factor/vm/bignumint.hpp

/* -*-C-*-

$Id: s48_bignumint.h,v 1.14 2005/12/21 02:36:52 spestov Exp $

Copyright (c) 1989-1992 Massachusetts Institute of Technology

This material was developed by the Scheme project at the Massachusetts
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2. Users of this software agree to make their best efforts (a) to
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to inform MIT of noteworthy uses of this software.

3. All materials developed as a consequence of the use of this
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4. MIT has made no warrantee or representation that the operation of
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namespace factor
{

/* 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 fixnum bignum_digit_type;
typedef fixnum bignum_length_type;

/* BIGNUM_TO_POINTER casts a bignum object to a digit array pointer. */
#define BIGNUM_TO_POINTER(bignum) ((bignum_digit_type *)(bignum + 1))

/* 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 (bignum_digit_type)(((cell) 1) << BIGNUM_DIGIT_LENGTH)
#define BIGNUM_RADIX_ROOT (((bignum_digit_type) 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_LENGTH(bignum) (untag_fixnum((bignum)->capacity) - 1)

#define BIGNUM_NEGATIVE_P(bignum) (bignum->data()[0] != 0)
#define BIGNUM_SET_NEGATIVE_P(bignum,neg) (bignum->data()[0] = neg)

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

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

/* These definitions are here to facilitate caching of the constants
   0, 1, and -1. */
#define BIGNUM_ZERO() untag<bignum>(bignum_zero)
#define BIGNUM_ONE(neg_p) \
   untag<bignum>(neg_p ? bignum_neg_one : bignum_pos_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(type) \
  (BIGNUM_BITS_TO_DIGITS ((sizeof (type)) * CHAR_BIT))

#ifndef BIGNUM_DISABLE_ASSERTION_CHECKS

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

#endif /* not BIGNUM_DISABLE_ASSERTION_CHECKS */

}