265 lines
10 KiB
C
265 lines
10 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.
|
||
|
|
//
|
||
|
|
// -----------------------------------------------------------------------------
|
||
|
|
// File: marshalling.h
|
||
|
|
// -----------------------------------------------------------------------------
|
||
|
|
//
|
||
|
|
// This header file defines the API for extending Abseil flag support to
|
||
|
|
// custom types, and defines the set of overloads for fundamental types.
|
||
|
|
//
|
||
|
|
// Out of the box, the Abseil flags library supports the following types:
|
||
|
|
//
|
||
|
|
// * `bool`
|
||
|
|
// * `int16_t`
|
||
|
|
// * `uint16_t`
|
||
|
|
// * `int32_t`
|
||
|
|
// * `uint32_t`
|
||
|
|
// * `int64_t`
|
||
|
|
// * `uint64_t`
|
||
|
|
// * `float`
|
||
|
|
// * `double`
|
||
|
|
// * `std::string`
|
||
|
|
// * `std::vector<std::string>`
|
||
|
|
// * `absl::LogSeverity` (provided natively for layering reasons)
|
||
|
|
//
|
||
|
|
// Note that support for integral types is implemented using overloads for
|
||
|
|
// variable-width fundamental types (`short`, `int`, `long`, etc.). However,
|
||
|
|
// you should prefer the fixed-width integral types (`int32_t`, `uint64_t`,
|
||
|
|
// etc.) we've noted above within flag definitions.
|
||
|
|
//
|
||
|
|
// In addition, several Abseil libraries provide their own custom support for
|
||
|
|
// Abseil flags. Documentation for these formats is provided in the type's
|
||
|
|
// `AbslParseFlag()` definition.
|
||
|
|
//
|
||
|
|
// The Abseil time library provides the following support for civil time values:
|
||
|
|
//
|
||
|
|
// * `absl::CivilSecond`
|
||
|
|
// * `absl::CivilMinute`
|
||
|
|
// * `absl::CivilHour`
|
||
|
|
// * `absl::CivilDay`
|
||
|
|
// * `absl::CivilMonth`
|
||
|
|
// * `absl::CivilYear`
|
||
|
|
//
|
||
|
|
// and also provides support for the following absolute time values:
|
||
|
|
//
|
||
|
|
// * `absl::Duration`
|
||
|
|
// * `absl::Time`
|
||
|
|
//
|
||
|
|
// Additional support for Abseil types will be noted here as it is added.
|
||
|
|
//
|
||
|
|
// You can also provide your own custom flags by adding overloads for
|
||
|
|
// `AbslParseFlag()` and `AbslUnparseFlag()` to your type definitions. (See
|
||
|
|
// below.)
|
||
|
|
//
|
||
|
|
// -----------------------------------------------------------------------------
|
||
|
|
// Adding Type Support for Abseil Flags
|
||
|
|
// -----------------------------------------------------------------------------
|
||
|
|
//
|
||
|
|
// To add support for your user-defined type, add overloads of `AbslParseFlag()`
|
||
|
|
// and `AbslUnparseFlag()` as free (non-member) functions to your type. If `T`
|
||
|
|
// is a class type, these functions can be friend function definitions. These
|
||
|
|
// overloads must be added to the same namespace where the type is defined, so
|
||
|
|
// that they can be discovered by Argument-Dependent Lookup (ADL).
|
||
|
|
//
|
||
|
|
// Example:
|
||
|
|
//
|
||
|
|
// namespace foo {
|
||
|
|
//
|
||
|
|
// enum OutputMode { kPlainText, kHtml };
|
||
|
|
//
|
||
|
|
// // AbslParseFlag converts from a string to OutputMode.
|
||
|
|
// // Must be in same namespace as OutputMode.
|
||
|
|
//
|
||
|
|
// // Parses an OutputMode from the command line flag value `text`. Returns
|
||
|
|
// // `true` and sets `*mode` on success; returns `false` and sets `*error`
|
||
|
|
// // on failure.
|
||
|
|
// bool AbslParseFlag(absl::string_view text,
|
||
|
|
// OutputMode* mode,
|
||
|
|
// std::string* error) {
|
||
|
|
// if (text == "plaintext") {
|
||
|
|
// *mode = kPlainText;
|
||
|
|
// return true;
|
||
|
|
// }
|
||
|
|
// if (text == "html") {
|
||
|
|
// *mode = kHtml;
|
||
|
|
// return true;
|
||
|
|
// }
|
||
|
|
// *error = "unknown value for enumeration";
|
||
|
|
// return false;
|
||
|
|
// }
|
||
|
|
//
|
||
|
|
// // AbslUnparseFlag converts from an OutputMode to a string.
|
||
|
|
// // Must be in same namespace as OutputMode.
|
||
|
|
//
|
||
|
|
// // Returns a textual flag value corresponding to the OutputMode `mode`.
|
||
|
|
// std::string AbslUnparseFlag(OutputMode mode) {
|
||
|
|
// switch (mode) {
|
||
|
|
// case kPlainText: return "plaintext";
|
||
|
|
// case kHtml: return "html";
|
||
|
|
// }
|
||
|
|
// return absl::StrCat(mode);
|
||
|
|
// }
|
||
|
|
//
|
||
|
|
// Notice that neither `AbslParseFlag()` nor `AbslUnparseFlag()` are class
|
||
|
|
// members, but free functions. `AbslParseFlag/AbslUnparseFlag()` overloads
|
||
|
|
// for a type should only be declared in the same file and namespace as said
|
||
|
|
// type. The proper `AbslParseFlag/AbslUnparseFlag()` implementations for a
|
||
|
|
// given type will be discovered via Argument-Dependent Lookup (ADL).
|
||
|
|
//
|
||
|
|
// `AbslParseFlag()` may need, in turn, to parse simpler constituent types
|
||
|
|
// using `absl::ParseFlag()`. For example, a custom struct `MyFlagType`
|
||
|
|
// consisting of a `std::pair<int, std::string>` would add an `AbslParseFlag()`
|
||
|
|
// overload for its `MyFlagType` like so:
|
||
|
|
//
|
||
|
|
// Example:
|
||
|
|
//
|
||
|
|
// namespace my_flag_type {
|
||
|
|
//
|
||
|
|
// struct MyFlagType {
|
||
|
|
// std::pair<int, std::string> my_flag_data;
|
||
|
|
// };
|
||
|
|
//
|
||
|
|
// bool AbslParseFlag(absl::string_view text, MyFlagType* flag,
|
||
|
|
// std::string* err);
|
||
|
|
//
|
||
|
|
// std::string AbslUnparseFlag(const MyFlagType&);
|
||
|
|
//
|
||
|
|
// // Within the implementation, `AbslParseFlag()` will, in turn invoke
|
||
|
|
// // `absl::ParseFlag()` on its constituent `int` and `std::string` types
|
||
|
|
// // (which have built-in Abseil flag support).
|
||
|
|
//
|
||
|
|
// bool AbslParseFlag(absl::string_view text, MyFlagType* flag,
|
||
|
|
// std::string* err) {
|
||
|
|
// std::pair<absl::string_view, absl::string_view> tokens =
|
||
|
|
// absl::StrSplit(text, ',');
|
||
|
|
// if (!absl::ParseFlag(tokens.first, &flag->my_flag_data.first, err))
|
||
|
|
// return false;
|
||
|
|
// if (!absl::ParseFlag(tokens.second, &flag->my_flag_data.second, err))
|
||
|
|
// return false;
|
||
|
|
// return true;
|
||
|
|
// }
|
||
|
|
//
|
||
|
|
// // Similarly, for unparsing, we can simply invoke `absl::UnparseFlag()` on
|
||
|
|
// // the constituent types.
|
||
|
|
// std::string AbslUnparseFlag(const MyFlagType& flag) {
|
||
|
|
// return absl::StrCat(absl::UnparseFlag(flag.my_flag_data.first),
|
||
|
|
// ",",
|
||
|
|
// absl::UnparseFlag(flag.my_flag_data.second));
|
||
|
|
// }
|
||
|
|
#ifndef ABSL_FLAGS_MARSHALLING_H_
|
||
|
|
#define ABSL_FLAGS_MARSHALLING_H_
|
||
|
|
|
||
|
|
#include <string>
|
||
|
|
#include <vector>
|
||
|
|
|
||
|
|
#include "absl/base/config.h"
|
||
|
|
#include "absl/strings/string_view.h"
|
||
|
|
|
||
|
|
namespace absl {
|
||
|
|
ABSL_NAMESPACE_BEGIN
|
||
|
|
namespace flags_internal {
|
||
|
|
|
||
|
|
// Overloads of `AbslParseFlag()` and `AbslUnparseFlag()` for fundamental types.
|
||
|
|
bool AbslParseFlag(absl::string_view, bool*, std::string*);
|
||
|
|
bool AbslParseFlag(absl::string_view, short*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, unsigned short*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, int*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, unsigned int*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, long*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, unsigned long*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, long long*, std::string*); // NOLINT
|
||
|
|
bool AbslParseFlag(absl::string_view, unsigned long long*, // NOLINT
|
||
|
|
std::string*);
|
||
|
|
bool AbslParseFlag(absl::string_view, float*, std::string*);
|
||
|
|
bool AbslParseFlag(absl::string_view, double*, std::string*);
|
||
|
|
bool AbslParseFlag(absl::string_view, std::string*, std::string*);
|
||
|
|
bool AbslParseFlag(absl::string_view, std::vector<std::string>*, std::string*);
|
||
|
|
|
||
|
|
template <typename T>
|
||
|
|
bool InvokeParseFlag(absl::string_view input, T* dst, std::string* err) {
|
||
|
|
// Comment on next line provides a good compiler error message if T
|
||
|
|
// does not have AbslParseFlag(absl::string_view, T*, std::string*).
|
||
|
|
return AbslParseFlag(input, dst, err); // Is T missing AbslParseFlag?
|
||
|
|
}
|
||
|
|
|
||
|
|
// Strings and std:: containers do not have the same overload resolution
|
||
|
|
// considerations as fundamental types. Naming these 'AbslUnparseFlag' means we
|
||
|
|
// can avoid the need for additional specializations of Unparse (below).
|
||
|
|
std::string AbslUnparseFlag(absl::string_view v);
|
||
|
|
std::string AbslUnparseFlag(const std::vector<std::string>&);
|
||
|
|
|
||
|
|
template <typename T>
|
||
|
|
std::string Unparse(const T& v) {
|
||
|
|
// Comment on next line provides a good compiler error message if T does not
|
||
|
|
// have UnparseFlag.
|
||
|
|
return AbslUnparseFlag(v); // Is T missing AbslUnparseFlag?
|
||
|
|
}
|
||
|
|
|
||
|
|
// Overloads for builtin types.
|
||
|
|
std::string Unparse(bool v);
|
||
|
|
std::string Unparse(short v); // NOLINT
|
||
|
|
std::string Unparse(unsigned short v); // NOLINT
|
||
|
|
std::string Unparse(int v); // NOLINT
|
||
|
|
std::string Unparse(unsigned int v); // NOLINT
|
||
|
|
std::string Unparse(long v); // NOLINT
|
||
|
|
std::string Unparse(unsigned long v); // NOLINT
|
||
|
|
std::string Unparse(long long v); // NOLINT
|
||
|
|
std::string Unparse(unsigned long long v); // NOLINT
|
||
|
|
std::string Unparse(float v);
|
||
|
|
std::string Unparse(double v);
|
||
|
|
|
||
|
|
} // namespace flags_internal
|
||
|
|
|
||
|
|
// ParseFlag()
|
||
|
|
//
|
||
|
|
// Parses a string value into a flag value of type `T`. Do not add overloads of
|
||
|
|
// this function for your type directly; instead, add an `AbslParseFlag()`
|
||
|
|
// free function as documented above.
|
||
|
|
//
|
||
|
|
// Some implementations of `AbslParseFlag()` for types which consist of other,
|
||
|
|
// constituent types which already have Abseil flag support, may need to call
|
||
|
|
// `absl::ParseFlag()` on those consituent string values. (See above.)
|
||
|
|
template <typename T>
|
||
|
|
inline bool ParseFlag(absl::string_view input, T* dst, std::string* error) {
|
||
|
|
return flags_internal::InvokeParseFlag(input, dst, error);
|
||
|
|
}
|
||
|
|
|
||
|
|
// UnparseFlag()
|
||
|
|
//
|
||
|
|
// Unparses a flag value of type `T` into a string value. Do not add overloads
|
||
|
|
// of this function for your type directly; instead, add an `AbslUnparseFlag()`
|
||
|
|
// free function as documented above.
|
||
|
|
//
|
||
|
|
// Some implementations of `AbslUnparseFlag()` for types which consist of other,
|
||
|
|
// constituent types which already have Abseil flag support, may want to call
|
||
|
|
// `absl::UnparseFlag()` on those constituent types. (See above.)
|
||
|
|
template <typename T>
|
||
|
|
inline std::string UnparseFlag(const T& v) {
|
||
|
|
return flags_internal::Unparse(v);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Overloads for `absl::LogSeverity` can't (easily) appear alongside that type's
|
||
|
|
// definition because it is layered below flags. See proper documentation in
|
||
|
|
// base/log_severity.h.
|
||
|
|
enum class LogSeverity : int;
|
||
|
|
bool AbslParseFlag(absl::string_view, absl::LogSeverity*, std::string*);
|
||
|
|
std::string AbslUnparseFlag(absl::LogSeverity);
|
||
|
|
|
||
|
|
ABSL_NAMESPACE_END
|
||
|
|
} // namespace absl
|
||
|
|
|
||
|
|
#endif // ABSL_FLAGS_MARSHALLING_H_
|