tvl-depot/absl/flags/internal/flag.h
Abseil Team aa468ad755 Export of internal Abseil changes.
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78293ba4eb4981991ae7e6edd25eb9245fcd7515 by Andy Soffer <asoffer@google.com>:

internal changes

PiperOrigin-RevId: 247073879

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7bd97e3aad0c3012b89a39392a6ad3f254e9f3c3 by Derek Mauro <dmauro@google.com>:

Release commandline flags

PiperOrigin-RevId: 247065920

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2a991849fd7b140a43b073076d194b61533fd199 by Tom Manshreck <shreck@google.com>:

Add documentation for built-in usage flags

PiperOrigin-RevId: 247058863

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14157b0de45841706bbd631284191fd94c313db9 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 247058292

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ed67e0a80468596e30540b367727a250fa415b68 by Abseil Team <absl-team@google.com>:

Internal Change.

PiperOrigin-RevId: 246828655

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e1bc8c2aa3f90b3d56c55c5b7244e718c919265d by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 246822325

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907a68f287199f749cb9bdb48571b50bc34731e1 by Eric Fiselier <ericwf@google.com>:

Accept vector<bool>::reference in StrCat and friends.

Converting vector<bool>::reference to alphanum requires
two user defined conversions, which isn't allowed.
In order to accept this, we need a special constructor that
is only enabled for the bool proxy types.

PiperOrigin-RevId: 246626732

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fe4295fa95cc65dee8c881ba12dd8f516e68c40d by Abseil Team <absl-team@google.com>:

Clarify the proper way to define AbslHashValue, and fix confusing indentation.

PiperOrigin-RevId: 246406528

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d7174681a72d4a25c8fd2b4d9f515a0763eff87c by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 246358214

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a7fdc19683cf1a5885e9e1af52fcdb2db1eda53b by Abseil Team <absl-team@google.com>:

Fix sample template instantiation.

PiperOrigin-RevId: 246354617

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29a23c6835f872948d09b24d890385bf195bc995 by Abseil Team <absl-team@google.com>:

Fix incorrectly copy-pasted static_assert in absl::optional::value_or

The static_assert for a move-constructible type previously said the type must be copy-constructible.

PiperOrigin-RevId: 246313827

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41884d5872d4ea2c67875b00144b8c8a5859a295 by Greg Falcon <gfalcon@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 245418790

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7f90a7f94cdd5e21232c749efe952a750b5c43a2 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 245412658

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730a329cf047d54b46971fce1781edd857208c2a by Greg Falcon <gfalcon@google.com>:

internal change

PiperOrigin-RevId: 245293234

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cf0216be6338200cbb18167d3f3b2e98e372be77 by Greg Falcon <gfalcon@google.com>:

Internal change

PiperOrigin-RevId: 245288164
GitOrigin-RevId: 78293ba4eb4981991ae7e6edd25eb9245fcd7515
Change-Id: I5ea9a852c36c722bae2d6be65fb7f72473d94ab6
2019-05-07 16:32:35 -04:00

103 lines
3.5 KiB
C++

//
// 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_FLAG_H_
#define ABSL_FLAGS_INTERNAL_FLAG_H_
#include "absl/flags/internal/commandlineflag.h"
#include "absl/flags/internal/registry.h"
namespace absl {
namespace flags_internal {
// This is "unspecified" implementation of absl::Flag<T> type.
template <typename T>
class Flag {
public:
constexpr Flag(const char* name, const flags_internal::HelpGenFunc help_gen,
const char* filename,
const flags_internal::FlagMarshallingOpFn marshalling_op,
const flags_internal::InitialValGenFunc initial_value_gen)
: internal(name, flags_internal::HelpText::FromFunctionPointer(help_gen),
filename, &flags_internal::FlagOps<T>, marshalling_op,
initial_value_gen,
/*retired_arg=*/false, /*def_arg=*/nullptr,
/*cur_arg=*/nullptr) {}
// Not copyable/assignable.
Flag(const Flag<T>&) = delete;
Flag<T>& operator=(const Flag<T>&) = delete;
absl::string_view Name() const { return internal.Name(); }
std::string Help() const { return internal.Help(); }
std::string Filename() const { return internal.Filename(); }
absl::flags_internal::CommandLineFlag internal;
void SetCallback(const flags_internal::FlagCallback mutation_callback) {
internal.SetCallback(mutation_callback);
}
private:
// TODO(rogeeff): add these validations once UnparseFlag invocation is fixed
// for built-in types and when we cleanup existing code from operating on
// forward declared types.
// auto IsCopyConstructible(const T& v) -> decltype(T(v));
// auto HasAbslParseFlag(absl::string_view in, T* dst, std::string* err)
// -> decltype(AbslParseFlag(in, dst, GlobalStringADLGuard(err)));
// auto HasAbslUnparseFlag(const T& v) -> decltype(AbslUnparseFlag(v));
};
// This class facilitates Flag object registration and tail expression-based
// flag definition, for example:
// ABSL_FLAG(int, foo, 42, "Foo help").OnUpdate(NotifyFooWatcher);
template <typename T, bool do_register>
class FlagRegistrar {
public:
explicit FlagRegistrar(Flag<T>* flag) : flag_(flag) {
if (do_register) flags_internal::RegisterCommandLineFlag(&flag_->internal);
}
FlagRegistrar& OnUpdate(flags_internal::FlagCallback cb) && {
flag_->SetCallback(cb);
return *this;
}
// Make the registrar "die" gracefully as a bool on a line where registration
// happens. Registrar objects are intended to live only as temporary.
operator bool() const { return true; } // NOLINT
private:
Flag<T>* flag_; // Flag being registered (not owned).
};
// This struct and corresponding overload to MakeDefaultValue are used to
// facilitate usage of {} as default value in ABSL_FLAG macro.
struct EmptyBraces {};
template <typename T>
T* MakeFromDefaultValue(T t) {
return new T(std::move(t));
}
template <typename T>
T* MakeFromDefaultValue(EmptyBraces) {
return new T;
}
} // namespace flags_internal
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_FLAG_H_