static DWORD rng_decompress(BYTE *out, BYTE *in, DWORD in_len)
{
qsmodel qsm;
rangecoder rc;
int ch, syfreq, ltfreq;
DWORD act_uncomprlen = 0;
/* make an alphabet with 257 symbols, use 256 as end-of-file */
initqsmodel(&qsm, 257, 12, 2000, NULL, 0);
/* unknown crypt_index[0], seems to be always 0x00 */
start_decoding(&rc, in + 1);
while (1) {
ltfreq = decode_culshift(&rc, 12);
ch = qsgetsym(&qsm, ltfreq);
if (ch == 256) /* check for end-of-file */
break;
out[act_uncomprlen++] = ch;
qsgetfreq(&qsm, ch, &syfreq, <freq);
decode_update(&rc, syfreq, ltfreq, 1 << 12);
qsupdate(&qsm, ch);
}
qsgetfreq(&qsm, 256, &syfreq, <freq);
decode_update(&rc, syfreq, ltfreq, 1 << 12);
done_decoding(&rc);
deleteqsmodel(&qsm);
return act_uncomprlen;
}
/* rescale frequency counts */
static void dorescale( qsmodel *m)
{ int i, cf, missing;
if (m->nextleft) /* we have some more before actual rescaling */
{ m->incr++;
m->left = m->nextleft;
m->nextleft = 0;
return;
}
if (m->rescale < m->targetrescale) /* double rescale interval if needed */
{ m->rescale <<= 1;
if (m->rescale > m->targetrescale)
m->rescale = m->targetrescale;
}
cf = missing = m->cf[m->n]; /* do actual rescaling */
for(i=m->n-1; i; i--)
{ int tmp = m->newf[i];
cf -= tmp;
m->cf[i] = cf;
tmp = tmp>>1 | 1;
missing -= tmp;
m->newf[i] = tmp;
}
if (cf!=m->newf[0])
{ fprintf(stderr,"BUG: rescaling left %d total frequency\n",cf);
deleteqsmodel(m);
exit(1);
}
m->newf[0] = m->newf[0]>>1 | 1;
missing -= m->newf[0];
m->incr = missing / m->rescale;
m->nextleft = missing % m->rescale;
m->left = m->rescale - m->nextleft;
if (m->search != NULL)
{ i=m->n;
while (i)
{ int start, end;
end = (m->cf[i]-1) >> m->searchshift;
i--;
start = m->cf[i] >> m->searchshift;
while (start<=end)
{ m->search[start] = i;
start++;
}
}
}
