ascii_parser_policy.hpp

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/*
   This file is part of PLYwoot, a header-only PLY parser.
 
   Copyright (C) 2023-2025, Ton van den Heuvel
 
   PLYwoot is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#ifndef PLYWOOT_ASCII_PARSER_POLICY_HPP
#define PLYWOOT_ASCII_PARSER_POLICY_HPP
 
 
#include "buffered_istream.hpp"
#include "exceptions.hpp"
#include "reflect.hpp"
#include "std.hpp"
#include "types.hpp"
 
#include <cstdint>
#include <string>
 
namespace plywoot {
 
struct ParserException : Exception
{
  ParserException(const std::string &message) : Exception("parser error: " + message) {}
};
 
struct UnexpectedEof : ParserException
{
  UnexpectedEof() : ParserException("unexpected end of file") {}
};
 
namespace detail {
 
class AsciiParserPolicy
{
public:
  AsciiParserPolicy(std::istream &is) : is_{is} {}
 
  void skipElement(const PlyElement &e) const { is_.skipLines(e.size()); }
 
  void skipProperty(const PlyProperty &p) const
  {
    if (p.isList())
    {
      // TODO(ton): maybe switch on the list size type...?
      const auto size = readNumber<int>();
      for (int i = 0; i < size; ++i) { skipNumber(); }
    }
    else { skipNumber(); }
  }
 
  template<typename T>
  T readNumber() const
  {
    is_.skipWhitespace();
    if (is_.eof()) { throw UnexpectedEof(); }
 
    is_.buffer(256);
    return detail::to_number<T>(is_.data(), is_.data() + 256, &is_.data());
  }
 
  template<typename PlyT, typename DestT, std::size_t N>
  std::uint8_t *readNumbers(std::uint8_t *dest) const
  {
    // TODO(ton): needs to be specialized for improved performance.
    for (std::size_t i = 0; i < N; ++i, dest += sizeof(DestT))
    {
      *reinterpret_cast<DestT *>(dest) = readNumber<PlyT>();
    }
    return dest;
  }
 
  template<typename T = void>
  void skipNumber() const
  {
    is_.skipWhitespace();
    is_.skipNonWhitespace();
  }
 
  void skipProperties(std::size_t n) const
  {
    if (n > 0) is_.skipLines(1);
  }
 
private:
  mutable detail::BufferedIStream is_;
};
 
}
}
 
#endif