## Module (chicken random)

This module provides access to entropy (as provided by the operating system) and a pseudo random number generator.

On UNIX systems entropy is by default obtained from `/dev/urandom`. On Linux, the `getrandom(2)` system call is used instead, if available. On OpenBSD it is `arc4random_buf(3)`, on Windows `RtlGenRandom`.

The pseudo random number generator is an implementation of the WELL algorithm.

#### set-pseudo-random-seed!

*[procedure]*

`(set-pseudo-random-seed! SEED [SIZE])`

Set seed for the PRNG from the at most `SIZE` bytes of `SEED`. which should be a byte vector or a string containing random data. If `SIZE` is not given, it defaults to the size of `SEED`. If `SIZE` (or the size of `SEED`) is below the required size of the random state used by the PRNG, then it will necessarily be initialized in a less random manner as possible.

#### pseudo-random-integer

*[procedure]*

`(pseudo-random-integer RANGE)`

Returns a uniformly distributed pseudo random integer between 0 and `RANGE-1`, which may be a big integer.

#### pseudo-random-real

*[procedure]*

`(pseudo-random-real)`

Returns a uniformly distributed pseudo-random inexact number between 0 and 1.

#### random-bytes

*[procedure]*

`(random-bytes [BUF [SIZE]])`

Returns random bytes from the available entropy source. If `BUF` is given, it should be a string or byte vector which will be filled with up to `SIZE` random bytes. `SIZE` defaults to the size of the `BUF` argument. If no arguments are given, `random-bytes` returns a freshly allocated byte vector of sufficient size to be used as a seed for `set-pseudo-random-seed!`.

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