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source:
trunk/third/gmp/mpz/cdiv_q_ui.c
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18191

Revision 18191, 2.4 KB checked in by ghudson, 22 years ago (diff) |
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1 | /* mpz_cdiv_q_ui -- Division rounding the quotient towards +infinity. The |

2 | remainder gets the opposite sign as the denominator. In order to make it |

3 | always fit into the return type, the negative of the true remainder is |

4 | returned. |

5 | |

6 | Copyright 1994, 1996, 1999, 2001, 2002 Free Software Foundation, Inc. |

7 | |

8 | This file is part of the GNU MP Library. |

9 | |

10 | The GNU MP Library is free software; you can redistribute it and/or modify |

11 | it under the terms of the GNU Lesser General Public License as published by |

12 | the Free Software Foundation; either version 2.1 of the License, or (at your |

13 | option) any later version. |

14 | |

15 | The GNU MP Library is distributed in the hope that it will be useful, but |

16 | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |

17 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |

18 | License for more details. |

19 | |

20 | You should have received a copy of the GNU Lesser General Public License |

21 | along with the GNU MP Library; see the file COPYING.LIB. If not, write to |

22 | the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |

23 | MA 02111-1307, USA. */ |

24 | |

25 | #include "gmp.h" |

26 | #include "gmp-impl.h" |

27 | |

28 | unsigned long int |

29 | mpz_cdiv_q_ui (mpz_ptr quot, mpz_srcptr dividend, unsigned long int divisor) |

30 | { |

31 | mp_size_t ns, nn, qn; |

32 | mp_ptr np, qp; |

33 | mp_limb_t rl; |

34 | |

35 | if (divisor == 0) |

36 | DIVIDE_BY_ZERO; |

37 | |

38 | ns = SIZ(dividend); |

39 | if (ns == 0) |

40 | { |

41 | SIZ(quot) = 0; |

42 | return 0; |

43 | } |

44 | |

45 | nn = ABS(ns); |

46 | MPZ_REALLOC (quot, nn); |

47 | qp = PTR(quot); |

48 | np = PTR(dividend); |

49 | |

50 | #if GMP_NAIL_BITS != 0 |

51 | if (divisor > GMP_NUMB_MAX) |

52 | { |

53 | mp_limb_t dp[2], rp[2]; |

54 | |

55 | if (nn == 1) /* tdiv_qr requirements; tested above for 0 */ |

56 | { |

57 | qp[0] = 0; |

58 | rl = np[0]; |

59 | qn = 1; /* a white lie, fixed below */ |

60 | } |

61 | else |

62 | { |

63 | dp[0] = divisor & GMP_NUMB_MASK; |

64 | dp[1] = divisor >> GMP_NUMB_BITS; |

65 | mpn_tdiv_qr (qp, rp, (mp_size_t) 0, np, nn, dp, (mp_size_t) 2); |

66 | rl = rp[0] + (rp[1] << GMP_NUMB_BITS); |

67 | qn = nn - 2 + 1; |

68 | } |

69 | |

70 | if (rl != 0 && ns >= 0) |

71 | { |

72 | mpn_incr_u (qp, (mp_limb_t) 1); |

73 | rl = divisor - rl; |

74 | } |

75 | |

76 | qn -= qp[qn - 1] == 0; qn -= qn != 0 && qp[qn - 1] == 0; |

77 | } |

78 | else |

79 | #endif |

80 | { |

81 | rl = mpn_divrem_1 (qp, (mp_size_t) 0, np, nn, (mp_limb_t) divisor); |

82 | |

83 | if (rl != 0 && ns >= 0) |

84 | { |

85 | mpn_incr_u (qp, (mp_limb_t) 1); |

86 | rl = divisor - rl; |

87 | } |

88 | |

89 | qn = nn - (qp[nn - 1] == 0); |

90 | } |

91 | |

92 | SIZ(quot) = ns >= 0 ? qn : -qn; |

93 | return rl; |

94 | } |

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