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#import "XAD7ZipBCJ2Handle.h"
#define NumTopBits 24
#define TopValue (1<<NumTopBits)
#define BitModelTotalBits 11
#define BitModelTotal (1<<BitModelTotalBits)
#define NumMoveBits 5
@implementation XAD7ZipBCJ2Handle
static inline BOOL IsJ(int b0,int b1)
{
if((b1&0xfe)==0xe8) return YES;
if(b0==0x0f&&(b1&0xf0)==0x80) return YES;
return NO;
}
static inline int NextRangeBit(XAD7ZipBCJ2Handle *self,uint16_t *prob)
{
int res;
uint32_t bound=(self->range>>BitModelTotalBits)**prob;
if(self->code<bound)
{
res=0;
self->range=bound;
*prob=*prob+((BitModelTotal-*prob)>>NumMoveBits);
}
else
{
res=1;
self->range-=bound;
self->code-=bound;
*prob=*prob-(*prob>>NumMoveBits);
}
// Normalize
if(self->range<TopValue)
{
self->range<<=8;
self->code=(self->code<<8)|[self->ranges readUInt8];
}
return res;
}
-(id)initWithHandle:(CSHandle *)handle callHandle:(CSHandle *)callhandle
jumpHandle:(CSHandle *)jumphandle rangeHandle:(CSHandle *)rangehandle length:(off_t)length
{
if((self=[super initWithHandle:handle length:length]))
{
calls=[callhandle retain];
jumps=[jumphandle retain];
ranges=[rangehandle retain];
callstart=[calls offsetInFile];
jumpstart=[jumps offsetInFile];
rangestart=[ranges offsetInFile];
}
return self;
}
-(void)dealloc
{
[calls release];
[jumps release];
[ranges release];
[super dealloc];
}
-(void)resetByteStream
{
[calls seekToFileOffset:callstart];
[jumps seekToFileOffset:jumpstart];
[ranges seekToFileOffset:rangestart];
code=0;
range=0xffffffff;
for(int i=0;i<5;i++) code=(code<<8)|[ranges readUInt8];
for(int i=0;i<258;i++) probabilities[i]=BitModelTotal/2;
prevbyte=0;
valbyte=4;
}
-(uint8_t)produceByteAtOffset:(off_t)pos
{
if(valbyte<4)
{
prevbyte=(val>>valbyte*8)&0xff;
valbyte++;
return prevbyte;
}
uint8_t b=CSInputNextByte(input);
if(IsJ(prevbyte,b))
{
uint16_t *prob;
if(b==0xe8) prob=&probabilities[prevbyte];
else if (b==0xe9) prob=&probabilities[256];
else prob=&probabilities[257];
if(NextRangeBit(self,prob)==1)
{
CSHandle *handle;
if(b==0xe8) handle=calls;
else handle=jumps;
val=[handle readUInt32BE]-(pos+5);
valbyte=0;
}
}
return prevbyte=b;
}
@end
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