1/* Convert a floating-point number to string.
2 Copyright (C) 2016-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library 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 GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/* Generic implementation for strfrom functions. The implementation is generic
20 for several floating-point types (e.g.: float, double), so that each
21 function, such as strfromf and strfroml, share the same code, thus avoiding
22 code duplication. */
23
24#include <ctype.h>
25#include "../libio/libioP.h"
26#include "../libio/strfile.h"
27#include <printf.h>
28#include <string.h>
29#include <locale/localeinfo.h>
30
31#define UCHAR_T char
32#define L_(Str) Str
33#define ISDIGIT(Ch) isdigit (Ch)
34#include "stdio-common/printf-parse.h"
35
36int
37STRFROM (char *dest, size_t size, const char *format, FLOAT f)
38{
39 _IO_strnfile sfile;
40#ifdef _IO_MTSAFE_IO
41 sfile.f._sbf._f._lock = NULL;
42#endif
43
44 int done;
45
46 /* Single-precision values need to be stored in a double type, because
47 __printf_fp_l and __printf_fphex do not accept the float type. */
48 union {
49 double flt;
50 FLOAT value;
51 } fpnum;
52 const void *fpptr;
53 fpptr = &fpnum;
54
55 /* Variables to control the output format. */
56 int precision = -1; /* printf_fp and printf_fphex treat this internally. */
57 int specifier;
58 struct printf_info info;
59
60 /* Single-precision values need to be converted into double-precision,
61 because __printf_fp and __printf_fphex only accept double and long double
62 as the floating-point argument. */
63 if (__builtin_types_compatible_p (FLOAT, float))
64 fpnum.flt = f;
65 else
66 fpnum.value = f;
67
68 /* Check if the first character in the format string is indeed the '%'
69 character. Otherwise, abort. */
70 if (*format == '%')
71 format++;
72 else
73 abort ();
74
75 /* The optional precision specification always starts with a '.'. If such
76 character is present, read the precision. */
77 if (*format == '.')
78 {
79 format++;
80
81 /* Parse the precision. */
82 if (ISDIGIT (*format))
83 precision = read_int (&format);
84 /* If only the period is specified, the precision is taken as zero, as
85 described in ISO/IEC 9899:2011, section 7.21.6.1, 4th paragraph, 3rd
86 item. */
87 else
88 precision = 0;
89 }
90
91 /* Now there is only the conversion specifier to be read. */
92 switch (*format)
93 {
94 case 'a':
95 case 'A':
96 case 'e':
97 case 'E':
98 case 'f':
99 case 'F':
100 case 'g':
101 case 'G':
102 specifier = *format;
103 break;
104 default:
105 abort ();
106 }
107
108 /* The following code to prepare the virtual file has been adapted from the
109 function __vsnprintf_internal from libio. */
110
111 if (size == 0)
112 {
113 /* When size is zero, nothing is written and dest may be a null pointer.
114 This is specified for snprintf in ISO/IEC 9899:2011, Section 7.21.6.5,
115 in the second paragraph. Thus, if size is zero, prepare to use the
116 overflow buffer right from the start. */
117 dest = sfile.overflow_buf;
118 size = sizeof (sfile.overflow_buf);
119 }
120
121 /* Prepare the virtual string file. */
122 _IO_no_init (&sfile.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
123 _IO_JUMPS (&sfile.f._sbf) = &_IO_strn_jumps;
124 _IO_str_init_static_internal (&sfile.f, dest, size - 1, dest);
125
126 /* Prepare the format specification for printf_fp. */
127 memset (&info, '\0', sizeof (info));
128
129 /* The functions strfromd and strfromf pass a floating-point number with
130 double precision to printf_fp, whereas strfroml passes a floating-point
131 number with long double precision. The following line informs printf_fp
132 which type of floating-point number is being passed. */
133 info.is_long_double = __builtin_types_compatible_p (FLOAT, long double);
134
135 /* Similarly, the function strfromf128 passes a floating-point number in
136 _Float128 format to printf_fp. */
137#if __HAVE_DISTINCT_FLOAT128
138 info.is_binary128 = __builtin_types_compatible_p (FLOAT, _Float128);
139#endif
140
141 /* Set info according to the format string. */
142 info.prec = precision;
143 info.spec = specifier;
144
145 if (info.spec != 'a' && info.spec != 'A')
146 done = __printf_fp_l (&sfile.f._sbf._f, _NL_CURRENT_LOCALE, &info, &fpptr);
147 else
148 done = __printf_fphex (&sfile.f._sbf._f, &info, &fpptr);
149
150 /* Terminate the string. */
151 if (sfile.f._sbf._f._IO_buf_base != sfile.overflow_buf)
152 *sfile.f._sbf._f._IO_write_ptr = '\0';
153
154 return done;
155}
156