summaryrefslogtreecommitdiff
path: root/absl/strings/numbers.h
blob: adf706a4e26e7acf633fec2da5ea3add2813b5d8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
//
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// -----------------------------------------------------------------------------
// File: numbers.h
// -----------------------------------------------------------------------------
//
// This package contains functions for converting strings to numbers. For
// converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h,
// which automatically detect and convert most number values appropriately.

#ifndef ABSL_STRINGS_NUMBERS_H_
#define ABSL_STRINGS_NUMBERS_H_

#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <limits>
#include <string>
#include <type_traits>

#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/numeric/int128.h"
#include "absl/strings/string_view.h"

namespace absl {

// SimpleAtoi()
//
// Converts the given std::string into an integer value, returning `true` if
// successful. The std::string must reflect a base-10 integer (optionally followed or
// preceded by ASCII whitespace) whose value falls within the range of the
// integer type,
template <typename int_type>
ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out);

// SimpleAtof()
//
// Converts the given std::string (optionally followed or preceded by ASCII
// whitespace) into a float, which may be rounded on overflow or underflow.
ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* value);

// SimpleAtod()
//
// Converts the given std::string (optionally followed or preceded by ASCII
// whitespace) into a double, which may be rounded on overflow or underflow.
ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* value);

// SimpleAtob()
//
// Converts the given std::string into a boolean, returning `true` if successful.
// The following case-insensitive strings are interpreted as boolean `true`:
// "true", "t", "yes", "y", "1". The following case-insensitive strings
// are interpreted as boolean `false`: "false", "f", "no", "n", "0".
ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* value);

}  // namespace absl

// End of public API.  Implementation details follow.

namespace absl {
namespace numbers_internal {

// safe_strto?() functions for implementing SimpleAtoi()
bool safe_strto32_base(absl::string_view text, int32_t* value, int base);
bool safe_strto64_base(absl::string_view text, int64_t* value, int base);
bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base);
bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base);

static const int kFastToBufferSize = 32;
static const int kSixDigitsToBufferSize = 16;

// Helper function for fast formatting of floating-point values.
// The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six
// significant digits are returned, trailing zeros are removed, and numbers
// outside the range 0.0001-999999 are output using scientific notation
// (1.23456e+06). This routine is heavily optimized.
// Required buffer size is `kSixDigitsToBufferSize`.
size_t SixDigitsToBuffer(double d, char* buffer);

// These functions are intended for speed. All functions take an output buffer
// as an argument and return a pointer to the last byte they wrote, which is the
// terminating '\0'. At most `kFastToBufferSize` bytes are written.
char* FastIntToBuffer(int32_t, char*);
char* FastIntToBuffer(uint32_t, char*);
char* FastIntToBuffer(int64_t, char*);
char* FastIntToBuffer(uint64_t, char*);

// For enums and integer types that are not an exact match for the types above,
// use templates to call the appropriate one of the four overloads above.
template <typename int_type>
char* FastIntToBuffer(int_type i, char* buffer) {
  static_assert(sizeof(i) <= 64 / 8,
                "FastIntToBuffer works only with 64-bit-or-less integers.");
  // TODO(jorg): This signed-ness check is used because it works correctly
  // with enums, and it also serves to check that int_type is not a pointer.
  // If one day something like std::is_signed<enum E> works, switch to it.
  if (static_cast<int_type>(1) - 2 < 0) {  // Signed
    if (sizeof(i) > 32 / 8) {           // 33-bit to 64-bit
      return FastIntToBuffer(static_cast<int64_t>(i), buffer);
    } else {  // 32-bit or less
      return FastIntToBuffer(static_cast<int32_t>(i), buffer);
    }
  } else {                     // Unsigned
    if (sizeof(i) > 32 / 8) {  // 33-bit to 64-bit
      return FastIntToBuffer(static_cast<uint64_t>(i), buffer);
    } else {  // 32-bit or less
      return FastIntToBuffer(static_cast<uint32_t>(i), buffer);
    }
  }
}

}  // namespace numbers_internal

// SimpleAtoi()
//
// Converts a std::string to an integer, using `safe_strto?()` functions for actual
// parsing, returning `true` if successful. The `safe_strto?()` functions apply
// strict checking; the std::string must be a base-10 integer, optionally followed or
// preceded by ASCII whitespace, with a value in the range of the corresponding
// integer type.
template <typename int_type>
ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out) {
  static_assert(sizeof(*out) == 4 || sizeof(*out) == 8,
                "SimpleAtoi works only with 32-bit or 64-bit integers.");
  static_assert(!std::is_floating_point<int_type>::value,
                "Use SimpleAtof or SimpleAtod instead.");
  bool parsed;
  // TODO(jorg): This signed-ness check is used because it works correctly
  // with enums, and it also serves to check that int_type is not a pointer.
  // If one day something like std::is_signed<enum E> works, switch to it.
  if (static_cast<int_type>(1) - 2 < 0) {  // Signed
    if (sizeof(*out) == 64 / 8) {       // 64-bit
      int64_t val;
      parsed = numbers_internal::safe_strto64_base(s, &val, 10);
      *out = static_cast<int_type>(val);
    } else {  // 32-bit
      int32_t val;
      parsed = numbers_internal::safe_strto32_base(s, &val, 10);
      *out = static_cast<int_type>(val);
    }
  } else {                         // Unsigned
    if (sizeof(*out) == 64 / 8) {  // 64-bit
      uint64_t val;
      parsed = numbers_internal::safe_strtou64_base(s, &val, 10);
      *out = static_cast<int_type>(val);
    } else {  // 32-bit
      uint32_t val;
      parsed = numbers_internal::safe_strtou32_base(s, &val, 10);
      *out = static_cast<int_type>(val);
    }
  }
  return parsed;
}

}  // namespace absl

#endif  // ABSL_STRINGS_NUMBERS_H_