/*

 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.

 *

 *  Use of this source code is governed by a BSD-style license

 *  that can be found in the LICENSE file in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

 */

#include <stdlib.h>

#include "./vpx_config.h"

#include "vpx_dsp/bitreader.h"

#include "vpx_dsp/prob.h"

#include "vpx_dsp/vpx_dsp_common.h"

#include "vpx_ports/mem.h"

#include "vpx_mem/vpx_mem.h"

#include "vpx_util/endian_inl.h"

int vpx_reader_init(vpx_reader *r, const uint8_t *buffer, size_t size,

                    vpx_decrypt_cb decrypt_cb, void *decrypt_state) {

  if (size && !buffer) {

    return 1;

  } else {

    r->buffer_end = buffer + size;

    r->buffer = buffer;

    r->value = 0;

    r->count = -8;

    r->range = 255;

    r->decrypt_cb = decrypt_cb;

    r->decrypt_state = decrypt_state;

    vpx_reader_fill(r);

    return vpx_read_bit(r) != 0;  // marker bit

  }

}

void vpx_reader_fill(vpx_reader *r) {

  const uint8_t *const buffer_end = r->buffer_end;

  const uint8_t *buffer = r->buffer;

  const uint8_t *buffer_start = buffer;

  BD_VALUE value = r->value;

  int count = r->count;

  const size_t bytes_left = buffer_end - buffer;

  const size_t bits_left = bytes_left * CHAR_BIT;

  int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);

  if (r->decrypt_cb) {

    size_t n = VPXMIN(sizeof(r->clear_buffer), bytes_left);

    r->decrypt_cb(r->decrypt_state, buffer, r->clear_buffer, (int)n);

    buffer = r->clear_buffer;

    buffer_start = r->clear_buffer;

  }

  if (bits_left > BD_VALUE_SIZE) {

    const int bits = (shift & 0xfffffff8) + CHAR_BIT;

    BD_VALUE nv;

    BD_VALUE big_endian_values;

    memcpy(&big_endian_values, buffer, sizeof(BD_VALUE));

#if SIZE_MAX == 0xffffffffffffffffULL

    big_endian_values = HToBE64(big_endian_values);

#else

    big_endian_values = HToBE32(big_endian_values);

#endif

    nv = big_endian_values >> (BD_VALUE_SIZE - bits);

    count += bits;

    buffer += (bits >> 3);

    value = r->value | (nv << (shift & 0x7));

  } else {

    const int bits_over = (int)(shift + CHAR_BIT - (int)bits_left);

    int loop_end = 0;

    if (bits_over >= 0) {

      count += LOTS_OF_BITS;

      loop_end = bits_over;

    }

    if (bits_over < 0 || bits_left) {

      while (shift >= loop_end) {

        count += CHAR_BIT;

        value |= (BD_VALUE)*buffer++ << shift;

        shift -= CHAR_BIT;

      }

    }

  }

  // NOTE: Variable 'buffer' may not relate to 'r->buffer' after decryption,

  // so we increase 'r->buffer' by the amount that 'buffer' moved, rather than

  // assign 'buffer' to 'r->buffer'.

  r->buffer += buffer - buffer_start;

  r->value = value;

  r->count = count;

}

const uint8_t *vpx_reader_find_end(vpx_reader *r) {

  // Find the end of the coded buffer

  while (r->count > CHAR_BIT && r->count < BD_VALUE_SIZE) {

    r->count -= CHAR_BIT;

    r->buffer--;

  }

  return r->buffer;

}