jbitstream.cpp
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/***************************************************************************
* Copyright (C) 2005 by Jeff Ferr *
* root@sat *
* *
* 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 2 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, write to the *
* Free Software Foundation, Inc., *
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
***************************************************************************/
#include "Stdafx.h"
#include "jbitstream.h"
#include "jruntimeexception.h"
namespace jcommon {
const int mask[][8] = {
{0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01},
{0xc0, 0x60, 0x30, 0x18, 0x0c, 0x06, 0x03, 0x00},
{0xe0, 0x70, 0x38, 0x1c, 0x0e, 0x07, 0x00, 0x00},
{0xf0, 0x78, 0x3c, 0x1e, 0x0f, 0x00, 0x00, 0x00},
{0xf8, 0x7c, 0x3e, 0x1f, 0x00, 0x00, 0x00, 0x00},
{0xfc, 0x7e, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00},
{0xfe, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
{0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
};
BitStream::BitStream(char *stream, int size):
jcommon::Object()
{
jcommon::Object::SetClassName("jcommon::BitStream");
if (stream == NULL || size == 0) {
_stream = NULL;
throw RuntimeException("Null pointer reference !");
}
_stream = stream;
_size = size;
Reset();
}
BitStream::~BitStream()
{
if (_stream != NULL) {
delete [] _stream;
}
}
void BitStream::Reset() {
_index = 0;
_offset = 0;
_consumed = 0;
}
uint64_t BitStream::GetBits(int n)
{
// WARNNING: veridy bug when n > 24
uint64_t result = 0LL;
int bitsToConsume = n;
int bitsToConsumeNow;
while (bitsToConsume != 0) {
bitsToConsumeNow = 8 - _offset;
if (bitsToConsumeNow > bitsToConsume) {
bitsToConsumeNow = bitsToConsume;
}
result |= mask[bitsToConsumeNow - 1][_offset] & _stream[_index];
bitsToConsume -= bitsToConsumeNow;
_offset += bitsToConsumeNow;
if (_offset == 8) {
result <<= 8;
_index += 1;
_offset = 0;
_consumed++;
}
}
result >>= 8 - _offset;
return result;
}
uint8_t* BitStream::GetBitsArray(int size)
{
int i,
len8 = size / 8,
mod8 = size % 8;
try {
uint8_t*array = new uint8_t[len8];
for (i=0; i<len8; i++) {
array[i] = (uint8_t)GetBits(8);
}
array[i] = (uint8_t)(GetBits(mod8) << (8 - mod8));
return array;
} catch (std::bad_alloc &) {
return NULL;
}
return NULL;
}
int BitStream::Skip(int n) {
_index += n / 8;
_offset += n % 8;
if (_offset >= 8) {
_offset %= 8;
_index++;
}
return _index * 8 + _offset;
}
int BitStream::Back(int n) {
_offset -= n % 8;
if (_offset < 0) {
_offset += 8;
_index--;
}
return _index * 8 + _offset;
}
int BitStream::GetAvailable()
{
return (_size - _index) * 8 + (8 - _offset);
}
int BitStream::GetPosition()
{
return _index * 8 + _offset;
}
int BitStream::SetPosition(int p)
{
_index = p / 8;
_offset = p % 8;
return _index * 8 + _offset;
}
bool BitStream::TestBit(int index)
{
if (index > _size) {
throw std::out_of_range("Index is out of range !");
}
return (_stream[(unsigned int)(index/8)] & (1 << (unsigned int)(index%8))) != 0;
}
}