Result.h

/*
 * Copyright (c) 2008-2014, Pedigree Developers
 *
 * Please see the CONTRIB file in the root of the source tree for a full
 * list of contributors.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
#ifndef KERNEL_UTILITIES_RESULT_H
#define KERNEL_UTILITIES_RESULT_H
 
#include "pedigree/kernel/utilities/assert.h"
#include "pedigree/kernel/utilities/utility.h"
 
template <class T, class E>
class Result {
 public:
  static Result<T, E> withValue(const T& v) {
    return Result<T, E>(v);
  }
 
  static Result<T, E> withError(const E& e) {
    return Result<T, E>(e, true);
  }
 
  const T& value() const {
    assert(hasValue());
    return m_Value;
  }
 
  const E& error() const {
    assert(hasError());
    return m_Error;
  }
 
  bool hasError() const {
    return m_HasError;
  }
 
  bool hasValue() const {
    return !hasError();
  }
 
 private:
  Result() = delete;
 
  Result(const T& v) : m_Value(v), m_Error(), m_HasError(false) {}
 
  Result(const E& e, bool) : m_Value(m_DefaultValue), m_Error(e), m_HasError(true) {}
 
  T m_Value;
  E m_Error;
  bool m_HasError;
 
  typedef typename pedigree_std::remove_reference<T>::type BaseValueType;
  static const BaseValueType m_DefaultValue;
};
 
template <class T, class E>
const typename Result<T, E>::BaseValueType Result<T, E>::m_DefaultValue =
    Result<T, E>::BaseValueType();
 
#endif  // KERNEL_UTILITIES_RESULT_H