From: Ben Pfaff <blp@cs.stanford.edu>
Date: Mon, 20 Feb 2023 23:47:52 +0000 (-0800)
Subject: casereader: Make casereader_random_class function 'advance' optional.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a0fcc49e7e459973bb01891eb9f34b154f433b30;p=pspp

casereader: Make casereader_random_class function 'advance' optional.

Stateless casereaders don't necessarily need to do anything for it.
---

diff --git a/src/data/casereader-provider.h b/src/data/casereader-provider.h
index 2069eb678d..37bde24310 100644
--- a/src/data/casereader-provider.h
+++ b/src/data/casereader-provider.h
@@ -148,7 +148,7 @@ struct casereader_random_class
        function should call casereader_force_error on READER. */
     void (*destroy) (struct casereader *reader, void *aux);
 
-    /* Mandatory.
+    /* Optional.
 
        A call to this function tells the callee that the N
        cases at the beginning of READER will never be read again.
diff --git a/src/data/casereader.c b/src/data/casereader.c
index 1b06f42e8a..a410afcbcb 100644
--- a/src/data/casereader.c
+++ b/src/data/casereader.c
@@ -501,7 +501,8 @@ advance_random_reader (struct casereader *reader,
   if (new > old)
     {
       shared->min_offset = new;
-      shared->class->advance (reader, shared->aux, new - old);
+      if (shared->class->advance)
+        shared->class->advance (reader, shared->aux, new - old);
     }
 }