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

Revision 18191, 2.6 KB checked in by ghudson, 22 years ago (diff) |
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1 | /* mpz_fdiv_qr_ui -- Division rounding the quotient towards -infinity. |

2 | The remainder gets the same sign as the denominator. |

3 | |

4 | Copyright 1994, 1995, 1996, 1999, 2001, 2002 Free Software Foundation, Inc. |

5 | |

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

7 | |

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

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

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

11 | option) any later version. |

12 | |

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

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

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

16 | License for more details. |

17 | |

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

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

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

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

22 | |

23 | #include "gmp.h" |

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

25 | |

26 | unsigned long int |

27 | mpz_fdiv_qr_ui (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, unsigned long int divisor) |

28 | { |

29 | mp_size_t ns, nn, qn; |

30 | mp_ptr np, qp; |

31 | mp_limb_t rl; |

32 | |

33 | if (divisor == 0) |

34 | DIVIDE_BY_ZERO; |

35 | |

36 | ns = SIZ(dividend); |

37 | if (ns == 0) |

38 | { |

39 | SIZ(quot) = 0; |

40 | SIZ(rem) = 0; |

41 | return 0; |

42 | } |

43 | |

44 | nn = ABS(ns); |

45 | MPZ_REALLOC (quot, nn); |

46 | qp = PTR(quot); |

47 | np = PTR(dividend); |

48 | |

49 | #if GMP_NAIL_BITS != 0 |

50 | if (divisor > GMP_NUMB_MAX) |

51 | { |

52 | mp_limb_t dp[2]; |

53 | mp_ptr rp; |

54 | mp_size_t rn; |

55 | |

56 | MPZ_REALLOC (rem, 2); |

57 | rp = PTR(rem); |

58 | |

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

60 | { |

61 | qp[0] = 0; |

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

63 | rl = np[0]; |

64 | rp[0] = rl; |

65 | } |

66 | else |

67 | { |

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

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

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

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

72 | qn = nn - 2 + 1; |

73 | } |

74 | |

75 | if (rl != 0 && ns < 0) |

76 | { |

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

78 | rl = divisor - rl; |

79 | rp[0] = rl & GMP_NUMB_MASK; |

80 | rp[1] = rl >> GMP_NUMB_BITS; |

81 | } |

82 | |

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

84 | rn = 1 + (rl > GMP_NUMB_MAX); rn -= (rp[rn - 1] == 0); |

85 | SIZ(rem) = rn; |

86 | } |

87 | else |

88 | #endif |

89 | { |

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

91 | if (rl == 0) |

92 | SIZ(rem) = 0; |

93 | else |

94 | { |

95 | if (ns < 0) |

96 | { |

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

98 | rl = divisor - rl; |

99 | } |

100 | |

101 | PTR(rem)[0] = rl; |

102 | SIZ(rem) = rl != 0; |

103 | } |

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

105 | } |

106 | |

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

108 | return rl; |

109 | } |

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