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json/include/nlohmann/detail/input/input_adapters.hpp
Niels Lohmann 16c5bfeaad
👌 fixed compiler warnings #1031
2018-04-02 13:01:56 +02:00

441 lines
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#pragma once
#include <algorithm> // min
#include <array> // array
#include <cassert> // assert
#include <cstddef> // size_t
#include <cstring> // strlen
#include <ios> // streamsize, streamoff, streampos
#include <istream> // istream
#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
#include <nlohmann/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;
};
template<typename WideStringType>
class wide_string_input_adapter : public input_adapter_protocol
{
public:
wide_string_input_adapter(const WideStringType& w) : str(w) {}
std::char_traits<char>::int_type get_character() noexcept override
{
// unget_character() was called previously: return the last character
if (next_unget)
{
next_unget = false;
return last_char;
}
// check if buffer needs to be filled
if (utf8_bytes_index == utf8_bytes_filled)
{
if (sizeof(typename WideStringType::value_type) == 2)
{
fill_buffer_utf16();
}
else
{
fill_buffer_utf32();
}
assert(utf8_bytes_filled > 0);
assert(utf8_bytes_index == 0);
}
// use buffer
assert(utf8_bytes_filled > 0);
assert(utf8_bytes_index < utf8_bytes_filled);
return (last_char = utf8_bytes[utf8_bytes_index++]);
}
void unget_character() noexcept override
{
next_unget = true;
}
private:
void fill_buffer_utf16()
{
utf8_bytes_index = 0;
if (current_wchar == str.size())
{
utf8_bytes[0] = std::char_traits<char>::eof();
utf8_bytes_filled = 1;
}
else
{
// get the current character
const int wc = static_cast<int>(str[current_wchar++]);
// UTF-16 to UTF-8 encoding
if (wc < 0x80)
{
utf8_bytes[0] = wc;
utf8_bytes_filled = 1;
}
else if (wc <= 0x7FF)
{
utf8_bytes[0] = 0xC0 | ((wc >> 6));
utf8_bytes[1] = 0x80 | (wc & 0x3F);
utf8_bytes_filled = 2;
}
else if (0xD800 > wc or wc >= 0xE000)
{
utf8_bytes[0] = 0xE0 | ((wc >> 12));
utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
utf8_bytes[2] = 0x80 | (wc & 0x3F);
utf8_bytes_filled = 3;
}
else
{
if (current_wchar < str.size())
{
const int wc2 = static_cast<int>(str[current_wchar++]);
const int charcode = 0x10000 + (((wc & 0x3FF) << 10) | (wc2 & 0x3FF));
utf8_bytes[0] = 0xf0 | (charcode >> 18);
utf8_bytes[1] = 0x80 | ((charcode >> 12) & 0x3F);
utf8_bytes[2] = 0x80 | ((charcode >> 6) & 0x3F);
utf8_bytes[3] = 0x80 | (charcode & 0x3F);
utf8_bytes_filled = 4;
}
else
{
// unknown character
++current_wchar;
utf8_bytes[0] = wc;
utf8_bytes_filled = 1;
}
}
}
}
void fill_buffer_utf32()
{
utf8_bytes_index = 0;
if (current_wchar == str.size())
{
utf8_bytes[0] = std::char_traits<char>::eof();
utf8_bytes_filled = 1;
}
else
{
// get the current character
const int wc = static_cast<int>(str[current_wchar++]);
// UTF-32 to UTF-8 encoding
if (wc < 0x80)
{
utf8_bytes[0] = wc;
utf8_bytes_filled = 1;
}
else if (wc <= 0x7FF)
{
utf8_bytes[0] = 0xC0 | ((wc >> 6) & 0x1F);
utf8_bytes[1] = 0x80 | (wc & 0x3F);
utf8_bytes_filled = 2;
}
else if (wc <= 0xFFFF)
{
utf8_bytes[0] = 0xE0 | ((wc >> 12) & 0x0F);
utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
utf8_bytes[2] = 0x80 | (wc & 0x3F);
utf8_bytes_filled = 3;
}
else if (wc <= 0x10FFFF)
{
utf8_bytes[0] = 0xF0 | ((wc >> 18 ) & 0x07);
utf8_bytes[1] = 0x80 | ((wc >> 12) & 0x3F);
utf8_bytes[2] = 0x80 | ((wc >> 6) & 0x3F);
utf8_bytes[3] = 0x80 | (wc & 0x3F);
utf8_bytes_filled = 4;
}
else
{
// unknown character
utf8_bytes[0] = wc;
utf8_bytes_filled = 1;
}
}
}
private:
/// the wstring to process
const WideStringType& str;
/// index of the current wchar in str
std::size_t current_wchar = 0;
/// 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;
/// the last character (returned after unget_character() is called)
std::char_traits<char>::int_type last_char = 0;
/// whether get_character() should return last_char
bool next_unget = false;
};
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(const std::wstring& ws)
: ia(std::make_shared<wide_string_input_adapter<std::wstring>>(ws)) {}
input_adapter(const std::u16string& ws)
: ia(std::make_shared<wide_string_input_adapter<std::u16string>>(ws)) {}
input_adapter(const std::u32string& ws)
: ia(std::make_shared<wide_string_input_adapter<std::u32string>>(ws)) {}
/// 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;
};
}
}
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