hash.pseudocode

# Note 1: All variables are unsigned 32 bits and wrap modulo 232 when calculating
# Note 2: All constants in this pseudo code are in big endian

# Initialize variables
# (first 32 bits of the fractional parts of the square roots of the first 8 primes 2..19):
h[0..7] :=
   0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
# Initialize table of round constants
# (first 32 bits of the fractional parts of the cube roots of the first 64 primes 2..311):
k[0..63] :=
   0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
   0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
   0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
   0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
   0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
   0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
   0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
   0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
# Pre-processing:
append the bit '1' to the message
append k bits '0', where k is the minimum number >= 0 such that the resulting message
    length (in bits) is congruent to 448 (mod 512)
append length of message (before pre-processing), in bits, as 64-bit big-endian integer
# Process the message in successive 512-bit chunks:
break message into 512-bit chunks
for each chunk
    break chunk into sixteen 32-bit big-endian words w[0..15]
    # Extend the sixteen 32-bit words into sixty-four 32-bit words:
    for i from 16 to 63
        s0 := (w[i-15] rightrotate 7) xor (w[i-15] rightrotate 18) xor (w[i-15] rightshift 3)
        s1 := (w[i-2] rightrotate 17) xor (w[i-2] rightrotate 19) xor (w[i-2] rightshift 10)
        w[i] := w[i-16] + s0 + w[i-7] + s1
    # Initialize hash value for this chunk:
    a := h0
    b := h1
    c := h2
    d := h3
    e := h4
    f := h5
    g := h6
    h := h7
    # Main loop:
    for i from 0 to 63
        s0 := (a rightrotate 2) xor (a rightrotate 13) xor (a rightrotate 22)
        maj := (a and b) xor (a and c) xor (b and c)
        t2 := s0 + maj
        s1 := (e rightrotate 6) xor (e rightrotate 11) xor (e rightrotate 25)
        ch := (e and f) xor ((not e) and g)
        t1 := h + s1 + ch + k[i] + w[i]

        h := g
        g := f
        f := e
        e := d + t1
        d := c
        c := b
        b := a
        a := t1 + t2
    # Add this chunk's hash to result so far:
    h0 := h0 + a
    h1 := h1 + b
    h2 := h2 + c
    h3 := h3 + d
    h4 := h4 + e
    h5 := h5 + f
    h6 := h6 + g
    h7 := h7 + h
# Produce the final hash value (big-endian):
digest = hash = h0 append h1 append h2 append h3 append h4 append h5 append h6 append h7

hash.rb

def rightrotate(value, shift)
  return ( ((value >> shift) | (value << (32 - shift))) & 0xffffffff)
end

hash = [0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19]
k = [0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
     0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
     0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
     0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
     0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
     0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
     0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
     0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2]

message = @context[:data]
bit_string = message.unpack('B*').join
message_length = bit_string.length
bit_string << '1'
bit_string = bit_string.ljust(message_length + (448 - (message_length % 512)), '0')
bit_string << message_length.to_s(2).rjust(64,'0')
pad_string = [bit_string].pack('B*').unpack('N*')
pad_string.each_slice(16) do |chunk|
  (16..63).each do |i|
    s0 = (rightrotate(chunk[i-15], 7) ^ rightrotate(chunk[i-15], 18) ^ (chunk[i-15] >> 3)) & 0xffffffff
    s1 = (rightrotate(chunk[i-2], 17) ^ rightrotate(chunk[i-2], 19) ^ (chunk[i-2] >> 10)) & 0xffffffff
    chunk << ((chunk[i-16] + s0 + chunk[i-7] + s1) & 0xffffffff)
  end

  working = Array(hash)

  (0..63).each do |i|
    s0 = (rightrotate(working[0], 2) ^ rightrotate(working[0], 13) ^ rightrotate(working[0], 22))
    maj = ((working[0] & working[1]) ^ (working[0] & working[2]) ^ (working[1] & working[2]))
    t2 = (s0 + maj)
    s1 = (rightrotate(working[4], 6) ^ rightrotate(working[4], 11) ^ rightrotate(working[4], 25))
    ch = ((working[4] & working[5]) ^ ((~working[4]) & working[6]))
    t1 = (working[7] + s1 + ch + k[i] + chunk[i])

    working = [t1+t2, working[0], working[1], working[2], working[3]+t1, working[4], working[5], working[6]]
  end

  working.each_with_index { |a, i| hash[i] = ((hash[i] + a) & 0xffffffff)}
end

hash.pack('N*')