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

Revision 18191, 3.7 KB checked in by ghudson, 22 years ago (diff) |
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1 | /* mpf_ui_div -- Divide an unsigned integer with a float. |

2 | |

3 | Copyright 1993, 1994, 1995, 1996, 2000, 2001, 2002 Free Software Foundation, |

4 | 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 | #include "longlong.h" |

26 | |

27 | void |

28 | mpf_ui_div (mpf_ptr r, unsigned long int u, mpf_srcptr v) |

29 | { |

30 | mp_srcptr vp; |

31 | mp_ptr rp, tp; |

32 | mp_size_t vsize; |

33 | mp_size_t rsize, tsize; |

34 | mp_size_t sign_quotient; |

35 | mp_size_t prec; |

36 | mp_limb_t q_limb; |

37 | mp_exp_t rexp; |

38 | TMP_DECL (marker); |

39 | |

40 | vsize = v->_mp_size; |

41 | sign_quotient = vsize; |

42 | vsize = ABS (vsize); |

43 | prec = r->_mp_prec; |

44 | |

45 | if (vsize == 0) |

46 | DIVIDE_BY_ZERO; |

47 | |

48 | if (u == 0) |

49 | { |

50 | r->_mp_size = 0; |

51 | r->_mp_exp = 0; |

52 | return; |

53 | } |

54 | |

55 | TMP_MARK (marker); |

56 | rexp = 1 - v->_mp_exp; |

57 | |

58 | rp = r->_mp_d; |

59 | vp = v->_mp_d; |

60 | |

61 | if (vsize > prec) |

62 | { |

63 | vp += vsize - prec; |

64 | vsize = prec; |

65 | } |

66 | |

67 | tsize = vsize + prec; |

68 | tp = (mp_ptr) TMP_ALLOC ((tsize + 1) * BYTES_PER_MP_LIMB); |

69 | MPN_ZERO (tp, tsize); |

70 | |

71 | /* Normalize the divisor and the dividend. */ |

72 | if ((vp[vsize - 1] & GMP_NUMB_HIGHBIT) == 0) |

73 | { |

74 | mp_ptr tmp; |

75 | mp_limb_t dividend_high, dividend_low; |

76 | unsigned normalization_steps; |

77 | |

78 | count_leading_zeros (normalization_steps, vp[vsize - 1]); |

79 | normalization_steps -= GMP_NAIL_BITS; |

80 | |

81 | /* Shift up the divisor setting the most significant bit of |

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

83 | the original contents of the divisor. */ |

84 | tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB); |

85 | mpn_lshift (tmp, vp, vsize, normalization_steps); |

86 | vp = tmp; |

87 | |

88 | /* Shift up the dividend, possibly introducing a new most |

89 | significant word. */ |

90 | dividend_high = (mp_limb_t) u >> (GMP_NUMB_BITS - normalization_steps); |

91 | dividend_low = ((mp_limb_t) u << normalization_steps) & GMP_NUMB_MASK; |

92 | |

93 | tp[tsize - 1] = dividend_low; |

94 | if (dividend_high != 0) |

95 | { |

96 | #if GMP_NAIL_BITS != 0 |

97 | if (dividend_high > vp[vsize - 1]) |

98 | { |

99 | tp[tsize - 2] = dividend_low; |

100 | tp[tsize - 1] = dividend_high & GMP_NUMB_MASK; |

101 | tp[tsize] = dividend_high >> GMP_NUMB_BITS; |

102 | tsize++; |

103 | rexp += 2; |

104 | } |

105 | else |

106 | #endif |

107 | { |

108 | tp[tsize] = dividend_high; |

109 | tsize++; |

110 | rexp++; |

111 | } |

112 | } |

113 | } |

114 | else |

115 | { |

116 | /* The divisor is already normalized, as required. |

117 | Copy it to temporary space if it overlaps with the quotient. */ |

118 | if (vp - rp <= tsize - vsize) |

119 | { |

120 | mp_ptr tmp = (mp_ptr) TMP_ALLOC (vsize * BYTES_PER_MP_LIMB); |

121 | MPN_COPY (tmp, vp, vsize); |

122 | vp = (mp_srcptr) tmp; |

123 | } |

124 | |

125 | tp[tsize - 1] = u & GMP_NUMB_MASK; |

126 | #if GMP_NAIL_BITS != 0 |

127 | if (u > GMP_NUMB_MAX) |

128 | { |

129 | tp[tsize] = u >> GMP_NUMB_BITS; |

130 | tsize++; |

131 | rexp++; |

132 | } |

133 | #endif |

134 | } |

135 | |

136 | q_limb = mpn_divmod (rp, tp, tsize, vp, vsize); |

137 | rsize = tsize - vsize; |

138 | if (q_limb) |

139 | { |

140 | rp[rsize] = q_limb; |

141 | rsize++; |

142 | rexp++; |

143 | } |

144 | |

145 | r->_mp_size = sign_quotient >= 0 ? rsize : -rsize; |

146 | r->_mp_exp = rexp; |

147 | TMP_FREE (marker); |

148 | } |

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