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bignumint.h

/* -*-C-*-

$Id: bignmint.h,v 1.4 1993/10/27 23:57:07 gjr Exp $

Copyright 1989,1992,1993,2004 Massachusetts Institute of Technology

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

   2. Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimer in the documentation and/or other materials provided
      with the distribution.

   3. The name of the author may not be used to endorse or promote
      products derived from this software without specific prior
      written permission.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

/* License changed to modified BSD by cph on 2004-11-08.  */

/* Internal Interface to Bignum Code */
#undef BIGNUM_ZERO_P
#undef BIGNUM_NEGATIVE_P

/* The memory model is based on the following definitions, and on the
   definition of the type `bignum_type'.  The only other special
   definition is `CHAR_BIT', which is defined in the Ansi C header
   file "limits.h". */

typedef long bignum_digit_type;
typedef long bignum_length_type;

/* BIGNUM_ALLOCATE allocates a (length + 1)-element array of
   `bignum_digit_type'; deallocation is the responsibility of the
   user (in Scheme, the garbage collector handles this). */
#define BIGNUM_ALLOCATE_TAGGED(length_in_digits)            \
    ((long *) s48_allocate_bignum((length_in_digits + 1) *  \
                                  sizeof(bignum_digit_type)))
#define BIGNUM_ALLOCATE(length_in_digits)             \
    (S48_ADDRESS_AFTER_HEADER(((char *)                     \
                         BIGNUM_ALLOCATE_TAGGED((length_in_digits))), \
                         long))
extern char *     s48_allocate_bignum(long size);

/* BIGNUM_TO_POINTER casts a bignum object to a digit array pointer. */
#define BIGNUM_TO_POINTER(bignum) ((bignum_digit_type *) (bignum))

/* BIGNUM_REDUCE_LENGTH allows the memory system to reclaim some
   space when a bignum's length is reduced from its original value. */
#define BIGNUM_REDUCE_LENGTH(target, source, length)            \
     target = (long *) s48_shorten_bignum((char *) source, length)
extern char *     s48_shorten_bignum(char*, long);

/* BIGNUM_DEALLOCATE is called when disposing of bignums which are
   created as intermediate temporaries; Scheme doesn't need this. */
#define BIGNUM_DEALLOCATE(bignum)

/* If BIGNUM_FORCE_NEW_RESULTS is defined, all bignum-valued operations
   return freshly-allocated results.  This is useful for some kinds of
   memory deallocation strategies. */
/* #define BIGNUM_FORCE_NEW_RESULTS */

/* BIGNUM_EXCEPTION is invoked to handle assertion violations. */
#define BIGNUM_EXCEPTION abort


#define BIGNUM_DIGIT_LENGTH (((sizeof (bignum_digit_type)) * CHAR_BIT) - 2)
#define BIGNUM_HALF_DIGIT_LENGTH (BIGNUM_DIGIT_LENGTH / 2)
#define BIGNUM_RADIX (((unsigned long) 1) << BIGNUM_DIGIT_LENGTH)
#define BIGNUM_RADIX_ROOT (((unsigned long) 1) << BIGNUM_HALF_DIGIT_LENGTH)
#define BIGNUM_DIGIT_MASK      (BIGNUM_RADIX - 1)
#define BIGNUM_HALF_DIGIT_MASK       (BIGNUM_RADIX_ROOT - 1)

#define BIGNUM_START_PTR(bignum)                            \
  ((BIGNUM_TO_POINTER (bignum)) + 1)

#define BIGNUM_SET_HEADER(bignum, length, negative_p)             \
  (* (BIGNUM_TO_POINTER (bignum))) =                              \
    ((length) | ((negative_p) ? BIGNUM_RADIX : 0))

#define BIGNUM_LENGTH(bignum)                               \
  ((* (BIGNUM_TO_POINTER (bignum))) & ((bignum_length_type) BIGNUM_DIGIT_MASK))

#define BIGNUM_NEGATIVE_P(bignum)                           \
  (((* (BIGNUM_TO_POINTER (bignum))) & BIGNUM_RADIX) != 0)

#define BIGNUM_ZERO_P(bignum)                               \
  ((BIGNUM_LENGTH (bignum)) == 0)

#define BIGNUM_REF(bignum, index)                           \
  (* ((BIGNUM_START_PTR (bignum)) + (index)))

#ifdef BIGNUM_FORCE_NEW_RESULTS
#define BIGNUM_MAYBE_COPY bignum_copy
#else
#define BIGNUM_MAYBE_COPY(bignum) bignum
#endif

/* These definitions are here to facilitate caching of the constants
   0, 1, and -1. */
#define BIGNUM_ZERO() S48_ADDRESS_AFTER_HEADER(s48_bignum_zero, long)
#define BIGNUM_ONE(neg_p)                                               \
   (neg_p ? S48_ADDRESS_AFTER_HEADER(s48_bignum_neg_one, long) : \
            S48_ADDRESS_AFTER_HEADER(s48_bignum_pos_one, long))

#define HD_LOW(digit) ((digit) & BIGNUM_HALF_DIGIT_MASK)
#define HD_HIGH(digit) ((digit) >> BIGNUM_HALF_DIGIT_LENGTH)
#define HD_CONS(high, low) (((high) << BIGNUM_HALF_DIGIT_LENGTH) | (low))

#define BIGNUM_BITS_TO_DIGITS(n)                            \
  (((n) + (BIGNUM_DIGIT_LENGTH - 1)) / BIGNUM_DIGIT_LENGTH)

#define BIGNUM_DIGITS_FOR_LONG                                    \
  (BIGNUM_BITS_TO_DIGITS ((sizeof (long)) * CHAR_BIT))

#ifndef BIGNUM_DISABLE_ASSERTION_CHECKS

#define BIGNUM_ASSERT(expression)                           \
{                                                     \
  if (! (expression))                                       \
    BIGNUM_EXCEPTION ();                                    \
}

#endif /* not BIGNUM_DISABLE_ASSERTION_CHECKS */

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