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add detail/parsing/input_adapters.hpp

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Théo DELRIEU 2017-08-14 16:48:55 +02:00
parent 21881606f2
commit 7ab3e8d7b3
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3 changed files with 261 additions and 240 deletions
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3
Makefile
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@ -9,7 +9,8 @@ SRCS = ${SRCDIR}/json.hpp \
${SRCDIR}/detail/exceptions.hpp \
${SRCDIR}/detail/value_t.hpp \
${SRCDIR}/detail/conversions/from_json.hpp \
${SRCDIR}/detail/conversions/to_json.hpp
${SRCDIR}/detail/conversions/to_json.hpp \
${SRCDIR}/detail/parsing/input_adapters.hpp

258
src/detail/parsing/input_adapters.hpp Normal file
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@ -0,0 +1,258 @@
#ifndef NLOHMANN_JSON_DETAIL_PARSING_INPUT_ADAPTERS_HPP
#define NLOHMANN_JSON_DETAIL_PARSING_INPUT_ADAPTERS_HPP
#include <algorithm>
#include <array>
#include <cstddef>
#include <iosfwd>
#include <memory>
#include <string>
#include "detail/macro_scope.hpp"
namespace nlohmann
{
namespace detail
{
////////////////////
// input adapters //
////////////////////
/*!
@brief abstract input adapter interface
Produces a stream of std::char_traits<char>::int_type characters from a
std::istream, a buffer, or some other input type. Accepts the return of exactly
one non-EOF character for future input. The int_type characters returned
consist of all valid char values as positive values (typically unsigned char),
plus an EOF value outside that range, specified by the value of the function
std::char_traits<char>::eof(). This value is typically -1, but could be any
arbitrary value which is not a valid char value.
*/
struct input_adapter_protocol
{
/// get a character [0,255] or std::char_traits<char>::eof().
virtual std::char_traits<char>::int_type get_character() = 0;
/// restore the last non-eof() character to input
virtual void unget_character() = 0;
virtual ~input_adapter_protocol() = default;
};
/// a type to simplify interfaces
using input_adapter_t = std::shared_ptr<input_adapter_protocol>;
/*!
Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
beginning of input. Does not support changing the underlying std::streambuf
in mid-input. Maintains underlying std::istream and std::streambuf to support
subsequent use of standard std::istream operations to process any input
characters following those used in parsing the JSON input. Clears the
std::istream flags; any input errors (e.g., EOF) will be detected by the first
subsequent call for input from the std::istream.
*/
class input_stream_adapter : public input_adapter_protocol
{
public:
~input_stream_adapter() override
{
// clear stream flags; we use underlying streambuf I/O, do not
// maintain ifstream flags
is.clear();
}
explicit input_stream_adapter(std::istream& i)
: is(i), sb(*i.rdbuf())
{
// skip byte order mark
std::char_traits<char>::int_type c;
if ((c = get_character()) == 0xEF)
{
if ((c = get_character()) == 0xBB)
{
if ((c = get_character()) == 0xBF)
{
return; // Ignore BOM
}
else if (c != std::char_traits<char>::eof())
{
is.unget();
}
is.putback('\xBB');
}
else if (c != std::char_traits<char>::eof())
{
is.unget();
}
is.putback('\xEF');
}
else if (c != std::char_traits<char>::eof())
{
is.unget(); // no byte order mark; process as usual
}
}
// delete because of pointer members
input_stream_adapter(const input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&) = delete;
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, eg. 0xFFFFFFFF.
std::char_traits<char>::int_type get_character() override
{
return sb.sbumpc();
}
void unget_character() override
{
sb.sungetc(); // is.unget() avoided for performance
}
private:
/// the associated input stream
std::istream& is;
std::streambuf& sb;
};
/// input adapter for buffer input
class input_buffer_adapter : public input_adapter_protocol
{
public:
input_buffer_adapter(const char* b, const std::size_t l)
: cursor(b), limit(b + l), start(b)
{
// skip byte order mark
if (l >= 3 and b[0] == '\xEF' and b[1] == '\xBB' and b[2] == '\xBF')
{
cursor += 3;
}
}
// delete because of pointer members
input_buffer_adapter(const input_buffer_adapter&) = delete;
input_buffer_adapter& operator=(input_buffer_adapter&) = delete;
std::char_traits<char>::int_type get_character() noexcept override
{
if (JSON_LIKELY(cursor < limit))
{
return std::char_traits<char>::to_int_type(*(cursor++));
}
return std::char_traits<char>::eof();
}
void unget_character() noexcept override
{
if (JSON_LIKELY(cursor > start))
{
--cursor;
}
}
private:
/// pointer to the current character
const char* cursor;
/// pointer past the last character
const char* limit;
/// pointer to the first character
const char* start;
};
class input_adapter
{
public:
// native support
/// input adapter for input stream
input_adapter(std::istream& i)
: ia(std::make_shared<input_stream_adapter>(i)) {}
/// input adapter for input stream
input_adapter(std::istream&& i)
: ia(std::make_shared<input_stream_adapter>(i)) {}
/// input adapter for buffer
template<typename CharT,
typename std::enable_if<
std::is_pointer<CharT>::value and
std::is_integral<typename std::remove_pointer<CharT>::type>::value and
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int>::type = 0>
input_adapter(CharT b, std::size_t l)
: ia(std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(b), l)) {}
// derived support
/// input adapter for string literal
template<typename CharT,
typename std::enable_if<
std::is_pointer<CharT>::value and
std::is_integral<typename std::remove_pointer<CharT>::type>::value and
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int>::type = 0>
input_adapter(CharT b)
: input_adapter(reinterpret_cast<const char*>(b),
std::strlen(reinterpret_cast<const char*>(b))) {}
/// input adapter for iterator range with contiguous storage
template<class IteratorType,
typename std::enable_if<
std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
int>::type = 0>
input_adapter(IteratorType first, IteratorType last)
{
// assertion to check that the iterator range is indeed contiguous,
// see http://stackoverflow.com/a/35008842/266378 for more discussion
assert(std::accumulate(
first, last, std::pair<bool, int>(true, 0),
[&first](std::pair<bool, int> res, decltype(*first) val)
{
res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
return res;
}).first);
// assertion to check that each element is 1 byte long
static_assert(
sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
"each element in the iterator range must have the size of 1 byte");
const auto len = static_cast<size_t>(std::distance(first, last));
if (JSON_LIKELY(len > 0))
{
// there is at least one element: use the address of first
ia = std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(&(*first)), len);
}
else
{
// the address of first cannot be used: use nullptr
ia = std::make_shared<input_buffer_adapter>(nullptr, len);
}
}
/// input adapter for array
template<class T, std::size_t N>
input_adapter(T (&array)[N])
: input_adapter(std::begin(array), std::end(array)) {}
/// input adapter for contiguous container
template<class ContiguousContainer, typename
std::enable_if<not std::is_pointer<ContiguousContainer>::value and
std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
int>::type = 0>
input_adapter(const ContiguousContainer& c)
: input_adapter(std::begin(c), std::end(c)) {}
operator input_adapter_t()
{
return ia;
}
private:
/// the actual adapter
input_adapter_t ia = nullptr;
};
}
}
#endif

240
src/json.hpp
View File

@ -57,6 +57,7 @@ SOFTWARE.
#include "detail/value_t.hpp"
#include "detail/conversions/from_json.hpp"
#include "detail/conversions/to_json.hpp"
#include "detail/parsing/input_adapters.hpp"
/*!
@brief namespace for Niels Lohmann
@ -67,245 +68,6 @@ namespace nlohmann
{
namespace detail
{
////////////////////
// input adapters //
////////////////////
/*!
@brief abstract input adapter interface
Produces a stream of std::char_traits<char>::int_type characters from a
std::istream, a buffer, or some other input type. Accepts the return of exactly
one non-EOF character for future input. The int_type characters returned
consist of all valid char values as positive values (typically unsigned char),
plus an EOF value outside that range, specified by the value of the function
std::char_traits<char>::eof(). This value is typically -1, but could be any
arbitrary value which is not a valid char value.
*/
struct input_adapter_protocol
{
/// get a character [0,255] or std::char_traits<char>::eof().
virtual std::char_traits<char>::int_type get_character() = 0;
/// restore the last non-eof() character to input
virtual void unget_character() = 0;
virtual ~input_adapter_protocol() = default;
};
/// a type to simplify interfaces
using input_adapter_t = std::shared_ptr<input_adapter_protocol>;
/*!
Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
beginning of input. Does not support changing the underlying std::streambuf
in mid-input. Maintains underlying std::istream and std::streambuf to support
subsequent use of standard std::istream operations to process any input
characters following those used in parsing the JSON input. Clears the
std::istream flags; any input errors (e.g., EOF) will be detected by the first
subsequent call for input from the std::istream.
*/
class input_stream_adapter : public input_adapter_protocol
{
public:
~input_stream_adapter() override
{
// clear stream flags; we use underlying streambuf I/O, do not
// maintain ifstream flags
is.clear();
}
explicit input_stream_adapter(std::istream& i)
: is(i), sb(*i.rdbuf())
{
// skip byte order mark
std::char_traits<char>::int_type c;
if ((c = get_character()) == 0xEF)
{
if ((c = get_character()) == 0xBB)
{
if ((c = get_character()) == 0xBF)
{
return; // Ignore BOM
}
else if (c != std::char_traits<char>::eof())
{
is.unget();
}
is.putback('\xBB');
}
else if (c != std::char_traits<char>::eof())
{
is.unget();
}
is.putback('\xEF');
}
else if (c != std::char_traits<char>::eof())
{
is.unget(); // no byte order mark; process as usual
}
}
// delete because of pointer members
input_stream_adapter(const input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&) = delete;
// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
// ensure that std::char_traits<char>::eof() and the character 0xFF do not
// end up as the same value, eg. 0xFFFFFFFF.
std::char_traits<char>::int_type get_character() override
{
return sb.sbumpc();
}
void unget_character() override
{
sb.sungetc(); // is.unget() avoided for performance
}
private:
/// the associated input stream
std::istream& is;
std::streambuf& sb;
};
/// input adapter for buffer input
class input_buffer_adapter : public input_adapter_protocol
{
public:
input_buffer_adapter(const char* b, const std::size_t l)
: cursor(b), limit(b + l), start(b)
{
// skip byte order mark
if (l >= 3 and b[0] == '\xEF' and b[1] == '\xBB' and b[2] == '\xBF')
{
cursor += 3;
}
}
// delete because of pointer members
input_buffer_adapter(const input_buffer_adapter&) = delete;
input_buffer_adapter& operator=(input_buffer_adapter&) = delete;
std::char_traits<char>::int_type get_character() noexcept override
{
if (JSON_LIKELY(cursor < limit))
{
return std::char_traits<char>::to_int_type(*(cursor++));
}
return std::char_traits<char>::eof();
}
void unget_character() noexcept override
{
if (JSON_LIKELY(cursor > start))
{
--cursor;
}
}
private:
/// pointer to the current character
const char* cursor;
/// pointer past the last character
const char* limit;
/// pointer to the first character
const char* start;
};
class input_adapter
{
public:
// native support
/// input adapter for input stream
input_adapter(std::istream& i)
: ia(std::make_shared<input_stream_adapter>(i)) {}
/// input adapter for input stream
input_adapter(std::istream&& i)
: ia(std::make_shared<input_stream_adapter>(i)) {}
/// input adapter for buffer
template<typename CharT,
typename std::enable_if<
std::is_pointer<CharT>::value and
std::is_integral<typename std::remove_pointer<CharT>::type>::value and
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int>::type = 0>
input_adapter(CharT b, std::size_t l)
: ia(std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(b), l)) {}
// derived support
/// input adapter for string literal
template<typename CharT,
typename std::enable_if<
std::is_pointer<CharT>::value and
std::is_integral<typename std::remove_pointer<CharT>::type>::value and
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int>::type = 0>
input_adapter(CharT b)
: input_adapter(reinterpret_cast<const char*>(b),
std::strlen(reinterpret_cast<const char*>(b))) {}
/// input adapter for iterator range with contiguous storage
template<class IteratorType,
typename std::enable_if<
std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
int>::type = 0>
input_adapter(IteratorType first, IteratorType last)
{
// assertion to check that the iterator range is indeed contiguous,
// see http://stackoverflow.com/a/35008842/266378 for more discussion
assert(std::accumulate(
first, last, std::pair<bool, int>(true, 0),
[&first](std::pair<bool, int> res, decltype(*first) val)
{
res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
return res;
}).first);
// assertion to check that each element is 1 byte long
static_assert(
sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
"each element in the iterator range must have the size of 1 byte");
const auto len = static_cast<size_t>(std::distance(first, last));
if (JSON_LIKELY(len > 0))
{
// there is at least one element: use the address of first
ia = std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(&(*first)), len);
}
else
{
// the address of first cannot be used: use nullptr
ia = std::make_shared<input_buffer_adapter>(nullptr, len);
}
}
/// input adapter for array
template<class T, std::size_t N>
input_adapter(T (&array)[N])
: input_adapter(std::begin(array), std::end(array)) {}
/// input adapter for contiguous container
template<class ContiguousContainer, typename
std::enable_if<not std::is_pointer<ContiguousContainer>::value and
std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
int>::type = 0>
input_adapter(const ContiguousContainer& c)
: input_adapter(std::begin(c), std::end(c)) {}
operator input_adapter_t()
{
return ia;
}
private:
/// the actual adapter
input_adapter_t ia = nullptr;
};
//////////////////////
// lexer and parser //
//////////////////////