UTF8.hpp

/*	MCM file compressor

  Copyright (C) 2013, Google Inc.
  Authors: Mathieu Chartier

  LICENSE

    This file is part of the MCM file compressor.

    MCM 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.

    MCM 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 MCM.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef _UTF_8_HPP_
#define _UTF_8_HPP_

#include "Util.hpp"

template <bool error_check = false>
class UTF8Decoder {
  // Accumulator word.
  uint32_t extra;
  uint32_t acc;
  bool error;
public:
  UTF8Decoder() {
    init();
    error = false;
  }

  void init() {
    extra = 0;
    acc = 0;
    error = false;
  }

  ALWAYS_INLINE bool done() const {
    return !extra;
  }

  ALWAYS_INLINE uint32_t getAcc() const {
    return acc;
  }

  ALWAYS_INLINE bool err() const {
    return error;
  }

  ALWAYS_INLINE void clear_err() const {
    error = false;
  }

  ALWAYS_INLINE void update(uint32_t c) {// 5 extra bits
    if (extra) {
      // Add another char to the UTF char.
      acc = (acc << 6) | (c & 0x3F);
      --extra;
      if (error_check && (c >> 6) != 2) {
        error = true;
      }
    } else if (!(c & 0x80)) {
      acc = c & 0x7F;
    } else if ((c & (0xFF << 1)) == ((0xFE << 1) & 0xFF)) {
      acc = c & 0x1; // 1
      extra = 5;
    } else if ((c & (0xFF << 2)) == ((0xFE << 2) & 0xFF)) {
      acc = c & 0x3; // 2
      extra = 4;
    } else if ((c & (0xFF << 3)) == ((0xFE << 3) & 0xFF)) {
      acc = c & 0x7; // 3
      extra = 3;
    } else if ((c & (0xFF << 4)) == ((0xFE << 4) & 0xFF)) {
      acc = c & 0xF; // 4
      extra = 2;
    } else if ((c & (0xFF << 5)) == ((0xFE << 5) & 0xFF)) {
      acc = c & 0x1F; // 5
      extra = 1;
    } else {
      acc = c;
      if (error_check) {
        error = true;
      }
    }
  }
};

#endif