internal void gen_bitlen(Deflate s){
short[] tree = dyn_tree;
short[] stree = stat_desc.static_tree;
int[] extra = stat_desc.extra_bits;
int based = stat_desc.extra_base;
int max_length = stat_desc.max_length;
int h; // heap index
int n, m; // iterate over the tree elements
int bits; // bit length
int xbits; // extra bits
short f; // frequency
int overflow = 0; // number of elements with bit length too large
for (bits = 0; bits <= MAX_BITS; bits++) s.bl_count[bits] = 0;
// In a first pass, compute the optimal bit lengths (which may
// overflow in the case of the bit length tree).
tree[s.heap[s.heap_max]*2+1] = 0; // root of the heap
for(h=s.heap_max+1; h<HEAP_SIZE; h++){
n = s.heap[h];
bits = tree[tree[n*2+1]*2+1] + 1;
if (bits > max_length){ bits = max_length; overflow++; }
tree[n*2+1] = (short)bits;
// We overwrite tree[n*2+1] which is no longer needed
if (n > max_code) continue; // not a leaf node
s.bl_count[bits]++;
xbits = 0;
if (n >= based) xbits = extra[n-based];
f = tree[n*2];
s.opt_len += f * (bits + xbits);
if (stree!=null) s.static_len += f * (stree[n*2+1] + xbits);
}
if (overflow == 0) return;
// This happens for example on obj2 and pic of the Calgary corpus
// Find the first bit length which could increase:
do {
bits = max_length-1;
while(s.bl_count[bits]==0) bits--;
s.bl_count[bits]--; // move one leaf down the tree
s.bl_count[bits+1]+=2; // move one overflow item as its brother
s.bl_count[max_length]--;
// The brother of the overflow item also moves one step up,
// but this does not affect bl_count[max_length]
overflow -= 2;
}
while (overflow > 0);
for (bits = max_length; bits != 0; bits--) {
n = s.bl_count[bits];
while (n != 0) {
m = s.heap[--h];
if (m > max_code) continue;
if (tree[m*2+1] != bits) {
s.opt_len += (int)(((long)bits - (long)tree[m*2+1])*(long)tree[m*2]);
tree[m*2+1] = (short)bits;
}
n--;
}
}
}
