version 1.1.1.2, 2000/09/09 14:13:00 |
version 1.1.1.3, 2003/08/25 16:06:34 |
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/* mpz_ui_pow_ui(res, base, exp) -- Set RES to BASE**EXP. |
/* mpz_ui_pow_ui -- ulong raised to ulong. |
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Copyright (C) 1991, 1993, 1994, 1996, 1997, 2000 Free Software Foundation, |
Copyright 2001, 2002 Free Software Foundation, Inc. |
Inc. |
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This file is part of the GNU MP Library. |
This file is part of the GNU MP Library. |
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Line 22 MA 02111-1307, USA. */ |
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Line 21 MA 02111-1307, USA. */ |
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#include "gmp.h" |
#include "gmp.h" |
#include "gmp-impl.h" |
#include "gmp-impl.h" |
#include "longlong.h" |
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static void mpz_pow2 _PROTO ((mpz_ptr r, mp_limb_t blimb, unsigned long int e, mp_limb_t rl)); |
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void |
void |
#if __STDC__ |
mpz_ui_pow_ui (mpz_ptr r, unsigned long b, unsigned long e) |
mpz_ui_pow_ui (mpz_ptr r, unsigned long int b, unsigned long int e) |
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#else |
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mpz_ui_pow_ui (r, b, e) |
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mpz_ptr r; |
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unsigned long int b; |
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unsigned long int e; |
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#endif |
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{ |
{ |
mp_limb_t blimb = b; |
#if GMP_NAIL_BITS != 0 |
mp_limb_t rl; |
if (b > GMP_NUMB_MAX) |
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if (e == 0) |
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{ |
{ |
/* For x^0 we return 1, even if x is 0. */ |
mp_limb_t bb[2]; |
r->_mp_d[0] = 1; |
bb[0] = b & GMP_NUMB_MASK; |
r->_mp_size = 1; |
bb[1] = b >> GMP_NUMB_BITS; |
return; |
mpz_n_pow_ui (r, bb, (mp_size_t) 2, e); |
} |
} |
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else |
/* Compute b^e as (b^n)^(e div n) * b^(e mod n), where n is chosen such that |
#endif |
the latter factor is the largest number small enough to fit in a limb. */ |
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rl = 1; |
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while (e != 0 && blimb < ((mp_limb_t) 1 << BITS_PER_MP_LIMB/2)) |
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{ |
{ |
if ((e & 1) != 0) |
#ifdef _LONG_LONG_LIMB |
rl = rl * blimb; |
/* i386 gcc 2.95.3 doesn't recognise blimb can be eliminated when |
blimb = blimb * blimb; |
mp_limb_t is an unsigned long, so only use a separate blimb when |
e = e >> 1; |
necessary. */ |
} |
mp_limb_t blimb = b; |
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mpz_n_pow_ui (r, &blimb, (mp_size_t) (b != 0), e); |
/* rl is now b^(e mod n). (I.e., the latter factor above.) */ |
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if (e == 0) |
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{ |
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r->_mp_d[0] = rl; |
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r->_mp_size = rl != 0; |
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return; |
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} |
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mpz_pow2 (r, blimb, e, rl); |
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} |
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/* Multi-precision part of expontialization code. */ |
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static void |
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#if __STDC__ |
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mpz_pow2 (mpz_ptr r, mp_limb_t blimb, unsigned long int e, mp_limb_t rl) |
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#else |
#else |
mpz_pow2 (r, blimb, e, rl) |
mpz_n_pow_ui (r, &b, (mp_size_t) (b != 0), e); |
mpz_ptr r; |
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mp_limb_t blimb; |
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unsigned long int e; |
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mp_limb_t rl; |
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#endif |
#endif |
{ |
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mp_ptr rp, tp; |
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mp_size_t ralloc, rsize; |
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int cnt, i; |
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TMP_DECL (marker); |
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TMP_MARK (marker); |
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/* Over-estimate temporary space requirements somewhat. */ |
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count_leading_zeros (cnt, blimb); |
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ralloc = e - cnt * e / BITS_PER_MP_LIMB + 1; |
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/* The two areas are used to alternatingly hold the input and receive the |
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product for mpn_mul. (Needed since mpn_mul_n requires that the product |
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is distinct from either input operand.) */ |
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rp = (mp_ptr) TMP_ALLOC (ralloc * BYTES_PER_MP_LIMB); |
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tp = (mp_ptr) TMP_ALLOC (ralloc * BYTES_PER_MP_LIMB); |
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rp[0] = blimb; |
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rsize = 1; |
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count_leading_zeros (cnt, e); |
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for (i = BITS_PER_MP_LIMB - cnt - 2; i >= 0; i--) |
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{ |
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mpn_mul_n (tp, rp, rp, rsize); |
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rsize = 2 * rsize; |
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rsize -= tp[rsize - 1] == 0; |
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MP_PTR_SWAP (rp, tp); |
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if ((e & ((mp_limb_t) 1 << i)) != 0) |
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{ |
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mp_limb_t cy; |
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cy = mpn_mul_1 (rp, rp, rsize, blimb); |
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rp[rsize] = cy; |
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rsize += cy != 0; |
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} |
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} |
} |
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/* We will need rsize or rsize+1 limbs for the result. */ |
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if (r->_mp_alloc <= rsize) |
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_mpz_realloc (r, rsize + 1); |
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/* Multiply the two factors (in rp,rsize and rl) and put the final result |
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in place. */ |
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{ |
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mp_limb_t cy; |
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cy = mpn_mul_1 (r->_mp_d, rp, rsize, rl); |
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(r->_mp_d)[rsize] = cy; |
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rsize += cy != 0; |
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} |
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r->_mp_size = rsize; |
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TMP_FREE (marker); |
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} |
} |
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