update_model(AcModel acm, int sym)
{
int i;
if (acm.getCFreq(0) == Max_frequency)
{
int cum = 0;
acm.setCFreq(acm.getNSym(), 0);
for (i = acm.getNSym() - 1; i >= 0; i--)
{
acm.setFreq(i, (acm.getFreq(i) + 1) / 2);
cum += acm.getFreq(i);
acm.setCFreq(i, cum);
}
}
acm.setFreq(sym, acm.getFreq(sym) + 1);
for (i = sym; i >= 0; i--)
{
acm.setCFreq(i, acm.getCFreq(i) + 1);
}
return;
}
public ArithCoding()
{
bits_to_go = 8;
low = 0;
high = Top_value;
fbits = 0;
buffer = 0;
total_bits = 0;
buffer = 0;
N = 0;
acm = new AcModel(256, null, 1);
}
encode_symbol(AcModel acm, int sym)
{
int range;
range = (high - low) + 1;
high = low + (range * acm.getCFreq(sym)) / acm.getCFreq(0) - 1;
low = low + (range * acm.getCFreq(sym + 1)) / acm.getCFreq(0);
for (;;)
{
if (high < Half)
{
bit_plus_follow(0);
}
else if (low >= Half)
{
bit_plus_follow(1);
low -= Half;
high -= Half;
}
else if (low >= First_qtr && high < Third_qtr)
{
fbits += 1;
low -= First_qtr;
high -= First_qtr;
}
else
{
break;
}
low = 2 * low;
high = 2 * high + 1;
}
if (acm.getAdapt() == 1)
{
update_model(acm, sym);
}
return;
}
