Enhance FromHumanSize to parse float64 string

[WeiZhang555]

Currently FromHumanSize can only interpret format of '32kB', this commit
enhance it to interpret float64 string with blank such as '32.3 kB'.

Signed-off-by: Zhang Wei zhangwei555@huawei.com

I need this function for doing docker stats integration test, because docker stats use HumanSize to format byte into human readable string, now I need to revert the string to byte number. But FromHumanSize can't interpret 23.3 kB, so this commit add float64 support.

I also add the blank support but it doesn't matter if you don't like it.

I think you may have special considerations for only supporting int64, but I'm not sure what's it.
I can make relevant change based on your ideas.
Ping @calavera

[calavera]

should this be 32.5?

[WeiZhang555]

FromHumanSize will always return int64 instead of float64, it will truncate float64 into int64. That's because in my opinion, 32.5 B isn't meaningful, user don't need to care bit, unit as Byte is already good enough.

I was thinking to produce error for 32.5 B and only support 32.5 KB or MB etc, but it will make regexp complicated, so I didn't do that.

[WeiZhang555]

And there's some other situations, for example, 32.5634663 kB which is 32563.4663 B which is not meaningful, and it's hard to detect this format.
But I really need FromHumanSize to support parsing float64, because you know HumanSize will print 32.56 kB, I need this FromHumanSize to reverse the result.

So I think if we can't stop unmeaning input, we can still give meaningful output as some programming languages do.

[calavera]

LGTM

[WeiZhang555]

@calavera Can we have another one's eye on this? So that we can move forward, my integration tests still count on it. Thank you 😄

[calavera]

Merging, thanks!