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1//===-- Float type specifier converter for scanf ----------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_LIBC_SRC_STDIO_SCANF_CORE_FLOAT_CONVERTER_H
10#define LLVM_LIBC_SRC_STDIO_SCANF_CORE_FLOAT_CONVERTER_H
11
12#include "src/__support/CPP/limits.h"
13#include "src/__support/char_vector.h"
14#include "src/__support/ctype_utils.h"
15#include "src/__support/macros/config.h"
16#include "src/stdio/scanf_core/converter_utils.h"
17#include "src/stdio/scanf_core/core_structs.h"
18#include "src/stdio/scanf_core/reader.h"
19
20#include <stddef.h>
21
22namespace LIBC_NAMESPACE_DECL {
23namespace scanf_core {
24
25// All of the floating point conversions are the same for scanf, every name will
26// accept every style.
27template <typename T>
28int convert_float(Reader<T> *reader, const FormatSection &to_conv) {
29 // %a/A/e/E/f/F/g/G "Matches an optionally signed floating-point number,
30 // infinity, or NaN, whose format is the same as expected for the subject
31 // sequence of the strtod function. The corresponding argument shall be a
32 // pointer to floating."
33
34 CharVector out_str = CharVector();
35 bool is_number = false;
36
37 size_t max_width = cpp::numeric_limits<size_t>::max();
38 if (to_conv.max_width > 0) {
39 max_width = to_conv.max_width;
40 }
41
42 char cur_char = reader->getc();
43 // Handle the sign.
44 if (cur_char == '+' || cur_char == '-') {
45 if (!out_str.append(cur_char)) {
46 return ALLOCATION_FAILURE;
47 }
48 if (out_str.length() == max_width) {
49 return MATCHING_FAILURE;
50 } else {
51 cur_char = reader->getc();
52 }
53 }
54
55 static constexpr char DECIMAL_POINT = '.';
56 static const char inf_string[] = "infinity";
57
58 // Handle inf
59
60 if (internal::tolower(cur_char) == inf_string[0]) {
61 size_t inf_index = 0;
62
63 for (;
64 inf_index < (sizeof(inf_string) - 1) && out_str.length() < max_width &&
65 internal::tolower(cur_char) == inf_string[inf_index];
66 ++inf_index) {
67 if (!out_str.append(cur_char)) {
68 return ALLOCATION_FAILURE;
69 }
70 cur_char = reader->getc();
71 }
72
73 if (inf_index == 3 || inf_index == sizeof(inf_string) - 1) {
74 write_float_with_length(out_str.c_str(), to_conv);
75 return READ_OK;
76 } else {
77 return MATCHING_FAILURE;
78 }
79 }
80
81 static const char nan_string[] = "nan";
82
83 // Handle nan
84 if (internal::tolower(cur_char) == nan_string[0]) {
85 size_t nan_index = 0;
86
87 for (;
88 nan_index < (sizeof(nan_string) - 1) && out_str.length() < max_width &&
89 internal::tolower(cur_char) == nan_string[nan_index];
90 ++nan_index) {
91 if (!out_str.append(cur_char)) {
92 return ALLOCATION_FAILURE;
93 }
94 cur_char = reader->getc();
95 }
96
97 if (nan_index == sizeof(nan_string) - 1) {
98 write_float_with_length(out_str.c_str(), to_conv);
99 return READ_OK;
100 } else {
101 return MATCHING_FAILURE;
102 }
103 }
104
105 // Assume base of 10 by default but check if it is actually base 16.
106 int base = 10;
107
108 // If the string starts with 0 it might be in hex.
109 if (cur_char == '0') {
110 is_number = true;
111 // Read the next character to check.
112 if (!out_str.append(cur_char)) {
113 return ALLOCATION_FAILURE;
114 }
115 // If we've hit the end, then this is "0", which is valid.
116 if (out_str.length() == max_width) {
117 write_float_with_length(out_str.c_str(), to_conv);
118 return READ_OK;
119 } else {
120 cur_char = reader->getc();
121 }
122
123 // If that next character is an 'x' then this is a hexadecimal number.
124 if (internal::tolower(cur_char) == 'x') {
125 base = 16;
126
127 if (!out_str.append(cur_char)) {
128 return ALLOCATION_FAILURE;
129 }
130 // If we've hit the end here, we have "0x" which is a valid prefix to a
131 // floating point number, and will be evaluated to 0.
132 if (out_str.length() == max_width) {
133 write_float_with_length(out_str.c_str(), to_conv);
134 return READ_OK;
135 } else {
136 cur_char = reader->getc();
137 }
138 }
139 }
140
141 const char exponent_mark = ((base == 10) ? 'e' : 'p');
142 bool after_decimal = false;
143
144 // The format for the remaining characters at this point is DD.DDe+/-DD for
145 // base 10 and XX.XXp+/-DD for base 16
146
147 // This handles the digits before and after the decimal point, but not the
148 // exponent.
149 while (out_str.length() < max_width) {
150 if (internal::isalnum(cur_char) &&
151 internal::b36_char_to_int(cur_char) < base) {
152 is_number = true;
153 if (!out_str.append(cur_char)) {
154 return ALLOCATION_FAILURE;
155 }
156 cur_char = reader->getc();
157 } else if (cur_char == DECIMAL_POINT && !after_decimal) {
158 after_decimal = true;
159 if (!out_str.append(cur_char)) {
160 return ALLOCATION_FAILURE;
161 }
162 cur_char = reader->getc();
163 } else {
164 break;
165 }
166 }
167
168 // Handle the exponent, which has an exponent mark, an optional sign, and
169 // decimal digits.
170 if (internal::tolower(cur_char) == exponent_mark) {
171 if (!out_str.append(cur_char)) {
172 return ALLOCATION_FAILURE;
173 }
174 if (out_str.length() == max_width) {
175 // This is laid out in the standard as being a matching error (100e is not
176 // a valid float) but may conflict with existing implementations.
177 return MATCHING_FAILURE;
178 } else {
179 cur_char = reader->getc();
180 }
181
182 if (cur_char == '+' || cur_char == '-') {
183 if (!out_str.append(cur_char)) {
184 return ALLOCATION_FAILURE;
185 }
186 if (out_str.length() == max_width) {
187 return MATCHING_FAILURE;
188 } else {
189 cur_char = reader->getc();
190 }
191 }
192
193 // It is specified by the standard that "100er" is a matching failure since
194 // the longest prefix of a possibly valid floating-point number (which is
195 // "100e") is not a valid floating-point number. If there is an exponent
196 // mark then there must be a digit after it else the number is not valid.
197 // Some implementations will roll back two characters (to just "100") and
198 // accept that since the prefix is not valid, and some will interpret an
199 // exponent mark followed by no digits as an additional exponent of 0
200 // (accepting "100e" and returning 100.0). Both of these behaviors are wrong
201 // by the standard, but they may be used in real code, see Hyrum's law. This
202 // code follows the standard, but may be incompatible due to code expecting
203 // these bugs.
204 if (!internal::isdigit(cur_char)) {
205 return MATCHING_FAILURE;
206 }
207
208 while (internal::isdigit(cur_char) && out_str.length() < max_width) {
209 if (!out_str.append(cur_char)) {
210 return ALLOCATION_FAILURE;
211 }
212 cur_char = reader->getc();
213 }
214 }
215
216 // We always read one more character than will be used, so we have to put the
217 // last one back.
218 reader->ungetc(cur_char);
219
220 // If we haven't actually found any digits, this is a matching failure (this
221 // catches cases like "+.")
222 if (!is_number) {
223 return MATCHING_FAILURE;
224 }
225 write_float_with_length(out_str.c_str(), to_conv);
226
227 return READ_OK;
228}
229
230} // namespace scanf_core
231} // namespace LIBC_NAMESPACE_DECL
232
233#endif // LLVM_LIBC_SRC_STDIO_SCANF_CORE_FLOAT_CONVERTER_H
234

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source code of libc/src/stdio/scanf_core/float_converter.h