serialization-inl.h

 
#ifndef SIMDJSON_SERIALIZATION_INL_H
#define SIMDJSON_SERIALIZATION_INL_H
 
#include "simdjson/dom/serialization.h"
 
#include <cinttypes>
#include <type_traits>
 
namespace simdjson {
namespace dom {
inline bool parser::print_json(std::ostream &os) const noexcept {
  if (!valid) { return false; }
  simdjson::internal::string_builder<> sb;
  sb.append(doc.root());
  std::string_view answer = sb.str();
  os << answer;
  return true;
}
}
/***
 * Number utility functions
 **/
 
 
namespace {
struct escape_sequence {
    uint8_t length;
    const char string[7]; // technically, we only ever need 6 characters, we pad to 8
};
char *fast_itoa(char *output, int64_t value) noexcept {
  // This is a standard implementation of itoa.
  char buffer[20];
  uint64_t value_positive;
  // In general, negating a signed integer is unsafe.
  if(value < 0) {
    *output++ = '-';
    // Doing value_positive = -value; while avoiding
    // undefined behavior warnings.
    // It assumes two complement's which is universal at this
    // point in time.
    std::memcpy(&value_positive, &value, sizeof(value));
    value_positive = (~value_positive) + 1; // this is a negation
  } else {
    value_positive = value;
  }
  // We work solely with value_positive. It *might* be easier
  // for an optimizing compiler to deal with an unsigned variable
  // as far as performance goes.
  const char *const end_buffer = buffer + 20;
  char *write_pointer = buffer + 19;
  // A faster approach is possible if we expect large integers:
  // unroll the loop (work in 100s, 1000s) and use some kind of
  // memoization.
  while(value_positive >= 10) {
    *write_pointer-- = char('0' + (value_positive % 10));
    value_positive /= 10;
  }
  *write_pointer = char('0' + value_positive);
  size_t len = end_buffer - write_pointer;
  std::memcpy(output, write_pointer, len);
  return output + len;
}
char *fast_itoa(char *output, uint64_t value) noexcept {
  // This is a standard implementation of itoa.
  char buffer[20];
  const char *const end_buffer = buffer + 20;
  char *write_pointer = buffer + 19;
  // A faster approach is possible if we expect large integers:
  // unroll the loop (work in 100s, 1000s) and use some kind of
  // memoization.
  while(value >= 10) {
    *write_pointer-- = char('0' + (value % 10));
    value /= 10;
  };
  *write_pointer = char('0' + value);
  size_t len = end_buffer - write_pointer;
  std::memcpy(output, write_pointer, len);
  return output + len;
}
} // anonymous namespace
namespace internal {
 
/***
 * Minifier/formatter code.
 **/
 
simdjson_inline void mini_formatter::number(uint64_t x) {
  char number_buffer[24];
  char *newp = fast_itoa(number_buffer, x);
  buffer.insert(buffer.end(), number_buffer, newp);
}
 
simdjson_inline void mini_formatter::number(int64_t x) {
  char number_buffer[24];
  char *newp = fast_itoa(number_buffer, x);
  buffer.insert(buffer.end(), number_buffer, newp);
}
 
simdjson_inline void mini_formatter::number(double x) {
  char number_buffer[24];
  // Currently, passing the nullptr to the second argument is
  // safe because our implementation does not check the second
  // argument.
  char *newp = internal::to_chars(number_buffer, nullptr, x);
  buffer.insert(buffer.end(), number_buffer, newp);
}
 
simdjson_inline void mini_formatter::start_array() { one_char('['); }
simdjson_inline void mini_formatter::end_array() { one_char(']'); }
simdjson_inline void mini_formatter::start_object() { one_char('{'); }
simdjson_inline void mini_formatter::end_object() { one_char('}'); }
simdjson_inline void mini_formatter::comma() { one_char(','); }
 
 
simdjson_inline void mini_formatter::true_atom() {
  const char * s = "true";
  buffer.insert(buffer.end(), s, s + 4);
}
simdjson_inline void mini_formatter::false_atom() {
  const char * s = "false";
  buffer.insert(buffer.end(), s, s + 5);
}
simdjson_inline void mini_formatter::null_atom() {
  const char * s = "null";
  buffer.insert(buffer.end(), s, s + 4);
}
simdjson_inline void mini_formatter::one_char(char c) { buffer.push_back(c); }
simdjson_inline void mini_formatter::key(std::string_view unescaped) {
  string(unescaped);
  one_char(':');
}
simdjson_inline void mini_formatter::string(std::string_view unescaped) {
  one_char('\"');
  size_t i = 0;
  // Fast path for the case where we have no control character, no ", and no backslash.
  // This should include most keys.
  //
  // We would like to use 'bool' but some compilers take offense to bitwise operation
  // with bool types.
  constexpr static char needs_escaping[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
  for(;i + 8 <= unescaped.length(); i += 8) {
    // Poor's man vectorization. This could get much faster if we used SIMD.
    //
    // It is not the case that replacing '|' with '||' would be neutral performance-wise.
    if(needs_escaping[uint8_t(unescaped[i])] | needs_escaping[uint8_t(unescaped[i+1])]
      | needs_escaping[uint8_t(unescaped[i+2])] | needs_escaping[uint8_t(unescaped[i+3])]
      | needs_escaping[uint8_t(unescaped[i+4])] | needs_escaping[uint8_t(unescaped[i+5])]
      | needs_escaping[uint8_t(unescaped[i+6])] | needs_escaping[uint8_t(unescaped[i+7])]
      ) { break; }
  }
  for(;i < unescaped.length(); i++) {
    if(needs_escaping[uint8_t(unescaped[i])]) { break; }
  }
  // The following is also possible and omits a 256-byte table, but it is slower:
  // for (; (i < unescaped.length()) && (uint8_t(unescaped[i]) > 0x1F)
  //      && (unescaped[i] != '\"') && (unescaped[i] != '\\'); i++) {}
 
  // At least for long strings, the following should be fast. We could
  // do better by integrating the checks and the insertion.
  buffer.insert(buffer.end(), unescaped.data(), unescaped.data() + i);
  // We caught a control character if we enter this loop (slow).
  // Note that we are do not restart from the beginning, but rather we continue
  // from the point where we encountered something that requires escaping.
  for (; i < unescaped.length(); i++) {
    switch (unescaped[i]) {
    case '\"':
      {
        const char * s = "\\\"";
        buffer.insert(buffer.end(), s, s + 2);
      }
      break;
    case '\\':
      {
        const char * s = "\\\\";
        buffer.insert(buffer.end(), s, s + 2);
      }
      break;
    default:
      if (uint8_t(unescaped[i]) <= 0x1F) {
        // If packed, this uses 8 * 32 bytes.
        // Note that we expect most compilers to embed this code in the data
        // section.
        constexpr static escape_sequence escaped[32] = {
          {6, "\\u0000"}, {6, "\\u0001"}, {6, "\\u0002"}, {6, "\\u0003"},
          {6, "\\u0004"}, {6, "\\u0005"}, {6, "\\u0006"}, {6, "\\u0007"},
          {2, "\\b"},     {2, "\\t"},     {2, "\\n"},     {6, "\\u000b"},
          {2, "\\f"},     {2, "\\r"},     {6, "\\u000e"}, {6, "\\u000f"},
          {6, "\\u0010"}, {6, "\\u0011"}, {6, "\\u0012"}, {6, "\\u0013"},
          {6, "\\u0014"}, {6, "\\u0015"}, {6, "\\u0016"}, {6, "\\u0017"},
          {6, "\\u0018"}, {6, "\\u0019"}, {6, "\\u001a"}, {6, "\\u001b"},
          {6, "\\u001c"}, {6, "\\u001d"}, {6, "\\u001e"}, {6, "\\u001f"}};
        auto u = escaped[uint8_t(unescaped[i])];
        buffer.insert(buffer.end(), u.string, u.string + u.length);
      } else {
        one_char(unescaped[i]);
      }
    } // switch
  }   // for
  one_char('\"');
}
 
inline void mini_formatter::clear() {
  buffer.clear();
}
 
simdjson_inline std::string_view mini_formatter::str() const {
  return std::string_view(buffer.data(), buffer.size());
}
 
 
/***
 * String building code.
 **/
 
template <class serializer>
inline void string_builder<serializer>::append(simdjson::dom::element value) {
  // using tape_type = simdjson::internal::tape_type;
  size_t depth = 0;
  constexpr size_t MAX_DEPTH = 16;
  bool is_object[MAX_DEPTH];
  is_object[0] = false;
  bool after_value = false;
 
  internal::tape_ref iter(value.tape);
  do {
    // print commas after each value
    if (after_value) {
      format.comma();
    }
    // If we are in an object, print the next key and :, and skip to the next
    // value.
    if (is_object[depth]) {
      format.key(iter.get_string_view());
      iter.json_index++;
    }
    switch (iter.tape_ref_type()) {
 
    // Arrays
    case tape_type::START_ARRAY: {
      // If we're too deep, we need to recurse to go deeper.
      depth++;
      if (simdjson_unlikely(depth >= MAX_DEPTH)) {
        append(simdjson::dom::array(iter));
        iter.json_index = iter.matching_brace_index() - 1; // Jump to the ]
        depth--;
        break;
      }
 
      // Output start [
      format.start_array();
      iter.json_index++;
 
      // Handle empty [] (we don't want to come back around and print commas)
      if (iter.tape_ref_type() == tape_type::END_ARRAY) {
        format.end_array();
        depth--;
        break;
      }
 
      is_object[depth] = false;
      after_value = false;
      continue;
    }
 
    // Objects
    case tape_type::START_OBJECT: {
      // If we're too deep, we need to recurse to go deeper.
      depth++;
      if (simdjson_unlikely(depth >= MAX_DEPTH)) {
        append(simdjson::dom::object(iter));
        iter.json_index = iter.matching_brace_index() - 1; // Jump to the }
        depth--;
        break;
      }
 
      // Output start {
      format.start_object();
      iter.json_index++;
 
      // Handle empty {} (we don't want to come back around and print commas)
      if (iter.tape_ref_type() == tape_type::END_OBJECT) {
        format.end_object();
        depth--;
        break;
      }
 
      is_object[depth] = true;
      after_value = false;
      continue;
    }
 
    // Scalars
    case tape_type::STRING:
      format.string(iter.get_string_view());
      break;
    case tape_type::INT64:
      format.number(iter.next_tape_value<int64_t>());
      iter.json_index++; // numbers take up 2 spots, so we need to increment
                         // extra
      break;
    case tape_type::UINT64:
      format.number(iter.next_tape_value<uint64_t>());
      iter.json_index++; // numbers take up 2 spots, so we need to increment
                         // extra
      break;
    case tape_type::DOUBLE:
      format.number(iter.next_tape_value<double>());
      iter.json_index++; // numbers take up 2 spots, so we need to increment
                         // extra
      break;
    case tape_type::TRUE_VALUE:
      format.true_atom();
      break;
    case tape_type::FALSE_VALUE:
      format.false_atom();
      break;
    case tape_type::NULL_VALUE:
      format.null_atom();
      break;
 
    // These are impossible
    case tape_type::END_ARRAY:
    case tape_type::END_OBJECT:
    case tape_type::ROOT:
      SIMDJSON_UNREACHABLE();
    }
    iter.json_index++;
    after_value = true;
 
    // Handle multiple ends in a row
    while (depth != 0 && (iter.tape_ref_type() == tape_type::END_ARRAY ||
                          iter.tape_ref_type() == tape_type::END_OBJECT)) {
      if (iter.tape_ref_type() == tape_type::END_ARRAY) {
        format.end_array();
      } else {
        format.end_object();
      }
      depth--;
      iter.json_index++;
    }
 
    // Stop when we're at depth 0
  } while (depth != 0);
}
 
template <class serializer>
inline void string_builder<serializer>::append(simdjson::dom::object value) {
  format.start_object();
  auto pair = value.begin();
  auto end = value.end();
  if (pair != end) {
    append(*pair);
    for (++pair; pair != end; ++pair) {
      format.comma();
      append(*pair);
    }
  }
  format.end_object();
}
 
template <class serializer>
inline void string_builder<serializer>::append(simdjson::dom::array value) {
  format.start_array();
  auto iter = value.begin();
  auto end = value.end();
  if (iter != end) {
    append(*iter);
    for (++iter; iter != end; ++iter) {
      format.comma();
      append(*iter);
    }
  }
  format.end_array();
}
 
template <class serializer>
simdjson_inline void string_builder<serializer>::append(simdjson::dom::key_value_pair kv) {
  format.key(kv.key);
  append(kv.value);
}
 
template <class serializer>
simdjson_inline void string_builder<serializer>::clear() {
  format.clear();
}
 
template <class serializer>
simdjson_inline std::string_view string_builder<serializer>::str() const {
  return format.str();
}
 
 
} // namespace internal
} // namespace simdjson
 
#endif