/* -*-C-*-

$Id: bignmint.h,v 1.6 1999/01/02 06:11:34 cph Exp $

Copyright (c) 1989-1999 Massachusetts Institute of Technology

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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/* 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;

#ifdef MIT_SCHEME

#include "prims.h"

/* 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(length)						\
  (allocate_non_marked_vector						\
   (TC_BIG_FIXNUM, (BIGNUM_LENGTH_TO_GC_LENGTH (length)), 1))

/* BIGNUM_TO_POINTER casts a bignum object to a digit array pointer. */
#define BIGNUM_TO_POINTER(bignum)					\
  ((bignum_digit_type *) (VECTOR_LOC ((bignum), 0)))

/* 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)			\
{									\
  SET_VECTOR_LENGTH ((source), (BIGNUM_LENGTH_TO_GC_LENGTH (length)));	\
  (target) = (source);							\
}

#define BIGNUM_LENGTH_TO_GC_LENGTH(length)				\
  (BYTES_TO_WORDS (((length) + 1) * (sizeof (bignum_digit_type))))

/* 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 error_external_return

#else /* not MIT_SCHEME */

#define BIGNUM_ALLOCATE bignum_malloc
#define BIGNUM_TO_POINTER(bignum) ((bignum_digit_type *) (bignum))
#define BIGNUM_REDUCE_LENGTH(target, source, length)			\
  (target) = (bignum_realloc ((source), (length)))
#define BIGNUM_DEALLOCATE free
#define BIGNUM_FORCE_NEW_RESULTS
#define BIGNUM_EXCEPTION abort
#define fast register
extern void free ();
extern void abort ();

#endif /* MIT_SCHEME */

#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_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 bignum_make_zero
#define BIGNUM_ONE bignum_make_one

#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 */