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// Copyright 2017 Elias Kosunen
//
// 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
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// 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.
//
// This file is a part of scnlib:
// https://github.com/eliaskosunen/scnlib
#ifndef SCN_SCAN_ISTREAM_H
#define SCN_SCAN_ISTREAM_H
#include "../reader/common.h"
#include "../detail/result.h"
#include <istream>
namespace scn {
SCN_BEGIN_NAMESPACE
namespace detail {
template <typename WrappedRange>
class range_streambuf
: public std::basic_streambuf<typename WrappedRange::char_type> {
using base = std::basic_streambuf<typename WrappedRange::char_type>;
public:
using range_type = WrappedRange;
using char_type = typename WrappedRange::char_type;
using traits_type = typename base::traits_type;
using int_type = typename base::int_type;
explicit range_streambuf(range_type& r) : m_range(std::addressof(r))
{
}
private:
int_type underflow() override
{
// already read
if (!traits_type::eq_int_type(m_ch, traits_type::eof())) {
return m_ch;
}
auto ret = read_code_unit(*m_range);
if (!ret) {
// error
// m_ch is already eof
return traits_type::eof();
}
m_ch = traits_type::to_int_type(ret.value());
return m_ch;
}
int_type uflow() override
{
auto ret = underflow();
if (ret != traits_type::eof()) {
m_ch = traits_type::eof();
}
return ret;
}
std::streamsize showmanyc() override
{
return traits_type::eq_int_type(m_ch, traits_type::eof()) ? 0
: 1;
}
int_type pbackfail(int_type) override
{
auto e = putback_n(*m_range, 1);
if (!e) {
return traits_type::eof();
}
return traits_type::to_int_type(0);
}
range_type* m_range;
int_type m_ch{traits_type::eof()};
};
// Trick stolen from {fmt}
template <typename CharT>
struct test_std_stream : std::basic_istream<CharT> {
private:
struct null;
// Hide all operator>> from std::basic_istream<CharT>
void operator>>(null);
};
// Check for user-defined operator>>
template <typename CharT, typename T, typename = void>
struct is_std_streamable : std::false_type {
};
template <typename CharT, typename T>
struct is_std_streamable<
CharT,
T,
void_t<decltype(SCN_DECLVAL(test_std_stream<CharT>&) >>
SCN_DECLVAL(T&))>> : std::true_type {
};
} // namespace detail
template <typename T>
struct scanner<T,
typename std::enable_if<
detail::is_std_streamable<char, T>::value ||
detail::is_std_streamable<wchar_t, T>::value>::type>
: public empty_parser {
template <typename Context>
error scan(T& val, Context& ctx)
{
static_assert(detail::is_std_streamable<typename Context::char_type,
T>::value,
"Type can not be read from a basic_istream of this "
"character type");
detail::range_streambuf<typename Context::range_type> streambuf(
ctx.range());
std::basic_istream<typename Context::char_type> stream(
std::addressof(streambuf));
if (!(stream >> val)) {
if (stream.eof()) {
return {error::end_of_range, "EOF"};
}
if (stream.bad()) {
return {error::unrecoverable_source_error,
"Bad std::istream after reading"};
}
return {error::invalid_scanned_value,
"Failed to read with std::istream"};
}
return {};
}
};
SCN_END_NAMESPACE
} // namespace scn
#endif // SCN_DETAIL_ISTREAM_H
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