X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdata%2Fcasereader.c;h=8b78645627e1243f4efb875612b97eac2666cc70;hb=c90c44ab307b3ba49f606d2bae80e6aff1e228d7;hp=3c062d9068b6355ace4f8e3caf005b89cd7c25ad;hpb=d908f52b818f4fdf2ab23797756812ec2986bd2b;p=pspp

diff --git a/src/data/casereader.c b/src/data/casereader.c
index 3c062d9068..8b78645627 100644
--- a/src/data/casereader.c
+++ b/src/data/casereader.c
@@ -1,20 +1,18 @@
-/* PSPP - computes sample statistics.
+/* PSPP - a program for statistical analysis.
    Copyright (C) 2007 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 the Free Software Foundation; either version 2 of the
-   License, or (at your option) any later version.
+   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
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
 
-   This program is distributed in the hope that it will be useful, but
-   WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-   02110-1301, USA. */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
 #include <config.h>
 
@@ -58,19 +56,30 @@ static void insert_shim (struct casereader *);
 bool
 casereader_read (struct casereader *reader, struct ccase *c)
 {
-  if (reader->case_cnt != 0 && reader->class->read (reader, reader->aux, c))
+  if (reader->case_cnt != 0)
     {
-      assert (case_get_value_cnt (c) == reader->value_cnt);
+      /* ->read may use casereader_swap to replace itself by
+         another reader and then delegate to that reader by
+         recursively calling casereader_read.  Currently only
+         lazy_casereader does this and, with luck, nothing else
+         ever will.
+
+         To allow this to work, however, we must decrement
+         case_cnt before calling ->read.  If we decremented
+         case_cnt after calling ->read, then this would actually
+         drop two cases from case_cnt instead of one, and we'd
+         lose the last case in the casereader. */
       if (reader->case_cnt != CASENUMBER_MAX)
         reader->case_cnt--;
-      return true;
-    }
-  else
-    {
-      reader->case_cnt = 0;
-      case_nullify (c);
-      return false;
+      if (reader->class->read (reader, reader->aux, c))
+        {
+          assert (case_get_value_cnt (c) >= reader->value_cnt);
+          return true;
+        }
     }
+  reader->case_cnt = 0;
+  case_nullify (c);
+  return false;
 }
 
 /* Destroys READER.
@@ -313,6 +322,26 @@ casereader_create_sequential (const struct taint *taint,
   reader->aux = aux;
   return reader;
 }
+
+/* If READER is a casereader of the given CLASS, returns its
+   associated auxiliary data; otherwise, returns a null pointer.
+
+   This function is intended for use from casereader
+   implementations, not by casereader users.  Even within
+   casereader implementations, its usefulness is quite limited,
+   for at least two reasons.  First, every casereader member
+   function already receives a pointer to the casereader's
+   auxiliary data.  Second, a casereader's class can change
+   (through a call to casereader_swap) and this is in practice
+   quite common (e.g. any call to casereader_clone on a
+   casereader that does not directly support clone will cause the
+   casereader to be replaced by a shim caseader). */
+void *
+casereader_dynamic_cast (struct casereader *reader,
+                         struct casereader_class *class)
+{
+  return reader->class == class ? reader->aux : NULL;
+}
 
 /* Random-access casereader implementation.