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# = Secure random number generator interface.
#
# This library is an interface for secure random number generator which is
# suitable for generating session key in HTTP cookies, etc.
#
# It supports following secure random number generators.
#
# * Java's java.security.SecureRandom.
#
# == Example
#
# # random hexadecimal string.
# p SecureRandom.hex(10) #=> "52750b30ffbc7de3b362"
# p SecureRandom.hex(10) #=> "92b15d6c8dc4beb5f559"
# p SecureRandom.hex(11) #=> "6aca1b5c58e4863e6b81b8"
# p SecureRandom.hex(12) #=> "94b2fff3e7fd9b9c391a2306"
# p SecureRandom.hex(13) #=> "39b290146bea6ce975c37cfc23"
# ...
#
# # random base64 string.
# p SecureRandom.base64(10) #=> "EcmTPZwWRAozdA=="
# p SecureRandom.base64(10) #=> "9b0nsevdwNuM/w=="
# p SecureRandom.base64(10) #=> "KO1nIU+p9DKxGg=="
# p SecureRandom.base64(11) #=> "l7XEiFja+8EKEtY="
# p SecureRandom.base64(12) #=> "7kJSM/MzBJI+75j8"
# p SecureRandom.base64(13) #=> "vKLJ0tXBHqQOuIcSIg=="
# ...
#
# # random binary string.
# p SecureRandom.random_bytes(10) #=> "\016\t{\370g\310pbr\301"
# p SecureRandom.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337"
# ...
require 'java'
# Implements 1.8.7/1.9's SecureRandom class with java.security.SecureRandom.
class SecureRandom
# SecureRandom.random_bytes generates a random binary string.
#
# The argument n specifies the length of the result string.
#
# If n is not specified, 16 is assumed.
# It may be larger in future.
#
# If secure random number generator is not available,
# NotImplementedError is raised.
def self.random_bytes(n=nil)
n = (n.nil?) ? 16 : n.to_int
raise ArgumentError, "non-integer argument: #{n}" unless n.is_a?(Fixnum)
raise ArgumentError, "negative argument: #{n}" if n < 0
bytes = Java::byte[n].new
java.security.SecureRandom.new.nextBytes(bytes)
String.from_java_bytes bytes
end
# SecureRandom.hex generates a random hex string.
#
# The argument n specifies the length of the random length.
# The length of the result string is twice of n.
#
# If n is not specified, 16 is assumed.
# It may be larger in future.
#
# If secure random number generator is not available,
# NotImplementedError is raised.
def self.hex(n=nil)
random_bytes(n).unpack("H*")[0]
end
# SecureRandom.base64 generates a random base64 string.
#
# The argument n specifies the length of the random length.
# The length of the result string is about 4/3 of n.
#
# If n is not specified, 16 is assumed.
# It may be larger in future.
#
# If secure random number generator is not available,
# NotImplementedError is raised.
def self.base64(n=nil)
[random_bytes(n)].pack("m*").delete("\n")
end
# SecureRandom.random_number generates a random number.
#
# If an positive integer is given as n,
# SecureRandom.random_number returns an integer:
# 0 <= SecureRandom.random_number(n) < n.
#
# If 0 is given or an argument is not given,
# SecureRandom.random_number returns an float:
# 0.0 <= SecureRandom.random_number() < 1.0.
def self.random_number(n=0)
if 0 < n
java.security.SecureRandom.new.nextInt(n)
else
java.security.SecureRandom.new.nextDouble
end
end
end
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