__all__ = [
    'sign_extend64',
    'sign_extend32',
    'sign_extend16',
    'sign_extend12',
    'sign_extend8',
    'zero_extend32',
    'zero_extend16',
    'zero_extend8',
    'zero_extend4',
    'zero_extend1',
    'signed_saturate48',
    'signed_saturate32',
    'register',
    'bit',
]

#
# sign_extend
#

def sign_extend(x, b):
    m = 1 << (b - 1)
    x = x & ((1 << b) - 1)
    r = (x ^ m) - m
    return r

def sign_extend64(x):
    return sign_extend(x, 64)

def sign_extend32(x):
    return sign_extend(x, 32)

def sign_extend16(x):
    return sign_extend(x, 16)

def sign_extend12(x):
    return sign_extend(x, 12)

def sign_extend8(x):
    return sign_extend(x, 8)

#
# zero_extend
#

def zero_extend(x, b):
    x = x & ((1 << b) - 1)
    return x

def zero_extend32(x):
    return zero_extend(x, 32)

def zero_extend16(x):
    return zero_extend(x, 16)

def zero_extend8(x):
    return zero_extend(x, 8)

def zero_extend4(x):
    return zero_extend(x, 4)

def zero_extend1(x):
    return zero_extend(x, 1)

#
# signed_saturate
#

def signed_saturate(x, b):
    upper = (2 ** (b - 1)) - 1
    lower = -(2 ** (b - 1))
    if x > upper:
        return upper
    elif x < lower:
        return lower
    else:
        return x

def signed_saturate48(x):
    return signed_saturate(x, 48)

def signed_saturate32(x):
    return signed_saturate(x, 32)

#
# "convenience" functions
#

def register(x):
    return zero_extend(x, 32)

def bit(x):
    return zero_extend(x, 1)