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
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
//
// Copyright 2019 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
//
// https://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.
#ifndef ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
#define ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <string>
#include <typeinfo>
#include "absl/base/config.h"
#include "absl/base/macros.h"
#include "absl/flags/config.h"
#include "absl/flags/marshalling.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// An alias for flag static type id. Values of type identify the flag value type
// simialarly to typeid(T), but without relying on RTTI being available. In most
// cases this id is enough to uniquely identify the flag's value type. In a few
// cases we'll have to resort to using actual RTTI implementation if it is
// available.
using FlagStaticTypeId = void* (*)();
// Address of this function template is used in current implementation as a flag
// static type id.
template <typename T>
void* FlagStaticTypeIdGen() {
#if defined(ABSL_FLAGS_INTERNAL_HAS_RTTI)
return const_cast<std::type_info*>(&typeid(T));
#else
return nullptr;
#endif
}
// Options that control SetCommandLineOptionWithMode.
enum FlagSettingMode {
// update the flag's value unconditionally (can call this multiple times).
SET_FLAGS_VALUE,
// update the flag's value, but *only if* it has not yet been updated
// with SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef".
SET_FLAG_IF_DEFAULT,
// set the flag's default value to this. If the flag has not been updated
// yet (via SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef")
// change the flag's current value to the new default value as well.
SET_FLAGS_DEFAULT
};
// Options that control SetFromString: Source of a value.
enum ValueSource {
// Flag is being set by value specified on a command line.
kCommandLine,
// Flag is being set by value specified in the code.
kProgrammaticChange,
};
// Handle to FlagState objects. Specific flag state objects will restore state
// of a flag produced this flag state from method CommandLineFlag::SaveState().
class FlagStateInterface {
public:
virtual ~FlagStateInterface() {}
// Restores the flag originated this object to the saved state.
virtual void Restore() const = 0;
};
// Holds all information for a flag.
class CommandLineFlag {
public:
constexpr CommandLineFlag() = default;
// Not copyable/assignable.
CommandLineFlag(const CommandLineFlag&) = delete;
CommandLineFlag& operator=(const CommandLineFlag&) = delete;
// Non-polymorphic access methods.
// Return true iff flag has type T.
template <typename T>
inline bool IsOfType() const {
return TypeId() == &flags_internal::FlagStaticTypeIdGen<T>;
}
// Attempts to retrieve the flag value. Returns value on success,
// absl::nullopt otherwise.
template <typename T>
absl::optional<T> Get() const {
if (IsRetired() || !IsOfType<T>()) {
return absl::nullopt;
}
// Implementation notes:
//
// We are wrapping a union around the value of `T` to serve three purposes:
//
// 1. `U.value` has correct size and alignment for a value of type `T`
// 2. The `U.value` constructor is not invoked since U's constructor does
// not do it explicitly.
// 3. The `U.value` destructor is invoked since U's destructor does it
// explicitly. This makes `U` a kind of RAII wrapper around non default
// constructible value of T, which is destructed when we leave the
// scope. We do need to destroy U.value, which is constructed by
// CommandLineFlag::Read even though we left it in a moved-from state
// after std::move.
//
// All of this serves to avoid requiring `T` being default constructible.
union U {
T value;
U() {}
~U() { value.~T(); }
};
U u;
Read(&u.value);
return std::move(u.value);
}
// Polymorphic access methods
// Returns name of this flag.
virtual absl::string_view Name() const = 0;
// Returns name of the file where this flag is defined.
virtual std::string Filename() const = 0;
// Returns name of the flag's value type for some built-in types or empty
// std::string.
virtual absl::string_view Typename() const = 0;
// Returns help message associated with this flag.
virtual std::string Help() const = 0;
// Returns true iff this object corresponds to retired flag.
virtual bool IsRetired() const { return false; }
// Returns true iff this is a handle to an Abseil Flag.
virtual bool IsAbseilFlag() const { return true; }
// Returns id of the flag's value type.
virtual FlagStaticTypeId TypeId() const = 0;
virtual bool IsModified() const = 0;
virtual bool IsSpecifiedOnCommandLine() const = 0;
virtual std::string DefaultValue() const = 0;
virtual std::string CurrentValue() const = 0;
// Interfaces to operate on validators.
virtual bool ValidateInputValue(absl::string_view value) const = 0;
// Interface to save flag to some persistent state. Returns current flag state
// or nullptr if flag does not support saving and restoring a state.
virtual std::unique_ptr<FlagStateInterface> SaveState() = 0;
// Sets the value of the flag based on specified std::string `value`. If the flag
// was successfully set to new value, it returns true. Otherwise, sets `error`
// to indicate the error, leaves the flag unchanged, and returns false. There
// are three ways to set the flag's value:
// * Update the current flag value
// * Update the flag's default value
// * Update the current flag value if it was never set before
// The mode is selected based on `set_mode` parameter.
virtual bool SetFromString(absl::string_view value,
flags_internal::FlagSettingMode set_mode,
flags_internal::ValueSource source,
std::string* error) = 0;
// Checks that flags default value can be converted to std::string and back to the
// flag's value type.
virtual void CheckDefaultValueParsingRoundtrip() const = 0;
protected:
~CommandLineFlag() = default;
private:
// Copy-construct a new value of the flag's type in a memory referenced by
// the dst based on the current flag's value.
virtual void Read(void* dst) const = 0;
};
// This macro is the "source of truth" for the list of supported flag built-in
// types.
#define ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(A) \
A(bool) \
A(short) \
A(unsigned short) \
A(int) \
A(unsigned int) \
A(long) \
A(unsigned long) \
A(long long) \
A(unsigned long long) \
A(double) \
A(float) \
A(std::string) \
A(std::vector<std::string>)
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
|
