final
Specifies how much memory should be allocated for the internal compression
state. 1 uses minimum memory but is slow and reduces compression ratio;
9 uses maximum memory for optimal speed. The default value is 8.
The memory requirements for deflate are (in bytes):
(1 << (windowBits + 2)) + (1 << (memLevel + 9))
that is: 128K for windowBits = 15 + 128K for memLevel = 8 (default values)