numbers.h
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1 //
2 // Copyright 2017 The Abseil Authors.
3 //
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
7 //
8 // https://www.apache.org/licenses/LICENSE-2.0
9 //
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
15 //
16 // -----------------------------------------------------------------------------
17 // File: numbers.h
18 // -----------------------------------------------------------------------------
19 //
20 // This package contains functions for converting strings to numbers. For
21 // converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h,
22 // which automatically detect and convert most number values appropriately.
23 
24 #ifndef ABSL_STRINGS_NUMBERS_H_
25 #define ABSL_STRINGS_NUMBERS_H_
26 
27 #include <cstddef>
28 #include <cstdlib>
29 #include <cstring>
30 #include <ctime>
31 #include <limits>
32 #include <string>
33 #include <type_traits>
34 
35 #include "absl/base/macros.h"
36 #include "absl/base/port.h"
37 #include "absl/numeric/int128.h"
39 
40 namespace absl {
41 
42 // SimpleAtoi()
43 //
44 // Converts the given string into an integer value, returning `true` if
45 // successful. The string must reflect a base-10 integer (optionally followed or
46 // preceded by ASCII whitespace) whose value falls within the range of the
47 // integer type. If any errors are encountered, this function returns `false`,
48 // leaving `out` in an unspecified state.
49 template <typename int_type>
51 
52 // SimpleAtof()
53 //
54 // Converts the given string (optionally followed or preceded by ASCII
55 // whitespace) into a float, which may be rounded on overflow or underflow.
56 // See https://en.cppreference.com/w/c/string/byte/strtof for details about the
57 // allowed formats for `str`. If any errors are encountered, this function
58 // returns `false`, leaving `out` in an unspecified state.
60 
61 // SimpleAtod()
62 //
63 // Converts the given string (optionally followed or preceded by ASCII
64 // whitespace) into a double, which may be rounded on overflow or underflow.
65 // See https://en.cppreference.com/w/c/string/byte/strtof for details about the
66 // allowed formats for `str`. If any errors are encountered, this function
67 // returns `false`, leaving `out` in an unspecified state.
69 
70 // SimpleAtob()
71 //
72 // Converts the given string into a boolean, returning `true` if successful.
73 // The following case-insensitive strings are interpreted as boolean `true`:
74 // "true", "t", "yes", "y", "1". The following case-insensitive strings
75 // are interpreted as boolean `false`: "false", "f", "no", "n", "0". If any
76 // errors are encountered, this function returns `false`, leaving `out` in an
77 // unspecified state.
79 
80 } // namespace absl
81 
82 // End of public API. Implementation details follow.
83 
84 namespace absl {
85 namespace numbers_internal {
86 
87 // safe_strto?() functions for implementing SimpleAtoi()
88 bool safe_strto32_base(absl::string_view text, int32_t* value, int base);
89 bool safe_strto64_base(absl::string_view text, int64_t* value, int base);
90 bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base);
91 bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base);
92 
93 static const int kFastToBufferSize = 32;
94 static const int kSixDigitsToBufferSize = 16;
95 
96 // Helper function for fast formatting of floating-point values.
97 // The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six
98 // significant digits are returned, trailing zeros are removed, and numbers
99 // outside the range 0.0001-999999 are output using scientific notation
100 // (1.23456e+06). This routine is heavily optimized.
101 // Required buffer size is `kSixDigitsToBufferSize`.
102 size_t SixDigitsToBuffer(double d, char* buffer);
103 
104 // These functions are intended for speed. All functions take an output buffer
105 // as an argument and return a pointer to the last byte they wrote, which is the
106 // terminating '\0'. At most `kFastToBufferSize` bytes are written.
107 char* FastIntToBuffer(int32_t, char*);
108 char* FastIntToBuffer(uint32_t, char*);
109 char* FastIntToBuffer(int64_t, char*);
110 char* FastIntToBuffer(uint64_t, char*);
111 
112 // For enums and integer types that are not an exact match for the types above,
113 // use templates to call the appropriate one of the four overloads above.
114 template <typename int_type>
115 char* FastIntToBuffer(int_type i, char* buffer) {
116  static_assert(sizeof(i) <= 64 / 8,
117  "FastIntToBuffer works only with 64-bit-or-less integers.");
118  // TODO(jorg): This signed-ness check is used because it works correctly
119  // with enums, and it also serves to check that int_type is not a pointer.
120  // If one day something like std::is_signed<enum E> works, switch to it.
121  if (static_cast<int_type>(1) - 2 < 0) { // Signed
122  if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
123  return FastIntToBuffer(static_cast<int64_t>(i), buffer);
124  } else { // 32-bit or less
125  return FastIntToBuffer(static_cast<int32_t>(i), buffer);
126  }
127  } else { // Unsigned
128  if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
129  return FastIntToBuffer(static_cast<uint64_t>(i), buffer);
130  } else { // 32-bit or less
131  return FastIntToBuffer(static_cast<uint32_t>(i), buffer);
132  }
133  }
134 }
135 
136 // Implementation of SimpleAtoi, generalized to support arbitrary base (used
137 // with base different from 10 elsewhere in Abseil implementation).
138 template <typename int_type>
140  int base) {
141  static_assert(sizeof(*out) == 4 || sizeof(*out) == 8,
142  "SimpleAtoi works only with 32-bit or 64-bit integers.");
144  "Use SimpleAtof or SimpleAtod instead.");
145  bool parsed;
146  // TODO(jorg): This signed-ness check is used because it works correctly
147  // with enums, and it also serves to check that int_type is not a pointer.
148  // If one day something like std::is_signed<enum E> works, switch to it.
149  if (static_cast<int_type>(1) - 2 < 0) { // Signed
150  if (sizeof(*out) == 64 / 8) { // 64-bit
151  int64_t val;
152  parsed = numbers_internal::safe_strto64_base(s, &val, base);
153  *out = static_cast<int_type>(val);
154  } else { // 32-bit
155  int32_t val;
156  parsed = numbers_internal::safe_strto32_base(s, &val, base);
157  *out = static_cast<int_type>(val);
158  }
159  } else { // Unsigned
160  if (sizeof(*out) == 64 / 8) { // 64-bit
161  uint64_t val;
162  parsed = numbers_internal::safe_strtou64_base(s, &val, base);
163  *out = static_cast<int_type>(val);
164  } else { // 32-bit
165  uint32_t val;
166  parsed = numbers_internal::safe_strtou32_base(s, &val, base);
167  *out = static_cast<int_type>(val);
168  }
169  }
170  return parsed;
171 }
172 
173 } // namespace numbers_internal
174 
175 // SimpleAtoi()
176 //
177 // Converts a string to an integer, using `safe_strto?()` functions for actual
178 // parsing, returning `true` if successful. The `safe_strto?()` functions apply
179 // strict checking; the string must be a base-10 integer, optionally followed or
180 // preceded by ASCII whitespace, with a value in the range of the corresponding
181 // integer type.
182 template <typename int_type>
184  return numbers_internal::safe_strtoi_base(s, out, 10);
185 }
186 
187 } // namespace absl
188 
189 #endif // ABSL_STRINGS_NUMBERS_H_
bool safe_strtou64_base(absl::string_view text, uint64_t *value, int base)
Definition: numbers.cc:900
char * FastIntToBuffer(int32_t, char *)
Definition: numbers.cc:241
size_t SixDigitsToBuffer(double d, char *buffer)
Definition: numbers.cc:510
Definition: algorithm.h:29
bool safe_strtou32_base(absl::string_view text, uint32_t *value, int base)
Definition: numbers.cc:896
bool SimpleAtod(absl::string_view str, double *out)
Definition: numbers.cc:69
bool SimpleAtof(absl::string_view str, float *out)
Definition: numbers.cc:43
bool safe_strto32_base(absl::string_view text, int32_t *value, int base)
Definition: numbers.cc:888
ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type *out)
Definition: numbers.h:183
size_t value
#define ABSL_MUST_USE_RESULT
Definition: attributes.h:449
static const int kSixDigitsToBufferSize
Definition: numbers.h:94
ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type *out, int base)
Definition: numbers.h:139
bool safe_strto64_base(absl::string_view text, int64_t *value, int base)
Definition: numbers.cc:892
static const int kFastToBufferSize
Definition: numbers.h:93
char * out
Definition: mutex.h:1013
bool SimpleAtob(absl::string_view str, bool *out)
Definition: numbers.cc:132


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autogenerated on Tue Jun 18 2019 19:44:36