2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 2004-2008 David Schultz <das@FreeBSD.ORG>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
36 #include "../stdio/floatio.h"
40 /* Strings values used by dtoa() */
41 #define INFSTR "Infinity"
44 #define DBL_ADJ (DBL_MAX_EXP - 2)
45 #define SIGFIGS ((DBL_MANT_DIG + 3) / 4 + 1)
47 static const float one[] = { 1.0f, -1.0f };
50 * This procedure converts a double-precision number in IEEE format
51 * into a string of hexadecimal digits and an exponent of 2. Its
52 * behavior is bug-for-bug compatible with dtoa() in mode 2, with the
53 * following exceptions:
55 * - An ndigits < 0 causes it to use as many digits as necessary to
56 * represent the number exactly.
57 * - The additional xdigs argument should point to either the string
58 * "0123456789ABCDEF" or the string "0123456789abcdef", depending on
59 * which case is desired.
60 * - This routine does not repeat dtoa's mistake of setting decpt
61 * to 9999 in the case of an infinity or NaN. INT_MAX is used
62 * for this purpose instead.
64 * Note that the C99 standard does not specify what the leading digit
65 * should be for non-zero numbers. For instance, 0x1.3p3 is the same
66 * as 0x2.6p2 is the same as 0x4.cp3. This implementation always makes
67 * the leading digit a 1. This ensures that the exponent printed is the
68 * actual base-2 exponent, i.e., ilogb(d).
70 * Inputs: d, xdigs, ndigits
71 * Outputs: decpt, sign, rve
74 __hdtoa(double d, const char *xdigs, int ndigits, int *decpt, int *sign,
85 switch (fpclassify(d)) {
87 *decpt = u.bits.exp - DBL_ADJ;
91 return (nrv_alloc("0", rve, 1));
94 *decpt = u.bits.exp - (514 + DBL_ADJ);
98 return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
99 default: /* FP_NAN or unrecognized */
101 return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
104 /* FP_NORMAL or FP_SUBNORMAL */
106 if (ndigits == 0) /* dtoa() compatibility */
110 * If ndigits < 0, we are expected to auto-size, so we allocate
111 * enough space for all the digits.
113 bufsize = (ndigits > 0) ? ndigits : SIGFIGS;
114 s0 = rv_alloc(bufsize);
116 /* Round to the desired number of digits. */
117 if (SIGFIGS > ndigits && ndigits > 0) {
118 float redux = one[u.bits.sign];
119 int offset = 4 * ndigits + DBL_MAX_EXP - 4 - DBL_MANT_DIG;
123 *decpt += u.bits.exp - offset;
129 for (s = s0 + 1; s < s0 + bufsize; s++) {
130 *s = xdigs[(manh >> (DBL_MANH_SIZE - 4)) & 0xf];
131 manh = (manh << 4) | (manl >> (DBL_MANL_SIZE - 4));
135 /* If ndigits < 0, we are expected to auto-size the precision. */
137 for (ndigits = SIGFIGS; s0[ndigits - 1] == '0'; ndigits--)