/* mpq_cmp(u,v) -- Compare U, V.  Return postive, zero, or negative
   based on if U > V, U == V, or U < V.

Copyright (C) 1991, 1994, 1996 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MP Library 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 Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"

int
#if __STDC__
mpq_cmp (const MP_RAT *op1, const MP_RAT *op2)
#else
mpq_cmp (op1, op2)
     const MP_RAT *op1;
     const MP_RAT *op2;
#endif
{
  mp_size_t num1_size = op1->_mp_num._mp_size;
  mp_size_t den1_size = op1->_mp_den._mp_size;
  mp_size_t num2_size = op2->_mp_num._mp_size;
  mp_size_t den2_size = op2->_mp_den._mp_size;
  mp_size_t tmp1_size, tmp2_size;
  mp_ptr tmp1_ptr, tmp2_ptr;
  mp_size_t num1_sign;
  int cc;
  TMP_DECL (marker);

  if (num1_size == 0)
    return -num2_size;
  if (num2_size == 0)
    return num1_size;
  if ((num1_size ^ num2_size) < 0) /* I.e. are the signs different? */
    return num1_size;

  num1_sign = num1_size;
  num1_size = ABS (num1_size);
  num2_size = ABS (num2_size);

  tmp1_size = num1_size + den2_size;
  tmp2_size = num2_size + den1_size;

  /* 1. Check to see if we can tell which operand is larger by just looking at
     the number of limbs.  */

  /* NUM1 x DEN2 is either TMP1_SIZE limbs or TMP1_SIZE-1 limbs.
     Same for NUM1 x DEN1 with respect to TMP2_SIZE.  */
  if (tmp1_size > tmp2_size + 1)
    /* NUM1 x DEN2 is surely larger in magnitude than NUM2 x DEN1.  */
    return num1_sign;
  if (tmp2_size > tmp1_size + 1)
    /* NUM1 x DEN2 is surely smaller in magnitude than NUM2 x DEN1.  */
    return -num1_sign;

  /* 2. Same, but compare the number of significant bits.  */
  {
    int cnt1, cnt2;
    unsigned long int bits1, bits2;

    count_leading_zeros (cnt1, op1->_mp_num._mp_d[num1_size - 1]);
    count_leading_zeros (cnt2, op2->_mp_den._mp_d[den2_size - 1]);
    bits1 = tmp1_size * BITS_PER_MP_LIMB - cnt1 - cnt2;

    count_leading_zeros (cnt1, op2->_mp_num._mp_d[num2_size - 1]);
    count_leading_zeros (cnt2, op1->_mp_den._mp_d[den1_size - 1]);
    bits2 = tmp2_size * BITS_PER_MP_LIMB - cnt1 - cnt2;

    if (bits1 > bits2 + 1)
      return num1_sign;
    if (bits2 > bits1 + 1)
      return -num1_sign;
  }

  /* 3. Finally, cross multiply and compare.  */

  TMP_MARK (marker);
  tmp1_ptr = (mp_ptr) TMP_ALLOC (tmp1_size * BYTES_PER_MP_LIMB);
  tmp2_ptr = (mp_ptr) TMP_ALLOC (tmp2_size * BYTES_PER_MP_LIMB);

  if (num1_size >= den2_size)
    tmp1_size -= 0 == mpn_mul (tmp1_ptr,
			       op1->_mp_num._mp_d, num1_size,
			       op2->_mp_den._mp_d, den2_size);
  else
    tmp1_size -= 0 == mpn_mul (tmp1_ptr,
			       op2->_mp_den._mp_d, den2_size,
			       op1->_mp_num._mp_d, num1_size);

   if (num2_size >= den1_size)
     tmp2_size -= 0 == mpn_mul (tmp2_ptr,
				op2->_mp_num._mp_d, num2_size,
				op1->_mp_den._mp_d, den1_size);
   else
     tmp2_size -= 0 == mpn_mul (tmp2_ptr,
				op1->_mp_den._mp_d, den1_size,
				op2->_mp_num._mp_d, num2_size);


  cc = tmp1_size - tmp2_size != 0
    ? tmp1_size - tmp2_size : mpn_cmp (tmp1_ptr, tmp2_ptr, tmp1_size);
  TMP_FREE (marker);
  return num1_sign < 0 ? -cc : cc;
}
