GSL/include/string_view.h

///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
///////////////////////////////////////////////////////////////////////////////

#pragma once

#ifndef GSL_STRING_VIEW_H
#define GSL_STRING_VIEW_H

#include "array_view.h"
#include <cstring>

namespace gsl
{
//
// czstring and wzstring
//
// These are "tag" typedef's for C-style strings (i.e. null-terminated character arrays)
// that allow static analysis to help find bugs.
//
// There are no additional features/semantics that we can find a way to add inside the
// type system for these types that will not either incur significant runtime costs or
// (sometimes needlessly) break existing programs when introduced.
//
template <size_t Max = dynamic_range> using czstring = const char*;

template <size_t Max = dynamic_range> using cwzstring = const wchar_t*;

template <size_t Max = dynamic_range> using zstring = char*;

template <size_t Max = dynamic_range> using wzstring = wchar_t*;

//
// string_view and relatives
//
// Note that Extent is always single-dimension only
// Note that SizeType is defaulted to be smaller than size_t which is the array_view default
//
// TODO (neilmac) once array_view regains configurable size_type, update these typedef's
//
template <class CharT, size_t Extent = dynamic_range>
using basic_string_view = array_view<CharT, Extent>;

template <size_t Extent = dynamic_range> using string_view = basic_string_view<char, Extent>;

template <size_t Extent = dynamic_range> using cstring_view = basic_string_view<const char, Extent>;

template <size_t Extent = dynamic_range> using wstring_view = basic_string_view<wchar_t, Extent>;

template <size_t Extent = dynamic_range>
using cwstring_view = basic_string_view<const wchar_t, Extent>;


//
// ensure_sentinel()
//
// Provides a way to obtain an array_view from a contiguous sequence
// that ends with a (non-inclusive) sentinel value.
//
// Will fail-fast if sentinel cannot be found before max elements are examined.
//
template <class T, class SizeType, const T Sentinel>
array_view<T, dynamic_range>
ensure_sentinel(const T* seq, SizeType max = std::numeric_limits<SizeType>::max())
{
    auto cur = seq;
    while ((cur - seq) < max && *cur != Sentinel)
        ++cur;
    fail_fast_assert(*cur == Sentinel);
    return { seq, cur - seq };
}


//
// ensure_z - creates a string_view for a czstring or cwzstring.
// Will fail fast if a null-terminator cannot be found before
// the limit of size_type.
//
template <class T>
inline basic_string_view<T, dynamic_range>
ensure_z(T* const& sz, size_t max = std::numeric_limits<size_t>::max())
{
    return ensure_sentinel<0>(sz, max);
}

// TODO (neilmac) there is probably a better template-magic way to get the const and non-const
// overloads to share an implementation
inline basic_string_view<char, dynamic_range> ensure_z(char* const& sz, size_t max)
{
    auto len = strnlen(sz, max);
    fail_fast_assert(sz[len] == 0);
    return { sz, len };
}

inline basic_string_view<const char, dynamic_range> ensure_z(const char* const& sz, size_t max)
{
    auto len = strnlen(sz, max);
    fail_fast_assert(sz[len] == 0);
    return { sz, len };
}

inline basic_string_view<wchar_t, dynamic_range> ensure_z(wchar_t* const& sz, size_t max)
{
    auto len = wcsnlen(sz, max);
    fail_fast_assert(sz[len] == 0);
    return { sz, len };
}

inline basic_string_view<const wchar_t, dynamic_range> ensure_z(const wchar_t* const& sz, size_t max)
{
    auto len = wcsnlen(sz, max);
    fail_fast_assert(sz[len] == 0);
    return { sz, len };
}

template <class T, size_t N> basic_string_view<T, dynamic_range> ensure_z(T(&sz)[N])
{
    return ensure_z(&sz[0], N);
}

template <class Cont>
basic_string_view<typename std::remove_pointer<typename Cont::pointer>::type, dynamic_range>
ensure_z(Cont& cont)
{
    return ensure_z(cont.data(), cont.length());
}

//
// to_string() allow (explicit) conversions from string_view to string
//
template <class CharT, size_t Extent>
std::basic_string<typename std::remove_const<CharT>::type> to_string(basic_string_view<CharT, Extent> view)
{
    return { view.data(), view.length() };
}


template <class CharT, size_t Extent = dynamic_range> class basic_zstring_builder
{
    public:
    using string_view_type = basic_string_view<CharT, Extent>;
    using value_type = CharT;
    using pointer = CharT*;
    using size_type = typename string_view_type::size_type;
    using iterator = typename string_view_type::iterator;

    basic_zstring_builder(CharT* data, size_type length) : sv_(data, length)
    {
    }

    template <size_t Size> basic_zstring_builder(CharT(&arr)[Size]) : sv_(arr)
    {
    }

    pointer data() const
    {
        return sv_.data();
    }
    string_view_type view() const
    {
        return sv_;
    }

    size_type length() const
    {
        return sv_.length();
    }

    pointer assume0() const
    {
        return data();
    }
    string_view_type ensure_z() const
    {
        return gsl::ensure_z(sv_);
    }

    iterator begin() const
    {
        return sv_.begin();
    }
    iterator end() const
    {
        return sv_.end();
    }

    private:
    string_view_type sv_;
};

template <size_t Max = dynamic_range> using zstring_builder = basic_zstring_builder<char, Max>;

template <size_t Max = dynamic_range> using wzstring_builder = basic_zstring_builder<wchar_t, Max>;
}

#endif // GSL_STRING_VIEW_H