newgrf_bytereader.h

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/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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 OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#ifndef NEWGRF_BYTEREADER_H
#define NEWGRF_BYTEREADER_H
 
#include "../core/label_type.hpp"
#include "../core/string_consumer.hpp"
 
class OTTDByteReaderSignal { };

class ByteReader {
  StringConsumer consumer;
public:
  ByteReader(const uint8_t *data, size_t len) : consumer(std::string_view{reinterpret_cast<const char *>(data), len}) { }
 
  const uint8_t *ReadBytes(size_t size)
  {
    auto result = this->consumer.Read(size);
    if (result.size() != size) throw OTTDByteReaderSignal();
    return reinterpret_cast<const uint8_t *>(result.data());
  }

  uint8_t ReadByte()
  {
    auto result = this->consumer.TryReadUint8();
    if (!result.has_value()) throw OTTDByteReaderSignal();
    return *result;
  }

  uint16_t ReadWord()
  {
    auto result = this->consumer.TryReadUint16LE();
    if (!result.has_value()) throw OTTDByteReaderSignal();
    return *result;
  }

  uint16_t ReadExtendedByte()
  {
    uint16_t val = this->ReadByte();
    return val == 0xFF ? this->ReadWord() : val;
  }

  uint32_t ReadDWord()
  {
    auto result = this->consumer.TryReadUint32LE();
    if (!result.has_value()) throw OTTDByteReaderSignal();
    return *result;
  }

  uint32_t PeekDWord()
  {
    auto result = this->consumer.PeekUint32LE();
    if (!result.has_value()) throw OTTDByteReaderSignal();
    return *result;
  }
 
  uint32_t ReadVarSize(uint8_t size);

  std::string_view ReadString()
  {
    /* Terminating NUL may be missing at the end of sprite. */
    return this->consumer.ReadUntilChar('\0', StringConsumer::SKIP_ONE_SEPARATOR);
  }

  template <typename T> requires std::is_base_of_v<BaseLabel, T>
  T ReadLabel()
  {
    T label{};
    std::ranges::copy(this->consumer.Read(label.size()), label.data());
    return label;
  }
 
  size_t Remaining() const
  {
    return this->consumer.GetBytesLeft();
  }
 
  bool HasData(size_t count = 1) const
  {
    return count <= this->consumer.GetBytesLeft();
  }
 
  void Skip(size_t len)
  {
    auto result = this->consumer.Read(len);
    if (result.size() != len) throw OTTDByteReaderSignal();
  }
 
};
 
#endif /* NEWGRF_BYTEREADER_H */