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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "json.h"

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstring>
#include <limits>
#include <stack>

#include "cbor.h"
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#include "json_platform.h"
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namespace v8_crdtp {
namespace json {
// =============================================================================
// json::NewJSONEncoder - for encoding streaming parser events as JSON
// =============================================================================

namespace {
// Prints |value| to |out| with 4 hex digits, most significant chunk first.
template <typename C>
void PrintHex(uint16_t value, C* out) {
  for (int ii = 3; ii >= 0; --ii) {
    int four_bits = 0xf & (value >> (4 * ii));
    out->push_back(four_bits + ((four_bits <= 9) ? '0' : ('a' - 10)));
  }
}

// In the writer below, we maintain a stack of State instances.
// It is just enough to emit the appropriate delimiters and brackets
// in JSON.
enum class Container {
  // Used for the top-level, initial state.
  NONE,
  // Inside a JSON object.
  MAP,
  // Inside a JSON array.
  ARRAY
};

class State {
 public:
  explicit State(Container container) : container_(container) {}
  void StartElement(std::vector<uint8_t>* out) { StartElementTmpl(out); }
  void StartElement(std::string* out) { StartElementTmpl(out); }
  Container container() const { return container_; }

 private:
  template <typename C>
  void StartElementTmpl(C* out) {
    assert(container_ != Container::NONE || size_ == 0);
    if (size_ != 0) {
      char delim = (!(size_ & 1) || container_ == Container::ARRAY) ? ',' : ':';
      out->push_back(delim);
    }
    ++size_;
  }

  Container container_ = Container::NONE;
  int size_ = 0;
};

constexpr char kBase64Table[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz0123456789+/";

template <typename C>
void Base64Encode(const span<uint8_t>& in, C* out) {
  // The following three cases are based on the tables in the example
  // section in https://en.wikipedia.org/wiki/Base64. We process three
  // input bytes at a time, emitting 4 output bytes at a time.
  size_t ii = 0;

  // While possible, process three input bytes.
  for (; ii + 3 <= in.size(); ii += 3) {
    uint32_t twentyfour_bits = (in[ii] << 16) | (in[ii + 1] << 8) | in[ii + 2];
    out->push_back(kBase64Table[(twentyfour_bits >> 18)]);
    out->push_back(kBase64Table[(twentyfour_bits >> 12) & 0x3f]);
    out->push_back(kBase64Table[(twentyfour_bits >> 6) & 0x3f]);
    out->push_back(kBase64Table[twentyfour_bits & 0x3f]);
  }
  if (ii + 2 <= in.size()) {  // Process two input bytes.
    uint32_t twentyfour_bits = (in[ii] << 16) | (in[ii + 1] << 8);
    out->push_back(kBase64Table[(twentyfour_bits >> 18)]);
    out->push_back(kBase64Table[(twentyfour_bits >> 12) & 0x3f]);
    out->push_back(kBase64Table[(twentyfour_bits >> 6) & 0x3f]);
    out->push_back('=');  // Emit padding.
    return;
  }
  if (ii + 1 <= in.size()) {  // Process a single input byte.
    uint32_t twentyfour_bits = (in[ii] << 16);
    out->push_back(kBase64Table[(twentyfour_bits >> 18)]);
    out->push_back(kBase64Table[(twentyfour_bits >> 12) & 0x3f]);
    out->push_back('=');  // Emit padding.
    out->push_back('=');  // Emit padding.
  }
}

// Implements a handler for JSON parser events to emit a JSON string.
template <typename C>
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class JSONEncoder : public ParserHandler {
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 public:
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  JSONEncoder(C* out, Status* status) : out_(out), status_(status) {
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    *status_ = Status();
    state_.emplace(Container::NONE);
  }

  void HandleMapBegin() override {
    if (!status_->ok())
      return;
    assert(!state_.empty());
    state_.top().StartElement(out_);
    state_.emplace(Container::MAP);
    Emit('{');
  }

  void HandleMapEnd() override {
    if (!status_->ok())
      return;
    assert(state_.size() >= 2 && state_.top().container() == Container::MAP);
    state_.pop();
    Emit('}');
  }

  void HandleArrayBegin() override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    state_.emplace(Container::ARRAY);
    Emit('[');
  }

  void HandleArrayEnd() override {
    if (!status_->ok())
      return;
    assert(state_.size() >= 2 && state_.top().container() == Container::ARRAY);
    state_.pop();
    Emit(']');
  }

  void HandleString16(span<uint16_t> chars) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit('"');
    for (const uint16_t ch : chars) {
      if (ch == '"') {
        Emit("\\\"");
      } else if (ch == '\\') {
        Emit("\\\\");
      } else if (ch == '\b') {
        Emit("\\b");
      } else if (ch == '\f') {
        Emit("\\f");
      } else if (ch == '\n') {
        Emit("\\n");
      } else if (ch == '\r') {
        Emit("\\r");
      } else if (ch == '\t') {
        Emit("\\t");
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      } else if (ch >= 32 && ch <= 127) {
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        Emit(ch);
      } else {
        Emit("\\u");
        PrintHex(ch, out_);
      }
    }
    Emit('"');
  }

  void HandleString8(span<uint8_t> chars) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit('"');
    for (size_t ii = 0; ii < chars.size(); ++ii) {
      uint8_t c = chars[ii];
      if (c == '"') {
        Emit("\\\"");
      } else if (c == '\\') {
        Emit("\\\\");
      } else if (c == '\b') {
        Emit("\\b");
      } else if (c == '\f') {
        Emit("\\f");
      } else if (c == '\n') {
        Emit("\\n");
      } else if (c == '\r') {
        Emit("\\r");
      } else if (c == '\t') {
        Emit("\\t");
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      } else if (c >= 32 && c <= 127) {
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        Emit(c);
      } else if (c < 32) {
        Emit("\\u");
        PrintHex(static_cast<uint16_t>(c), out_);
      } else {
        // Inspect the leading byte to figure out how long the utf8
        // byte sequence is; while doing this initialize |codepoint|
        // with the first few bits.
        // See table in: https://en.wikipedia.org/wiki/UTF-8
        // byte one is 110x xxxx -> 2 byte utf8 sequence
        // byte one is 1110 xxxx -> 3 byte utf8 sequence
        // byte one is 1111 0xxx -> 4 byte utf8 sequence
        uint32_t codepoint;
        int num_bytes_left;
        if ((c & 0xe0) == 0xc0) {  // 2 byte utf8 sequence
          num_bytes_left = 1;
          codepoint = c & 0x1f;
        } else if ((c & 0xf0) == 0xe0) {  // 3 byte utf8 sequence
          num_bytes_left = 2;
          codepoint = c & 0x0f;
        } else if ((c & 0xf8) == 0xf0) {  // 4 byte utf8 sequence
          codepoint = c & 0x07;
          num_bytes_left = 3;
        } else {
          continue;  // invalid leading byte
        }

        // If we have enough bytes in our input, decode the remaining ones
        // belonging to this Unicode character into |codepoint|.
        if (ii + num_bytes_left >= chars.size())
          continue;
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        bool invalid_byte_seen = false;
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        while (num_bytes_left > 0) {
          c = chars[++ii];
          --num_bytes_left;
          // Check the next byte is a continuation byte, that is 10xx xxxx.
          if ((c & 0xc0) != 0x80)
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            invalid_byte_seen = true;
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          codepoint = (codepoint << 6) | (c & 0x3f);
        }
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        if (invalid_byte_seen)
          continue;
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        // Disallow overlong encodings for ascii characters, as these
        // would include " and other characters significant to JSON
        // string termination / control.
        if (codepoint <= 0x7f)
          continue;
        // Invalid in UTF8, and can't be represented in UTF16 anyway.
        if (codepoint > 0x10ffff)
          continue;

        // So, now we transcode to UTF16,
        // using the math described at https://en.wikipedia.org/wiki/UTF-16,
        // for either one or two 16 bit characters.
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        if (codepoint <= 0xffff) {
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          Emit("\\u");
          PrintHex(static_cast<uint16_t>(codepoint), out_);
          continue;
        }
        codepoint -= 0x10000;
        // high surrogate
        Emit("\\u");
        PrintHex(static_cast<uint16_t>((codepoint >> 10) + 0xd800), out_);
        // low surrogate
        Emit("\\u");
        PrintHex(static_cast<uint16_t>((codepoint & 0x3ff) + 0xdc00), out_);
      }
    }
    Emit('"');
  }

  void HandleBinary(span<uint8_t> bytes) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit('"');
    Base64Encode(bytes, out_);
    Emit('"');
  }

  void HandleDouble(double value) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    // JSON cannot represent NaN or Infinity. So, for compatibility,
    // we behave like the JSON object in web browsers: emit 'null'.
    if (!std::isfinite(value)) {
      Emit("null");
      return;
    }
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    // If |value| is a scalar, emit it as an int. Taken from json_writer.cc in
    // Chromium.
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    if (value < static_cast<double>(std::numeric_limits<int64_t>::max()) &&
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        value >= std::numeric_limits<int64_t>::min() &&
        std::floor(value) == value) {
      Emit(std::to_string(static_cast<int64_t>(value)));
      return;
    }
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    std::string str_value = json::platform::DToStr(value);
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    // The following is somewhat paranoid, but also taken from json_writer.cc
    // in Chromium:
    // Ensure that the number has a .0 if there's no decimal or 'e'.  This
    // makes sure that when we read the JSON back, it's interpreted as a
    // real rather than an int.
    if (str_value.find_first_of(".eE") == std::string::npos)
      str_value.append(".0");
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    // DToStr may fail to emit a 0 before the decimal dot. E.g. this is
    // the case in base::NumberToString in Chromium (which is based on
    // dmg_fp). So, much like
    // https://cs.chromium.org/chromium/src/base/json/json_writer.cc
    // we probe for this and emit the leading 0 anyway if necessary.
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    const char* chars = str_value.c_str();
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    if (chars[0] == '.') {
      Emit('0');
    } else if (chars[0] == '-' && chars[1] == '.') {
      Emit("-0");
      ++chars;
    }
    Emit(chars);
  }

  void HandleInt32(int32_t value) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit(std::to_string(value));
  }

  void HandleBool(bool value) override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit(value ? "true" : "false");
  }

  void HandleNull() override {
    if (!status_->ok())
      return;
    state_.top().StartElement(out_);
    Emit("null");
  }

  void HandleError(Status error) override {
    assert(!error.ok());
    *status_ = error;
    out_->clear();
  }

 private:
  void Emit(char c) { out_->push_back(c); }
  void Emit(const char* str) {
    out_->insert(out_->end(), str, str + strlen(str));
  }
  void Emit(const std::string& str) {
    out_->insert(out_->end(), str.begin(), str.end());
  }

  C* out_;
  Status* status_;
  std::stack<State> state_;
};
}  // namespace

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std::unique_ptr<ParserHandler> NewJSONEncoder(std::vector<uint8_t>* out,
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                                              Status* status) {
  return std::unique_ptr<ParserHandler>(
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      new JSONEncoder<std::vector<uint8_t>>(out, status));
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}

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std::unique_ptr<ParserHandler> NewJSONEncoder(std::string* out,
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                                              Status* status) {
  return std::unique_ptr<ParserHandler>(
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      new JSONEncoder<std::string>(out, status));
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}

// =============================================================================
// json::ParseJSON - for receiving streaming parser events for JSON.
// =============================================================================

namespace {
const int kStackLimit = 300;

enum Token {
  ObjectBegin,
  ObjectEnd,
  ArrayBegin,
  ArrayEnd,
  StringLiteral,
  Number,
  BoolTrue,
  BoolFalse,
  NullToken,
  ListSeparator,
  ObjectPairSeparator,
  InvalidToken,
  NoInput
};

const char* const kNullString = "null";
const char* const kTrueString = "true";
const char* const kFalseString = "false";

template <typename Char>
class JsonParser {
 public:
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  explicit JsonParser(ParserHandler* handler) : handler_(handler) {}
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  void Parse(const Char* start, size_t length) {
    start_pos_ = start;
    const Char* end = start + length;
    const Char* tokenEnd = nullptr;
    ParseValue(start, end, &tokenEnd, 0);
    if (error_)
      return;
    if (tokenEnd != end) {
      HandleError(Error::JSON_PARSER_UNPROCESSED_INPUT_REMAINS, tokenEnd);
    }
  }

 private:
  bool CharsToDouble(const uint16_t* chars, size_t length, double* result) {
    std::string buffer;
    buffer.reserve(length + 1);
    for (size_t ii = 0; ii < length; ++ii) {
      bool is_ascii = !(chars[ii] & ~0x7F);
      if (!is_ascii)
        return false;
      buffer.push_back(static_cast<char>(chars[ii]));
    }
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    return platform::StrToD(buffer.c_str(), result);
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  }

  bool CharsToDouble(const uint8_t* chars, size_t length, double* result) {
    std::string buffer(reinterpret_cast<const char*>(chars), length);
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    return platform::StrToD(buffer.c_str(), result);
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  }

  static bool ParseConstToken(const Char* start,
                              const Char* end,
                              const Char** token_end,
                              const char* token) {
    // |token| is \0 terminated, it's one of the constants at top of the file.
    while (start < end && *token != '\0' && *start++ == *token++) {
    }
    if (*token != '\0')
      return false;
    *token_end = start;
    return true;
  }

  static bool ReadInt(const Char* start,
                      const Char* end,
                      const Char** token_end,
                      bool allow_leading_zeros) {
    if (start == end)
      return false;
    bool has_leading_zero = '0' == *start;
    int length = 0;
    while (start < end && '0' <= *start && *start <= '9') {
      ++start;
      ++length;
    }
    if (!length)
      return false;
    if (!allow_leading_zeros && length > 1 && has_leading_zero)
      return false;
    *token_end = start;
    return true;
  }

  static bool ParseNumberToken(const Char* start,
                               const Char* end,
                               const Char** token_end) {
    // We just grab the number here. We validate the size in DecodeNumber.
    // According to RFC4627, a valid number is: [minus] int [frac] [exp]
    if (start == end)
      return false;
    Char c = *start;
    if ('-' == c)
      ++start;

    if (!ReadInt(start, end, &start, /*allow_leading_zeros=*/false))
      return false;
    if (start == end) {
      *token_end = start;
      return true;
    }

    // Optional fraction part
    c = *start;
    if ('.' == c) {
      ++start;
      if (!ReadInt(start, end, &start, /*allow_leading_zeros=*/true))
        return false;
      if (start == end) {
        *token_end = start;
        return true;
      }
      c = *start;
    }

    // Optional exponent part
    if ('e' == c || 'E' == c) {
      ++start;
      if (start == end)
        return false;
      c = *start;
      if ('-' == c || '+' == c) {
        ++start;
        if (start == end)
          return false;
      }
      if (!ReadInt(start, end, &start, /*allow_leading_zeros=*/true))
        return false;
    }

    *token_end = start;
    return true;
  }

  static bool ReadHexDigits(const Char* start,
                            const Char* end,
                            const Char** token_end,
                            int digits) {
    if (end - start < digits)
      return false;
    for (int i = 0; i < digits; ++i) {
      Char c = *start++;
      if (!(('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
            ('A' <= c && c <= 'F')))
        return false;
    }
    *token_end = start;
    return true;
  }

  static bool ParseStringToken(const Char* start,
                               const Char* end,
                               const Char** token_end) {
    while (start < end) {
      Char c = *start++;
      if ('\\' == c) {
        if (start == end)
          return false;
        c = *start++;
        // Make sure the escaped char is valid.
        switch (c) {
          case 'x':
            if (!ReadHexDigits(start, end, &start, 2))
              return false;
            break;
          case 'u':
            if (!ReadHexDigits(start, end, &start, 4))
              return false;
            break;
          case '\\':
          case '/':
          case 'b':
          case 'f':
          case 'n':
          case 'r':
          case 't':
          case 'v':
          case '"':
            break;
          default:
            return false;
        }
      } else if ('"' == c) {
        *token_end = start;
        return true;
      }
    }
    return false;
  }

  static bool SkipComment(const Char* start,
                          const Char* end,
                          const Char** comment_end) {
    if (start == end)
      return false;

    if (*start != '/' || start + 1 >= end)
      return false;
    ++start;

    if (*start == '/') {
      // Single line comment, read to newline.
      for (++start; start < end; ++start) {
        if (*start == '\n' || *start == '\r') {
          *comment_end = start + 1;
          return true;
        }
      }
      *comment_end = end;
      // Comment reaches end-of-input, which is fine.
      return true;
    }

    if (*start == '*') {
      Char previous = '\0';
      // Block comment, read until end marker.
      for (++start; start < end; previous = *start++) {
        if (previous == '*' && *start == '/') {
          *comment_end = start + 1;
          return true;
        }
      }
      // Block comment must close before end-of-input.
      return false;
    }

    return false;
  }

  static bool IsSpaceOrNewLine(Char c) {
    // \v = vertial tab; \f = form feed page break.
    return c == ' ' || c == '\n' || c == '\v' || c == '\f' || c == '\r' ||
           c == '\t';
  }

  static void SkipWhitespaceAndComments(const Char* start,
                                        const Char* end,
                                        const Char** whitespace_end) {
    while (start < end) {
      if (IsSpaceOrNewLine(*start)) {
        ++start;
      } else if (*start == '/') {
        const Char* comment_end = nullptr;
        if (!SkipComment(start, end, &comment_end))
          break;
        start = comment_end;
      } else {
        break;
      }
    }
    *whitespace_end = start;
  }

  static Token ParseToken(const Char* start,
                          const Char* end,
                          const Char** tokenStart,
                          const Char** token_end) {
    SkipWhitespaceAndComments(start, end, tokenStart);
    start = *tokenStart;

    if (start == end)
      return NoInput;

    switch (*start) {
      case 'n':
        if (ParseConstToken(start, end, token_end, kNullString))
          return NullToken;
        break;
      case 't':
        if (ParseConstToken(start, end, token_end, kTrueString))
          return BoolTrue;
        break;
      case 'f':
        if (ParseConstToken(start, end, token_end, kFalseString))
          return BoolFalse;
        break;
      case '[':
        *token_end = start + 1;
        return ArrayBegin;
      case ']':
        *token_end = start + 1;
        return ArrayEnd;
      case ',':
        *token_end = start + 1;
        return ListSeparator;
      case '{':
        *token_end = start + 1;
        return ObjectBegin;
      case '}':
        *token_end = start + 1;
        return ObjectEnd;
      case ':':
        *token_end = start + 1;
        return ObjectPairSeparator;
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
      case '-':
        if (ParseNumberToken(start, end, token_end))
          return Number;
        break;
      case '"':
        if (ParseStringToken(start + 1, end, token_end))
          return StringLiteral;
        break;
    }
    return InvalidToken;
  }

  static int HexToInt(Char c) {
    if ('0' <= c && c <= '9')
      return c - '0';
    if ('A' <= c && c <= 'F')
      return c - 'A' + 10;
    if ('a' <= c && c <= 'f')
      return c - 'a' + 10;
    assert(false);  // Unreachable.
    return 0;
  }

  static bool DecodeString(const Char* start,
                           const Char* end,
                           std::vector<uint16_t>* output) {
    if (start == end)
      return true;
    if (start > end)
      return false;
    output->reserve(end - start);
    while (start < end) {
      uint16_t c = *start++;
      // If the |Char| we're dealing with is really a byte, then
      // we have utf8 here, and we need to check for multibyte characters
      // and transcode them to utf16 (either one or two utf16 chars).
      if (sizeof(Char) == sizeof(uint8_t) && c > 0x7f) {
        // Inspect the leading byte to figure out how long the utf8
        // byte sequence is; while doing this initialize |codepoint|
        // with the first few bits.
        // See table in: https://en.wikipedia.org/wiki/UTF-8
        // byte one is 110x xxxx -> 2 byte utf8 sequence
        // byte one is 1110 xxxx -> 3 byte utf8 sequence
        // byte one is 1111 0xxx -> 4 byte utf8 sequence
        uint32_t codepoint;
        int num_bytes_left;
        if ((c & 0xe0) == 0xc0) {  // 2 byte utf8 sequence
          num_bytes_left = 1;
          codepoint = c & 0x1f;
        } else if ((c & 0xf0) == 0xe0) {  // 3 byte utf8 sequence
          num_bytes_left = 2;
          codepoint = c & 0x0f;
        } else if ((c & 0xf8) == 0xf0) {  // 4 byte utf8 sequence
          codepoint = c & 0x07;
          num_bytes_left = 3;
        } else {
          return false;  // invalid leading byte
        }

        // If we have enough bytes in our inpput, decode the remaining ones
        // belonging to this Unicode character into |codepoint|.
        if (start + num_bytes_left > end)
          return false;
        while (num_bytes_left > 0) {
          c = *start++;
          --num_bytes_left;
          // Check the next byte is a continuation byte, that is 10xx xxxx.
          if ((c & 0xc0) != 0x80)
            return false;
          codepoint = (codepoint << 6) | (c & 0x3f);
        }

        // Disallow overlong encodings for ascii characters, as these
        // would include " and other characters significant to JSON
        // string termination / control.
        if (codepoint <= 0x7f)
          return false;
        // Invalid in UTF8, and can't be represented in UTF16 anyway.
        if (codepoint > 0x10ffff)
          return false;

        // So, now we transcode to UTF16,
        // using the math described at https://en.wikipedia.org/wiki/UTF-16,
        // for either one or two 16 bit characters.
773
        if (codepoint <= 0xffff) {
774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981
          output->push_back(codepoint);
          continue;
        }
        codepoint -= 0x10000;
        output->push_back((codepoint >> 10) + 0xd800);    // high surrogate
        output->push_back((codepoint & 0x3ff) + 0xdc00);  // low surrogate
        continue;
      }
      if ('\\' != c) {
        output->push_back(c);
        continue;
      }
      if (start == end)
        return false;
      c = *start++;

      if (c == 'x') {
        // \x is not supported.
        return false;
      }

      switch (c) {
        case '"':
        case '/':
        case '\\':
          break;
        case 'b':
          c = '\b';
          break;
        case 'f':
          c = '\f';
          break;
        case 'n':
          c = '\n';
          break;
        case 'r':
          c = '\r';
          break;
        case 't':
          c = '\t';
          break;
        case 'v':
          c = '\v';
          break;
        case 'u':
          c = (HexToInt(*start) << 12) + (HexToInt(*(start + 1)) << 8) +
              (HexToInt(*(start + 2)) << 4) + HexToInt(*(start + 3));
          start += 4;
          break;
        default:
          return false;
      }
      output->push_back(c);
    }
    return true;
  }

  void ParseValue(const Char* start,
                  const Char* end,
                  const Char** value_token_end,
                  int depth) {
    if (depth > kStackLimit) {
      HandleError(Error::JSON_PARSER_STACK_LIMIT_EXCEEDED, start);
      return;
    }
    const Char* token_start = nullptr;
    const Char* token_end = nullptr;
    Token token = ParseToken(start, end, &token_start, &token_end);
    switch (token) {
      case NoInput:
        HandleError(Error::JSON_PARSER_NO_INPUT, token_start);
        return;
      case InvalidToken:
        HandleError(Error::JSON_PARSER_INVALID_TOKEN, token_start);
        return;
      case NullToken:
        handler_->HandleNull();
        break;
      case BoolTrue:
        handler_->HandleBool(true);
        break;
      case BoolFalse:
        handler_->HandleBool(false);
        break;
      case Number: {
        double value;
        if (!CharsToDouble(token_start, token_end - token_start, &value)) {
          HandleError(Error::JSON_PARSER_INVALID_NUMBER, token_start);
          return;
        }
        if (value >= std::numeric_limits<int32_t>::min() &&
            value <= std::numeric_limits<int32_t>::max() &&
            static_cast<int32_t>(value) == value)
          handler_->HandleInt32(static_cast<int32_t>(value));
        else
          handler_->HandleDouble(value);
        break;
      }
      case StringLiteral: {
        std::vector<uint16_t> value;
        bool ok = DecodeString(token_start + 1, token_end - 1, &value);
        if (!ok) {
          HandleError(Error::JSON_PARSER_INVALID_STRING, token_start);
          return;
        }
        handler_->HandleString16(span<uint16_t>(value.data(), value.size()));
        break;
      }
      case ArrayBegin: {
        handler_->HandleArrayBegin();
        start = token_end;
        token = ParseToken(start, end, &token_start, &token_end);
        while (token != ArrayEnd) {
          ParseValue(start, end, &token_end, depth + 1);
          if (error_)
            return;

          // After a list value, we expect a comma or the end of the list.
          start = token_end;
          token = ParseToken(start, end, &token_start, &token_end);
          if (token == ListSeparator) {
            start = token_end;
            token = ParseToken(start, end, &token_start, &token_end);
            if (token == ArrayEnd) {
              HandleError(Error::JSON_PARSER_UNEXPECTED_ARRAY_END, token_start);
              return;
            }
          } else if (token != ArrayEnd) {
            // Unexpected value after list value. Bail out.
            HandleError(Error::JSON_PARSER_COMMA_OR_ARRAY_END_EXPECTED,
                        token_start);
            return;
          }
        }
        handler_->HandleArrayEnd();
        break;
      }
      case ObjectBegin: {
        handler_->HandleMapBegin();
        start = token_end;
        token = ParseToken(start, end, &token_start, &token_end);
        while (token != ObjectEnd) {
          if (token != StringLiteral) {
            HandleError(Error::JSON_PARSER_STRING_LITERAL_EXPECTED,
                        token_start);
            return;
          }
          std::vector<uint16_t> key;
          if (!DecodeString(token_start + 1, token_end - 1, &key)) {
            HandleError(Error::JSON_PARSER_INVALID_STRING, token_start);
            return;
          }
          handler_->HandleString16(span<uint16_t>(key.data(), key.size()));
          start = token_end;

          token = ParseToken(start, end, &token_start, &token_end);
          if (token != ObjectPairSeparator) {
            HandleError(Error::JSON_PARSER_COLON_EXPECTED, token_start);
            return;
          }
          start = token_end;

          ParseValue(start, end, &token_end, depth + 1);
          if (error_)
            return;
          start = token_end;

          // After a key/value pair, we expect a comma or the end of the
          // object.
          token = ParseToken(start, end, &token_start, &token_end);
          if (token == ListSeparator) {
            start = token_end;
            token = ParseToken(start, end, &token_start, &token_end);
            if (token == ObjectEnd) {
              HandleError(Error::JSON_PARSER_UNEXPECTED_MAP_END, token_start);
              return;
            }
          } else if (token != ObjectEnd) {
            // Unexpected value after last object value. Bail out.
            HandleError(Error::JSON_PARSER_COMMA_OR_MAP_END_EXPECTED,
                        token_start);
            return;
          }
        }
        handler_->HandleMapEnd();
        break;
      }

      default:
        // We got a token that's not a value.
        HandleError(Error::JSON_PARSER_VALUE_EXPECTED, token_start);
        return;
    }

    SkipWhitespaceAndComments(token_end, end, value_token_end);
  }

  void HandleError(Error error, const Char* pos) {
    assert(error != Error::OK);
    if (!error_) {
      handler_->HandleError(
          Status{error, static_cast<size_t>(pos - start_pos_)});
      error_ = true;
    }
  }

  const Char* start_pos_ = nullptr;
  bool error_ = false;
982
  ParserHandler* handler_;
983 984 985
};
}  // namespace

986 987
void ParseJSON(span<uint8_t> chars, ParserHandler* handler) {
  JsonParser<uint8_t> parser(handler);
988 989 990
  parser.Parse(chars.data(), chars.size());
}

991 992
void ParseJSON(span<uint16_t> chars, ParserHandler* handler) {
  JsonParser<uint16_t> parser(handler);
993 994 995 996 997 998 999
  parser.Parse(chars.data(), chars.size());
}

// =============================================================================
// json::ConvertCBORToJSON, json::ConvertJSONToCBOR - for transcoding
// =============================================================================
template <typename C>
1000
Status ConvertCBORToJSONTmpl(span<uint8_t> cbor, C* json) {
1001
  Status status;
1002
  std::unique_ptr<ParserHandler> json_writer = NewJSONEncoder(json, &status);
1003 1004 1005 1006
  cbor::ParseCBOR(cbor, json_writer.get());
  return status;
}

1007 1008
Status ConvertCBORToJSON(span<uint8_t> cbor, std::vector<uint8_t>* json) {
  return ConvertCBORToJSONTmpl(cbor, json);
1009 1010
}

1011 1012
Status ConvertCBORToJSON(span<uint8_t> cbor, std::string* json) {
  return ConvertCBORToJSONTmpl(cbor, json);
1013 1014
}

1015 1016
template <typename T>
Status ConvertJSONToCBORTmpl(span<T> json, std::vector<uint8_t>* cbor) {
1017
  Status status;
1018
  std::unique_ptr<ParserHandler> encoder = cbor::NewCBOREncoder(cbor, &status);
1019
  ParseJSON(json, encoder.get());
1020 1021 1022
  return status;
}

1023 1024
Status ConvertJSONToCBOR(span<uint8_t> json, std::vector<uint8_t>* cbor) {
  return ConvertJSONToCBORTmpl(json, cbor);
1025 1026
}

1027 1028
Status ConvertJSONToCBOR(span<uint16_t> json, std::vector<uint8_t>* cbor) {
  return ConvertJSONToCBORTmpl(json, cbor);
1029 1030 1031
}
}  // namespace json
}  // namespace v8_crdtp