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author | Feng Xiao <xfxyjwf@gmail.com> | 2015-06-15 18:21:48 -0700 |
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committer | Feng Xiao <xfxyjwf@gmail.com> | 2015-06-15 18:24:01 -0700 |
commit | e96ff30120a3834f7d1e31e43e591bf7cfbd731f (patch) | |
tree | 7e4c317912ac3809fbff11bb692084debd4a27eb /src/google/protobuf/stubs/statusor.h | |
parent | 4cbb612299eaf8259db25f5dcda46022fbd1db54 (diff) | |
download | protobuf-e96ff30120a3834f7d1e31e43e591bf7cfbd731f.tar.gz protobuf-e96ff30120a3834f7d1e31e43e591bf7cfbd731f.tar.bz2 protobuf-e96ff30120a3834f7d1e31e43e591bf7cfbd731f.zip |
Down-integrate from internal code base.
[ci skip]
Change-Id: I9391c09640e0b0b2b21c45a97a1fc91814d95c5d
Diffstat (limited to 'src/google/protobuf/stubs/statusor.h')
-rw-r--r-- | src/google/protobuf/stubs/statusor.h | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/src/google/protobuf/stubs/statusor.h b/src/google/protobuf/stubs/statusor.h new file mode 100644 index 00000000..9495107e --- /dev/null +++ b/src/google/protobuf/stubs/statusor.h @@ -0,0 +1,259 @@ +// Protocol Buffers - Google's data interchange format +// Copyright 2008 Google Inc. All rights reserved. +// https://developers.google.com/protocol-buffers/ +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following disclaimer +// in the documentation and/or other materials provided with the +// distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +// StatusOr<T> is the union of a Status object and a T +// object. StatusOr models the concept of an object that is either a +// usable value, or an error Status explaining why such a value is +// not present. To this end, StatusOr<T> does not allow its Status +// value to be Status::OK. Further, StatusOr<T*> does not allow the +// contained pointer to be NULL. +// +// The primary use-case for StatusOr<T> is as the return value of a +// function which may fail. +// +// Example client usage for a StatusOr<T>, where T is not a pointer: +// +// StatusOr<float> result = DoBigCalculationThatCouldFail(); +// if (result.ok()) { +// float answer = result.ValueOrDie(); +// printf("Big calculation yielded: %f", answer); +// } else { +// LOG(ERROR) << result.status(); +// } +// +// Example client usage for a StatusOr<T*>: +// +// StatusOr<Foo*> result = FooFactory::MakeNewFoo(arg); +// if (result.ok()) { +// std::unique_ptr<Foo> foo(result.ValueOrDie()); +// foo->DoSomethingCool(); +// } else { +// LOG(ERROR) << result.status(); +// } +// +// Example client usage for a StatusOr<std::unique_ptr<T>>: +// +// StatusOr<std::unique_ptr<Foo>> result = FooFactory::MakeNewFoo(arg); +// if (result.ok()) { +// std::unique_ptr<Foo> foo = result.ConsumeValueOrDie(); +// foo->DoSomethingCool(); +// } else { +// LOG(ERROR) << result.status(); +// } +// +// Example factory implementation returning StatusOr<T*>: +// +// StatusOr<Foo*> FooFactory::MakeNewFoo(int arg) { +// if (arg <= 0) { +// return ::util::Status(::util::error::INVALID_ARGUMENT, +// "Arg must be positive"); +// } else { +// return new Foo(arg); +// } +// } +// + +#ifndef GOOGLE_PROTOBUF_STUBS_STATUSOR_H_ +#define GOOGLE_PROTOBUF_STUBS_STATUSOR_H_ + +#include <new> +#include <string> +#include <utility> + +#include <google/protobuf/stubs/status.h> + +namespace google { +namespace protobuf { +namespace util { + +template<typename T> +class StatusOr { + template<typename U> friend class StatusOr; + + public: + // Construct a new StatusOr with Status::UNKNOWN status + StatusOr(); + + // Construct a new StatusOr with the given non-ok status. After calling + // this constructor, calls to ValueOrDie() will CHECK-fail. + // + // NOTE: Not explicit - we want to use StatusOr<T> as a return + // value, so it is convenient and sensible to be able to do 'return + // Status()' when the return type is StatusOr<T>. + // + // REQUIRES: status != Status::OK. This requirement is DCHECKed. + // In optimized builds, passing Status::OK here will have the effect + // of passing PosixErrorSpace::EINVAL as a fallback. + StatusOr(const Status& status); // NOLINT + + // Construct a new StatusOr with the given value. If T is a plain pointer, + // value must not be NULL. After calling this constructor, calls to + // ValueOrDie() will succeed, and calls to status() will return OK. + // + // NOTE: Not explicit - we want to use StatusOr<T> as a return type + // so it is convenient and sensible to be able to do 'return T()' + // when when the return type is StatusOr<T>. + // + // REQUIRES: if T is a plain pointer, value != NULL. This requirement is + // DCHECKed. In optimized builds, passing a NULL pointer here will have + // the effect of passing PosixErrorSpace::EINVAL as a fallback. + StatusOr(const T& value); // NOLINT + + // Copy constructor. + StatusOr(const StatusOr& other); + + // Conversion copy constructor, T must be copy constructible from U + template<typename U> + StatusOr(const StatusOr<U>& other); + + // Assignment operator. + StatusOr& operator=(const StatusOr& other); + + // Conversion assignment operator, T must be assignable from U + template<typename U> + StatusOr& operator=(const StatusOr<U>& other); + + // Returns a reference to our status. If this contains a T, then + // returns Status::OK. + const Status& status() const; + + // Returns this->status().ok() + bool ok() const; + + // Returns a reference to our current value, or CHECK-fails if !this->ok(). + // If you need to initialize a T object from the stored value, + // ConsumeValueOrDie() may be more efficient. + const T& ValueOrDie() const; + + private: + Status status_; + T value_; +}; + +//////////////////////////////////////////////////////////////////////////////// +// Implementation details for StatusOr<T> + +namespace internal { + +class StatusOrHelper { + public: + // Move type-agnostic error handling to the .cc. + static void Crash(const util::Status& status); + + // Customized behavior for StatusOr<T> vs. StatusOr<T*> + template<typename T> + struct Specialize; +}; + +template<typename T> +struct StatusOrHelper::Specialize { + // For non-pointer T, a reference can never be NULL. + static inline bool IsValueNull(const T& t) { return false; } +}; + +template<typename T> +struct StatusOrHelper::Specialize<T*> { + static inline bool IsValueNull(const T* t) { return t == NULL; } +}; + +} // namespace internal + +template<typename T> +inline StatusOr<T>::StatusOr() + : status_(util::Status::UNKNOWN) { +} + +template<typename T> +inline StatusOr<T>::StatusOr(const Status& status) { + if (status.ok()) { + status_ = Status(error::INTERNAL, "Status::OK is not a valid argument."); + } else { + status_ = status; + } +} + +template<typename T> +inline StatusOr<T>::StatusOr(const T& value) { + if (internal::StatusOrHelper::Specialize<T>::IsValueNull(value)) { + status_ = Status(error::INTERNAL, "NULL is not a vaild argument."); + } else { + status_ = Status::OK; + value_ = value; + } +} + +template<typename T> +inline StatusOr<T>::StatusOr(const StatusOr<T>& other) + : status_(other.status_), value_(other.value_) { +} + +template<typename T> +inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<T>& other) { + status_ = other.status_; + value_ = other.value_; + return *this; +} + +template<typename T> +template<typename U> +inline StatusOr<T>::StatusOr(const StatusOr<U>& other) + : status_(other.status_), value_(other.value_) { +} + +template<typename T> +template<typename U> +inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<U>& other) { + status_ = other.status_; + value_ = other.value_; + return *this; +} + +template<typename T> +inline const Status& StatusOr<T>::status() const { + return status_; +} + +template<typename T> +inline bool StatusOr<T>::ok() const { + return status().ok(); +} + +template<typename T> +inline const T& StatusOr<T>::ValueOrDie() const { + if (!status_.ok()) { + internal::StatusOrHelper::Crash(status_); + } + return value_; +} +} // namespace util +} // namespace protobuf +} // namespace google + +#endif // GOOGLE_PROTOBUF_STUBS_STATUSOR_H_ |