oracle.sol base64decode() about contracts

[nostdm]

The helper functions Base64 and Date are taken from this contract (oraclize+melonport), (but I haven't reviewed them in depth):
https://github.com/vcealicu/melonport-price-feed/blob/master/pricefeed/PriceFeed.sol

[i-stam]

check if there is a widely used library

[mischat]

@i-stam did you manage to find another, more widely used library ?

[i-stam]

I have already checked, I didn't find any official version/lib, most people say that you shouldn't do it on chain because it is expensive but the ones who need it are (like us) validating signatures.

[mischat]

Yannis, do you think we have underflow/overflow issues here ?

[mischat]

@i-stam ^^?

[mischat]

this is fixed and closed by a PR