json/include/nlohmann/detail/input/input_adapters.hpp
Niels Lohmann 29cd970b94
Consolidate documentation (#3071)
* 🔥 consolidate documentation
* ♻️ overwork std specializations
* 🚚 move images files to mkdocs
* ♻️ fix URLs
* 🔧 tweak MkDocs configuration
* 🔧 add namespaces
* 📝 document deprecations
* 📝 document documentation generation
* 🚸 improve search
* 🚸 add examples
* 🚧 start adding documentation for macros
* 📝 add note for https://github.com/nlohmann/json/issues/874#issuecomment-1001699139
* 📝 overwork example handling
* 📝 fix Markdown tables
2021-12-29 13:41:01 +01:00

484 lines
17 KiB
C++

#pragma once
#include <array> // array
#include <cstddef> // size_t
#include <cstring> // strlen
#include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next
#include <memory> // shared_ptr, make_shared, addressof
#include <numeric> // accumulate
#include <string> // string, char_traits
#include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
#include <utility> // pair, declval
#ifndef JSON_NO_IO
#include <cstdio> // FILE *
#include <istream> // istream
#endif // JSON_NO_IO
#include <nlohmann/detail/iterators/iterator_traits.hpp>
#include <nlohmann/detail/macro_scope.hpp>
namespace nlohmann
{
namespace detail
{
/// the supported input formats
enum class input_format_t { json, cbor, msgpack, ubjson, bson };
////////////////////
// input adapters //
////////////////////
#ifndef JSON_NO_IO
/*!
Input adapter for stdio file access. This adapter read only 1 byte and do not use any
buffer. This adapter is a very low level adapter.
*/
class file_input_adapter
{
public:
using char_type = char;
JSON_HEDLEY_NON_NULL(2)
explicit file_input_adapter(std::FILE* f) noexcept
: m_file(f)
{}
// make class move-only
file_input_adapter(const file_input_adapter&) = delete;
file_input_adapter(file_input_adapter&&) noexcept = default;
file_input_adapter& operator=(const file_input_adapter&) = delete;
file_input_adapter& operator=(file_input_adapter&&) = delete;
~file_input_adapter() = default;
std::char_traits<char>::int_type get_character() noexcept
{
return std::fgetc(m_file);
}
private:
/// the file pointer to read from
std::FILE* m_file;
};
/*!
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:
using char_type = char;
~input_stream_adapter()
{
// clear stream flags; we use underlying streambuf I/O, do not
// maintain ifstream flags, except eof
if (is != nullptr)
{
is->clear(is->rdstate() & std::ios::eofbit);
}
}
explicit input_stream_adapter(std::istream& i)
: is(&i), sb(i.rdbuf())
{}
// delete because of pointer members
input_stream_adapter(const input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&) = delete;
input_stream_adapter& operator=(input_stream_adapter&&) = delete;
input_stream_adapter(input_stream_adapter&& rhs) noexcept
: is(rhs.is), sb(rhs.sb)
{
rhs.is = nullptr;
rhs.sb = nullptr;
}
// 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, e.g. 0xFFFFFFFF.
std::char_traits<char>::int_type get_character()
{
auto res = sb->sbumpc();
// set eof manually, as we don't use the istream interface.
if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
{
is->clear(is->rdstate() | std::ios::eofbit);
}
return res;
}
private:
/// the associated input stream
std::istream* is = nullptr;
std::streambuf* sb = nullptr;
};
#endif // JSON_NO_IO
// General-purpose iterator-based adapter. It might not be as fast as
// theoretically possible for some containers, but it is extremely versatile.
template<typename IteratorType>
class iterator_input_adapter
{
public:
using char_type = typename std::iterator_traits<IteratorType>::value_type;
iterator_input_adapter(IteratorType first, IteratorType last)
: current(std::move(first)), end(std::move(last))
{}
typename std::char_traits<char_type>::int_type get_character()
{
if (JSON_HEDLEY_LIKELY(current != end))
{
auto result = std::char_traits<char_type>::to_int_type(*current);
std::advance(current, 1);
return result;
}
return std::char_traits<char_type>::eof();
}
private:
IteratorType current;
IteratorType end;
template<typename BaseInputAdapter, size_t T>
friend struct wide_string_input_helper;
bool empty() const
{
return current == end;
}
};
template<typename BaseInputAdapter, size_t T>
struct wide_string_input_helper;
template<typename BaseInputAdapter>
struct wide_string_input_helper<BaseInputAdapter, 4>
{
// UTF-32
static void fill_buffer(BaseInputAdapter& input,
std::array<std::char_traits<char>::int_type, 4>& utf8_bytes,
size_t& utf8_bytes_index,
size_t& utf8_bytes_filled)
{
utf8_bytes_index = 0;
if (JSON_HEDLEY_UNLIKELY(input.empty()))
{
utf8_bytes[0] = std::char_traits<char>::eof();
utf8_bytes_filled = 1;
}
else
{
// get the current character
const auto wc = input.get_character();
// UTF-32 to UTF-8 encoding
if (wc < 0x80)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
}
else if (wc <= 0x7FF)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u) & 0x1Fu));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
utf8_bytes_filled = 2;
}
else if (wc <= 0xFFFF)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u) & 0x0Fu));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
utf8_bytes_filled = 3;
}
else if (wc <= 0x10FFFF)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | ((static_cast<unsigned int>(wc) >> 18u) & 0x07u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
utf8_bytes_filled = 4;
}
else
{
// unknown character
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
}
}
}
};
template<typename BaseInputAdapter>
struct wide_string_input_helper<BaseInputAdapter, 2>
{
// UTF-16
static void fill_buffer(BaseInputAdapter& input,
std::array<std::char_traits<char>::int_type, 4>& utf8_bytes,
size_t& utf8_bytes_index,
size_t& utf8_bytes_filled)
{
utf8_bytes_index = 0;
if (JSON_HEDLEY_UNLIKELY(input.empty()))
{
utf8_bytes[0] = std::char_traits<char>::eof();
utf8_bytes_filled = 1;
}
else
{
// get the current character
const auto wc = input.get_character();
// UTF-16 to UTF-8 encoding
if (wc < 0x80)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
}
else if (wc <= 0x7FF)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u)));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
utf8_bytes_filled = 2;
}
else if (0xD800 > wc || wc >= 0xE000)
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u)));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
utf8_bytes_filled = 3;
}
else
{
if (JSON_HEDLEY_UNLIKELY(!input.empty()))
{
const auto wc2 = static_cast<unsigned int>(input.get_character());
const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
utf8_bytes[3] = static_cast<std::char_traits<char>::int_type>(0x80u | (charcode & 0x3Fu));
utf8_bytes_filled = 4;
}
else
{
utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(wc);
utf8_bytes_filled = 1;
}
}
}
}
};
// Wraps another input apdater to convert wide character types into individual bytes.
template<typename BaseInputAdapter, typename WideCharType>
class wide_string_input_adapter
{
public:
using char_type = char;
wide_string_input_adapter(BaseInputAdapter base)
: base_adapter(base) {}
typename std::char_traits<char>::int_type get_character() noexcept
{
// check if buffer needs to be filled
if (utf8_bytes_index == utf8_bytes_filled)
{
fill_buffer<sizeof(WideCharType)>();
JSON_ASSERT(utf8_bytes_filled > 0);
JSON_ASSERT(utf8_bytes_index == 0);
}
// use buffer
JSON_ASSERT(utf8_bytes_filled > 0);
JSON_ASSERT(utf8_bytes_index < utf8_bytes_filled);
return utf8_bytes[utf8_bytes_index++];
}
private:
BaseInputAdapter base_adapter;
template<size_t T>
void fill_buffer()
{
wide_string_input_helper<BaseInputAdapter, T>::fill_buffer(base_adapter, utf8_bytes, utf8_bytes_index, utf8_bytes_filled);
}
/// a buffer for UTF-8 bytes
std::array<std::char_traits<char>::int_type, 4> utf8_bytes = {{0, 0, 0, 0}};
/// index to the utf8_codes array for the next valid byte
std::size_t utf8_bytes_index = 0;
/// number of valid bytes in the utf8_codes array
std::size_t utf8_bytes_filled = 0;
};
template<typename IteratorType, typename Enable = void>
struct iterator_input_adapter_factory
{
using iterator_type = IteratorType;
using char_type = typename std::iterator_traits<iterator_type>::value_type;
using adapter_type = iterator_input_adapter<iterator_type>;
static adapter_type create(IteratorType first, IteratorType last)
{
return adapter_type(std::move(first), std::move(last));
}
};
template<typename T>
struct is_iterator_of_multibyte
{
using value_type = typename std::iterator_traits<T>::value_type;
enum
{
value = sizeof(value_type) > 1
};
};
template<typename IteratorType>
struct iterator_input_adapter_factory<IteratorType, enable_if_t<is_iterator_of_multibyte<IteratorType>::value>>
{
using iterator_type = IteratorType;
using char_type = typename std::iterator_traits<iterator_type>::value_type;
using base_adapter_type = iterator_input_adapter<iterator_type>;
using adapter_type = wide_string_input_adapter<base_adapter_type, char_type>;
static adapter_type create(IteratorType first, IteratorType last)
{
return adapter_type(base_adapter_type(std::move(first), std::move(last)));
}
};
// General purpose iterator-based input
template<typename IteratorType>
typename iterator_input_adapter_factory<IteratorType>::adapter_type input_adapter(IteratorType first, IteratorType last)
{
using factory_type = iterator_input_adapter_factory<IteratorType>;
return factory_type::create(first, last);
}
// Convenience shorthand from container to iterator
// Enables ADL on begin(container) and end(container)
// Encloses the using declarations in namespace for not to leak them to outside scope
namespace container_input_adapter_factory_impl
{
using std::begin;
using std::end;
template<typename ContainerType, typename Enable = void>
struct container_input_adapter_factory {};
template<typename ContainerType>
struct container_input_adapter_factory< ContainerType,
void_t<decltype(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>()))>>
{
using adapter_type = decltype(input_adapter(begin(std::declval<ContainerType>()), end(std::declval<ContainerType>())));
static adapter_type create(const ContainerType& container)
{
return input_adapter(begin(container), end(container));
}
};
} // namespace container_input_adapter_factory_impl
template<typename ContainerType>
typename container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::adapter_type input_adapter(const ContainerType& container)
{
return container_input_adapter_factory_impl::container_input_adapter_factory<ContainerType>::create(container);
}
#ifndef JSON_NO_IO
// Special cases with fast paths
inline file_input_adapter input_adapter(std::FILE* file)
{
return file_input_adapter(file);
}
inline input_stream_adapter input_adapter(std::istream& stream)
{
return input_stream_adapter(stream);
}
inline input_stream_adapter input_adapter(std::istream&& stream)
{
return input_stream_adapter(stream);
}
#endif // JSON_NO_IO
using contiguous_bytes_input_adapter = decltype(input_adapter(std::declval<const char*>(), std::declval<const char*>()));
// Null-delimited strings, and the like.
template < typename CharT,
typename std::enable_if <
std::is_pointer<CharT>::value&&
!std::is_array<CharT>::value&&
std::is_integral<typename std::remove_pointer<CharT>::type>::value&&
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int >::type = 0 >
contiguous_bytes_input_adapter input_adapter(CharT b)
{
auto length = std::strlen(reinterpret_cast<const char*>(b));
const auto* ptr = reinterpret_cast<const char*>(b);
return input_adapter(ptr, ptr + length);
}
template<typename T, std::size_t N>
auto input_adapter(T (&array)[N]) -> decltype(input_adapter(array, array + N)) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
{
return input_adapter(array, array + N);
}
// This class only handles inputs of input_buffer_adapter type.
// It's required so that expressions like {ptr, len} can be implicitly cast
// to the correct adapter.
class span_input_adapter
{
public:
template < typename CharT,
typename std::enable_if <
std::is_pointer<CharT>::value&&
std::is_integral<typename std::remove_pointer<CharT>::type>::value&&
sizeof(typename std::remove_pointer<CharT>::type) == 1,
int >::type = 0 >
span_input_adapter(CharT b, std::size_t l)
: ia(reinterpret_cast<const char*>(b), reinterpret_cast<const char*>(b) + l) {}
template<class IteratorType,
typename std::enable_if<
std::is_same<typename iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
int>::type = 0>
span_input_adapter(IteratorType first, IteratorType last)
: ia(input_adapter(first, last)) {}
contiguous_bytes_input_adapter&& get()
{
return std::move(ia); // NOLINT(hicpp-move-const-arg,performance-move-const-arg)
}
private:
contiguous_bytes_input_adapter ia;
};
} // namespace detail
} // namespace nlohmann