crypto_rand v1.0.2 CryptoRand

CryptoRand provides fast and efficient crytographically strong versions of several Enum functions that rely on :rand uniform for underlying randomness. CryptoRand functions also operate on String.t() where appropriate.

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Functions

Clear CryptoRand process dictionary entries

Takes count random items from an enumerable source or graphemes from a string source

Generate random uniform integer in the range 1 to max

Generate a random binary such that n integers in the range 0 to max-1 can be parsed by processing the binary k bits at a time, where k is the number of bits required to represent max-1

Generate n random uniform integers in the range 1 to max

Link to this section Functions

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clear()
clear() :: :ok

Clear CryptoRand process dictionary entries.

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random(source, rand_bytes \\ &:crypto.strong_rand_bytes/1)
random(Enumerable.t() | String.t(), (non_neg_integer() -> binary())) :: any()

Returns a random element of source.

Randomness is generated using rand_bytes/1.

Raises Enum.EmptyError if sourceis empty.

This function uses bytes from the function rand_bytes to generate a random integer in the range [0, n-1], where n is the number of elements in the source enumerable or graphemes in the source string. The element at the random integer index is returned.

Example

iex> CryptoRand.random(1..10)
7

iex> CryptoRand.random("aeiou")
"i"
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shuffle(source, rand_bytes \\ &:crypto.strong_rand_bytes/1)
shuffle(Enumerable.t() | String.t(), (non_neg_integer() -> binary())) ::
  list() | String.t()

Shuffles the elements of source.

Randomness is generated using rand_bytes/1.

Returns a list with the elements of an enumerable source shuffled or a String.t() with the graphemes of a string source shuffled.

Example

iex> CryptoRand.shuffle([1,2,3,4,5])
[5, 2, 3, 4, 1]

iex> CryptoRand.shuffle(?a..?z)
'chivgpxldtrokyuqsnjmawzfeb'

iex> CryptoRand.shuffle("dingosky")
"ndsyigok"
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take_random(source, count, rand_bytes \\ &:crypto.strong_rand_bytes/1)
take_random(
  Enumerable.t() | String.t(),
  non_neg_integer(),
  (non_neg_integer() -> binary())
) :: list() | String.t()

Takes count random items from an enumerable source or graphemes from a string source.

Returns a list for a source enumerable and a String.t() for a source string.

Examples

iex> CryptoRand.take_random(?a..?z, 5)
'kwvhn'

iex> CryptoRand.take_random([?a,?e,?i,?o,?u], 3)
'eao'

iex> CryptoRand.take_random("dingosky", 3)
"dgi"
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uniform(max, rand_bytes \\ &:crypto.strong_rand_bytes/1)

Generate random uniform integer in the range 1 to max.

Randomness is generated using rand_bytes/1.

Example

iex> CryptoRand.uniform(16)
13
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uniform_bytes(max, n, rand_bytes \\ &:crypto.strong_rand_bytes/1)
uniform_bytes(pos_integer(), non_neg_integer(), (non_neg_integer() -> binary())) ::
  binary()

Generate a random binary such that n integers in the range 0 to max-1 can be parsed by processing the binary k bits at a time, where k is the number of bits required to represent max-1.

Randomness is generated using rand_bytes/1.

This function provides bytes such that each k bits can be used to index into an enumerable or String.t() of length max.

Example

iex> CryptoRand.uniform_bytes(12, 9) |> IO.inspect() |> binary_digits()
<<148, 137, 83, 155, 160>>
"10010100 10001001 01010011 10011011 10100000"
iex> k = max |> :math.log2() |> :math.ceil() |> round()
4

For the bytes returned above, 9 integers can be parsed 4 bits at a time with each integer value being less than 12. Note none of the 4-bit clusters starts with 11, which means each 4-bit integer will be less than 12, as desired.

The function binary_digits/1 is not shown.

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uniform_list(max, n, rand_bytes \\ &:crypto.strong_rand_bytes/1)
uniform_list(pos_integer(), non_neg_integer(), (non_neg_integer() -> binary())) ::
  list()

Generate n random uniform integers in the range 1 to max.

Randomness is generated using rand_bytes/1.

Example

iex> CryptoRand.uniform_list(16, 8)
[6, 9, 16, 4, 12, 4, 4, 10]