import struct

SHA_BLOCKSIZE = 64
SHA_DIGESTSIZE = 32


def new_shaobject():
    return {
        'digest': [0]*8,
        'count_lo': 0,
        'count_hi': 0,
        'data': [0]* SHA_BLOCKSIZE,
        'local': 0,
        'digestsize': 0
    }

ROR = lambda x, y: (((x & 0xffffffff) >> (y & 31)) | (x << (32 - (y & 31)))) & 0xffffffff
Ch = lambda x, y, z: (z ^ (x & (y ^ z)))
Maj = lambda x, y, z: (((x | y) & z) | (x & y))
S = lambda x, n: ROR(x, n)
R = lambda x, n: (x & 0xffffffff) >> n
Sigma0 = lambda x: (S(x, 2) ^ S(x, 13) ^ S(x, 22))
Sigma1 = lambda x: (S(x, 6) ^ S(x, 11) ^ S(x, 25))
Gamma0 = lambda x: (S(x, 7) ^ S(x, 18) ^ R(x, 3))
Gamma1 = lambda x: (S(x, 17) ^ S(x, 19) ^ R(x, 10))

def sha_transform(sha_info):
    W = []

    d = sha_info['data']
    for i in xrange(0,16):
        W.append( (d[4*i]<<24) + (d[4*i+1]<<16) + (d[4*i+2]<<8) + d[4*i+3])

    for i in xrange(16,64):
        W.append( (Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16]) & 0xffffffff )

    ss = sha_info['digest'][:]

    def RND(a,b,c,d,e,f,g,h,i,ki):
        t0 = h + Sigma1(e) + Ch(e, f, g) + ki + W[i];
        t1 = Sigma0(a) + Maj(a, b, c);
        d += t0;
        h  = t0 + t1;
        return d & 0xffffffff, h & 0xffffffff

    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],0,0x428a2f98);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],1,0x71374491);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],2,0xb5c0fbcf);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],3,0xe9b5dba5);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],4,0x3956c25b);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],5,0x59f111f1);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],6,0x923f82a4);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],7,0xab1c5ed5);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],8,0xd807aa98);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],9,0x12835b01);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],10,0x243185be);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],11,0x550c7dc3);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],12,0x72be5d74);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],13,0x80deb1fe);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],14,0x9bdc06a7);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],15,0xc19bf174);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],16,0xe49b69c1);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],17,0xefbe4786);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],18,0x0fc19dc6);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],19,0x240ca1cc);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],20,0x2de92c6f);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],21,0x4a7484aa);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],22,0x5cb0a9dc);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],23,0x76f988da);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],24,0x983e5152);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],25,0xa831c66d);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],26,0xb00327c8);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],27,0xbf597fc7);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],28,0xc6e00bf3);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],29,0xd5a79147);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],30,0x06ca6351);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],31,0x14292967);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],32,0x27b70a85);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],33,0x2e1b2138);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],34,0x4d2c6dfc);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],35,0x53380d13);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],36,0x650a7354);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],37,0x766a0abb);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],38,0x81c2c92e);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],39,0x92722c85);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],40,0xa2bfe8a1);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],41,0xa81a664b);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],42,0xc24b8b70);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],43,0xc76c51a3);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],44,0xd192e819);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],45,0xd6990624);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],46,0xf40e3585);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],47,0x106aa070);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],48,0x19a4c116);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],49,0x1e376c08);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],50,0x2748774c);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],51,0x34b0bcb5);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],52,0x391c0cb3);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],53,0x4ed8aa4a);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],54,0x5b9cca4f);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],55,0x682e6ff3);
    ss[3], ss[7] = RND(ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],56,0x748f82ee);
    ss[2], ss[6] = RND(ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],57,0x78a5636f);
    ss[1], ss[5] = RND(ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],ss[5],58,0x84c87814);
    ss[0], ss[4] = RND(ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],ss[4],59,0x8cc70208);
    ss[7], ss[3] = RND(ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],ss[3],60,0x90befffa);
    ss[6], ss[2] = RND(ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],ss[2],61,0xa4506ceb);
    ss[5], ss[1] = RND(ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],ss[1],62,0xbef9a3f7);
    ss[4], ss[0] = RND(ss[1],ss[2],ss[3],ss[4],ss[5],ss[6],ss[7],ss[0],63,0xc67178f2);

    dig = []
    for i, x in enumerate(sha_info['digest']):
        dig.append( (x + ss[i]) & 0xffffffff )
    sha_info['digest'] = dig

def sha_init():
    sha_info = new_shaobject()
    sha_info['digest'] = [0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19]
    sha_info['count_lo'] = 0
    sha_info['count_hi'] = 0
    sha_info['local'] = 0
    sha_info['digestsize'] = 32
    return sha_info

def sha224_init():
    sha_info = new_shaobject()
    sha_info['digest'] = [0xc1059ed8, 0x367cd507, 0x3070dd17, 0xf70e5939, 0xffc00b31, 0x68581511, 0x64f98fa7, 0xbefa4fa4]
    sha_info['count_lo'] = 0
    sha_info['count_hi'] = 0
    sha_info['local'] = 0
    sha_info['digestsize'] = 28
    return sha_info

def getbuf(s):
    if isinstance(s, str):
        return s
    elif isinstance(s, unicode):
        return str(s)
    else:
        return buffer(s)

def sha_update(sha_info, buffer):
    count = len(buffer)
    buffer_idx = 0
    clo = (sha_info['count_lo'] + (count << 3)) & 0xffffffff
    if clo < sha_info['count_lo']:
        sha_info['count_hi'] += 1
    sha_info['count_lo'] = clo

    sha_info['count_hi'] += (count >> 29)

    if sha_info['local']:
        i = SHA_BLOCKSIZE - sha_info['local']
        if i > count:
            i = count

        # copy buffer
        for x in enumerate(buffer[buffer_idx:buffer_idx+i]):
            sha_info['data'][sha_info['local']+x[0]] = struct.unpack('B', x[1])[0]

        count -= i
        buffer_idx += i

        sha_info['local'] += i
        if sha_info['local'] == SHA_BLOCKSIZE:
            sha_transform(sha_info)
            sha_info['local'] = 0
        else:
            return

    while count >= SHA_BLOCKSIZE:
        # copy buffer
        sha_info['data'] = [struct.unpack('B',c)[0] for c in buffer[buffer_idx:buffer_idx + SHA_BLOCKSIZE]]
        count -= SHA_BLOCKSIZE
        buffer_idx += SHA_BLOCKSIZE
        sha_transform(sha_info)


    # copy buffer
    pos = sha_info['local']
    sha_info['data'][pos:pos+count] = [struct.unpack('B',c)[0] for c in buffer[buffer_idx:buffer_idx + count]]
    sha_info['local'] = count

def sha_final(sha_info):
    lo_bit_count = sha_info['count_lo']
    hi_bit_count = sha_info['count_hi']
    count = (lo_bit_count >> 3) & 0x3f
    sha_info['data'][count] = 0x80;
    count += 1
    if count > SHA_BLOCKSIZE - 8:
        # zero the bytes in data after the count
        sha_info['data'] = sha_info['data'][:count] + ([0] * (SHA_BLOCKSIZE - count))
        sha_transform(sha_info)
        # zero bytes in data
        sha_info['data'] = [0] * SHA_BLOCKSIZE
    else:
        sha_info['data'] = sha_info['data'][:count] + ([0] * (SHA_BLOCKSIZE - count))

    sha_info['data'][56] = (hi_bit_count >> 24) & 0xff
    sha_info['data'][57] = (hi_bit_count >> 16) & 0xff
    sha_info['data'][58] = (hi_bit_count >>  8) & 0xff
    sha_info['data'][59] = (hi_bit_count >>  0) & 0xff
    sha_info['data'][60] = (lo_bit_count >> 24) & 0xff
    sha_info['data'][61] = (lo_bit_count >> 16) & 0xff
    sha_info['data'][62] = (lo_bit_count >>  8) & 0xff
    sha_info['data'][63] = (lo_bit_count >>  0) & 0xff

    sha_transform(sha_info)

    dig = []
    for i in sha_info['digest']:
        dig.extend([ ((i>>24) & 0xff), ((i>>16) & 0xff), ((i>>8) & 0xff), (i & 0xff) ])
    return ''.join([chr(i) for i in dig])

class sha256(object):
    digest_size = digestsize = SHA_DIGESTSIZE
    block_size = SHA_BLOCKSIZE

    def __init__(self, s=None):
        self._sha = sha_init()
        if s:
            sha_update(self._sha, getbuf(s))

    def update(self, s):
        sha_update(self._sha, getbuf(s))

    def digest(self):
        return sha_final(self._sha.copy())[:self._sha['digestsize']]

    def hexdigest(self):
        return ''.join(['%.2x' % ord(i) for i in self.digest()])

    def copy(self):
        new = sha256.__new__(sha256)
        new._sha = self._sha.copy()
        return new

class sha224(sha256):
    digest_size = digestsize = 28

    def __init__(self, s=None):
        self._sha = sha224_init()
        if s:
            sha_update(self._sha, getbuf(s))

    def copy(self):
        new = sha224.__new__(sha224)
        new._sha = self._sha.copy()
        return new

if __name__ == "__main__":
    a_str = "just a test string"

    assert 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855' == sha256().hexdigest()
    assert 'd7b553c6f09ac85d142415f857c5310f3bbbe7cdd787cce4b985acedd585266f' == sha256(a_str).hexdigest()
    assert '8113ebf33c97daa9998762aacafe750c7cefc2b2f173c90c59663a57fe626f21' == sha256(a_str*7).hexdigest()

    s = sha256(a_str)
    s.update(a_str)
    assert '03d9963e05a094593190b6fc794cb1a3e1ac7d7883f0b5855268afeccc70d461' == s.hexdigest()
