X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdata%2Fcasereader.c;h=a410afcbcbfab2c826735d9ef94e4daffdca10f5;hb=df1d194af32e35739355981252785e768f21ebb0;hp=379e351edc781098558a24cecc0d2dc6e266f2c3;hpb=339f1956cc727eda788638644ef93ab7852b31cd;p=pspp

diff --git a/src/data/casereader.c b/src/data/casereader.c
index 379e351edc..a410afcbcb 100644
--- a/src/data/casereader.c
+++ b/src/data/casereader.c
@@ -147,8 +147,9 @@ casereader_swap (struct casereader *a, struct casereader *b)
    when it is no longer needed.  Returns a null pointer if cases
    have been exhausted or upon detection of an I/O error. */
 struct ccase *
-casereader_peek (struct casereader *reader, casenumber idx)
+casereader_peek (const struct casereader *reader_, casenumber idx)
 {
+  struct casereader *reader = CONST_CAST (struct casereader *, reader_);
   if (idx < reader->n_cases)
     {
       struct ccase *c;
@@ -171,7 +172,7 @@ casereader_peek (struct casereader *reader, casenumber idx)
    casereader_read will return true, because an error can occur
    in the meantime.) */
 bool
-casereader_is_empty (struct casereader *reader)
+casereader_is_empty (const struct casereader *reader)
 {
   if (reader->n_cases == 0)
     return true;
@@ -500,7 +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);
     }
 }