SeqProxy.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2018 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or 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 RIPPLE_PROTOCOL_SEQ_PROXY_H_INCLUDED
#define RIPPLE_PROTOCOL_SEQ_PROXY_H_INCLUDED
 
#include <cstdint>
#include <ostream>
 
namespace ripple {
 
class SeqProxy
{
public:
    enum Type : std::uint8_t { seq = 0, ticket };
 
private:
    std::uint32_t value_;
    Type type_;
 
public:
    constexpr explicit SeqProxy(Type t, std::uint32_t v) : value_{v}, type_{t}
    {
    }
 
    SeqProxy(SeqProxy const& other) = default;
 
    SeqProxy&
    operator=(SeqProxy const& other) = default;
 
    static constexpr SeqProxy
    sequence(std::uint32_t v)
    {
        return SeqProxy{Type::seq, v};
    }
 
    constexpr std::uint32_t
    value() const
    {
        return value_;
    }
 
    constexpr bool
    isSeq() const
    {
        return type_ == seq;
    }
 
    constexpr bool
    isTicket() const
    {
        return type_ == ticket;
    }
 
    // Occasionally it is convenient to be able to increase the value_
    // of a SeqProxy.  But it's unusual.  So, rather than putting in an
    // addition operator, you must invoke the method by name.  That makes
    // if more difficult to invoke accidentally.
    SeqProxy&
    advanceBy(std::uint32_t amount)
    {
        value_ += amount;
        return *this;
    }
 
    // Comparison
    //
    // The comparison is designed specifically so _all_ Sequence
    // representations sort in front of Ticket representations.  This
    // is true even if the Ticket value() is less that the Sequence
    // value().
    //
    // This somewhat surprising sort order has benefits for transaction
    // processing.  It guarantees that transactions creating Tickets are
    // sorted in from of transactions that consume Tickets.
    friend constexpr bool
    operator==(SeqProxy lhs, SeqProxy rhs)
    {
        if (lhs.type_ != rhs.type_)
            return false;
        return (lhs.value() == rhs.value());
    }
 
    friend constexpr bool
    operator!=(SeqProxy lhs, SeqProxy rhs)
    {
        return !(lhs == rhs);
    }
 
    friend constexpr bool
    operator<(SeqProxy lhs, SeqProxy rhs)
    {
        if (lhs.type_ != rhs.type_)
            return lhs.type_ < rhs.type_;
        return lhs.value() < rhs.value();
    }
 
    friend constexpr bool
    operator>(SeqProxy lhs, SeqProxy rhs)
    {
        return rhs < lhs;
    }
 
    friend constexpr bool
    operator>=(SeqProxy lhs, SeqProxy rhs)
    {
        return !(lhs < rhs);
    }
 
    friend constexpr bool
    operator<=(SeqProxy lhs, SeqProxy rhs)
    {
        return !(lhs > rhs);
    }
 
    friend std::ostream&
    operator<<(std::ostream& os, SeqProxy seqProx)
    {
        os << (seqProx.isSeq() ? "sequence " : "ticket ");
        os << seqProx.value();
        return os;
    }
};
}  // namespace ripple
 
#endif