libcruft-util/view.hpp

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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
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* http://www.apache.org/licenses/LICENSE-2.0
*
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2015-2017 Danny Robson <danny@nerdcruft.net>
*/
#ifndef CRUFT_UTIL_VIEW_HPP
#define CRUFT_UTIL_VIEW_HPP
#include "./types/traits.hpp"
#include <cassert>
#include <cstdlib>
#include <ostream>
#include <string>
#include <cstring>
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#include <stdexcept>
namespace util {
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template <typename IteratorT>
struct view {
public:
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//---------------------------------------------------------------------
using value_type = typename std::iterator_traits<
remove_restrict_t<IteratorT>
>::value_type;
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//---------------------------------------------------------------------
constexpr
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view (const IteratorT &first, const IteratorT &last) noexcept:
m_begin (first),
m_end (last)
{ ; }
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//---------------------------------------------------------------------
constexpr view (const view &rhs) noexcept = default;
view& operator= (const view &rhs) noexcept = default;
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//---------------------------------------------------------------------
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// technically we could get away without explicitly defining a move
// constructor here, but by nulling rhs we can more easily use this
// class as a base for unique owning pointers without exposing
// begin/end to them directly.
constexpr view (view &&rhs) noexcept:
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view (IteratorT{}, IteratorT{})
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{
std::swap (m_begin, rhs.m_begin);
std::swap (m_end, rhs.m_end);
}
template <std::size_t N>
constexpr view (const char (&str)[N]):
m_begin (std::begin (str)),
m_end (std::begin (str) + N - 1)
{ ; }
explicit constexpr view (std::nullptr_t):
m_begin (nullptr),
m_end (nullptr)
{ ; }
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//---------------------------------------------------------------------
template <typename ContainerT>
constexpr explicit
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view (ContainerT &klass):
m_begin (std::begin (klass)),
m_end (std::end (klass))
{ ; }
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//---------------------------------------------------------------------
template <typename ContainerT>
constexpr explicit
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view (const ContainerT &klass):
m_begin (std::begin (klass)),
m_end (std::end (klass))
{ ; }
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//---------------------------------------------------------------------
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view&
operator= (view &&rhs) noexcept
{
m_begin = rhs.m_begin;
m_end = rhs.m_end;
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rhs.m_begin = IteratorT{};
rhs.m_end = IteratorT{};
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return *this;
};
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///////////////////////////////////////////////////////////////////////
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constexpr IteratorT begin (void) noexcept { return m_begin; }
constexpr IteratorT end (void) noexcept { return m_end; }
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//---------------------------------------------------------------------
constexpr const IteratorT begin (void) const noexcept { return cbegin (); }
constexpr const IteratorT end (void) const noexcept { return cend (); }
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//---------------------------------------------------------------------
constexpr const IteratorT cbegin (void) const noexcept { return m_begin; }
constexpr const IteratorT cend (void) const noexcept { return m_end; }
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//---------------------------------------------------------------------
auto data (void) { return begin (); }
auto data (void) const { return begin (); }
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///////////////////////////////////////////////////////////////////////
constexpr bool
empty (void) const noexcept
{
return m_begin == m_end;
}
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//---------------------------------------------------------------------
constexpr auto
size (void) const noexcept
{
return std::distance (m_begin, m_end);
}
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//---------------------------------------------------------------------
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constexpr auto
redim (int count) const
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{
assert (count > 0);
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if (count > size ())
throw std::invalid_argument ("redim to higher size not allowed");
return view { m_begin, m_begin + count };
};
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///////////////////////////////////////////////////////////////////////
constexpr value_type&
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operator[] (size_t idx)& noexcept
{
auto it = begin ();
std::advance (it, idx);
return *it;
}
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//---------------------------------------------------------------------
constexpr const value_type&
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operator[] (size_t idx) const& noexcept
{
auto it = begin ();
std::advance (it, idx);
return *it;
}
private:
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///////////////////////////////////////////////////////////////////////
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IteratorT m_begin;
IteratorT m_end;
};
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///////////////////////////////////////////////////////////////////////////
template <typename ValueT, size_t N>
auto
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make_view (const ValueT (&arr)[N])
{
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return util::view<const ValueT*> (arr + 0, arr + N);
}
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//-------------------------------------------------------------------------
template <typename ContainerT>
auto
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make_view (ContainerT &t)
{
return util::view<decltype(std::begin (t))> { std::begin (t), std::end (t) };
}
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//-------------------------------------------------------------------------
template <typename ContainerT>
auto
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make_view (const ContainerT &t)
{
return util::view<decltype(std::cbegin (t))> { std::cbegin (t), std::cend (t) };
}
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//-------------------------------------------------------------------------
// disable the possibility of creating a view to a temporary. note that
// this only works if an lval version has already been defined otherwise
// universal reference rules will capture both lval and rval here.
template <typename ContainerT>
auto
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make_view (ContainerT&&) = delete;
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///////////////////////////////////////////////////////////////////////////
template <typename ContainerT>
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auto
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make_cview (const ContainerT &t)
{
return util::view<decltype(std::cbegin (t))> { std::cbegin (t), std::cend (t) };
}
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//-------------------------------------------------------------------------
template <typename IteratorT>
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auto
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make_view (IteratorT first, IteratorT last)
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{
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return view<IteratorT> {first, last};
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}
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//-------------------------------------------------------------------------
template <typename ValueT>
auto
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make_cview (ValueT *first, ValueT *last)
{
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return view<const ValueT*> {first, last};
}
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///////////////////////////////////////////////////////////////////////////
inline
view<const char*> make_view (const char *str)
{
return { str, str + strlen (str) };
}
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//-------------------------------------------------------------------------
inline
view<char*> make_view (char *str)
{
return { str, str + strlen (str) };
}
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//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<const CharT*>
make_view (const std::basic_string<CharT,TraitsT,AllocT> &str)
{
return {
std::data (str),
std::data (str) + std::size (str)
};
}
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//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<CharT*>
make_view (std::basic_string<CharT,TraitsT,AllocT> &str)
{
return {
std::data (str),
std::data (str) + std::size (str)
};
}
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//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<const CharT*>
make_view (const std::basic_string<CharT,TraitsT,AllocT>&&) = delete;
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//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<CharT*>
make_view (std::basic_string<CharT,TraitsT,AllocT>&&) = delete;
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///////////////////////////////////////////////////////////////////////////
template <typename IteratorT>
constexpr bool
operator== (const view<IteratorT> &a, const view<IteratorT> &b)
{
return std::cbegin (a) == std::cbegin (b) &&
std::cend (a) == std::cend (b);
}
//-------------------------------------------------------------------------
template <typename IteratorT>
constexpr bool
operator!= (const view<IteratorT> &a, const view<IteratorT> &b)
{
return !(a == b);
}
//-------------------------------------------------------------------------
// equality operations for string-like views against std::strings
bool equal (const std::string&, view<const char*>);
bool equal (const std::string&, view<char*>);
bool equal (const std::string&, view<std::string::const_iterator>);
bool equal (const std::string&, view<std::string::iterator>);
bool equal (view<const char*>, const std::string&);
bool equal (view<char*>, const std::string&);
bool equal (view<std::string::const_iterator>, const std::string&);
bool equal (view<std::string::iterator>, const std::string&);
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///////////////////////////////////////////////////////////////////////////
template <typename IteratorT>
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std::ostream&
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operator<< (std::ostream&, view<IteratorT>);
}
#endif