/* -*- tab-width:4; c-basic-offset:4 -*- */

/*

 * libopenraw - bititerator.cpp

 *

 * Copyright (C) 2008 Rafael Avila de Espindola.

 *

 * This library is free software: you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation, either version 3 of

 * the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library.  If not, see

 * <http://www.gnu.org/licenses/>.

 */

#include <assert.h>

#include <algorithm>

#include "bititerator.hpp"

namespace OpenRaw {

namespace Internals {

BitIterator::BitIterator(const uint8_t * const p, size_t size)

    : m_p(p)

    , m_size(size)

    , m_bitBuffer(0)

    , m_bitsOnBuffer(0)

{

}

void BitIterator::load(size_t numBits)

{

    size_t numBytes = (numBits + 7) / 8;

    //align the bits on the right

    m_bitBuffer >>= (32 - m_bitsOnBuffer);

    m_bitsOnBuffer += 8 * numBytes;

    //load the new bits from the right

    for (size_t i = 0; i < numBytes && m_size > 0; ++i) {

        m_bitBuffer = (m_bitBuffer << 8) | *m_p;

        ++m_p;

        m_size--;

    }

    //align the bits on the left

    m_bitBuffer = m_bitBuffer << (32 - m_bitsOnBuffer);

}

uint32_t BitIterator::get(size_t n)

{

	uint32_t ret = peek(n);

	skip(n);

	return ret;

}

uint32_t BitIterator::peek(size_t n)

{

	assert(n <= 25);

	if (n == 0)

		return 0;

	if (n > m_bitsOnBuffer)

		load(n - m_bitsOnBuffer);

	assert(n <= m_bitsOnBuffer);

	return m_bitBuffer >> (32 - n);

}

void BitIterator::skip(size_t n)

{

	size_t num_bits = std::min(n, m_bitsOnBuffer);

	m_bitsOnBuffer -= num_bits;

	m_bitBuffer <<= num_bits;

}

}

}