def generate_random_bits(n_bits, rand_func=generate_random_bytes):
"""
Generates the specified number of random bits as a byte string.
For example::
f(x) -> y such that
f(16) -> 1111 1111 1111 1111; bytes_to_integer(y) => 65535L
f(17) -> 0000 0001 1111 1111 1111 1111; bytes_to_integer(y) => 131071L
:param n_bits:
Number of random bits.
if n is divisible by 8, (n / 8) bytes will be returned.
if n is not divisible by 8, ((n / 8) + 1) bytes will be returned
and the prefixed offset-byte will have `(n % 8)` number of random bits,
(that is, `8 - (n % 8)` high bits will be cleared).
The range of the numbers is 0 to (2**n)-1 inclusive.
:param rand_func:
Random bytes generator function.
:returns:
Bytes.
"""
if not builtins.is_integer(n_bits):
raise TypeError("unsupported operand type: %r" % type(n_bits).__name__)
if n_bits <= 0:
raise ValueError("number of bits must be greater than 0.")
# Doesn't perform any floating-point operations.
quotient, remainder = divmod(n_bits, 8)
random_bytes = rand_func(quotient)
if remainder:
offset = ord(rand_func(1)) >> (8 - remainder)
random_bytes = builtins.byte(offset) + random_bytes
return random_bytes
def generate_random_bits(n_bits, rand_func=generate_random_bytes):
"""
Generates the specified number of random bits as a byte string.
For example::
f(x) -> y such that
f(16) -> 1111 1111 1111 1111; bytes_to_integer(y) => 65535L
f(17) -> 0000 0001 1111 1111 1111 1111; bytes_to_integer(y) => 131071L
:param n_bits:
Number of random bits.
if n is divisible by 8, (n / 8) bytes will be returned.
if n is not divisible by 8, ((n / 8) + 1) bytes will be returned
and the prefixed offset-byte will have `(n % 8)` number of random bits,
(that is, `8 - (n % 8)` high bits will be cleared).
The range of the numbers is 0 to (2**n)-1 inclusive.
:param rand_func:
Random bytes generator function.
:returns:
Bytes.
"""
if not builtins.is_integer(n_bits):
raise TypeError("unsupported operand type: %r" % type(n_bits).__name__)
if n_bits <= 0:
raise ValueError("number of bits must be greater than 0.")
# Doesn't perform any floating-point operations.
quotient, remainder = divmod(n_bits, 8)
random_bytes = rand_func(quotient)
if remainder:
offset = ord(rand_func(1)) >> (8 - remainder)
random_bytes = builtins.byte(offset) + random_bytes
return random_bytes
def generate_random_uint_between(low, high, rand_func=generate_random_bytes):
"""
Generates a random long integer between low and high, not including high.
:param low:
Low
:param high:
High
:param rand_func:
Random bytes generator function.
:returns:
Random unsigned long integer value.
"""
if not (builtins.is_integer(low) and builtins.is_integer(high)):
raise TypeError("unsupported argument types(s): %r and %r" %
(type(low).__name__, type(high).__name__))
if low >= high:
raise ValueError("high value must be greater than low value.")
substrate = high - low - 1
bits = builtins.integer_bit_size(substrate)
value = generate_random_uint_atmost(bits, rand_func=rand_func)
while value > substrate:
value = generate_random_uint_atmost(bits, rand_func=rand_func)
return low + value
def generate_random_uint_between(low, high, rand_func=generate_random_bytes):
"""
Generates a random long integer between low and high, not including high.
:param low:
Low
:param high:
High
:param rand_func:
Random bytes generator function.
:returns:
Random unsigned long integer value.
"""
if not (builtins.is_integer(low) and builtins.is_integer(high)):
raise TypeError("unsupported argument types(s): %r and %r" %
(type(low).__name__, type(high).__name__))
if low >= high:
raise ValueError("high value must be greater than low value.")
substrate = high - low - 1
bits = builtins.integer_bit_size(substrate)
value = generate_random_uint_atmost(bits, rand_func=rand_func)
while value > substrate:
value = generate_random_uint_atmost(bits, rand_func=rand_func)
return low + value
def generate_random_sequence(length, pool, rand_func=generate_random_bytes):
"""
Generates a random sequence of given length using the sequence
pool specified.
:param length:
The length of the random sequence.
:param pool:
A sequence of elements to be used as the pool from which
random elements will be chosen.
:returns:
A list of elements randomly chosen from the pool.
"""
if not builtins.is_integer(length):
raise TypeError("Length must be a positive integer: got `%r`" %
type(length).__name__)
if length <= 0:
raise ValueError("length must be a positive integer: got %d" % length)
return [random_choice(pool, rand_func) for _ in builtins.range(length)]
def generate_random_sequence(length, pool, rand_func=generate_random_bytes):
"""
Generates a random sequence of given length using the sequence
pool specified.
:param length:
The length of the random sequence.
:param pool:
A sequence of elements to be used as the pool from which
random elements will be chosen.
:returns:
A list of elements randomly chosen from the pool.
"""
if not builtins.is_integer(length):
raise TypeError("Length must be a positive integer: got `%r`" %
type(length).__name__)
if length <= 0:
raise ValueError("length must be a positive integer: got %d" % length)
return [random_choice(pool, rand_func) for _ in builtins.range(length)]
def generate_random_uint_atmost(n_bits, rand_func=generate_random_bytes):
"""
Generates a random unsigned integer with `n_bits` random bits.
:param n_bits:
Number of random bits to be generated at most.
:param rand_func:
Random bytes generator function.
:returns:
Returns an unsigned long integer with at most `n_bits` random bits.
The generated unsigned long integer will be between 0 and
(2**n_bits)-1 both inclusive.
"""
if not builtins.is_integer(n_bits):
raise TypeError("unsupported operand type: %r" % type(n_bits).__name__)
if n_bits <= 0:
raise ValueError("number of bits must be greater than 0.")
# Doesn't perform any floating-point operations.
quotient, remainder = divmod(n_bits, 8)
if remainder:
quotient += 1
random_bytes = rand_func(quotient)
mask = (1 << n_bits) - 1
return mask & integer.bytes_to_uint(random_bytes)
def generate_random_uint_atmost(n_bits, rand_func=generate_random_bytes):
"""
Generates a random unsigned integer with `n_bits` random bits.
:param n_bits:
Number of random bits to be generated at most.
:param rand_func:
Random bytes generator function.
:returns:
Returns an unsigned long integer with at most `n_bits` random bits.
The generated unsigned long integer will be between 0 and
(2**n_bits)-1 both inclusive.
"""
if not builtins.is_integer(n_bits):
raise TypeError("unsupported operand type: %r" % type(n_bits).__name__)
if n_bits <= 0:
raise ValueError("number of bits must be greater than 0.")
# Doesn't perform any floating-point operations.
quotient, remainder = divmod(n_bits, 8)
if remainder:
quotient += 1
random_bytes = rand_func(quotient)
mask = (1 << n_bits) - 1
return mask & integer.bytes_to_uint(random_bytes)
