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Re: a64l (and l64a) implementation is INCORRECT?


From: Andreas Schwab
Subject: Re: a64l (and l64a) implementation is INCORRECT?
Date: 23 Oct 2001 13:59:02 +0200
User-agent: Gnus/5.090003 (Oort Gnus v0.03) Emacs/21.1

Masaki Hasegawa <address@hidden> writes:

|> Dear Project members
|> 
|> Few years ago, I wrote a little program using a64l(3) on HP-UX machine.
|> And I have tried to port it to my Linux box that is running with glibc
|> 2.2.2, I have found that glibc's a64l returns differnt value than HP's.
|> For example:
|>   on HP machine ... a64l("./") returns 64 , but
|>   on glibc      ... a64l("./") returns 1 .
|> 
|> According to the Open Group "The Single UNIX Specification, Version 2"
|> (http://www.opengroup.org/onlinepubs/007908799/xsh/a64l.html):
|> > The a64l() function takes a pointer to a radix-64 representation,
|> > in which the first digit is the least significant, and returns ...
|>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|> It seems that the glibc's implementation is INCORRECT.

Thanks for your report.  The following patch will fix the problem:

2001-10-23  Andreas Schwab  <address@hidden>

        * stdlib/a64l.c: Expect least significant digit first.
        * stdlib/l64a.c: Produce least significant digit first.
        * stdlib/Makefile (tests): Add test-a64l.
        * stdlib/test-a64l.c: New file.
        Reported by Masaki Hasegawa <address@hidden>.

Index: stdlib/Makefile
===================================================================
RCS file: /cvs/glibc/libc/stdlib/Makefile,v
retrieving revision 1.78
diff -u -a -r1.78 stdlib/Makefile
--- stdlib/Makefile     2001/09/12 18:48:01     1.78
+++ stdlib/Makefile     2001/10/23 11:53:26
@@ -59,7 +59,7 @@
 tests          := tst-strtol tst-strtod testmb testrand testsort testdiv \
                   test-canon test-canon2 tst-strtoll tst-environ         \
                   tst-xpg-basename tst-random tst-bsearch tst-limits     \
-                  tst-rand48 bug-strtod tst-setcontext
+                  tst-rand48 bug-strtod tst-setcontext test-a64l
 
 
 # Several mpn functions from GNU MP are used by the strtod function.
Index: stdlib/a64l.c
===================================================================
RCS file: /cvs/glibc/libc/stdlib/a64l.c,v
retrieving revision 1.7
diff -u -a -r1.7 stdlib/a64l.c
--- stdlib/a64l.c       2001/07/06 04:55:41     1.7
+++ stdlib/a64l.c       2001/10/23 11:53:26
@@ -43,6 +43,7 @@
   const char *ptr = string;
   unsigned long int result = 0ul;
   const char *end = ptr + 6;
+  int shift = 0;
 
   do
     {
@@ -55,9 +56,9 @@
       value = (int) a64l_table[index];
       if (value == (int) XX)
        break;
-      result <<= 6;
       ++ptr;
-      result |= value;
+      result |= value << shift;
+      shift += 6;
     }
   while (ptr != end);
 
Index: stdlib/l64a.c
===================================================================
RCS file: /cvs/glibc/libc/stdlib/l64a.c,v
retrieving revision 1.8
diff -u -a -r1.8 stdlib/l64a.c
--- stdlib/l64a.c       2001/07/06 04:55:41     1.8
+++ stdlib/l64a.c       2001/10/23 11:53:26
@@ -47,13 +47,12 @@
     /* The value for N == 0 is defined to be the empty string. */
     return (char *) "";
 
-  result[6] = '\0';
-
-  for (cnt = 5; m > 0ul; --cnt)
+  for (cnt = 0; m > 0ul; ++cnt)
     {
       result[cnt] = conv_table[m & 0x3f];
       m >>= 6;
     }
+  result[cnt] = '\0';
 
-  return &result[cnt + 1];
+  return result;
 }
Index: stdlib/test-a64l.c
===================================================================
RCS file: stdlib/test-a64l.c
diff -N stdlib/test-a64l.c
--- /dev/null   Tue May  5 13:32:27 1998
+++ stdlib/test-a64l.c  Tue Oct 23 04:53:26 2001
@@ -0,0 +1,75 @@
+/* Test program for the l64a and a64l functions.
+   Copyright (C) 2001 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Andreas Schwab <address@hidden>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Prototype for our test function.  */
+extern int do_test (int argc, char *argv[]);
+#include <test-skeleton.c>
+
+struct a64l_test
+{
+  const char *base64;
+  long int value;
+};
+
+static const struct a64l_test tests[] =
+  {
+    { "./", 64 },
+    { "", 0 },
+    { "/", 1 },
+    { "FT", 2001 },
+    { NULL, 0 }
+  };
+
+int
+do_test (int argc, char ** argv)
+{
+  const struct a64l_test *at;
+  long int l;
+  const char *s;
+  int status = 0;
+
+  for (at = tests; at->base64 != NULL; ++at)
+    {
+      printf ("a64l (\"%s\")", at->base64);
+      l = a64l (at->base64);
+      if (l == at->value)
+       puts ("\tOK");
+      else
+       {
+         printf ("\tBAD\n  returns %ld, expected %ld\n", l, at->value);
+         status = 1;
+       }
+      printf ("l64a (%ld)", at->value);
+      s = l64a (at->value);
+      if (strcmp (s, at->base64) == 0)
+       puts ("\tOK");
+      else
+       {
+         printf ("\tBAD\n  returns \"%s\", expected \"%s\"\n", s, at->base64);
+         status = 1;
+       }
+    }
+
+  return status ? EXIT_FAILURE : EXIT_SUCCESS;
+}

-- 
Andreas Schwab                                  "And now for something
address@hidden                          completely different."
SuSE Labs, SuSE GmbH, Schanzäckerstr. 10, D-90443 Nürnberg
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5



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