status_macros.h

// Protocol Buffers - Google's data interchange format
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// From: util/task/contrib/status_macros/status_macros.h

#ifndef GOOGLE_PROTOBUF_STUBS_STATUS_MACROS_H_
#define GOOGLE_PROTOBUF_STUBS_STATUS_MACROS_H_

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/status.h>
#include <google/protobuf/stubs/statusor.h>

namespace google {
namespace protobuf {
namespace util {

// Run a command that returns a util::Status.  If the called code returns an
// error status, return that status up out of this method too.
//
// Example:
//   RETURN_IF_ERROR(DoThings(4));
#define RETURN_IF_ERROR(expr)                                                \
  do {                                                                       \
    /* Using _status below to avoid capture problems if expr is "status". */ \
    const PROTOBUF_NAMESPACE_ID::util::Status _status = (expr);              \
    if (PROTOBUF_PREDICT_FALSE(!_status.ok())) return _status;               \
  } while (0)

// Internal helper for concatenating macro values.
#define STATUS_MACROS_CONCAT_NAME_INNER(x, y) x##y
#define STATUS_MACROS_CONCAT_NAME(x, y) STATUS_MACROS_CONCAT_NAME_INNER(x, y)

template<typename T>
Status DoAssignOrReturn(T& lhs, StatusOr<T> result) {
  if (result.ok()) {
    lhs = result.value();
  }
  return result.status();
}

#define ASSIGN_OR_RETURN_IMPL(status, lhs, rexpr) \
  Status status = DoAssignOrReturn(lhs, (rexpr)); \
  if (PROTOBUF_PREDICT_FALSE(!status.ok())) return status;

// Executes an expression that returns a util::StatusOr, extracting its value
// into the variable defined by lhs (or returning on error).
//
// Example: Assigning to an existing value
//   ValueType value;
//   ASSIGN_OR_RETURN(value, MaybeGetValue(arg));
//
// WARNING: ASSIGN_OR_RETURN expands into multiple statements; it cannot be used
//  in a single statement (e.g. as the body of an if statement without {})!
#define ASSIGN_OR_RETURN(lhs, rexpr) \
  ASSIGN_OR_RETURN_IMPL( \
      STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr);

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

#endif  // GOOGLE_PROTOBUF_STUBS_STATUS_H_