chromium/third_party/protobuf/src/google/protobuf/stubs/statusor.h

// Protocol Buffers - Google's data interchange format
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// https://developers.google.com/protocol-buffers/
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// 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 OkStatus(). Further, StatusOr<T*> does not allow the
// contained pointer to be nullptr.
//
// 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.value();
//    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.value());
//    foo->DoSomethingCool();
//  } else {
//    LOG(ERROR) << result.status();
//  }
//
// Example factory implementation returning StatusOr<T*>:
//
//  StatusOr<Foo*> FooFactory::MakeNewFoo(int arg) {
//    if (arg <= 0) {
//      return InvalidArgumentError("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>

#include <google/protobuf/port_def.inc>

namespace google {
namespace protobuf {
namespace util {
namespace statusor_internal {

template<typename T>
class StatusOr { … };

////////////////////////////////////////////////////////////////////////////////
// Implementation details for StatusOr<T>

class PROTOBUF_EXPORT StatusOrHelper { … };

template<typename T>
struct StatusOrHelper::Specialize { … };

Specialize<T *>;

template <typename T>
inline StatusOr<T>::StatusOr() : … { … }

template<typename T>
inline StatusOr<T>::StatusOr(const Status& status) { … }

template<typename T>
inline StatusOr<T>::StatusOr(const T& value) { … }

template<typename T>
inline StatusOr<T>::StatusOr(const StatusOr<T>& other)
    : … { … }

template<typename T>
inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<T>& other) { … }

template<typename T>
template<typename U>
inline StatusOr<T>::StatusOr(const StatusOr<U>& other)
    : status_(other.status_), value_(other.status_.ok() ? other.value_ : T()) { … }

template<typename T>
template<typename U>
inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<U>& other) { … }

template<typename T>
inline const Status& StatusOr<T>::status() const { … }

template<typename T>
inline bool StatusOr<T>::ok() const { … }

template<typename T>
inline const T& StatusOr<T>::value() const { … }

}  // namespace statusor_internal

StatusOr;

}  // namespace util
}  // namespace protobuf
}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_STUBS_STATUSOR_H_