lib/Maybe_h.template

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef {{"_".join(config.protocol.namespace)}}_Maybe_h
#define {{"_".join(config.protocol.namespace)}}_Maybe_h

// This macro allows to test for the version of the GNU C++ compiler.
// Note that this also applies to compilers that masquerade as GCC,
// for example clang and the Intel C++ compiler for Linux.
// Use like:
//  #if IP_GNUC_PREREQ(4, 3, 1)
//   ...
//  #endif
#if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
#define IP_GNUC_PREREQ(major, minor, patchlevel)                      \
  ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= \
   ((major)*10000 + (minor)*100 + (patchlevel)))
#elif defined(__GNUC__) && defined(__GNUC_MINOR__)
#define IP_GNUC_PREREQ(major, minor, patchlevel) \
  ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100) >=  \
   ((major)*10000 + (minor)*100 + (patchlevel)))
#else
#define IP_GNUC_PREREQ(major, minor, patchlevel) 0
#endif

#if defined(__mips64)
#define IP_TARGET_ARCH_MIPS64 1
#elif defined(__MIPSEB__) || defined(__MIPSEL__)
#define IP_TARGET_ARCH_MIPS 1
#endif

// Allowing the use of noexcept by removing the keyword on older compilers that
// do not support adding noexcept to default members.
#if ((IP_GNUC_PREREQ(4, 9, 0) && !defined(IP_TARGET_ARCH_MIPS) && \
      !defined(IP_TARGET_ARCH_MIPS64)) ||                         \
     (defined(__clang__) && __cplusplus > 201300L))
#define IP_NOEXCEPT noexcept
#else
#define IP_NOEXCEPT
#endif

//#include "Forward.h"

{% for namespace in config.protocol.namespace %}
namespace {{namespace}} {
{% endfor %}

template<typename T>
class Maybe {
public:
    Maybe() : m_value() { }
    Maybe(std::unique_ptr<T> value) : m_value(std::move(value)) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : m_value(std::move(other.m_value)) {}
    void operator=(std::unique_ptr<T> value) { m_value = std::move(value); }
    T* fromJust() const { DCHECK(m_value); return m_value.get(); }
    T* fromMaybe(T* defaultValue) const { return m_value ? m_value.get() : defaultValue; }
    bool isJust() const { return !!m_value; }
    std::unique_ptr<T> takeJust() { DCHECK(m_value); return std::move(m_value); }
private:
    std::unique_ptr<T> m_value;
};

template<typename T>
class MaybeBase {
public:
    MaybeBase() : m_isJust(false) { }
    MaybeBase(T value) : m_isJust(true), m_value(value) { }
    MaybeBase(MaybeBase&& other) IP_NOEXCEPT
        : m_isJust(other.m_isJust),
          m_value(std::move(other.m_value)) {}
    void operator=(T value) { m_value = value; m_isJust = true; }
    T fromJust() const { DCHECK(m_isJust); return m_value; }
    T fromMaybe(const T& defaultValue) const { return m_isJust ? m_value : defaultValue; }
    bool isJust() const { return m_isJust; }
    T takeJust() { DCHECK(m_isJust); return m_value; }

protected:
    bool m_isJust;
    T m_value;
};

template<>
class Maybe<bool> : public MaybeBase<bool> {
public:
    Maybe() { m_value = false; }
    Maybe(bool value) : MaybeBase(value) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : MaybeBase(std::move(other)) {}
    using MaybeBase::operator=;
};

template<>
class Maybe<int> : public MaybeBase<int> {
public:
    Maybe() { m_value = 0; }
    Maybe(int value) : MaybeBase(value) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : MaybeBase(std::move(other)) {}
    using MaybeBase::operator=;
};

template<>
class Maybe<double> : public MaybeBase<double> {
public:
    Maybe() { m_value = 0; }
    Maybe(double value) : MaybeBase(value) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : MaybeBase(std::move(other)) {}
    using MaybeBase::operator=;
};

template<>
class Maybe<String> : public MaybeBase<String> {
public:
    Maybe() { }
    Maybe(const String& value) : MaybeBase(value) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : MaybeBase(std::move(other)) {}
    using MaybeBase::operator=;
};

template<>
class Maybe<Binary> : public MaybeBase<Binary> {
public:
    Maybe() { }
    Maybe(Binary value) : MaybeBase(value) { }
    Maybe(Maybe&& other) IP_NOEXCEPT : MaybeBase(std::move(other)) {}
    using MaybeBase::operator=;
};

{% for namespace in config.protocol.namespace %}
} // namespace {{namespace}}
{% endfor %}

#undef IP_GNUC_PREREQ
#undef IP_TARGET_ARCH_MIPS64
#undef IP_TARGET_ARCH_MIPS
#undef IP_NOEXCEPT

#endif // !defined({{"_".join(config.protocol.namespace)}}_Maybe_h)