daw_json_parse_policy_no_comments.h

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// Copyright (c) Darrell Wright
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/beached/daw_json_link
//
 
#pragma once
 
#include "daw/json/impl/version.h"
 
#include "daw/json/impl/daw_json_assert.h"
#include "daw/json/impl/daw_json_parse_common.h"
#include "daw/json/impl/daw_json_parse_policy_policy_details.h"
#include "daw/json/impl/daw_json_string_util.h"
#include "daw/json/impl/daw_not_const_ex_functions.h"
 
#include <daw/daw_attributes.h>
#include <daw/daw_constant.h>
#include <daw/daw_function_table.h>
#include <daw/daw_likely.h>
#include <daw/daw_not_null.h>
#include <daw/daw_traits.h>
 
#include <cstddef>
#include <cstdint>
#include <type_traits>
 
namespace daw::json {
  inline namespace DAW_JSON_VER {
    struct NoCommentSkippingPolicy {
      template<typename ParseState>
      DAW_ATTRIB_FLATINLINE static constexpr void
      trim_left_checked( ParseState &parse_state ) {
        if constexpr( not ParseState::minified_document ) {
          // SIMD here was much slower, most JSON has very minimal whitespace
          auto first = daw::not_null<char const *>( parse_state.first );
          auto const last = daw::not_null<char const *>( parse_state.last );
 
          // only used when not zero terminated string and gcc9 warns
          (void)last;
 
          if constexpr( ParseState::is_zero_terminated_string ) {
            // Ensure that zero terminator isn't included in skipable value
            while( DAW_UNLIKELY(
              ( static_cast<unsigned>( static_cast<unsigned char>( *first ) ) -
                1U ) <= 0x1FU ) ) {
 
              ++first;
            }
          } else {
            while(
              DAW_LIKELY( first < last ) and
              ( static_cast<unsigned>( static_cast<unsigned char>( *first ) ) -
                1U ) <= 0x1FU ) {
              ++first;
            }
          }
          parse_state.first = first;
        }
      }
 
      template<typename ParseState>
      DAW_ATTRIB_FLATINLINE static constexpr void
      trim_left_unchecked( ParseState &parse_state ) {
        if constexpr( not ParseState::minified_document ) {
          auto first =
            daw::not_null<char const *>( daw::never_null, parse_state.first );
          while( DAW_UNLIKELY(
            ( static_cast<unsigned>( static_cast<unsigned char>( *first ) ) -
              1U ) <= 0x1F ) ) {
 
            ++first;
          }
          parse_state.first = first;
        }
      }
 
      template<typename ParseState>
      DAW_ATTRIB_FLATINLINE static constexpr void
      move_next_member_unchecked( ParseState &parse_state ) {
        auto pf = daw::not_null( daw::never_null, parse_state.first );
        auto pl = daw::not_null( daw::never_null, parse_state.last );
        parse_state.first =
          json_details::memchr_unchecked<'"',
                                         typename ParseState::exec_tag_t,
                                         ParseState::expect_long_strings>( pf,
                                                                           pl );
      }
 
      template<char... keys, typename ParseState>
      DAW_ATTRIB_FLATINLINE static constexpr void
      move_to_next_of( ParseState &parse_state ) {
        static_assert( sizeof...( keys ) > 0 );
        static_assert( sizeof...( keys ) <= 16 );
 
        if( not json_details::use_constexpr_exec_mode<
              typename ParseState::exec_tag_t>( ) ) {
          auto pf = daw::not_null<char const *>{ parse_state.first };
          auto pl = daw::not_null<char const *>{ parse_state.last };
          parse_state.first =
            json_details::mempbrk<ParseState::is_unchecked_input,
                                  typename ParseState::exec_tag_t,
                                  ParseState::expect_long_strings,
                                  keys...>( pf, pl );
        } else {
          auto first = daw::not_null<char const *>( parse_state.first );
          auto const last = daw::not_null<char const *>( parse_state.last );
 
          // silencing gcc9 unused warning.  last is used inside if constexpr
          // blocks
          (void)last;
 
          if( ParseState::is_zero_terminated_string ) {
            daw_json_assert_weak( first < last and *first != '\0',
                                  ErrorReason::UnexpectedEndOfData,
                                  parse_state );
            while( not parse_policy_details::in<keys...>( *first ) ) {
              ++first;
            }
            daw_json_assert_weak(
              *first != '\0', ErrorReason::UnexpectedEndOfData, parse_state );
          } else {
            daw_json_assert_weak(
              first < last, ErrorReason::UnexpectedEndOfData, parse_state );
            while( not parse_policy_details::in<keys...>( *first ) ) {
              ++first;
              daw_json_assert_weak(
                first < last, ErrorReason::UnexpectedEndOfData, parse_state );
            }
          }
          parse_state.first = first;
        }
      }
 
      DAW_ATTRIB_INLINE static constexpr bool is_literal_end( char c ) {
        return ( c == '\0' ) | ( c == ',' ) | ( c == ']' ) | ( c == '}' );
      }
 
      template<char PrimLeft, typename ParseState>
      DAW_ATTRIB_FLATTEN static constexpr ParseState
      skip_bracketed_item_checked( ParseState &parse_state ) {
        using PrimRight = daw::constant<PrimLeft == '{' ? '}' : ']'>;
        using SecLeft = daw::constant<PrimLeft == '{' ? '[' : '{'>;
        using SecRight = daw::constant<SecLeft::value == '{' ? '}' : ']'>;
 
        // Not checking for Left as it is required to be skipped already
        auto ptr_first = daw::not_null<char const *>( parse_state.first );
        auto const ptr_last = daw::not_null<char const *>( parse_state.last );
        if( DAW_UNLIKELY( ptr_first >= ptr_last ) ) {
          return parse_state;
        }
        auto result = parse_state;
        std::size_t cnt = 0;
        std::uint32_t prime_bracket_count = 1;
        std::uint32_t second_bracket_count = 0;
 
        if( *ptr_first == PrimLeft ) {
          ++ptr_first;
        }
        while( DAW_LIKELY( ptr_first < ptr_last ) ) {
          switch( *ptr_first ) {
          case '\\':
            ++ptr_first;
            break;
          case '"':
            ++ptr_first;
            ptr_first = json_details::mem_skip_until_end_of_string<
              ParseState::is_unchecked_input,
              typename ParseState::exec_tag_t>( ptr_first, ptr_last );
            daw_json_ensure( ptr_first < ptr_last and *ptr_first == '"',
                             ErrorReason::UnexpectedEndOfData,
                             parse_state );
            break;
          case ',':
            if( DAW_UNLIKELY( ( prime_bracket_count == 1 ) &
                              ( second_bracket_count == 0 ) ) ) {
              ++cnt;
            }
            break;
          case PrimLeft:
            ++prime_bracket_count;
            break;
          case PrimRight::value:
            --prime_bracket_count;
            if( prime_bracket_count == 0 ) {
              ++ptr_first;
              daw_json_ensure( second_bracket_count == 0,
                               ErrorReason::InvalidBracketing,
                               parse_state );
              result.last = ptr_first;
              result.counter = cnt;
              parse_state.first = ptr_first;
              return result;
            }
            break;
          case SecLeft::value:
            ++second_bracket_count;
            break;
          case SecRight::value:
            --second_bracket_count;
            break;
          }
          ++ptr_first;
        }
        daw_json_ensure( ( prime_bracket_count == 0 ) &
                           ( second_bracket_count == 0 ),
                         ErrorReason::InvalidBracketing,
                         parse_state );
        // We include the close primary bracket in the range so that subsequent
        // parsers have a terminator inside their range
        result.last = ptr_first;
        result.counter = cnt;
        parse_state.first = ptr_first;
        return result;
      }
 
      template<char PrimLeft, typename ParseState>
      DAW_ATTRIB_NOINLINE static constexpr ParseState
      skip_bracketed_item_unchecked( ParseState &parse_state ) {
        // Not checking for Left as it is required to be skipped already
        using PrimRight = daw::constant<PrimLeft == '{' ? '}' : ']'>;
        using SecLeft = daw::constant<PrimLeft == '{' ? '[' : '{'>;
        using SecRight = daw::constant<SecLeft::value == '{' ? '}' : ']'>;
 
        auto result = parse_state;
        std::size_t cnt = 0;
        std::uint32_t prime_bracket_count = 1;
        std::uint32_t second_bracket_count = 0;
        auto ptr_first = daw::not_null<char const *>( parse_state.first );
        auto const ptr_last = daw::not_null<char const *>( parse_state.last );
 
        if( *ptr_first == PrimLeft ) {
          ++ptr_first;
        }
        while( true ) {
          switch( *ptr_first ) {
          case '\\':
            ++ptr_first;
            break;
          case '"':
            ++ptr_first;
            ptr_first = json_details::mem_skip_until_end_of_string<
              ParseState::is_unchecked_input,
              typename ParseState::exec_tag_t>( ptr_first, ptr_last );
            break;
          case ',':
            if( DAW_UNLIKELY( ( prime_bracket_count == 1 ) &
                              ( second_bracket_count == 0 ) ) ) {
              ++cnt;
            }
            break;
          case PrimLeft:
            ++prime_bracket_count;
            break;
          case PrimRight::value:
            --prime_bracket_count;
            if( prime_bracket_count == 0 ) {
              ++ptr_first;
              // We include the close primary bracket in the range so that
              // subsequent parsers have a terminator inside their range
              result.last = ptr_first;
              result.counter = cnt;
              parse_state.first = ptr_first;
              return result;
            }
            break;
          case SecLeft::value:
            ++second_bracket_count;
            break;
          case SecRight::value:
            --second_bracket_count;
            break;
          }
          ++ptr_first;
        }
        // Should never get here, only loop exit is when PrimaryRight is found
        // and count == 0
        DAW_UNREACHABLE( );
      }
    };
  } // namespace DAW_JSON_VER
} // namespace daw::json