Add lots of comments. Some minor substantive changes too:

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

diff --git a/src/data/casereader-translator.c b/src/data/casereader-translator.c
index f41dbb56fbc331af8adab5c6b93b472f09325158..28b9c180a18d7b433a8e8e20ae364f41ee8690bd 100644 (file)
--- a/src/data/casereader-translator.c
+++ b/src/data/casereader-translator.c
@@ -27,9 +27,13 @@
 
 #include "xalloc.h"
 
+/* Casereader that applies a user-supplied function to translate
+   each case into another in an arbitrary fashion. */
+
+/* A translating casereader. */
 struct casereader_translator
   {
-    struct casereader *subreader;
+    struct casereader *subreader; /* Source of input cases. */
 
     void (*translate) (const struct ccase *input, struct ccase *output,
                        void *aux);
@@ -39,6 +43,18 @@ struct casereader_translator
 
 static struct casereader_class casereader_translator_class;
 
+/* Creates and returns a new casereader whose cases are produced
+   by reading from SUBREADER and passing through TRANSLATE, which
+   must create case OUTPUT, with OUTPUT_VALUE_CNT values, and
+   populate it based on INPUT and auxiliary data AUX.  TRANSLATE
+   must also destroy INPUT.
+
+   When the translating casereader is destroyed, DESTROY will be
+   called to allow any state 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_create_translator (struct casereader *subreader,
                               size_t output_value_cnt,
@@ -46,7 +62,7 @@ casereader_create_translator (struct casereader *subreader,
                                                  struct ccase *output,
                                                  void *aux),
                               bool (*destroy) (void *aux),
-                              void *aux) 
+                              void *aux)
 {
   struct casereader_translator *ct = xmalloc (sizeof *ct);
   struct casereader *reader;
@@ -62,24 +78,26 @@ casereader_create_translator (struct casereader *subreader,
   return reader;
 }
 
+/* Internal read function for translating casereader. */
 static bool
 casereader_translator_read (struct casereader *reader UNUSED,
-                            void *ct_, struct ccase *c) 
+                            void *ct_, struct ccase *c)
 {
   struct casereader_translator *ct = ct_;
   struct ccase tmp;
 
-  if (casereader_read (ct->subreader, &tmp)) 
+  if (casereader_read (ct->subreader, &tmp))
     {
       ct->translate (&tmp, c, ct->aux);
-      return true; 
+      return true;
     }
   else
     return false;
 }
 
+/* Internal destroy function for translating casereader. */
 static void
-casereader_translator_destroy (struct casereader *reader UNUSED, void *ct_) 
+casereader_translator_destroy (struct casereader *reader UNUSED, void *ct_)
 {
   struct casereader_translator *ct = ct_;
   casereader_destroy (ct->subreader);
@@ -87,7 +105,8 @@ casereader_translator_destroy (struct casereader *reader UNUSED, void *ct_)
   free (ct);
 }
 
-static struct casereader_class casereader_translator_class = 
+/* Casereader class for translating casereader. */
+static struct casereader_class casereader_translator_class =
   {
     casereader_translator_read,
     casereader_translator_destroy,