* test/lisp/mouse-tests.el: Fix tests broken by mouse.el change
[emacs.git] / lib / ftoastr.c
bloba6899b2c63c7b9621a6139dae8464ff345ae7dd4
1 /* floating point to accurate string
3 Copyright (C) 2010-2018 Free Software Foundation, Inc.
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18 /* Written by Paul Eggert. */
20 /* This code can misbehave on some buggy or older platforms, when
21 operating on arguments on floating types other than 'double', or
22 when given unusual combinations of options. Gnulib's
23 snprintf-posix module works around many of these problems.
25 This code relies on sprintf, strtod, etc. operating accurately;
26 otherwise, the resulting strings could be inaccurate or too long. */
28 #include <config.h>
30 #include "ftoastr.h"
32 #include <float.h>
33 #include <stdio.h>
34 #include <stdlib.h>
36 #if LENGTH == 3
37 # define FLOAT long double
38 # define FLOAT_DIG LDBL_DIG
39 # define FLOAT_MIN LDBL_MIN
40 # define FLOAT_PREC_BOUND _GL_LDBL_PREC_BOUND
41 # define FTOASTR ldtoastr
42 # define PROMOTED_FLOAT long double
43 # if HAVE_C99_STRTOLD
44 # define STRTOF strtold
45 # endif
46 #elif LENGTH == 2
47 # define FLOAT double
48 # define FLOAT_DIG DBL_DIG
49 # define FLOAT_MIN DBL_MIN
50 # define FLOAT_PREC_BOUND _GL_DBL_PREC_BOUND
51 # define FTOASTR dtoastr
52 # define PROMOTED_FLOAT double
53 #else
54 # define LENGTH 1
55 # define FLOAT float
56 # define FLOAT_DIG FLT_DIG
57 # define FLOAT_MIN FLT_MIN
58 # define FLOAT_PREC_BOUND _GL_FLT_PREC_BOUND
59 # define FTOASTR ftoastr
60 # define PROMOTED_FLOAT double
61 # if HAVE_STRTOF
62 # define STRTOF strtof
63 # endif
64 #endif
66 /* On pre-C99 hosts, approximate strtof and strtold with strtod. This
67 may generate one or two extra digits, but that's better than not
68 working at all. */
69 #ifndef STRTOF
70 # define STRTOF strtod
71 #endif
73 /* On hosts where it's not known that snprintf works, use sprintf to
74 implement the subset needed here. Typically BUFSIZE is big enough
75 and there's little or no performance hit. */
76 #if ! GNULIB_SNPRINTF
77 # undef snprintf
78 # define snprintf ftoastr_snprintf
79 static int
80 ftoastr_snprintf (char *buf, size_t bufsize, char const *format,
81 int width, int prec, FLOAT x)
83 PROMOTED_FLOAT promoted_x = x;
84 char width_0_buffer[LENGTH == 1 ? FLT_BUFSIZE_BOUND
85 : LENGTH == 2 ? DBL_BUFSIZE_BOUND
86 : LDBL_BUFSIZE_BOUND];
87 int n = width;
88 if (bufsize < sizeof width_0_buffer)
90 n = sprintf (width_0_buffer, format, 0, prec, promoted_x);
91 if (n < 0)
92 return n;
93 if (n < width)
94 n = width;
96 if (n < bufsize)
97 n = sprintf (buf, format, width, prec, promoted_x);
98 return n;
100 #endif
103 FTOASTR (char *buf, size_t bufsize, int flags, int width, FLOAT x)
105 /* The following method is simple but slow.
106 For ideas about speeding things up, please see:
108 Andrysco M, Jhala R, Lerner S. Printing floating-point numbers:
109 a faster, always correct method. ACM SIGPLAN notices - POPL '16.
110 2016;51(1):555-67 <http://dx.doi.org/10.1145/2914770.2837654>; draft at
111 <https://cseweb.ucsd.edu/~lerner/papers/fp-printing-popl16.pdf>. */
113 PROMOTED_FLOAT promoted_x = x;
114 char format[sizeof "%-+ 0*.*Lg"];
115 FLOAT abs_x = x < 0 ? -x : x;
116 int prec;
118 char *p = format;
119 *p++ = '%';
121 /* Support flags that generate output parsable by strtof. */
122 *p = '-'; p += (flags & FTOASTR_LEFT_JUSTIFY ) != 0;
123 *p = '+'; p += (flags & FTOASTR_ALWAYS_SIGNED ) != 0;
124 *p = ' '; p += (flags & FTOASTR_SPACE_POSITIVE) != 0;
125 *p = '0'; p += (flags & FTOASTR_ZERO_PAD ) != 0;
127 *p++ = '*';
128 *p++ = '.';
129 *p++ = '*';
130 *p = 'L'; p += 2 < LENGTH;
131 *p++ = flags & FTOASTR_UPPER_E ? 'G' : 'g';
132 *p = '\0';
134 for (prec = abs_x < FLOAT_MIN ? 1 : FLOAT_DIG; ; prec++)
136 int n = snprintf (buf, bufsize, format, width, prec, promoted_x);
137 if (n < 0
138 || FLOAT_PREC_BOUND <= prec
139 || (n < bufsize && STRTOF (buf, NULL) == x))
140 return n;