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add uuid4_seeded #67

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add uuid4_seeded #67

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25 changes: 23 additions & 2 deletions lib/uuid.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -385,6 +385,27 @@ defmodule UUID do
|> uuid_to_string(format)
end

@doc """
Generate a UUID v4 from a PRNG seed using the `rand` module.
This is useful if you want your UUIDs to
not necessarily be universally unique.

## Examples

```elixir
iex> seed = :rand.seed_s(:exsss, 0)
iex> {_updated_seed, uuid} = UUID.uuid4_seeded(seed)
iex> uuid
"7b17cdb2-dd7c-484d-9d77-42e52d99f72e"
```
"""
@spec uuid4_seeded(:rand.state()) :: {:rand.state, String.t()}
def uuid4_seeded(seed) do
{<<u0::48, _::4, u1::12, _::2, u2::62>>, seed} = :rand.bytes_s(16, seed)
{seed, <<u0::48, @uuid_v4::4, u1::12, @variant10::2, u2::62>>
|> uuid_to_string(:default)}
end

@doc """
Generate a new UUID v5. This version uses an SHA1 hash of fixed value (chosen
based on a namespace atom - see Appendix C of
Expand Down Expand Up @@ -618,7 +639,7 @@ defmodule UUID do
defp variant(_) do
raise ArgumentError, message: "Invalid argument; Not valid variant bits"
end

defp hex_str_to_binary(<< a1, a2, a3, a4, a5, a6, a7, a8,
b1, b2, b3, b4,
c1, c2, c3, c4,
Expand All @@ -633,7 +654,7 @@ defmodule UUID do
d(e5)::4, d(e6)::4, d(e7)::4, d(e8)::4,
d(e9)::4, d(e10)::4, d(e11)::4, d(e12)::4 >>
end

@compile {:inline, d: 1}

defp d(?0), do: 0
Expand Down