while(tmp>1) {tmp>>=1;entry_selector++;}
w->data[num_segments_pos++]=entry_selector>>8;
w->data[num_segments_pos++]=entry_selector;
/* backpatch range shift */
while(tmp>1) {tmp>>=1;entry_selector++;}
w->data[num_segments_pos++]=entry_selector>>8;
w->data[num_segments_pos++]=entry_selector;
/* backpatch range shift */