| /* mpfr_eq -- Compare two floats up to a specified bit #. |
| |
| Copyright 1999, 2001, 2003, 2004, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
| Contributed by the Arenaire and Cacao projects, INRIA. |
| |
| This file is part of the GNU MPFR Library. |
| |
| The GNU MPFR 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 MPFR 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 MPFR Library; see the file COPYING.LIB. If not, write to |
| the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, |
| MA 02110-1301, USA. */ |
| |
| |
| #include "mpfr-impl.h" |
| |
| /* return non-zero if the first n_bits bits of u, v are equal, |
| 0 otherwise */ |
| int |
| mpfr_eq (mpfr_srcptr u, mpfr_srcptr v, unsigned long int n_bits) |
| { |
| mp_srcptr up, vp; |
| mp_size_t usize, vsize, size, i; |
| mp_exp_t uexp, vexp; |
| int k; |
| |
| if (MPFR_ARE_SINGULAR(u, v)) |
| { |
| if (MPFR_IS_NAN(u) || MPFR_IS_NAN(v)) |
| return 0; /* non equal */ |
| else if (MPFR_IS_INF(u) && MPFR_IS_INF(v)) |
| return (MPFR_SIGN(u) == MPFR_SIGN(v)); |
| else if (MPFR_IS_ZERO(u) && MPFR_IS_ZERO(v)) |
| return 1; |
| else |
| return 0; |
| } |
| |
| /* 1. Are the signs different? */ |
| if (MPFR_SIGN(u) != MPFR_SIGN(v)) |
| return 0; |
| |
| uexp = MPFR_GET_EXP (u); |
| vexp = MPFR_GET_EXP (v); |
| |
| /* 2. Are the exponents different? */ |
| if (uexp != vexp) |
| return 0; /* no bit agree */ |
| |
| usize = (MPFR_PREC(u) - 1) / BITS_PER_MP_LIMB + 1; |
| vsize = (MPFR_PREC(v) - 1) / BITS_PER_MP_LIMB + 1; |
| |
| if (vsize > usize) /* exchange u and v */ |
| { |
| up = MPFR_MANT(v); |
| vp = MPFR_MANT(u); |
| size = vsize; |
| vsize = usize; |
| usize = size; |
| } |
| else |
| { |
| up = MPFR_MANT(u); |
| vp = MPFR_MANT(v); |
| } |
| |
| /* now usize >= vsize */ |
| MPFR_ASSERTD(usize >= vsize); |
| |
| if (usize > vsize) |
| { |
| if ((unsigned long) vsize * BITS_PER_MP_LIMB < n_bits) |
| { |
| /* check if low min(PREC(u), n_bits) - (vsize * BITS_PER_MP_LIMB) |
| bits from u are non-zero */ |
| unsigned long remains = n_bits - (vsize * BITS_PER_MP_LIMB); |
| k = usize - vsize - 1; |
| while (k >= 0 && remains >= BITS_PER_MP_LIMB && !up[k]) |
| { |
| k--; |
| remains -= BITS_PER_MP_LIMB; |
| } |
| /* now either k < 0: all low bits from u are zero |
| or remains < BITS_PER_MP_LIMB: check high bits from up[k] |
| or up[k] <> 0: different */ |
| if (k >= 0 && (((remains < BITS_PER_MP_LIMB) && |
| (up[k] >> (BITS_PER_MP_LIMB - remains))) || |
| (remains >= BITS_PER_MP_LIMB && up[k]))) |
| return 0; /* surely too different */ |
| } |
| size = vsize; |
| } |
| else |
| { |
| size = usize; |
| } |
| |
| /* now size = min (usize, vsize) */ |
| |
| /* If size is too large wrt n_bits, reduce it to look only at the |
| high n_bits bits. |
| Otherwise, if n_bits > size * BITS_PER_MP_LIMB, reduce n_bits to |
| size * BITS_PER_MP_LIMB, since the extra low bits of one of the |
| operands have already been check above. */ |
| if ((unsigned long) size > 1 + (n_bits - 1) / BITS_PER_MP_LIMB) |
| size = 1 + (n_bits - 1) / BITS_PER_MP_LIMB; |
| else if (n_bits > (unsigned long) size * BITS_PER_MP_LIMB) |
| n_bits = size * BITS_PER_MP_LIMB; |
| |
| up += usize - size; |
| vp += vsize - size; |
| |
| for (i = size - 1; i > 0 && n_bits >= BITS_PER_MP_LIMB; i--) |
| { |
| if (up[i] != vp[i]) |
| return 0; |
| n_bits -= BITS_PER_MP_LIMB; |
| } |
| |
| /* now either i=0 or n_bits<BITS_PER_MP_LIMB */ |
| |
| /* since n_bits <= size * BITS_PER_MP_LIMB before the above for-loop, |
| we have the invariant n_bits <= (i+1) * BITS_PER_MP_LIMB, thus |
| we always have n_bits <= BITS_PER_MP_LIMB here */ |
| MPFR_ASSERTD(n_bits <= BITS_PER_MP_LIMB); |
| |
| if (n_bits & (BITS_PER_MP_LIMB - 1)) |
| return (up[i] >> (BITS_PER_MP_LIMB - (n_bits & (BITS_PER_MP_LIMB - 1))) == |
| vp[i] >> (BITS_PER_MP_LIMB - (n_bits & (BITS_PER_MP_LIMB - 1)))); |
| else |
| return (up[i] == vp[i]); |
| } |