initially this was part of nimPDF project, then I decided to release it separately

example:

var sha = initSHA[SHA256]()
sha.update("test SHA256")
let digest = sha.final()

or:

let digest = computeSHA256("test SHA256")

conversion:

• to convert digest into string, use proc $
• to convert digest into hex string, use toHex

each version of SHA2 hash function will produce output according to it's name: SHA224 produce 224 bits hash, SHA256 produce 256 bits hash, and so on

already tested with test vector from here, see tests/test.nim