XADMaster/XADDiskDoublerMethod2Handle.m
2018-03-21 14:24:50 +02:00

110 lines
2.4 KiB
Objective-C

/*
* XADDiskDoublerMethod2Handle.m
*
* Copyright (c) 2017-present, MacPaw Inc. All rights reserved.
*
* 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 2.1 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301 USA
*/
#import "XADDiskDoublerMethod2Handle.h"
#import "XADException.h"
@implementation XADDiskDoublerMethod2Handle
-(id)initWithHandle:(CSHandle *)handle length:(off_t)length numberOfTrees:(int)num
{
if((self=[super initWithInputBufferForHandle:handle length:length]))
{
numtrees=num;
}
return self;
}
-(void)resetByteStream
{
for(int i=0;i<numtrees;i++)
{
for(int j=0;j<256;j++)
{
trees[i].parents[2*j]=j;
trees[i].parents[2*j+1]=j;
trees[i].leftchildren[j]=j*2;
trees[i].rightchildren[j]=j*2+1;
}
}
currtree=0;
}
-(uint8_t)produceByteAtOffset:(off_t)pos
{
int node=1;
for(;;)
{
int bit=CSInputNextBit(input);
if(bit==1) node=trees[currtree].rightchildren[node];
else node=trees[currtree].leftchildren[node];
if(node>=0x100)
{
int byte=node-0x100;
[self updateStateForByte:byte];
return byte;
}
}
}
-(void)updateStateForByte:(int)byte
{
uint8_t *parents=trees[currtree].parents;
uint16_t *leftchildren=trees[currtree].leftchildren;
uint16_t *rightchildren=trees[currtree].rightchildren;
int node=byte+0x100;
for(;;)
{
int parentnode=parents[node];
if(parentnode==1) break;
int grandparent=parents[parentnode];
int uncle=leftchildren[grandparent];
if(uncle==parentnode)
{
uncle=rightchildren[grandparent];
rightchildren[grandparent]=node;
}
else
{
leftchildren[grandparent]=node;
}
if(leftchildren[parentnode]!=node) rightchildren[parentnode]=uncle;
else leftchildren[parentnode]=uncle;
parents[node]=grandparent;
parents[uncle]=parentnode;
node=grandparent;
if(node==1) break;
}
currtree=byte%numtrees;
}
@end