1 /* Split a double into fraction and mantissa, for hexadecimal printf.
2 Copyright (C) 2007 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License along
15 with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
20 #if !(defined USE_LONG_DOUBLE && !HAVE_LONG_DOUBLE)
23 # ifdef USE_LONG_DOUBLE
24 # include "printf-frexpl.h"
26 # include "printf-frexp.h"
31 # ifdef USE_LONG_DOUBLE
35 /* This file assumes FLT_RADIX = 2. If FLT_RADIX is a power of 2 greater
36 than 2, or not even a power of 2, some rounding errors can occur, so that
37 then the returned mantissa is only guaranteed to be <= 2.0, not < 2.0. */
39 # ifdef USE_LONG_DOUBLE
40 # define FUNC printf_frexpl
41 # define DOUBLE long double
42 # define MIN_EXP LDBL_MIN_EXP
43 # if HAVE_FREXPL_IN_LIBC && HAVE_LDEXPL_IN_LIBC
44 # define USE_FREXP_LDEXP
48 # define DECL_ROUNDING DECL_LONG_DOUBLE_ROUNDING
49 # define BEGIN_ROUNDING() BEGIN_LONG_DOUBLE_ROUNDING ()
50 # define END_ROUNDING() END_LONG_DOUBLE_ROUNDING ()
51 # define L_(literal) literal##L
53 # define FUNC printf_frexp
54 # define DOUBLE double
55 # define MIN_EXP DBL_MIN_EXP
56 # if HAVE_FREXP_IN_LIBC && HAVE_LDEXP_IN_LIBC
57 # define USE_FREXP_LDEXP
61 # define DECL_ROUNDING
62 # define BEGIN_ROUNDING()
63 # define END_ROUNDING()
64 # define L_(literal) literal
68 FUNC (DOUBLE x, int *exp)
75 # ifdef USE_FREXP_LDEXP
76 /* frexp and ldexp are usually faster than the loop below. */
77 x = FREXP (x, &exponent);
82 if (exponent < MIN_EXP - 1)
84 x = LDEXP (x, exponent - (MIN_EXP - 1));
85 exponent = MIN_EXP - 1;
88 /* Since the exponent is an 'int', it fits in 64 bits. Therefore the
89 loops are executed no more than 64 times. */
90 DOUBLE pow2[64]; /* pow2[i] = 2^2^i */
91 DOUBLE powh[64]; /* powh[i] = 2^-2^i */
97 /* A nonnegative exponent. */
99 DOUBLE pow2_i; /* = pow2[i] */
100 DOUBLE powh_i; /* = powh[i] */
102 /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
103 x * 2^exponent = argument, x >= 1.0. */
104 for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
106 i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
110 exponent += (1 << i);
120 /* Here 1.0 <= x < 2^2^i. */
124 /* A negative exponent. */
126 DOUBLE pow2_i; /* = pow2[i] */
127 DOUBLE powh_i; /* = powh[i] */
129 /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
130 x * 2^exponent = argument, x < 1.0, exponent >= MIN_EXP - 1. */
131 for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
133 i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
135 if (exponent - (1 << i) < MIN_EXP - 1)
138 exponent -= (1 << i);
147 /* Here either x < 1.0 and exponent - 2^i < MIN_EXP - 1 <= exponent,
148 or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
151 /* Invariants: x * 2^exponent = argument, x < 1.0 and
152 exponent - 2^i < MIN_EXP - 1 <= exponent. */
156 if (exponent - (1 << i) >= MIN_EXP - 1)
158 exponent -= (1 << i);
165 /* Here either x < 1.0 and exponent = MIN_EXP - 1,
166 or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
169 /* Invariants: x * 2^exponent = argument, and
170 either x < 1.0 and exponent = MIN_EXP - 1,
171 or 1.0 <= x < 2^2^i and exponent >= MIN_EXP - 1. */
177 exponent += (1 << i);
181 /* Here either x < 1.0 and exponent = MIN_EXP - 1,
182 or 1.0 <= x < 2.0 and exponent >= MIN_EXP - 1. */
193 /* This declaration is solely to ensure that after preprocessing
194 this file is never empty. */