simdjson-simdjson/include/simdjson/document/parser.h

#ifndef SIMDJSON_DOCUMENT_PARSER_H
#define SIMDJSON_DOCUMENT_PARSER_H

#include <cstring>
#include <memory>
#include "simdjson/common_defs.h"
#include "simdjson/simdjson.h"
#include "simdjson/document.h"
#include "simdjson/padded_string.h"

namespace simdjson {

class document::parser {
public:
  //
  // Create a JSON parser with zero capacity. Call allocate_capacity() to initialize it.
  //
  parser()=default;
  ~parser()=default;

  // this is a move only class
  parser(parser &&p) = default;
  parser(const parser &p) = delete;
  parser &operator=(parser &&o) = default;
  parser &operator=(const parser &o) = delete;

  //
  // Parse a JSON document and return a reference to it.
  //
  // The JSON document still lives in the parser: this is the most efficient way to parse JSON
  // documents because it reuses the same buffers, but you *must* use the document before you
  // destroy the parser or call parse() again.
  //
  // Throws invalid_json if the JSON is invalid.
  //
  const document &parse(const uint8_t *buf, size_t len, bool realloc_if_needed = true);
  const document &parse(const char *buf, size_t len, bool realloc_if_needed = true) {
    return parse((const uint8_t *)buf, len, realloc_if_needed);
  }
  const document &parse(const std::string &s, bool realloc_if_needed = true) {
    return parse(s.data(), s.length(), realloc_if_needed);
  }
  const document &parse(const padded_string &s) {
    return parse(s.data(), s.length(), false);
  }

  //
  // Parse a JSON document and take the result.
  //
  // The document can be used even after the parser is deallocated or parse() is called again.
  //
  // Throws invalid_json if the JSON is invalid.
  //
  document parse_new(const uint8_t *buf, size_t len, bool realloc_if_needed = true);
  document parse_new(const char *buf, size_t len, bool realloc_if_needed = true) {
    return parse_new((const uint8_t *)buf, len, realloc_if_needed);
  }
  document parse_new(const std::string &s, bool realloc_if_needed = true) {
    return parse_new(s.data(), s.length(), realloc_if_needed);
  }
  document parse_new(const padded_string &s) {
    return parse_new(s.data(), s.length(), false);
  }

  //
  // Parse a JSON document and set doc to a pointer to it.
  //
  // The JSON document still lives in the parser: this is the most efficient way to parse JSON
  // documents because it reuses the same buffers, but you *must* use the document before you
  // destroy the parser or call parse() again.
  //
  // Returns != SUCCESS if the JSON is invalid.
  //
  WARN_UNUSED ErrorValues try_parse(const uint8_t *buf, size_t len, const document *& dst, bool realloc_if_needed = true) noexcept;
  WARN_UNUSED ErrorValues try_parse(const char *buf, size_t len, const document *& dst, bool realloc_if_needed = true) noexcept {
    return try_parse((const uint8_t *)buf, len, dst, realloc_if_needed);
  }
  WARN_UNUSED ErrorValues try_parse(const std::string &s, const document *&dst, bool realloc_if_needed = true) noexcept {
    return try_parse(s.data(), s.length(), dst, realloc_if_needed);
  }
  WARN_UNUSED ErrorValues try_parse(const padded_string &s, const document *&dst) noexcept {
    return try_parse(s.data(), s.length(), dst, false);
  }

  //
  // Parse a JSON document and fill in dst.
  //
  // The document can be used even after the parser is deallocated or parse() is called again.
  //
  // Returns != SUCCESS if the JSON is invalid.
  //
  WARN_UNUSED ErrorValues try_parse_into(const uint8_t *buf, size_t len, document &dst, bool realloc_if_needed = true) noexcept;
  WARN_UNUSED ErrorValues try_parse_into(const char *buf, size_t len, document &dst, bool realloc_if_needed = true) noexcept {
    return try_parse_into((const uint8_t *)buf, len, dst, realloc_if_needed);
  }
  WARN_UNUSED ErrorValues try_parse_into(const std::string &s, document &dst, bool realloc_if_needed = true) noexcept {
    return try_parse_into(s.data(), s.length(), dst, realloc_if_needed);
  }
  WARN_UNUSED ErrorValues try_parse_into(const padded_string &s, document &dst) noexcept {
    return try_parse_into(s.data(), s.length(), dst, false);
  }

  //
  // Current capacity: the largest document this parser can support without reallocating.
  //
  size_t capacity() {
    return _capacity;
  }

  //
  // The maximum level of nested object and arrays supported by this parser.
  //
  size_t max_depth() {
    return _max_depth;
  }

  // if needed, allocate memory so that the object is able to process JSON
  // documents having up to capacity bytes and max_depth "depth"
  WARN_UNUSED bool allocate_capacity(size_t capacity, size_t max_depth = DEFAULT_MAX_DEPTH) {
    return set_capacity(capacity) && set_max_depth(max_depth);
  }

  // type aliases for backcompat
  using Iterator = document::iterator;
  using InvalidJSON = invalid_json;

  // Next location to write to in the tape
  uint32_t current_loc{0};

  // structural indices passed from stage 1 to stage 2
  uint32_t n_structural_indexes{0};
  std::unique_ptr<uint32_t[]> structural_indexes;

  // location and return address of each open { or [
  std::unique_ptr<uint32_t[]> containing_scope_offset;
#ifdef SIMDJSON_USE_COMPUTED_GOTO
  std::unique_ptr<void*[]> ret_address;
#else
  std::unique_ptr<char[]> ret_address;
#endif

  // Next place to write a string
  uint8_t *current_string_buf_loc;

  bool valid{false};
  int error_code{simdjson::UNINITIALIZED};

  // Document we're writing to
  document doc;

  // returns true if the document parsed was valid
  bool is_valid() const;

  // return an error code corresponding to the last parsing attempt, see
  // simdjson.h will return simdjson::UNITIALIZED if no parsing was attempted
  int get_error_code() const;

  // return the string equivalent of "get_error_code"
  std::string get_error_message() const;

  //
  // for backcompat with ParsedJson
  //

  // print the json to std::ostream (should be valid)
  // return false if the tape is likely wrong (e.g., you did not parse a valid
  // JSON).
  WARN_UNUSED
  bool print_json(std::ostream &os) const;
  WARN_UNUSED
  bool dump_raw_tape(std::ostream &os) const;

  // this should be called when parsing (right before writing the tapes)
  void init_stage2();

  really_inline ErrorValues on_error(ErrorValues new_error_code) {
    error_code = new_error_code;
    return new_error_code;
  }
  really_inline ErrorValues on_success(ErrorValues success_code) {
    error_code = success_code;
    valid = true;
    return success_code;
  }
  really_inline bool on_start_document(uint32_t depth) {
    containing_scope_offset[depth] = current_loc;
    write_tape(0, 'r');
    return true;
  }
  really_inline bool on_start_object(uint32_t depth) {
    containing_scope_offset[depth] = current_loc;
    write_tape(0, '{');
    return true;
  }
  really_inline bool on_start_array(uint32_t depth) {
    containing_scope_offset[depth] = current_loc;
    write_tape(0, '[');
    return true;
  }
  // TODO we're not checking this bool
  really_inline bool on_end_document(uint32_t depth) {
    // write our doc.tape location to the header scope
    // The root scope gets written *at* the previous location.
    annotate_previous_loc(containing_scope_offset[depth], current_loc);
    write_tape(containing_scope_offset[depth], 'r');
    return true;
  }
  really_inline bool on_end_object(uint32_t depth) {
    // write our doc.tape location to the header scope
    write_tape(containing_scope_offset[depth], '}');
    annotate_previous_loc(containing_scope_offset[depth], current_loc);
    return true;
  }
  really_inline bool on_end_array(uint32_t depth) {
    // write our doc.tape location to the header scope
    write_tape(containing_scope_offset[depth], ']');
    annotate_previous_loc(containing_scope_offset[depth], current_loc);
    return true;
  }

  really_inline bool on_true_atom() {
    write_tape(0, 't');
    return true;
  }
  really_inline bool on_false_atom() {
    write_tape(0, 'f');
    return true;
  }
  really_inline bool on_null_atom() {
    write_tape(0, 'n');
    return true;
  }

  really_inline uint8_t *on_start_string() {
    /* we advance the point, accounting for the fact that we have a NULL
      * termination         */
    write_tape(current_string_buf_loc - doc.string_buf.get(), '"');
    return current_string_buf_loc + sizeof(uint32_t);
  }

  really_inline bool on_end_string(uint8_t *dst) {
    uint32_t str_length = dst - (current_string_buf_loc + sizeof(uint32_t));
    // TODO check for overflow in case someone has a crazy string (>=4GB?)
    // But only add the overflow check when the document itself exceeds 4GB
    // Currently unneeded because we refuse to parse docs larger or equal to 4GB.
    memcpy(current_string_buf_loc, &str_length, sizeof(uint32_t));
    // NULL termination is still handy if you expect all your strings to
    // be NULL terminated? It comes at a small cost
    *dst = 0;
    current_string_buf_loc = dst + 1;
    return true;
  }

  really_inline bool on_number_s64(int64_t value) {
    write_tape(0, 'l');
    std::memcpy(&doc.tape[current_loc], &value, sizeof(value));
    ++current_loc;
    return true;
  }
  really_inline bool on_number_u64(uint64_t value) {
    write_tape(0, 'u');
    doc.tape[current_loc++] = value;
    return true;
  }
  really_inline bool on_number_double(double value) {
    write_tape(0, 'd');
    static_assert(sizeof(value) == sizeof(doc.tape[current_loc]), "mismatch size");
    memcpy(&doc.tape[current_loc++], &value, sizeof(double));
    // doc.tape[doc.current_loc++] = *((uint64_t *)&d);
    return true;
  }

  //
  // Called before a parse is initiated.
  //
  // - Returns CAPACITY if the document is too large
  // - Returns MEMALLOC if we needed to allocate memory and could not
  //
  WARN_UNUSED ErrorValues init_parse(size_t len);

  const document &get_document() const {
    if (!is_valid()) {
      throw invalid_json(ErrorValues(error_code));
    }
    return doc;
  }

private:
  //
  // The maximum document length this parser supports.
  //
  // Buffers are large enough to handle any document up to this length.
  //
  size_t _capacity{0};

  //
  // The maximum depth (number of nested objects and arrays) supported by this parser.
  //
  // Defaults to DEFAULT_MAX_DEPTH.
  //
  size_t _max_depth{0};

  // all nodes are stored on the doc.tape using a 64-bit word.
  //
  // strings, double and ints are stored as
  //  a 64-bit word with a pointer to the actual value
  //
  //
  //
  // for objects or arrays, store [ or {  at the beginning and } and ] at the
  // end. For the openings ([ or {), we annotate them with a reference to the
  // location on the doc.tape of the end, and for then closings (} and ]), we
  // annotate them with a reference to the location of the opening
  //
  //

  // this should be considered a private function
  really_inline void write_tape(uint64_t val, uint8_t c) {
    doc.tape[current_loc++] = val | ((static_cast<uint64_t>(c)) << 56);
  }

  really_inline void annotate_previous_loc(uint32_t saved_loc, uint64_t val) {
    doc.tape[saved_loc] |= val;
  }

  WARN_UNUSED ErrorValues try_parse(const uint8_t *buf, size_t len, bool realloc_if_needed) noexcept;

  //
  // Set the current capacity: the largest document this parser can support without reallocating.
  //
  // This will allocate *or deallocate* as necessary.
  //
  // Returns false if allocation fails.
  //
  WARN_UNUSED bool set_capacity(size_t capacity);

  //
  // Set the maximum level of nested object and arrays supported by this parser.
  //
  // This will allocate *or deallocate* as necessary.
  //
  // Returns false if allocation fails.
  //
  WARN_UNUSED bool set_max_depth(size_t max_depth);
};

} // namespace simdjson

#endif // SIMDJSON_DOCUMENT_PARSER_H