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/* -*- 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;
}
}
}
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