Proposal: uncompressed input size

[natefoo]

Currently input_size is the size of the raw input, which can be either compressed or uncompressed. When scaling memory based on input size you probably only care about the uncompressed size. But gzip does store the uncompressed size, which we could read into a separate uncompressed_jnput_size variable. The uncompressed size is stored in the last 4 bytes, this seems to work for me:

#!/usr/bin/env python3
import os
import sys

path = sys.argv[1]

with open(path, 'rb') as f:
    f.seek(-4, os.SEEK_END)
    size = int.from_bytes(f.read(4), 'little')
    print(size)

The uncompressed size also isn't always set properly:

nate@pdp-11% gzip -l /home/nate/work/galaxy/test-data/1.bam
         compressed        uncompressed  ratio uncompressed_name
               3592                   0   0.0% /home/nate/work/galaxy/test-data/1.bam

So we should have a default... actual size, or actual size * some constant factor.