/*

 * Copyright (C) 2000, 2001, 2002, 2003 Håkan Hjort <d95hjort@dtek.chalmers.se>

 *

 * This file is part of libdvdread.

 *

 * libdvdread 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 2 of the License, or

 * (at your option) any later version.

 *

 * libdvdread 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 libdvdread; if not, write to the Free Software Foundation, Inc.,

 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#include "config.h"

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <inttypes.h>

#include "dvdread/bitreader.h"

int dvdread_getbits_init(getbits_state_t *state, uint8_t *start) {

  if ((state == NULL) || (start == NULL)) return 0;

  state->start = start;

  state->bit_position = 0;

  state->byte_position = 0;

  state->byte = start[0];

  return 1;

}

/* Non-optimized getbits. */

/* This can easily be optimized for particular platforms. */

uint32_t dvdread_getbits(getbits_state_t *state, uint32_t number_of_bits) {

  uint32_t result=0;

  uint8_t byte=0;

  if (number_of_bits > 32) {

    printf("Number of bits > 32 in getbits\n");

    abort();

  }

  if ((state->bit_position) > 0) {  /* Last getbits left us in the middle of a byte. */

    if (number_of_bits > (8-state->bit_position)) { /* this getbits will span 2 or more bytes. */

      byte = state->byte;

      byte = byte >> (state->bit_position);

      result = byte;

      number_of_bits -= (8-state->bit_position);

      state->bit_position = 0;

      state->byte_position++;

      state->byte = state->start[state->byte_position];

    } else {

      byte=state->byte;

      state->byte = state->byte << number_of_bits;

      byte = byte >> (8 - number_of_bits);

      result = byte;

      state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 8 */

      if (state->bit_position == 8) {

        state->bit_position = 0;

        state->byte_position++;

        state->byte = state->start[state->byte_position];

      }

      number_of_bits = 0;

    }

  }

  if ((state->bit_position) == 0) {

    while (number_of_bits > 7) {

      result = (result << 8) + state->byte;

      state->byte_position++;

      state->byte = state->start[state->byte_position];

      number_of_bits -= 8;

    }

    if (number_of_bits > 0) { /* number_of_bits < 8 */

      byte = state->byte;

      state->byte = state->byte << number_of_bits;

      state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 7 */

      byte = byte >> (8 - number_of_bits);

      result = (result << number_of_bits) + byte;

      number_of_bits = 0;

    }

  }

  return result;

}

#if 0  /* TODO: optimized versions not yet used */

/* WARNING: This function can only be used on a byte boundary.

            No checks are made that we are in fact on a byte boundary.

 */

uint16_t dvdread_get16bits(getbits_state_t *state) {

  uint16_t result;

  state->byte_position++;

  result = (state->byte << 8) + state->start[state->byte_position++];

  state->byte = state->start[state->byte_position];

  return result;

}

/* WARNING: This function can only be used on a byte boundary.

            No checks are made that we are in fact on a byte boundary.

 */

uint32_t dvdread_get32bits(getbits_state_t *state) {

  uint32_t result;

  state->byte_position++;

  result = (state->byte << 8) + state->start[state->byte_position++];

  result = (result << 8) + state->start[state->byte_position++];

  result = (result << 8) + state->start[state->byte_position++];

  state->byte = state->start[state->byte_position];

  return result;

}

#endif