json_serializer.h

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/*----------------------------------------------------------------------------*/
/* Modifications Copyright (c) 2017-2018 FIRST. All Rights Reserved.          */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
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/*
    __ _____ _____ _____
 __|  |   __|     |   | |  JSON for Modern C++
|  |  |__   |  |  | | | |  version 3.1.2
|_____|_____|_____|_|___|  https://github.com/nlohmann/json
 
Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
 
Permission is hereby  granted, free of charge, to any  person obtaining a copy
of this software and associated  documentation files (the "Software"), to deal
in the Software  without restriction, including without  limitation the rights
to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#include "wpi/json.h"
 
#include <clocale> // lconv, localeconv
#include <cmath>  // labs, isfinite, isnan, signbit, ldexp
#include <type_traits>
 
#include "wpi/raw_ostream.h"
 
namespace wpi {
 
class json::serializer
{
    static constexpr uint8_t UTF8_ACCEPT = 0;
    static constexpr uint8_t UTF8_REJECT = 1;
 
  public:
    /*!
    @param[in] s  output stream to serialize to
    @param[in] ichar  indentation character to use
    @param[in] indent_init_len  initial length of indentation string buffer
    */
    serializer(raw_ostream& s, const char ichar, size_t indent_init_len = 512)
        : o(s), indent_char(ichar),
          indent_string(indent_init_len, indent_char)
    {}
 
    // delete because of pointer members
    serializer(const serializer&) = delete;
    serializer& operator=(const serializer&) = delete;
 
    /*!
    @brief internal implementation of the serialization function
 
    This function is called by the public member function dump and organizes
    the serialization internally. The indentation level is propagated as
    additional parameter. In case of arrays and objects, the function is
    called recursively.
 
    - strings and object keys are escaped using `escape_string()`
    - integer numbers are converted implicitly via `operator<<`
    - floating-point numbers are converted to a string using `"%g"` format
 
    @param[in] val             value to serialize
    @param[in] pretty_print    whether the output shall be pretty-printed
    @param[in] ensure_ascii    whether the output shall only use ASCII chars
    @param[in] indent_step     the indent level
    @param[in] current_indent  the current indent level (only used internally)
    */
    void dump(const json& val, const bool pretty_print,
              const bool ensure_ascii,
              const unsigned int indent_step,
              const unsigned int current_indent = 0);
 
    /*!
    @brief dump escaped string
 
    Escape a string by replacing certain special characters by a sequence of an
    escape character (backslash) and another character and other control
    characters by a sequence of "\u" followed by a four-digit hex
    representation. The escaped string is written to output stream @a o.
 
    @param[in] s  the string to escape
    @param[in] ensure_ascii  whether to escape non-ASCII characters with
                             "\uXXXX" sequences
 
    Complexity: Linear in the length of string @a s.
    */
    void dump_escaped(std::string_view s, const bool ensure_ascii);
 
    template <typename NumberType,
              detail::enable_if_t<std::is_same_v<NumberType, uint64_t>, int> = 0>
    bool is_negative_integer(NumberType x) {
      return false;
    }
 
    template <typename NumberType,
              detail::enable_if_t<std::is_same_v<NumberType, int64_t>, int> = 0>
    bool is_negative_integer(NumberType x) {
      return x < 0;
    }
 
    /*!
    @brief dump an integer
 
    Dump a given integer to output stream @a o. Works internally with
    @a number_buffer.
 
    @param[in] x  integer number (signed or unsigned) to dump
    @tparam NumberType either @a int64_t or @a uint64_t
    */
    template<typename NumberType, detail::enable_if_t<
                 std::is_same<NumberType, uint64_t>::value or
                 std::is_same<NumberType, int64_t>::value,
                 int> = 0>
    void dump_integer(NumberType x)
    {
        // special case for "0"
        if (x == 0)
        {
            o << '0';
            return;
        }
 
        const bool is_negative = is_negative_integer(x);  // see issue #755
        std::size_t i = 0;
 
        while (x != 0)
        {
            // spare 1 byte for '\0'
            assert(i < number_buffer.size() - 1);
 
            const auto digit = std::labs(static_cast<long>(x % 10));
            number_buffer[i++] = static_cast<char>('0' + digit);
            x /= 10;
        }
 
        if (is_negative)
        {
            // make sure there is capacity for the '-'
            assert(i < number_buffer.size() - 2);
            number_buffer[i++] = '-';
        }
 
        std::reverse(number_buffer.begin(), number_buffer.begin() + i);
        o.write(number_buffer.data(), i);
    }
 
    /*!
    @brief dump a floating-point number
 
    Dump a given floating-point number to output stream @a o. Works internally
    with @a number_buffer.
 
    @param[in] x  floating-point number to dump
    */
    void dump_float(double x);
 
    /*!
    @brief check whether a string is UTF-8 encoded
 
    The function checks each byte of a string whether it is UTF-8 encoded. The
    result of the check is stored in the @a state parameter. The function must
    be called initially with state 0 (accept). State 1 means the string must
    be rejected, because the current byte is not allowed. If the string is
    completely processed, but the state is non-zero, the string ended
    prematurely; that is, the last byte indicated more bytes should have
    followed.
 
    @param[in,out] state  the state of the decoding
    @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
    @param[in] byte       next byte to decode
    @return               new state
 
    @note The function has been edited: a std::array is used.
 
    @copyright Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
    @sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
    */
    static uint8_t decode(uint8_t& state, uint32_t& codep, const uint8_t byte) noexcept;
 
  private:
    /// the output of the serializer
    raw_ostream& o;
 
    /// a (hopefully) large enough character buffer
    std::array<char, 64> number_buffer{{}};
 
    /// the indentation character
    const char indent_char;
    /// the indentation string
    std::string indent_string;
};
 
}  // namespace wpi