Fix some more fencepost errors in the bit string copying code.

diff --git a/v7/src/microcode/bitstr.c b/v7/src/microcode/bitstr.c
index 7eac1ea740df4ede15a0a819c78b6b9f92a6371b..4e3a0c50e1851e1c068234d7e7b07e8c880283f6 100644 (file)
--- a/v7/src/microcode/bitstr.c
+++ b/v7/src/microcode/bitstr.c
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: bitstr.c,v 9.53 1995/01/24 00:17:25 cph Exp $
+$Id: bitstr.c,v 9.54 1995/01/25 20:54:55 cph Exp $
 
 Copyright (c) 1987-95 Massachusetts Institute of Technology
 
@@ -504,58 +504,43 @@ DEFUN (copy_bits,
       else
        {
          long mask1 = (LOW_MASK (offset1));
-         long mask2 = (ANY_MASK (offset2, offset1));
          long dest_buffer;
          {
            long mask = (ANY_MASK (head, offset1));
            dest_buffer
-             = (((BIT_STRING_WORD (destination)) &~ mask)
-                | (((* (DEC_BIT_STRING_PTR (source))) << offset1) & mask));
+             = (((BIT_STRING_WORD (destination))
+                 &~ (LOW_MASK (head + offset1)))
+                | (((* (DEC_BIT_STRING_PTR (source))) & (LOW_MASK (head)))
+                   << offset1));
          }
          nbits -= head;
-         if (nbits >= OBJECT_LENGTH)
+         while (nbits >= OBJECT_LENGTH)
            {
-             dest_buffer &= mask2;
-             while (nbits >= OBJECT_LENGTH)
-               {
-                 (* (DEC_BIT_STRING_PTR (destination)))
-                   = (dest_buffer
-                      | (((BIT_STRING_WORD (source)) >> offset2) & mask1));
-                 dest_buffer = ((* (DEC_BIT_STRING_PTR (source))) << offset1);
-                 nbits -= OBJECT_LENGTH;
-               }
+             (* (DEC_BIT_STRING_PTR (destination)))
+               = (dest_buffer
+                  | (((BIT_STRING_WORD (source)) >> offset2) & mask1));
+             dest_buffer = ((* (DEC_BIT_STRING_PTR (source))) << offset1);
+             nbits -= OBJECT_LENGTH;
            }
-         if (nbits > 0)
+         if (nbits <= offset1)
+           (BIT_STRING_WORD (destination))
+             = (dest_buffer
+                | ((BIT_STRING_WORD (destination))
+                   & (LOW_MASK (offset1 - nbits)))
+                | (((BIT_STRING_WORD (source)) >> offset2)
+                   & (ANY_MASK (nbits, (offset1 - nbits)))));
+         else
            {
-             if (nbits <= offset1)
-               {
-                 long mask = (ANY_MASK (nbits, (offset1 - nbits)));
-                 /* This path through copy bits didn't work in certain
-                  cases.  The line below seems to fix it.  This was an
-                  empirical test, and I don't understand it enough to
-                  tell if it is correct, but I think it is, and I did
-                  a few tests.  This is probably what is broken if you
-                  are here poking around trying to fix something.
-                  ~JRM */
-                 dest_buffer &=~ mask;
-                 (BIT_STRING_WORD (destination))
-                   = (dest_buffer
-                      | ((BIT_STRING_WORD (destination))
-                         & (LOW_MASK (offset1 - nbits)))
-                      | (((BIT_STRING_WORD (source)) >> offset2)
-                         & mask));
-               }
-             else
-               {
-                 long mask;
-                 (* (DEC_BIT_STRING_PTR (destination)))
-                   = (dest_buffer
-                      | (((BIT_STRING_WORD (source)) >> offset2) & mask1));
-                 mask = (LOW_MASK (OBJECT_LENGTH - nbits));
-                 (BIT_STRING_WORD (destination))
-                   = (((BIT_STRING_WORD (destination)) &~ mask)
-                      | (((BIT_STRING_WORD (source)) << offset1) & mask));
-               }
+             (* (DEC_BIT_STRING_PTR (destination)))
+               = (dest_buffer
+                  | (((BIT_STRING_WORD (source)) >> offset2) & mask1));
+             nbits -= offset1;
+             {
+               long mask = (LOW_MASK (OBJECT_LENGTH - nbits));
+               (BIT_STRING_WORD (destination))
+                 = (((BIT_STRING_WORD (destination)) & mask)
+                    | (((BIT_STRING_WORD (source)) << offset1) &~ mask));
+             }
            }
        }
     }