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source:
trunk/third/gmp/mpf/set_q.c
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18191

Revision 18191, 3.4 KB checked in by ghudson, 22 years ago (diff) |
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1 | /* mpf_set_q (mpf_t rop, mpq_t op) -- Convert the rational op to the float rop. |

2 | |

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

4 | |

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

6 | |

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

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

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

10 | option) any later version. |

11 | |

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

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

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

15 | License for more details. |

16 | |

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

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

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

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

21 | |

22 | #include "gmp.h" |

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

24 | #include "longlong.h" |

25 | |

26 | void |

27 | mpf_set_q (mpf_t r, mpq_srcptr q) |

28 | { |

29 | mp_ptr np, dp; |

30 | mp_ptr rp; |

31 | mp_size_t nsize, dsize; |

32 | mp_size_t qsize, rsize; |

33 | mp_size_t sign_quotient; |

34 | mp_limb_t qlimb; |

35 | mp_ptr qp; |

36 | mp_size_t prec; |

37 | mp_exp_t exp; |

38 | TMP_DECL (marker); |

39 | |

40 | nsize = SIZ (&q->_mp_num); |

41 | dsize = SIZ (&q->_mp_den); |

42 | |

43 | if (nsize == 0) |

44 | { |

45 | SIZ (r) = 0; |

46 | EXP (r) = 0; |

47 | return; |

48 | } |

49 | |

50 | prec = PREC (r) + 1; |

51 | |

52 | TMP_MARK (marker); |

53 | |

54 | qp = PTR (r); |

55 | |

56 | sign_quotient = nsize ^ dsize; |

57 | nsize = ABS (nsize); |

58 | dsize = ABS (dsize); |

59 | np = PTR (&q->_mp_num); |

60 | dp = PTR (&q->_mp_den); |

61 | |

62 | exp = nsize - dsize; |

63 | |

64 | if (nsize > prec) |

65 | { |

66 | np += nsize - prec; |

67 | nsize = prec; |

68 | } |

69 | if (dsize > prec) |

70 | { |

71 | dp += dsize - prec; |

72 | dsize = prec; |

73 | } |

74 | |

75 | rsize = MAX (nsize, dsize); |

76 | rp = (mp_ptr) TMP_ALLOC ((rsize + 1) * BYTES_PER_MP_LIMB); |

77 | |

78 | /* Normalize the denominator, i.e. make its most significant bit set by |

79 | shifting it NORMALIZATION_STEPS bits to the left. Also shift the |

80 | numerator the same number of steps (to keep the quotient the same!). */ |

81 | if ((dp[dsize - 1] & GMP_NUMB_HIGHBIT) == 0) |

82 | { |

83 | mp_ptr tp; |

84 | mp_limb_t nlimb; |

85 | unsigned normalization_steps; |

86 | |

87 | count_leading_zeros (normalization_steps, dp[dsize - 1]); |

88 | normalization_steps -= GMP_NAIL_BITS; |

89 | |

90 | /* Shift up the denominator setting the most significant bit of |

91 | the most significant limb. Use temporary storage not to clobber |

92 | the original contents of the denominator. */ |

93 | tp = (mp_ptr) TMP_ALLOC (dsize * BYTES_PER_MP_LIMB); |

94 | mpn_lshift (tp, dp, dsize, normalization_steps); |

95 | dp = tp; |

96 | |

97 | if (rsize != nsize) |

98 | { |

99 | MPN_ZERO (rp, rsize - nsize); |

100 | nlimb = mpn_lshift (rp + (rsize - nsize), |

101 | np, nsize, normalization_steps); |

102 | } |

103 | else |

104 | { |

105 | nlimb = mpn_lshift (rp, np, rsize, normalization_steps); |

106 | } |

107 | if (nlimb != 0) |

108 | { |

109 | rp[rsize] = nlimb; |

110 | exp++; |

111 | /* Don't just increase rsize, chop off rp at the low end instead. */ |

112 | if (rsize == prec) |

113 | rp++; |

114 | else |

115 | rsize++; |

116 | } |

117 | } |

118 | else |

119 | { |

120 | if (rsize != nsize) |

121 | { |

122 | MPN_ZERO (rp, rsize - nsize); |

123 | MPN_COPY (rp + (rsize - nsize), np, nsize); |

124 | } |

125 | else |

126 | { |

127 | MPN_COPY (rp, np, rsize); |

128 | } |

129 | } |

130 | |

131 | qlimb = mpn_divrem (qp, prec - 1 - (rsize - dsize), rp, rsize, dp, dsize); |

132 | qsize = prec - 1; |

133 | if (qlimb) |

134 | { |

135 | qp[qsize] = qlimb; |

136 | qsize++; |

137 | exp++; |

138 | } |

139 | |

140 | EXP (r) = exp; |

141 | SIZ (r) = sign_quotient >= 0 ? qsize : -qsize; |

142 | |

143 | TMP_FREE (marker); |

144 | } |

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