1/* Compute complex base 10 logarithm.
2 Copyright (C) 1997-2016 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20#include <complex.h>
21#include <math.h>
22#include <math_private.h>
23#include <float.h>
24
25/* log_10 (2). */
26#define M_LOG10_2f 0.3010299956639811952137388947244930267682f
27
28/* pi * log10 (e). */
29#define M_PI_LOG10Ef 1.364376353841841347485783625431355770210f
30
31__complex__ float
32__clog10f (__complex__ float x)
33{
34 __complex__ float result;
35 int rcls = fpclassify (__real__ x);
36 int icls = fpclassify (__imag__ x);
37
38 if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
39 {
40 /* Real and imaginary part are 0.0. */
41 __imag__ result = signbit (__real__ x) ? M_PI_LOG10Ef : 0.0;
42 __imag__ result = __copysignf (__imag__ result, __imag__ x);
43 /* Yes, the following line raises an exception. */
44 __real__ result = -1.0 / fabsf (__real__ x);
45 }
46 else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
47 {
48 /* Neither real nor imaginary part is NaN. */
49 float absx = fabsf (__real__ x), absy = fabsf (__imag__ x);
50 int scale = 0;
51
52 if (absx < absy)
53 {
54 float t = absx;
55 absx = absy;
56 absy = t;
57 }
58
59 if (absx > FLT_MAX / 2.0f)
60 {
61 scale = -1;
62 absx = __scalbnf (absx, scale);
63 absy = (absy >= FLT_MIN * 2.0f ? __scalbnf (absy, scale) : 0.0f);
64 }
65 else if (absx < FLT_MIN && absy < FLT_MIN)
66 {
67 scale = FLT_MANT_DIG;
68 absx = __scalbnf (absx, scale);
69 absy = __scalbnf (absy, scale);
70 }
71
72 if (absx == 1.0f && scale == 0)
73 {
74 __real__ result = __log1pf (absy * absy) * ((float) M_LOG10E / 2.0f);
75 math_check_force_underflow_nonneg (__real__ result);
76 }
77 else if (absx > 1.0f && absx < 2.0f && absy < 1.0f && scale == 0)
78 {
79 float d2m1 = (absx - 1.0f) * (absx + 1.0f);
80 if (absy >= FLT_EPSILON)
81 d2m1 += absy * absy;
82 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
83 }
84 else if (absx < 1.0f
85 && absx >= 0.5f
86 && absy < FLT_EPSILON / 2.0f
87 && scale == 0)
88 {
89 float d2m1 = (absx - 1.0f) * (absx + 1.0f);
90 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
91 }
92 else if (absx < 1.0f
93 && absx >= 0.5f
94 && scale == 0
95 && absx * absx + absy * absy >= 0.5f)
96 {
97 float d2m1 = __x2y2m1f (absx, absy);
98 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
99 }
100 else
101 {
102 float d = __ieee754_hypotf (absx, absy);
103 __real__ result = __ieee754_log10f (d) - scale * M_LOG10_2f;
104 }
105
106 __imag__ result = M_LOG10E * __ieee754_atan2f (__imag__ x, __real__ x);
107 }
108 else
109 {
110 __imag__ result = __nanf ("");
111 if (rcls == FP_INFINITE || icls == FP_INFINITE)
112 /* Real or imaginary part is infinite. */
113 __real__ result = HUGE_VALF;
114 else
115 __real__ result = __nanf ("");
116 }
117
118 return result;
119}
120#ifndef __clog10f
121weak_alias (__clog10f, clog10f)
122#endif
123