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fdaa5e1392
libcruft-util/view.hpp
Danny Robson fdaa5e1392 assert: split CHECK_LIMIT into INCLUSIVE and INDEX 
LIMIT hid an off-by-one bug when tests used end iterators. We rename the
assertion to uncover all uses of the flawed implementation, and split it
into an identical assertion, and one intended to protect against
iterator ends.
2020-09-24 08:03:41 +10:00

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/*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Copyright 2015-2019 Danny Robson <danny@nerdcruft.net>
*/
#pragma once
#include "annotation.hpp"
#include "cast.hpp"
#include "debug/assert.hpp"
#include "maths.hpp"
#include "platform.hpp"
#include "types/traits.hpp"
#include <cstdlib>
#include <iosfwd>
#include <string>
#include <cstring>
#include <stdexcept>
#include <iterator>
#include <type_traits>
namespace cruft {
template <typename BeginT, typename EndT = BeginT>
struct view {
public:
using begin_type = BeginT;
using end_type = EndT;
//---------------------------------------------------------------------
using value_type = typename std::iterator_traits<
remove_restrict_t<BeginT>
>::value_type;
using size_type = size_t;
//---------------------------------------------------------------------
constexpr
view (const BeginT &first, const EndT &last) noexcept:
m_begin (first),
m_end (last)
{
if constexpr (cruft::is_lteq_orderable_v<BeginT,EndT>) {
CHECK (m_begin <= m_end);
}
}
template <
typename ContainerT,
typename = std::void_t<
decltype (std::declval<ContainerT&> ().begin ()),
decltype (std::declval<ContainerT&> ().end ())
>
>
view (ContainerT &rhs) noexcept (
noexcept (std::declval<ContainerT> ().begin ()) &&
noexcept (std::declval<ContainerT> ().end ())
)
: view (rhs.begin (), rhs.end ())
{ ; }
template <
typename ContainerT,
typename = std::void_t<
decltype (std::declval<ContainerT const&> ().begin ()),
decltype (std::declval<ContainerT const&> ().end ())
>
>
view (const ContainerT &rhs):
view (rhs.begin (), rhs.end ())
{ ; }
//---------------------------------------------------------------------
// Construction from pointer/size representations for ease of use with
// legacy C code.
template <
typename CountT,
typename = std::enable_if_t<std::is_integral_v<CountT>,void>
>
constexpr view (
const BeginT &_begin,
CountT _size
) : view (_begin, _begin + _size)
{ ; }
//---------------------------------------------------------------------
// implicit conversion from const pointer const views to const pointer views
template <
typename ValueT,
typename = std::enable_if_t<
std::is_same_v<BeginT, const ValueT**> &&
std::is_same_v<EndT, const ValueT**>
>
>
view (const view<const ValueT*const*,const ValueT*const*> &rhs):
view (
const_cast<const ValueT**> (rhs.begin ()),
const_cast<const ValueT**> (rhs.end ())
)
{ ; }
//---------------------------------------------------------------------
// implicit conversion from pointer views to const pointer views
template <
typename ValueT,
typename = std::enable_if_t<
std::is_same_v<BeginT, const ValueT*> &&
std::is_same_v<EndT, const ValueT*>
>
>
view (const view<ValueT*,ValueT*> &rhs):
view (rhs.begin (), rhs.end ())
{ ; }
//---------------------------------------------------------------------
// explicitly cater for the char array case so that we don't
// accidentally include the trailing null in the data.
template <std::size_t N>
view (const char (&value)[N]):
view {std::begin (value), std::begin (value) + N - 1}
{
static_assert (N > 0);
}
//---------------------------------------------------------------------
view (const char *str):
view { str, str + strlen (str) }
{ ; }
//---------------------------------------------------------------------
view (char *str):
view (str, str + strlen (str))
{ ; }
//---------------------------------------------------------------------
template <std::size_t N>
view (char (&value)[N]):
view {std::begin (value), std::begin (value) + N - 1}
{
static_assert (N > 0);
}
//---------------------------------------------------------------------
template <std::size_t N, typename ValueT>
view (const ValueT(&value)[N]):
view {std::begin (value), std::end (value)}
{ ; }
//---------------------------------------------------------------------
template <std::size_t N, typename ValueT>
view (ValueT(&value)[N]):
view {std::begin (value), std::end (value)}
{ ; }
//---------------------------------------------------------------------
constexpr view (const view &) noexcept (
std::is_nothrow_copy_constructible_v<BeginT> && std::is_nothrow_copy_constructible_v<EndT>
) = default;
constexpr view (view &&) noexcept (
std::is_nothrow_move_constructible_v<BeginT> && std::is_nothrow_move_constructible_v<EndT>
) = default;
view& operator= (view const &rhs) noexcept (
std::is_nothrow_copy_assignable_v<BeginT> && std::is_nothrow_copy_assignable_v<EndT>
) = default;
view& operator= (view &&rhs) noexcept (
std::is_nothrow_move_assignable_v<BeginT> && std::is_nothrow_move_assignable_v<EndT>
) = default;
//---------------------------------------------------------------------
// allow null construction of views where IteratorT is constructible
// from nullptr_t
//
// ideally we would avoid exposing this as it promotes use of nulls but
// it simplifies construction of views that are data members of classes
// when we may not immediately know the values we should contain.
constexpr view (std::nullptr_t) noexcept:
view {nullptr,nullptr}
{ ; }
//---------------------------------------------------------------------
template <typename CharT, typename Traits, typename Allocator>
view (std::basic_string<CharT,Traits,Allocator> &val):
view (std::data (val), std::size (val))
{ ; }
//---------------------------------------------------------------------
template <typename CharT, typename Traits, typename Allocator>
view (const std::basic_string<CharT,Traits,Allocator> &val):
view (std::data (val), std::size (val))
{ ; }
//---------------------------------------------------------------------
template <typename ValueT, typename AllocatorT>
view (const std::vector<ValueT,AllocatorT> &rhs):
view (std::data (rhs), std::size (rhs))
{ ; }
//---------------------------------------------------------------------
template <typename ValueT, typename AllocatorT>
view (std::vector<ValueT,AllocatorT> &rhs):
view (std::data (rhs), std::size (rhs))
{ ; }
//---------------------------------------------------------------------
template <typename ValueT, std::size_t N>
view (std::array<ValueT,N> &rhs):
view (std::data (rhs), std::size (rhs))
{ ; }
//---------------------------------------------------------------------
template <typename ValueT, std::size_t N>
view (const std::array<ValueT,N> &rhs):
view (std::data (rhs), std::size (rhs))
{ ; }
///////////////////////////////////////////////////////////////////////
constexpr BeginT begin (void) noexcept { return m_begin; }
constexpr EndT end (void) noexcept { return m_end; }
constexpr BeginT begin (void) const noexcept { return m_begin; }
constexpr EndT end (void) const noexcept { return m_end; }
//---------------------------------------------------------------------
constexpr BeginT cbegin (void) const noexcept { return m_begin; }
constexpr EndT cend (void) const noexcept { return m_end; }
//---------------------------------------------------------------------
auto data (void) noexcept { return begin (); }
auto data (void) const noexcept { return begin (); }
//---------------------------------------------------------------------
auto& front (void) noexcept { return *m_begin; }
auto& front (void) const noexcept { return *m_begin; }
//---------------------------------------------------------------------
auto& back (void) noexcept { return *(m_end - 1); }
auto& back (void) const noexcept { return *(m_end - 1); }
///////////////////////////////////////////////////////////////////////
/// Returns true if the size of the view is zero.
constexpr bool
empty (void) const noexcept
{
return m_begin == m_end;
}
///--------------------------------------------------------------------
/// Returns true if the view is not empty; ie, there is data remaining.
constexpr operator bool () const noexcept
{
return not empty ();
}
///--------------------------------------------------------------------
/// Returns the number of items in the view.
constexpr auto
size (void) const noexcept
{
return static_cast<size_type> (std::distance (m_begin, m_end));
}
///--------------------------------------------------------------------
/// Returns a signed count of items in the view.
constexpr ssize_t
ssize (void) const noexcept
{
return std::distance (m_begin, m_end);
}
///--------------------------------------------------------------------
/// Returns a subview of the first `count` elements of this view.
[[nodiscard]] constexpr auto
redim (size_type count) const
{
assert (count > 0);
if (count > size ())
throw std::invalid_argument ("redim to higher size not allowed");
return view { m_begin, m_begin + count };
};
///--------------------------------------------------------------------
/// Returns two subviews split at `pos`.
///
/// The first view extends from `begin` to `pos`, and the second view
/// extends from `pos` to `end`.
[[nodiscard]] constexpr std::pair<
view<BeginT,BeginT>,
view<BeginT,EndT>
>
split (BeginT pos) const
{
CHECK_GE (pos, m_begin);
CHECK_LE (pos, m_end );
return {
{ m_begin, pos },
{ pos, m_end }
};
}
///--------------------------------------------------------------------
template <
typename IndexT,
typename = std::enable_if_t<std::is_integral_v<IndexT>>
>
[[nodiscard]] constexpr auto
split (IndexT idx) const
{
// It's ok if `idx` points to the end iterator; this just means the
// second element of the returned pair is an empty view.
static_assert (
std::numeric_limits<IndexT>::max () <= std::numeric_limits<size_type>::max ()
);
CHECK_GE (idx, IndexT {0});
CHECK_LE (cruft::cast::lossless<size_type> (idx), size ());
auto last = m_begin;
std::advance (last, idx);
return split (last);
}
//---------------------------------------------------------------------
// slices a view using python indexing semantics. ie,
// "abc".slice(0, 3) == "abc"
// "abc".slice(0, -1) == "abc"
// "abc".slice(0, -2) == "ab"
template <typename IndexA, typename IndexB>
[[nodiscard]] constexpr
auto
slice (IndexA a, IndexB b) const
{
CHECK_INCLUSIVE (cruft::abs (a), IndexA {0}, cruft::cast::lossless<IndexA> (size ()));
CHECK_INCLUSIVE (cruft::abs (b), IndexB {0}, cruft::cast::lossless<IndexB> (size ()));
auto first = m_begin;
auto last = m_begin;
std::advance (first, a < 0 ? size () + a + 1 : a);
std::advance (last, b < 0 ? size () + b + 1 : b);
return view { first, last };
}
//---------------------------------------------------------------------
template <
typename IndexT,
typename = std::enable_if_t<std::is_integral_v<IndexT>>
>
[[nodiscard]] constexpr auto
head (IndexT idx) const
{
return std::get<0> (split (idx));
}
//---------------------------------------------------------------------
template <
typename IndexT,
typename = std::enable_if_t<std::is_integral_v<IndexT>>
>
[[nodiscard]] constexpr auto
tail (IndexT idx) const
{
return std::get<1> (split (idx));
}
//---------------------------------------------------------------------
template <
typename IndexT,
typename = std::enable_if_t<std::is_integral_v<IndexT>>
>
[[nodiscard]] constexpr auto
consume (IndexT count) const
{
auto [a,b] = split (count);
(void)a;
return b;
}
//---------------------------------------------------------------------
[[nodiscard]] constexpr view<BeginT,EndT>
consume (view<BeginT,EndT> prefix) const
{
assert (prefix.begin () == begin ());
assert (prefix.end () < end ());
return { prefix.end (), end () };
}
[[nodiscard]] constexpr view<BeginT,EndT>
consume (const BeginT pos) const
{
return { pos, end () };
}
///////////////////////////////////////////////////////////////////////
/// Explicitly cast to a view with different iterator types.
///
/// The source and destination iterator types must be:
/// * pointers
/// * alignable
///
/// It is undefined behaviour to cast with begin and/or end iterators
/// that do not have natural alignment. Instrumented builds _may_
/// provide diagnostics or assertions in this case.
///
/// \tparam ValueT The new iterator type
/// \return A view that uses the new iterator type
template <
typename ValueT,
typename = std::enable_if_t<
// We can only convert views that use pointer iterators
std::is_pointer_v<BeginT> &&
std::is_pointer_v<EndT> &&
std::is_same_v<BeginT,EndT> &&
std::is_pointer_v<ValueT>
>
>
view<ValueT>
cast (void) const
{
// The values they point to must allow for alignment in one
// direction or another.
//
// We prefer a static_assert over SFINAE because it reduces the
// header burden for users (they do not need to include the
// implementation of the pointer values to satisfy
// iterator_traits), and it is quite unlikely we want to disable
// this only if alignment is incompatible).
static_assert (
sizeof (typename std::iterator_traits<BeginT>::value_type) %
sizeof (typename std::iterator_traits<ValueT>::value_type) == 0 ||
sizeof (typename std::iterator_traits<ValueT>::value_type) %
sizeof (typename std::iterator_traits<BeginT>::value_type) == 0
);
return {
cast::alignment<ValueT> (m_begin),
cast::alignment<ValueT> (m_end)
};
}
///////////////////////////////////////////////////////////////////////
constexpr auto&&
operator[] (size_t idx) noexcept
{
CHECK_GE (idx, 0u);
CHECK_LT (idx, size ());
return *std::next (begin (), idx);
}
//---------------------------------------------------------------------
constexpr auto&&
operator[] (size_t idx) const noexcept
{
CHECK_GE (idx, 0u);
CHECK_LT (idx, size ());
return *std::next (begin (), idx);
}
private:
///////////////////////////////////////////////////////////////////////
BeginT m_begin;
EndT m_end;
};
//-------------------------------------------------------------------------
template <typename ValueT, std::size_t N>
view (ValueT(&)[N]) -> view<ValueT*,ValueT*>;
//-------------------------------------------------------------------------
view (const char*) -> view<const char*, const char*>;
view (char*) -> view<char*>;
//-------------------------------------------------------------------------
template <
typename IteratorT,
typename SizeT,
typename = std::enable_if_t<
std::is_integral_v<SizeT>
>
>
view (IteratorT, SizeT) -> view<IteratorT,IteratorT>;
template <typename CharT, typename Traits, typename Allocator>
view (
std::basic_string<CharT,Traits,Allocator> &
) -> view<
typename std::allocator_traits<Allocator>::pointer
>;
template <typename CharT, typename Traits, typename Allocator>
view (
const std::basic_string<CharT,Traits,Allocator> &
) -> view<
typename std::allocator_traits<Allocator>::const_pointer
>;
template <typename ValueT, typename AllocatorT>
view (
std::vector<ValueT,AllocatorT>&
) -> view<typename std::allocator_traits<AllocatorT>::pointer>;
template <typename ValueT, typename AllocatorT>
view (
const std::vector<ValueT,AllocatorT>&
) -> view<
typename std::allocator_traits<AllocatorT>::const_pointer
>;
template <typename ValueT, std::size_t N>
view (std::array<ValueT,N>&) -> view<ValueT*>;
template <typename ValueT, std::size_t N>
view (const std::array<ValueT,N>&) -> view<const ValueT*>;
template <typename ContainerT>
view (ContainerT&) -> view<
decltype (std::declval<ContainerT&> ().begin ()),
decltype (std::declval<ContainerT&> ().end ())
>;
template <typename ContainerT>
view (const ContainerT&) -> view<
decltype (std::declval<ContainerT const&> ().begin ()),
decltype (std::declval<ContainerT const&> ().end ())
>;
// base + count constructor
template <typename BeginT>
view (BeginT, std::uint64_t count) -> view<BeginT,BeginT>;
template <typename BeginT>
view (BeginT, std::uint32_t count) -> view<BeginT,BeginT>;
template <typename IteratorT>
view (IteratorT, int) -> view<IteratorT, IteratorT>;
///////////////////////////////////////////////////////////////////////////
template <typename ValueT, size_t N>
auto
make_view (const ValueT (&arr)[N])
{
return view<const ValueT*> (arr + 0, arr + N);
}
//-------------------------------------------------------------------------
template <typename ContainerT>
auto
make_view (ContainerT &t)
{
return view { std::begin (t), std::end (t) };
}
//-------------------------------------------------------------------------
template <typename ContainerT>
auto
make_view (const ContainerT &t)
{
return view { std::cbegin (t), std::cend (t) };
}
//-------------------------------------------------------------------------
// 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
make_view (ContainerT&&) = delete;
///////////////////////////////////////////////////////////////////////////
template <typename ContainerT>
auto
make_cview (const ContainerT &t)
{
return make_view (t);
//return view<decltype(std::cbegin (t))> { std::cbegin (t), std::cend (t) };
}
//-------------------------------------------------------------------------
template <typename BeginT, typename EndT>
auto
make_view (BeginT first, EndT last)
{
return view<BeginT, EndT> {first, last};
}
//-------------------------------------------------------------------------
template <typename ValueT>
auto
make_cview (ValueT *first, ValueT *last)
{
return view<const ValueT*> {first, last};
}
///////////////////////////////////////////////////////////////////////////
inline
view<const char*> make_view (const char *str)
{
return { str, str + strlen (str) };
}
//-------------------------------------------------------------------------
inline
view<char*> make_view (char *str)
{
return { str, str + strlen (str) };
}
//-------------------------------------------------------------------------
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)
};
}
//-------------------------------------------------------------------------
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)
};
}
//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<const CharT*>
make_view (const std::basic_string<CharT,TraitsT,AllocT>&&) = delete;
//-------------------------------------------------------------------------
template <typename CharT, typename TraitsT, typename AllocT>
view<CharT*>
make_view (std::basic_string<CharT,TraitsT,AllocT>&&) = delete;
///////////////////////////////////////////////////////////////////////////
/// Calculates a word oriented view over an arbitrary type
///
/// Useful for passing in memory structures to file descriptors and the
/// like. but the consequences of endian conversion is on the user...
///
/// We have to be careful that rval-references and other temporaries aren't
/// accepted in this signature.
template <
typename WordT = std::byte const,
typename T
>
cruft::view<WordT*>
make_byte_view (T &t)
{
static_assert (sizeof (T) % sizeof (WordT) == 0);
static_assert (std::is_const_v<T> ? std::is_const_v<WordT> : true);
return view {
cast::alignment<WordT*> (&t),
sizeof (T) / sizeof (WordT)
};
}
///////////////////////////////////////////////////////////////////////////
/// Returns a reference to a value of the designated type at the front of
/// the word-view. if there is insufficient data for the extraction an
/// exception will be thrown.
///
/// There are no validity or other checks performed on the returned data
/// this is deliberate, so that the function is safe to call on user
/// supplied data during parsing routines. it is up to the user to ensure
/// the object is valid.
///
/// The buffer object is advanced in place so that it no longer covers
/// the extract value
///
/// It is assumed the user has taken care of alignment concerns
template <
typename ValueT,
typename WordT
>
ValueT&
extract (view<WordT*> &buffer)
{
// Only allow calls if the value is a multiple of the word size.
// It's useful to allow non-unit words for areas like TCP/IP which
// tend to include protocols that utilise u16 words.
static_assert (
sizeof (ValueT) % sizeof (WordT) == 0,
"The value type must be a multiple of the word size"
);
static_assert (
!std::is_const_v<WordT> or std::is_const_v<ValueT>,
"buffer and output types must have matching constness"
);
if (unlikely (sizeof (ValueT) > buffer.size () * sizeof (WordT)))
throw std::runtime_error ("insufficient data for extraction");
auto ptr = cast::alignment<ValueT*> (buffer.data ());
buffer = buffer.consume (sizeof (ValueT) / sizeof (WordT));
return *ptr;
}
///////////////////////////////////////////////////////////////////////////
/// extracts an object of a specified type from the front of a byte-view.
///
/// in contrast to 'extract' this will always copy the bytes out from the
/// view, making the operation alignment safe.
template <
typename ValueT,
typename WordT,
typename = std::enable_if_t<sizeof (ValueT) % sizeof(WordT) == 0>
>
ValueT
read (view<WordT*> &buffer)
{
// We're going to use memcpy which requires that the type is
// trivially copyable.
static_assert (std::is_trivially_copyable_v<ValueT>);
if (unlikely (sizeof (ValueT) > buffer.size () * sizeof (WordT)))
throw std::runtime_error ("insufficient data for extraction");
std::aligned_storage_t<sizeof(ValueT),alignof(ValueT)> bytes;
memcpy (&bytes, buffer.data (), sizeof (ValueT));
buffer = buffer.consume (sizeof (ValueT) / sizeof (WordT));
return *reinterpret_cast<ValueT const*> (&bytes);
}
///////////////////////////////////////////////////////////////////////////
/// Tests whether an iterator falls within a given view.
template <typename IteratorT>
constexpr bool
intersects (view<IteratorT> a, IteratorT b)
{
return b >= a.begin () && b < a.end ();
}
///------------------------------------------------------------------------
/// Tests whether view `a` inclusively contains view `b`.
template <typename IteratorA, typename IteratorB>
constexpr bool
covers (
view<IteratorA,IteratorB> const &a,
view<IteratorA,IteratorB> const &b
) {
return a.begin () <= b.begin () && a.end () >= b.end ();
}
///////////////////////////////////////////////////////////////////////////
template <
typename BeginA, typename EndA,
typename BeginB, typename EndB,
typename ComparatorT
>
decltype(auto)
equal (
view<BeginA,EndA> const &a,
view<BeginB,EndB> const &b,
ComparatorT &&cmp
) {
return std::equal (
std::begin (a), std::end (a),
std::begin (b), std::end (b),
std::forward<ComparatorT> (cmp)
);
}
//-------------------------------------------------------------------------
template <
typename BeginA, typename EndA,
typename BeginB, typename EndB
>
constexpr bool
equal (const view<BeginA,EndA> &a, const view<BeginB,EndB> &b)
{
return ::cruft::equal (a, b, std::equal_to<void> {});
}
//-------------------------------------------------------------------------
// defer equality to the view/view operator by way of make_view
template <
typename IteratorA,
typename IteratorB,
typename ValueT,
typename = std::enable_if_t<
!std::is_same_v<ValueT, view<IteratorA,IteratorB>>,
void
>
>
constexpr bool
equal (const view<IteratorA,IteratorB> &a, const ValueT &b)
{
return equal (a, make_view (b));
}
//-------------------------------------------------------------------------
// reverse the arguments and forward to the above operator. we formumlate
// equality this way to avoid implementing the operator twice for each
// weird case.
template <
typename IteratorA,
typename IteratorB,
typename ValueT,
typename = std::enable_if_t<
!std::is_same_v<ValueT, view<IteratorA,IteratorB>>,
void
>
>
constexpr bool
equal (const ValueT &a, const view<IteratorA,IteratorB> &b)
{
return equal (b, a);
}
///////////////////////////////////////////////////////////////////////////
template <typename IteratorA, typename IteratorB>
constexpr bool
operator== (const view<IteratorA,IteratorB> &a, const view<IteratorA,IteratorB> &b)
{
return a.begin () == b.begin () && a.end () == b.end ();
}
//-------------------------------------------------------------------------
template <typename IteratorA, typename IteratorB>
constexpr bool
operator!= (const view<IteratorA,IteratorB> &a, const view<IteratorA,IteratorB> &b)
{
return !(a == b);
}
//-------------------------------------------------------------------------
template <
typename IteratorA,
typename IteratorB,
typename ValueT,
typename = std::enable_if_t<
!std::is_same_v<ValueT, view<IteratorA,IteratorB>>,
void
>
>
constexpr bool
operator!= (const view<IteratorA,IteratorB> &a, const ValueT &b)
{
return !(a == b);
}
//-------------------------------------------------------------------------
template <
typename IteratorA,
typename IteratorB,
typename ValueT,
typename = std::enable_if_t<
!std::is_same_v<ValueT, view<IteratorA,IteratorB>>,
void
>
>
constexpr bool
operator!= (const ValueT &a, const view<IteratorA,IteratorB> &b)
{
return !(a == b);
}
///////////////////////////////////////////////////////////////////////////
template <typename BeginT, typename EndT>
std::ostream&
operator<< (std::ostream &os, view<BeginT, EndT> val)
{
std::copy (
std::cbegin (val),
std::cend (val),
std::ostream_iterator<typename decltype(val)::value_type> (os)
);
return os;
}
///////////////////////////////////////////////////////////////////////////
/// a basic stringlike comparison operator that behaves as
/// std::string::compare would.
///
/// provided so that the common case of stringlike views can be used in a
/// std::map and similar without a great deal of work.
inline bool
operator< (view<const char*> a, view<const char*> b)
{
const auto la = std::size (a);
const auto lb = std::size (b);
const auto res = strncmp (
std::data (a),
std::data (b),
min (la, lb)
);
return res < 0 || (res == 0 && la < lb);
}
}
namespace cruft::debug {
///////////////////////////////////////////////////////////////////////////
template <typename IteratorT, typename ...ArgsT>
struct validator<
view<IteratorT>,
ArgsT&&...
> {
static bool
is_valid (view<IteratorT> data, ArgsT &&...args)
{
return std::all_of (
std::begin (data),
std::end (data),
[&] (auto const &i)
{
return ::cruft::debug::is_valid (i, args...);
});
}
};
};
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