Make cases simpler, faster, and easier to understand.

[pspp-builds.git] / src / data / casewriter-translator.c

diff --git a/src/data/casewriter-translator.c b/src/data/casewriter-translator.c
index c630b44cda397dfffccd980c9d3ecb65255e91dc..a19533d65d330b6f443b308522e88d61b25687f6 100644 (file)
--- a/src/data/casewriter-translator.c
+++ b/src/data/casewriter-translator.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
 /* PSPP - a program for statistical analysis.

-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 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
 
    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


@@ -29,7 +29,7 @@ struct casewriter_translator
   {
     struct casewriter *subwriter;
 
   {
     struct casewriter *subwriter;
 

-    void (*translate) (struct ccase *input, struct ccase *output, void *aux);
+    struct ccase *(*translate) (struct ccase *, void *aux);

     bool (*destroy) (void *aux);
     void *aux;
   };
     bool (*destroy) (void *aux);
     void *aux;
   };


@@ -37,10 +37,15 @@ struct casewriter_translator
 static const struct casewriter_class casewriter_translator_class;
 
 /* Creates and returns a new casewriter whose cases are passed
 static const struct casewriter_class casewriter_translator_class;
 
 /* Creates and returns a new casewriter whose cases are passed

-   through TRANSLATE, which must create case OUTPUT, with
-   OUTPUT_VALUE_CNT values, and populate it based on INPUT and
-   auxiliary data AUX.  The translated cases are then written to
-   SUBWRITER.  TRANSLATE must also destroy INPUT.
+   through TRANSLATE, which must return a case with
+   OUTPUT_VALUE_CNT values, based on INPUT and auxiliary data
+   AUX.  (TRANSLATE may also return a null pointer, in which case
+   no case is written to the output.)  The translated cases are
+   then written to SUBWRITER.
+
+   TRANSLATE takes ownership of each case passed to it.  Thus, it
+   should either unref each case and return a new case, or
+   (unshare and then) modify and return the same case.

 
    When the translating casewriter is destroyed, DESTROY will be
    called to allow any state maintained by TRANSLATE to be freed.
 
    When the translating casewriter is destroyed, DESTROY will be
    called to allow any state maintained by TRANSLATE to be freed.


@@ -51,9 +56,8 @@ static const struct casewriter_class casewriter_translator_class;
 struct casewriter *
 casewriter_create_translator (struct casewriter *subwriter,
                               size_t translated_value_cnt,
 struct casewriter *
 casewriter_create_translator (struct casewriter *subwriter,
                               size_t translated_value_cnt,

-                              void (*translate) (struct ccase *input,
-                                                 struct ccase *output,
-                                                 void *aux),
+                              struct ccase *(*translate) (struct ccase *,
+                                                          void *aux),

                               bool (*destroy) (void *aux),
                               void *aux)
 {
                               bool (*destroy) (void *aux),
                               void *aux)
 {


@@ -75,10 +79,9 @@ casewriter_translator_write (struct casewriter *writer UNUSED,
                              void *ct_, struct ccase *c)
 {
   struct casewriter_translator *ct = ct_;
                              void *ct_, struct ccase *c)
 {
   struct casewriter_translator *ct = ct_;

-  struct ccase tmp;
-
-  ct->translate (c, &tmp, ct->aux);
-  casewriter_write (ct->subwriter, &tmp);
+  c = ct->translate (c, ct->aux);
+  if (c != NULL)
+    casewriter_write (ct->subwriter, c);

 }
 
 static void
 }
 
 static void