[PATCH] grub2: commands/cmp.c: grub_cmd_cmp()

[Vincent Pelletier]

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Vincent Pelletier wrote:
> nb: I haven't tested these changes beyond "make", but I think they are
> trivial enough to be trusted...

My baaad...
There were 2 bugs left :
- -If the file size isn't a multiple of 512 bytes, we would read
non-initialised or non-updated memory (so it only affects results on
files whom size is < 512)
- -"The files are identical." is displayed when file size differ (was
corrected in Wanderley's version)

Reminds me Hagakure :
"Matters of small concern should be considered seriously".

I'm not sure if it is right to add a macro definition for block size,
and wether the name is good.

2005-06-29  Vincent Pelletier  <address@hidden>

    * commands/cmp.c
      (grub_cmd_cmp): Close the right file at the right time.  Compare
      only data just read.  Don't report files of different size as
      identical.  (BLOCK_SIZE): New macro.
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Index: commands/cmp.c
===================================================================
RCS file: /cvsroot/grub/grub2/commands/cmp.c,v
retrieving revision 1.2
diff -u -p -r1.2 cmp.c
--- commands/cmp.c      4 Apr 2004 13:46:00 -0000       1.2
+++ commands/cmp.c      29 Jun 2005 15:47:36 -0000
@@ -24,6 +24,8 @@
 #include <grub/misc.h>
 #include <grub/file.h>
 
+#define BLOCK_SIZE 512
+
 static grub_err_t
 grub_cmd_cmp (struct grub_arg_list *state __attribute__ ((unused)),
              int argc, char **args)
@@ -44,54 +46,53 @@ grub_cmd_cmp (struct grub_arg_list *stat
   file2 = grub_file_open (args[1]);
   if (! file2)
     {
-      grub_file_close (file2);
+      grub_file_close (file1);
       return grub_errno;
     }
 
   if (grub_file_size (file1) != grub_file_size (file2))
-    grub_printf ("Differ in size: %d [%s], %d [%s]\n", 
-                grub_file_size (file1), args[0], 
-                grub_file_size (file2), args[1]);
+    {
+      grub_printf ("Differ in size: %d [%s], %d [%s]\n", 
+                  grub_file_size (file1), args[0], 
+                  grub_file_size (file2), args[1]);
+    }
   
   else
     {
-      char buf1[512];
-      char buf2[512];
+      char buf1[BLOCK_SIZE];
+      char buf2[BLOCK_SIZE];
       grub_ssize_t rd1, rd2;
       grub_uint32_t pos = 0;
      
       do
        {
          int i;
-         rd1 = grub_file_read (file1, buf1, 512);
-         rd2 = grub_file_read (file2, buf2, 512);
+         rd1 = grub_file_read (file1, buf1, BLOCK_SIZE);
+         rd2 = grub_file_read (file2, buf2, BLOCK_SIZE);
 
          if (rd1 != rd2)
-           return 0;
+           goto cleanup;
 
-         for (i = 0; i < 512; i++)
+         for (i = 0; i < rd1; i++)
            {
              if (buf1[i] != buf2[i])
                {
                  grub_printf ("Differ at the offset %d: 0x%x [%s], 0x%x 
[%s]\n",
                               i + pos, buf1[i], args[0],
                               buf2[i], args[1]);
-
-                 grub_file_close (file1);
-                 grub_file_close (file2);
-                 return 0;
+                 goto cleanup;
                }
            }
-         pos += 512;
+         pos += BLOCK_SIZE;
          
        } while (rd2);
+      grub_printf ("The files are identical.\n");
     }
 
+cleanup:
   grub_file_close (file1);
   grub_file_close (file2);
 
-  grub_printf ("The files are identical.\n");
-
   return 0;
 }