| 1 | /* mpf_mul_2exp -- Multiply a float by 2^n. |
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| 2 | |
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| 3 | Copyright 1993, 1994, 1996, 2000, 2001, 2002 Free Software Foundation, Inc. |
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| 4 | |
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| 5 | This file is part of the GNU MP Library. |
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| 6 | |
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| 7 | The GNU MP Library is free software; you can redistribute it and/or modify |
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| 8 | it under the terms of the GNU Lesser General Public License as published by |
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| 9 | the Free Software Foundation; either version 2.1 of the License, or (at your |
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| 10 | option) any later version. |
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| 11 | |
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| 12 | The GNU MP Library is distributed in the hope that it will be useful, but |
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| 13 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
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| 15 | License for more details. |
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| 16 | |
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| 17 | You should have received a copy of the GNU Lesser General Public License |
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| 18 | along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
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| 19 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
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| 20 | MA 02111-1307, USA. */ |
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| 21 | |
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| 22 | #include "gmp.h" |
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| 23 | #include "gmp-impl.h" |
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| 24 | |
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| 25 | void |
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| 26 | mpf_mul_2exp (mpf_ptr r, mpf_srcptr u, unsigned long int exp) |
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| 27 | { |
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| 28 | mp_srcptr up; |
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| 29 | mp_ptr rp = r->_mp_d; |
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| 30 | mp_size_t usize; |
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| 31 | mp_size_t abs_usize; |
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| 32 | mp_size_t prec = r->_mp_prec; |
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| 33 | mp_exp_t uexp = u->_mp_exp; |
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| 34 | |
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| 35 | usize = u->_mp_size; |
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| 36 | |
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| 37 | if (usize == 0) |
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| 38 | { |
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| 39 | r->_mp_size = 0; |
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| 40 | r->_mp_exp = 0; |
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| 41 | return; |
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| 42 | } |
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| 43 | |
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| 44 | abs_usize = ABS (usize); |
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| 45 | up = u->_mp_d; |
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| 46 | |
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| 47 | if (exp % GMP_NUMB_BITS == 0) |
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| 48 | { |
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| 49 | prec++; /* retain more precision here as we don't need |
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| 50 | to account for carry-out here */ |
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| 51 | if (abs_usize > prec) |
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| 52 | { |
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| 53 | up += abs_usize - prec; |
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| 54 | abs_usize = prec; |
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| 55 | } |
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| 56 | if (rp != up) |
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| 57 | MPN_COPY_INCR (rp, up, abs_usize); |
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| 58 | r->_mp_exp = uexp + exp / GMP_NUMB_BITS; |
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| 59 | } |
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| 60 | else |
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| 61 | { |
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| 62 | mp_limb_t cy_limb; |
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| 63 | mp_size_t adj; |
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| 64 | if (abs_usize > prec) |
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| 65 | { |
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| 66 | up += abs_usize - prec; |
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| 67 | abs_usize = prec; |
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| 68 | /* Use mpn_rshift since mpn_lshift operates downwards, and we |
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| 69 | therefore would clobber part of U before using that part, in case |
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| 70 | R is the same variable as U. */ |
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| 71 | cy_limb = mpn_rshift (rp + 1, up, abs_usize, |
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| 72 | GMP_NUMB_BITS - exp % GMP_NUMB_BITS); |
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| 73 | rp[0] = cy_limb; |
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| 74 | adj = rp[abs_usize] != 0; |
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| 75 | } |
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| 76 | else |
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| 77 | { |
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| 78 | cy_limb = mpn_lshift (rp, up, abs_usize, exp % GMP_NUMB_BITS); |
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| 79 | rp[abs_usize] = cy_limb; |
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| 80 | adj = cy_limb != 0; |
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| 81 | } |
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| 82 | |
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| 83 | abs_usize += adj; |
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| 84 | r->_mp_exp = uexp + exp / GMP_NUMB_BITS + adj; |
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| 85 | } |
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| 86 | r->_mp_size = usize >= 0 ? abs_usize : -abs_usize; |
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| 87 | } |
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