Digest::SHA2

        # Digest::SHA2 < Digest::Class

(from ruby core)
---
A meta digest provider class for SHA256, SHA384 and SHA512.

FIPS 180-2 describes SHA2 family of digest algorithms. It defines three
algorithms:
*   one which works on chunks of 512 bits and returns a 256-bit digest
    (SHA256),
*   one which works on chunks of 1024 bits and returns a 384-bit digest
    (SHA384),
*   and one which works on chunks of 1024 bits and returns a 512-bit
    digest (SHA512).


## Examples
    require 'digest'

    # Compute a complete digest
    Digest::SHA2.hexdigest 'abc'          # => "ba7816bf8..."
    Digest::SHA2.new(256).hexdigest 'abc' # => "ba7816bf8..."
    Digest::SHA256.hexdigest 'abc'        # => "ba7816bf8..."

    Digest::SHA2.new(384).hexdigest 'abc' # => "cb00753f4..."
    Digest::SHA384.hexdigest 'abc'        # => "cb00753f4..."

    Digest::SHA2.new(512).hexdigest 'abc' # => "ddaf35a19..."
    Digest::SHA512.hexdigest 'abc'        # => "ddaf35a19..."

    # Compute digest by chunks
    sha2 = Digest::SHA2.new               # =>#<Digest::SHA2:256>
    sha2.update "ab"
    sha2 << "c"                           # alias for #update
    sha2.hexdigest                        # => "ba7816bf8..."

    # Use the same object to compute another digest
    sha2.reset
    sha2 << "message"
    sha2.hexdigest                        # => "ab530a13e..."
---
# Class methods:

    new

# Instance methods:

    <<
    block_length
    digest_length
    reset
    update