/// <summary>
///
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public BSInputStream Init(Stream input)
{
zp = new ZPCodec().Init(input);
for (int i = 0; i < ctx.Length;)
{
ctx[i++] = new MutableValue <sbyte>();
}
return(this);
}
public ZPCodec()
{
Ffzt = new sbyte[FFZT.Length];
Array.Copy(FFZT, 0, Ffzt, 0, Ffzt.Length);
for (int i = 0; i < _arraySize; i++)
{
Up[i] = new MutableValue <sbyte>();
Down[i] = new MutableValue <sbyte>();
}
}
public int Decoder(MutableValue <sbyte> ctx)
{
int ictx = 0xff & ctx.Value;
int z = AValue + PArray[ictx];
if (z <= _fence)
{
AValue = z;
return(ictx & 1);
}
else
{
return(DecodeSub(ctx, z));
}
}
public int DecodeSub(MutableValue <sbyte> ctx, int z)
{
int bit = ctx.Value & 1;
int d = 24576 + ((z + AValue) >> 2);
if (z > d)
{
z = d;
}
if (z > _code)
{
z = 0x10000 - z;
AValue += z;
_code += z;
ctx.Value = Down[0xff & ctx.Value].Value;
int shift = FFZ(AValue);
_scount = (short)(_scount - shift);
AValue = 0xffff & (AValue << shift);
_code = 0xffff & ((_code << shift) | ((_buffer >> _scount) & ((1 << shift) - 1)));
if (_scount < 16)
{
Preload();
}
_fence = _code;
if (_code >= 32768L)
{
_fence = 32767L;
}
return(bit ^ 1);
}
if ((unchecked ((int)0xffffffffL) & AValue) >= (unchecked ((int)0xffffffffL) & MArray[0xff & ctx.Value]))
{
ctx.Value = Up[0xff & ctx.Value].Value;
}
_scount--;
AValue = 0xffff & (z << 1);
_code = 0xffff & ((_code << 1) | ((_buffer >> _scount) & 1));
if (_scount < 16)
{
Preload();
}
_fence = _code;
if (_code >= 32768L)
{
_fence = 32767L;
}
return(bit);
}
