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/*
* scribiu -- read notebooks and voice memos from Livescribe pens
* Copyright (C) 2015 Javier S. Pedro <javier@javispedro.com>
*
* This program 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.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "bitreader.h"
namespace
{
inline qint64 signExtend(quint64 x, int n)
{
if (n < 64 && (x & (1 << (n-1)))) {
x |= -(1LL << n);
}
return x;
}
}
BitReader::BitReader(QIODevice *device)
: child(device), buf(0), avail(0)
{
}
BitReader::~BitReader()
{
}
quint64 BitReader::readBits(int n)
{
quint64 x = peekBits(n);
Q_ASSERT(avail >= n);
buf -= x << (avail - n);
avail -= n;
return x;
}
qint64 BitReader::readSignedBits(int n)
{
quint64 x = readBits(n);
return signExtend(x, n);
}
quint64 BitReader::peekBits(int n)
{
while (n > avail) {
char c;
child->getChar(&c);
buf = (buf << 8) | (quint8)(c);
avail += 8;
}
quint64 x = buf >> (avail - n);
return x;
}
qint64 BitReader::peekSignedBits(int n)
{
quint64 x = peekBits(n);
return signExtend(x, n);
}
void BitReader::skipUntilNextByte()
{
int skip = avail % 8;
readBits(skip);
}
bool BitReader::atEnd()
{
return avail == 0 && child->atEnd();
}
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