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--- Functions for generating random data
--
-- The strings generated here are not cryptographically secure, but they should
-- be sufficient for most purposes.
--
-- @author Daniel Miller
-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
-- @class module
-- @name rand
local require = require
local have_openssl, openssl = pcall(require, "openssl")
local math = require "math"
local random = math.random
local string = require "string"
local byte = string.byte
local char = string.char
local sub = string.sub
local table = require "table"
local concat = table.concat
local type = type
local _ENV = {}
local get_random_bytes
if have_openssl then
get_random_bytes = openssl.rand_pseudo_bytes
else
get_random_bytes = require "nmap".get_random_bytes
end
--- Generate a random string.
--
-- You can either provide your own charset or the function will generate random
-- bytes, which may include null bytes.
-- @param len Length of the string we want to generate.
-- @param charset Charset that will be used to generate the string. String or table
-- @return A random string of length <code>len</code> consisting of
-- characters from <code>charset</code> if one was provided, or random bytes otherwise.
random_string = function(len, charset)
local t = {}
if charset then
if type(charset) == "string" then
for i=1,len do
local r = random(#charset)
t[i] = sub(charset, r, r)
end
else
for i=1,len do
t[i]=charset[random(#charset)]
end
end
else
return get_random_bytes(len)
end
return concat(t)
end
local random_string = random_string
--- Generate a charset that can be passed to <code>random_string</code>
--
-- @param left_bound The lower bound character or byte value of the set
-- @param right_bound The upper bound character or byte value of the set
-- @param charset Optional, a charset table to augment. By default a new charset is created.
-- @return A charset table
function charset(left_bound, right_bound, charset)
local t = charset or {}
left_bound = type(left_bound)=="string" and byte(left_bound) or left_bound
right_bound = type(right_bound)=="string" and byte(right_bound) or right_bound
if left_bound > right_bound then
return t
end
for i=left_bound,right_bound do
t[#t+1] = char(i)
end
return t
end
local charset = charset
local alpha_charset = charset('a', 'z')
--- Generate a random alpha word
--
-- Convenience wrapper around <code>random_string</code> to generate a random
-- string of lowercase alphabetic characters.
-- @param len The length of word to return
-- @return A string of random characters between 'a' and 'z' inclusive.
function random_alpha (len)
return random_string(len, alpha_charset)
end
return _ENV
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