ComponentAce.Compression.Libs.ZLib.Deflate.build_bl_tree C# (CSharp) Method

        private int build_bl_tree()
        {
            int max_blindex; // index of last bit length code of non zero freq

            // Determine the bit length frequencies for literal and distance trees
            scan_tree(dyn_ltree, l_desc.MaxCode);
            scan_tree(dyn_dtree, d_desc.MaxCode);

            // Build the bit length tree:
            bl_desc.build_tree(this);
            // opt_len now includes the length of the tree representations, except
            // the lengths of the bit lengths codes and the 5+5+4 bits for the counts.

            // Determine the number of bit length codes to send. The pkzip format
            // requires that at least 4 bit length codes be sent. (appnote.txt says
            // 3 but the actual value used is 4.)
            for (max_blindex = BL_CODES - 1; max_blindex >= 3; max_blindex--)
            {
                if (bl_tree[ZLibUtil.bl_order[max_blindex] * 2 + 1] != 0)
                    break;
            }
            // Update opt_len to include the bit length tree and counts
            opt_len += 3 * (max_blindex + 1) + 5 + 5 + 4;

            return max_blindex;
        }