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#!/usr/bin/env racket
#lang racket/base
(require net/base64)

;; tunables
(define amount 32)
(define sources (list "/dev/urandom" "/dev/random"))


(define (read-entropy amt srcs)
    (let ((src (findf file-exists? srcs))
          (reader (lambda () (read-bytes amt))))
      (if (not src)
          (format "Error: can't find available source (in ~s)" srcs)
          (base64-encode (with-input-from-file src reader)))))

(display (read-entropy amount sources))