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construct/include/ircd/byte_view.h

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2017-11-16 02:21:26 +01:00
/*
* charybdis: 21st Century IRC++d
* util.h: Miscellaneous utilities
*
* Copyright (C) 2016 Charybdis Development Team
* Copyright (C) 2016 Jason Volk <jason@zemos.net>
*
* 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 is present in all copies.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
#pragma once
#define HAVE_IRCD_BYTE_VIEW_H
namespace ircd
{
template<class T = string_view> struct byte_view;
template<> struct byte_view<string_view>;
}
/// string_view -> bytes
template<class T>
struct ircd::byte_view
{
string_view s;
operator const T &() const
{
if(unlikely(sizeof(T) > s.size()))
throw std::bad_cast();
return *reinterpret_cast<const T *>(s.data());
}
byte_view(const string_view &s = {})
:s{s}
{
if(unlikely(sizeof(T) > s.size()))
throw std::bad_cast();
}
// bytes -> bytes (completeness)
byte_view(const T &t)
:s{byte_view<string_view>{t}}
{}
};
/// bytes -> string_view. A byte_view<string_view> is raw data of byte_view<T>.
///
/// This is an important specialization to take note of. When you see
/// byte_view<string_view> know that another type's bytes are being represented
/// by the string_view if that type is not string_view family itself.
template<>
struct ircd::byte_view<ircd::string_view>
:string_view
{
template<class T,
typename std::enable_if<!std::is_base_of<std::string_view, T>::value, int *>::type = nullptr>
byte_view(const T &t)
:string_view{reinterpret_cast<const char *>(&t), sizeof(T)}
{}
/// string_view -> string_view (completeness)
byte_view(const string_view &t)
:string_view{t}
{}
};