mirror of
https://github.com/nlohmann/json.git
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383 lines
12 KiB
C++
383 lines
12 KiB
C++
#pragma once
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#include <cassert> // assert
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#include <cstddef> // size_t
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#include <cstring> // strlen
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#include <istream> // istream
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#include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next
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#include <memory> // shared_ptr, make_shared, addressof
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#include <numeric> // accumulate
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#include <string> // string, char_traits
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#include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
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#include <utility> // pair, declval
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#include <nlohmann/detail/macro_scope.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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/// the supported input formats
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enum class input_format_t { json, cbor, msgpack, ubjson };
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////////////////////
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// input adapters //
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////////////////////
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/*!
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@brief abstract input adapter interface
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Produces a stream of std::char_traits<char>::int_type characters from a
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std::istream, a buffer, or some other input type. Accepts the return of
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exactly one non-EOF character for future input. The int_type characters
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returned consist of all valid char values as positive values (typically
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unsigned char), plus an EOF value outside that range, specified by the value
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of the function std::char_traits<char>::eof(). This value is typically -1, but
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could be any arbitrary value which is not a valid char value.
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*/
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struct input_adapter_protocol
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{
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/// get a character [0,255] or std::char_traits<char>::eof().
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virtual std::char_traits<char>::int_type get_character() = 0;
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virtual ~input_adapter_protocol() = default;
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};
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/// a type to simplify interfaces
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using input_adapter_t = std::shared_ptr<input_adapter_protocol>;
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/*!
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Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
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beginning of input. Does not support changing the underlying std::streambuf
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in mid-input. Maintains underlying std::istream and std::streambuf to support
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subsequent use of standard std::istream operations to process any input
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characters following those used in parsing the JSON input. Clears the
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std::istream flags; any input errors (e.g., EOF) will be detected by the first
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subsequent call for input from the std::istream.
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*/
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class input_stream_adapter : public input_adapter_protocol
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{
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public:
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~input_stream_adapter() override
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{
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// clear stream flags; we use underlying streambuf I/O, do not
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// maintain ifstream flags
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is.clear();
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}
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explicit input_stream_adapter(std::istream& i)
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: is(i), sb(*i.rdbuf())
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{}
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// delete because of pointer members
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input_stream_adapter(const input_stream_adapter&) = delete;
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input_stream_adapter& operator=(input_stream_adapter&) = delete;
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// std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
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// ensure that std::char_traits<char>::eof() and the character 0xFF do not
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// end up as the same value, eg. 0xFFFFFFFF.
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std::char_traits<char>::int_type get_character() override
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{
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return sb.sbumpc();
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}
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private:
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/// the associated input stream
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std::istream& is;
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std::streambuf& sb;
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};
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/// input adapter for buffer input
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class input_buffer_adapter : public input_adapter_protocol
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{
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public:
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input_buffer_adapter(const char* b, const std::size_t l)
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: cursor(b), limit(b + l)
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{}
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// delete because of pointer members
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input_buffer_adapter(const input_buffer_adapter&) = delete;
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input_buffer_adapter& operator=(input_buffer_adapter&) = delete;
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std::char_traits<char>::int_type get_character() noexcept override
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{
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if (JSON_LIKELY(cursor < limit))
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{
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return std::char_traits<char>::to_int_type(*(cursor++));
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}
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return std::char_traits<char>::eof();
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}
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private:
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/// pointer to the current character
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const char* cursor;
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/// pointer past the last character
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const char* const limit;
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};
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template<typename WideStringType>
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class wide_string_input_adapter : public input_adapter_protocol
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{
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public:
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explicit wide_string_input_adapter(const WideStringType& w) : str(w) {}
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std::char_traits<char>::int_type get_character() noexcept override
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{
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// check if buffer needs to be filled
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if (utf8_bytes_index == utf8_bytes_filled)
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{
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fill_buffer(sizeof(typename WideStringType::value_type));
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assert(utf8_bytes_filled > 0);
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assert(utf8_bytes_index == 0);
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}
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// use buffer
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assert(utf8_bytes_filled > 0);
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assert(utf8_bytes_index < utf8_bytes_filled);
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return utf8_bytes[utf8_bytes_index++];
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}
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private:
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void fill_buffer(size_t size)
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{
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if (2 == size)
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{
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fill_buffer_utf16();
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}
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else
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{
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fill_buffer_utf32();
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}
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}
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void fill_buffer_utf16()
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{
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utf8_bytes_index = 0;
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if (current_wchar == str.size())
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{
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utf8_bytes[0] = std::char_traits<char>::eof();
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utf8_bytes_filled = 1;
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}
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else
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{
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// get the current character
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const int wc = static_cast<int>(str[current_wchar++]);
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// UTF-16 to UTF-8 encoding
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if (wc < 0x80)
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{
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utf8_bytes[0] = wc;
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utf8_bytes_filled = 1;
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}
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else if (wc <= 0x7FF)
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{
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utf8_bytes[0] = 0xC0 | ((wc >> 6));
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utf8_bytes[1] = 0x80 | (wc & 0x3F);
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utf8_bytes_filled = 2;
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}
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else if (0xD800 > wc or wc >= 0xE000)
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{
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utf8_bytes[0] = 0xE0 | ((wc >> 12));
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utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
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utf8_bytes[2] = 0x80 | (wc & 0x3F);
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utf8_bytes_filled = 3;
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}
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else
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{
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if (current_wchar < str.size())
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{
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const int wc2 = static_cast<int>(str[current_wchar++]);
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const int charcode = 0x10000 + (((wc & 0x3FF) << 10) | (wc2 & 0x3FF));
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utf8_bytes[0] = 0xf0 | (charcode >> 18);
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utf8_bytes[1] = 0x80 | ((charcode >> 12) & 0x3F);
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utf8_bytes[2] = 0x80 | ((charcode >> 6) & 0x3F);
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utf8_bytes[3] = 0x80 | (charcode & 0x3F);
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utf8_bytes_filled = 4;
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}
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else
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{
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// unknown character
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++current_wchar;
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utf8_bytes[0] = wc;
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utf8_bytes_filled = 1;
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}
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}
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}
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}
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void fill_buffer_utf32()
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{
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utf8_bytes_index = 0;
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if (current_wchar == str.size())
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{
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utf8_bytes[0] = std::char_traits<char>::eof();
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utf8_bytes_filled = 1;
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}
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else
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{
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// get the current character
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const int wc = static_cast<int>(str[current_wchar++]);
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// UTF-32 to UTF-8 encoding
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if (wc < 0x80)
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{
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utf8_bytes[0] = wc;
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utf8_bytes_filled = 1;
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}
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else if (wc <= 0x7FF)
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{
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utf8_bytes[0] = 0xC0 | ((wc >> 6) & 0x1F);
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utf8_bytes[1] = 0x80 | (wc & 0x3F);
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utf8_bytes_filled = 2;
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}
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else if (wc <= 0xFFFF)
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{
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utf8_bytes[0] = 0xE0 | ((wc >> 12) & 0x0F);
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utf8_bytes[1] = 0x80 | ((wc >> 6) & 0x3F);
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utf8_bytes[2] = 0x80 | (wc & 0x3F);
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utf8_bytes_filled = 3;
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}
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else if (wc <= 0x10FFFF)
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{
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utf8_bytes[0] = 0xF0 | ((wc >> 18 ) & 0x07);
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utf8_bytes[1] = 0x80 | ((wc >> 12) & 0x3F);
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utf8_bytes[2] = 0x80 | ((wc >> 6) & 0x3F);
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utf8_bytes[3] = 0x80 | (wc & 0x3F);
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utf8_bytes_filled = 4;
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}
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else
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{
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// unknown character
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utf8_bytes[0] = wc;
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utf8_bytes_filled = 1;
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}
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}
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}
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private:
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/// the wstring to process
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const WideStringType& str;
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/// index of the current wchar in str
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std::size_t current_wchar = 0;
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/// a buffer for UTF-8 bytes
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std::array<std::char_traits<char>::int_type, 4> utf8_bytes = {{0, 0, 0, 0}};
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/// index to the utf8_codes array for the next valid byte
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std::size_t utf8_bytes_index = 0;
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/// number of valid bytes in the utf8_codes array
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std::size_t utf8_bytes_filled = 0;
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};
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class input_adapter
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{
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public:
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// native support
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/// input adapter for input stream
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input_adapter(std::istream& i)
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: ia(std::make_shared<input_stream_adapter>(i)) {}
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/// input adapter for input stream
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input_adapter(std::istream&& i)
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: ia(std::make_shared<input_stream_adapter>(i)) {}
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input_adapter(const std::wstring& ws)
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: ia(std::make_shared<wide_string_input_adapter<std::wstring>>(ws)) {}
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input_adapter(const std::u16string& ws)
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: ia(std::make_shared<wide_string_input_adapter<std::u16string>>(ws)) {}
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input_adapter(const std::u32string& ws)
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: ia(std::make_shared<wide_string_input_adapter<std::u32string>>(ws)) {}
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/// input adapter for buffer
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template<typename CharT,
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typename std::enable_if<
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std::is_pointer<CharT>::value and
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std::is_integral<typename std::remove_pointer<CharT>::type>::value and
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sizeof(typename std::remove_pointer<CharT>::type) == 1,
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int>::type = 0>
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input_adapter(CharT b, std::size_t l)
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: ia(std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(b), l)) {}
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// derived support
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/// input adapter for string literal
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template<typename CharT,
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typename std::enable_if<
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std::is_pointer<CharT>::value and
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std::is_integral<typename std::remove_pointer<CharT>::type>::value and
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sizeof(typename std::remove_pointer<CharT>::type) == 1,
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int>::type = 0>
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input_adapter(CharT b)
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: input_adapter(reinterpret_cast<const char*>(b),
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std::strlen(reinterpret_cast<const char*>(b))) {}
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/// input adapter for iterator range with contiguous storage
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template<class IteratorType,
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typename std::enable_if<
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std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value,
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int>::type = 0>
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input_adapter(IteratorType first, IteratorType last)
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{
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#ifndef NDEBUG
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// assertion to check that the iterator range is indeed contiguous,
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// see http://stackoverflow.com/a/35008842/266378 for more discussion
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const auto is_contiguous = std::accumulate(
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first, last, std::pair<bool, int>(true, 0),
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[&first](std::pair<bool, int> res, decltype(*first) val)
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{
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res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
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return res;
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}).first;
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assert(is_contiguous);
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#endif
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// assertion to check that each element is 1 byte long
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static_assert(
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sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
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"each element in the iterator range must have the size of 1 byte");
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const auto len = static_cast<size_t>(std::distance(first, last));
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if (JSON_LIKELY(len > 0))
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{
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// there is at least one element: use the address of first
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ia = std::make_shared<input_buffer_adapter>(reinterpret_cast<const char*>(&(*first)), len);
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}
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else
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{
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// the address of first cannot be used: use nullptr
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ia = std::make_shared<input_buffer_adapter>(nullptr, len);
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}
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}
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/// input adapter for array
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template<class T, std::size_t N>
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input_adapter(T (&array)[N])
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: input_adapter(std::begin(array), std::end(array)) {}
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/// input adapter for contiguous container
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template<class ContiguousContainer, typename
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std::enable_if<not std::is_pointer<ContiguousContainer>::value and
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std::is_base_of<std::random_access_iterator_tag, typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value,
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int>::type = 0>
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input_adapter(const ContiguousContainer& c)
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: input_adapter(std::begin(c), std::end(c)) {}
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operator input_adapter_t()
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{
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return ia;
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}
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private:
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/// the actual adapter
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input_adapter_t ia = nullptr;
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};
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}
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}
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