
+    struct casereader *subreader; /* Source of input cases. */
+
+    casenumber case_offset;
+    struct ccase *(*translate) (struct ccase *input, casenumber,
+                                const void *aux);
+    bool (*destroy) (void *aux);
+    void *aux;
+  };
 
+static const struct casereader_random_class
+casereader_stateless_translator_class;
+
+/* Creates and returns a new casereader whose cases are produced by reading
+   from SUBREADER and passing through the TRANSLATE function.  TRANSLATE must
+   takes ownership of its input case and returns a translated case, populating
+   the translated case based on INPUT and auxiliary data AUX.
+
+   TRANSLATE must be stateless, that is, the output for a given case must not
+   depend on previous cases.  This is because cases may be retrieved in
+   arbitrary order, and some cases may be retrieved multiple times, and some
+   cases may be skipped and never retrieved at all.  If TRANSLATE is stateful,
+   use casereader_create_translator instead.
+
+   The casenumber argument to the TRANSLATE function is the absolute case
+   number in SUBREADER, that is, 0 when the first case in SUBREADER is being
+   translated, 1 when the second case is being translated, and so on.
+
+   The cases returned by TRANSLATE must match OUTPUT_PROTO.
+
+   When the stateless translating casereader is destroyed, DESTROY will be
+   called to allow any auxiliary data maintained by TRANSLATE to be freed.
+
+   After this function is called, SUBREADER must not ever again be referenced
+   directly.  It will be destroyed automatically when the translating
+   casereader is destroyed. */
+struct casereader *
+casereader_translate_stateless (
+  struct casereader *subreader,
+  const struct caseproto *output_proto,
+  struct ccase *(*translate) (struct ccase *input, casenumber,
+                              const void *aux),
+  bool (*destroy) (void *aux),
+  void *aux)
+{
+  struct casereader_stateless_translator *cst = xmalloc (sizeof *cst);
+  struct casereader *reader;
+  cst->subreader = casereader_rename (subreader);
+  cst->translate = translate;
+  cst->destroy = destroy;
+  cst->aux = aux;
+  reader = casereader_create_random (
+    output_proto, casereader_get_case_cnt (cst->subreader),
+    &casereader_stateless_translator_class, cst);
+  taint_propagate (casereader_get_taint (cst->subreader),
+                   casereader_get_taint (reader));
+  return reader;
+}
+
+/* Internal read function for stateless translating casereader. */
+static struct ccase *
+casereader_stateless_translator_read (struct casereader *reader UNUSED,
+                                      void *cst_, casenumber idx)
+{
+  struct casereader_stateless_translator *cst = cst_;
+  struct ccase *tmp = casereader_peek (cst->subreader, idx);
+  if (tmp != NULL)
+    tmp = cst->translate (tmp, cst->case_offset + idx, cst->aux);
+  return tmp;
+}
+
+/* Internal destroy function for translating casereader. */
+static void
+casereader_stateless_translator_destroy (struct casereader *reader UNUSED,
+                                         void *cst_)
+{
+  struct casereader_stateless_translator *cst = cst_;
+  casereader_destroy (cst->subreader);
+  cst->destroy (cst->aux);
+  free (cst);
+}
+
+static void
+casereader_stateless_translator_advance (struct casereader *reader UNUSED,
+                                         void *cst_, casenumber cnt)
+{
+  struct casereader_stateless_translator *cst = cst_;
+  cst->case_offset += casereader_advance (cst->subreader, cnt);
+}
+
+/* Casereader class for stateless translating casereader. */
+static const struct casereader_random_class
+casereader_stateless_translator_class =
+  {
+    casereader_stateless_translator_read,
+    casereader_stateless_translator_destroy,
+    casereader_stateless_translator_advance,
+  };
 
 
 struct casereader_append_numeric
@@ -382,7 +491,7 @@ uniquify (const struct ccase *c, void *aux)
   const union value *current_value = case_data (c, cdr->key);
   const int key_width = var_get_width (cdr->key);
   const double weight = cdr->weight ? case_data (c, cdr->weight)->f : 1.0;
-  const struct ccase *next_case = casereader_peek (cdr->clone, cdr->n + 1);
+  struct ccase *next_case = casereader_peek (cdr->clone, cdr->n + 1);
   int dir = 0;
 
   cdr->n ++;
@@ -390,9 +499,10 @@ uniquify (const struct ccase *c, void *aux)
 
   if ( NULL == next_case)
       goto end;
-  
+
   dir = value_compare_3way (case_data (next_case, cdr->key),
 			    current_value, key_width);
+  case_unref (next_case);
   if ( dir != 0 )
     {
       /* Insist that the data are sorted */
@@ -400,7 +510,7 @@ uniquify (const struct ccase *c, void *aux)
       cdr->direction = dir;
       goto end;
     }
-  
+
   return false;
 
  end:
@@ -425,7 +535,7 @@ consolodate_weight (struct ccase *input, void *aux)
   else
     {
       c = case_unshare_and_resize (input, cdr->proto);
-      case_data_rw_idx (c, caseproto_get_n_widths (cdr->proto) - 1)->f = cdr->prev_cc;    
+      case_data_rw_idx (c, caseproto_get_n_widths (cdr->proto) - 1)->f = cdr->prev_cc;
     }
 
   return c;
@@ -446,7 +556,7 @@ uniquify_destroy (void *aux)
 
 
 
-/* Returns a new casereader which is based upon INPUT, but which contains a maximum 
+/* Returns a new casereader which is based upon INPUT, but which contains a maximum
    of one case for each distinct value of KEY.
    If WEIGHT is non-null, then the new casereader's values for this variable
    will be the sum of all values matching KEY.