src/Main.hs

   1 import Data.List (intercalate, intersperse)
   2 import System.Exit (ExitCode(..), exitWith)
   3 import System.IO (stderr, hPutStrLn)
   4
   5 import Cidr (Cidr(..),
   6              cidr_from_string)
   7
   8 import CommandLine (help_set,
   9                     help_text,
  10                     input_function,
  11                     Mode(..),
  12                     parse_errors,
  13                     parse_mode)
  14
  15 import IPv4Address
  16 import Octet
  17
  18 -- Some exit codes, used in the ExitFailure constructor.
  19 exit_invalid_cidr :: Int
  20 exit_invalid_cidr = 1
  21
  22 exit_args_parse_failed :: Int
  23 exit_args_parse_failed = 2
  24
  25
  26 -- A regular expression that matches a non-address character.
  27 non_addr_char :: String
  28 non_addr_char = "[^\\.0-9]"
  29
  30
  31 -- Add non_addr_chars on either side of the given String. This
  32 -- prevents (for example) the regex '127.0.0.1' from matching
  33 -- '127.0.0.100'.
  34 addr_barrier :: String -> String
  35 addr_barrier x = non_addr_char ++ x ++ non_addr_char
  36
  37
  38 -- The magic happens here. We take a CIDR String as an argument, and
  39 -- return the equivalent regular expression. We do this as follows:
  40 --
  41 -- 1. Compute the minimum possible value of each octet.
  42 -- 2. Compute the maximum possible value of each octet.
  43 -- 3. Generate a regex matching every value between those min and
  44 --    max values.
  45 -- 4. Join the regexes from step 3 with regexes matching periods.
  46 -- 5. Stick an address boundary on either side of the result.
  47 --cidr_to_regex :: String -> String
  48 cidr_to_regex :: Cidr.Cidr -> String
  49 cidr_to_regex cidr =
  50     addr_barrier (intercalate "\\." [range1, range2, range3, range4])
  51     where
  52       range1 = numeric_range min1 max1
  53       range2 = numeric_range min2 max2
  54       range3 = numeric_range min3 max3
  55       range4 = numeric_range min4 max4
  56       min1   = octet_to_int (min_octet1 (ipv4address cidr) (maskbits cidr))
  57       min2   = octet_to_int (min_octet2 (ipv4address cidr) (maskbits cidr))
  58       min3   = octet_to_int (min_octet3 (ipv4address cidr) (maskbits cidr))
  59       min4   = octet_to_int (min_octet4 (ipv4address cidr) (maskbits cidr))
  60       max1   = octet_to_int (max_octet1 (ipv4address cidr) (maskbits cidr))
  61       max2   = octet_to_int (max_octet2 (ipv4address cidr) (maskbits cidr))
  62       max3   = octet_to_int (max_octet3 (ipv4address cidr) (maskbits cidr))
  63       max4   = octet_to_int (max_octet4 (ipv4address cidr) (maskbits cidr))
  64
  65
  66
  67 -- Take a list of Strings, and return a regular expression matching
  68 -- any of them.
  69 alternate :: [String] -> String
  70 alternate terms = "(" ++ (concat (intersperse "|" terms)) ++ ")"
  71
  72
  73 -- Take two Ints as parameters, and return a regex matching any
  74 -- integer between them (inclusive).
  75 numeric_range :: Int -> Int -> String
  76 numeric_range x y =
  77     alternate (map show [lower..upper])
  78      where
  79        lower = minimum [x,y]
  80        upper = maximum [x,y]
  81
  82
  83 main :: IO ()
  84 main = do
  85   -- First, check for any errors that occurred while parsing
  86   -- the command line options.
  87   errors <- CommandLine.parse_errors
  88   if not (null errors)
  89     then do
  90       hPutStrLn stderr (concat errors)
  91       putStrLn CommandLine.help_text
  92       exitWith (ExitFailure exit_args_parse_failed)
  93     else do -- Nothing
  94
  95   -- Next, check to see if the 'help' option was passed to the
  96   -- program. If it was, display the help, and exit successfully.
  97   help_opt_set <- CommandLine.help_set
  98   if help_opt_set
  99     then do
 100       putStrLn CommandLine.help_text
 101       exitWith ExitSuccess
 102     else do -- Nothing
 103
 104   -- The input function we receive here should know what to read.
 105   inputfunc <- (CommandLine.input_function)
 106   input <- inputfunc
 107
 108   let cidr_strings = lines input
 109   let cidrs = map Cidr.cidr_from_string cidr_strings
 110
 111   if (any (== Cidr.None) cidrs)
 112     then do
 113       putStrLn "Error: not valid CIDR notation."
 114       exitWith (ExitFailure exit_invalid_cidr)
 115     else do -- Nothing
 116
 117   -- Get the mode of operation.
 118   mode <- CommandLine.parse_mode
 119
 120   case mode of
 121     Regex -> do
 122         let regexes = map cidr_to_regex cidrs
 123         putStrLn $ alternate regexes
 124     Reduce -> do
 125         putStr input