-- |
-- Module      : Data.ASN1.Internal
-- License     : BSD-style
-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
-- Stability   : experimental
-- Portability : unknown
--
module Data.ASN1.Internal
    ( uintOfBytes
    , intOfBytes
    , bytesOfUInt
    , bytesOfInt
    , putVarEncodingIntegral
    ) where

import Data.Word
import Data.Bits
import Data.ByteString (ByteString)
import qualified Data.ByteString as B

{- | uintOfBytes returns the number of bytes and the unsigned integer represented by the bytes -}
uintOfBytes :: ByteString -> (Int, Integer)
uintOfBytes :: ByteString -> (Int, Integer)
uintOfBytes ByteString
b = (ByteString -> Int
B.length ByteString
b, (Integer -> Word8 -> Integer) -> Integer -> ByteString -> Integer
forall a. (a -> Word8 -> a) -> a -> ByteString -> a
B.foldl (\Integer
acc Word8
n -> (Integer
acc Integer -> Int -> Integer
forall a. Bits a => a -> Int -> a
`shiftL` Int
8) Integer -> Integer -> Integer
forall a. Num a => a -> a -> a
+ Word8 -> Integer
forall a b. (Integral a, Num b) => a -> b
fromIntegral Word8
n) Integer
0 ByteString
b)

--bytesOfUInt i = B.unfoldr (\x -> if x == 0 then Nothing else Just (fromIntegral (x .&. 0xff), x `shiftR` 8)) i
bytesOfUInt :: Integer -> [Word8]
bytesOfUInt :: Integer -> [Word8]
bytesOfUInt Integer
x = [Word8] -> [Word8]
forall a. [a] -> [a]
reverse (Integer -> [Word8]
forall t a. (Integral t, Num a, Bits a, Bits t) => t -> [a]
list Integer
x)
    where list :: t -> [a]
list t
i = if t
i t -> t -> Bool
forall a. Ord a => a -> a -> Bool
<= t
0xff then [t -> a
forall a b. (Integral a, Num b) => a -> b
fromIntegral t
i] else (t -> a
forall a b. (Integral a, Num b) => a -> b
fromIntegral t
i a -> a -> a
forall a. Bits a => a -> a -> a
.&. a
0xff) a -> [a] -> [a]
forall a. a -> [a] -> [a]
: t -> [a]
list (t
i t -> Int -> t
forall a. Bits a => a -> Int -> a
`shiftR` Int
8)

{- | intOfBytes returns the number of bytes in the list and
   the represented integer by a two's completement list of bytes -}
intOfBytes :: ByteString -> (Int, Integer)
intOfBytes :: ByteString -> (Int, Integer)
intOfBytes ByteString
b
    | ByteString -> Int
B.length ByteString
b Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0   = (Int
0, Integer
0)
    | Bool
otherwise         = (Int
len, if Bool
isNeg then -(Integer
maxIntLen Integer -> Integer -> Integer
forall a. Num a => a -> a -> a
- Integer
v Integer -> Integer -> Integer
forall a. Num a => a -> a -> a
+ Integer
1) else Integer
v)
    where
        (Int
len, Integer
v)  = ByteString -> (Int, Integer)
uintOfBytes ByteString
b
        maxIntLen :: Integer
maxIntLen = Integer
2 Integer -> Int -> Integer
forall a b. (Num a, Integral b) => a -> b -> a
^ (Int
8 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
len) Integer -> Integer -> Integer
forall a. Num a => a -> a -> a
- Integer
1
        isNeg :: Bool
isNeg     = Word8 -> Int -> Bool
forall a. Bits a => a -> Int -> Bool
testBit (ByteString -> Word8
B.head ByteString
b) Int
7

{- | bytesOfInt convert an integer into a two's completemented list of bytes -}
bytesOfInt :: Integer -> [Word8]
bytesOfInt :: Integer -> [Word8]
bytesOfInt Integer
i
    | Integer
i Integer -> Integer -> Bool
forall a. Ord a => a -> a -> Bool
> Integer
0      = if Word8 -> Int -> Bool
forall a. Bits a => a -> Int -> Bool
testBit ([Word8] -> Word8
forall a. [a] -> a
head [Word8]
uints) Int
7 then Word8
0 Word8 -> [Word8] -> [Word8]
forall a. a -> [a] -> [a]
: [Word8]
uints else [Word8]
uints
    | Integer
i Integer -> Integer -> Bool
forall a. Eq a => a -> a -> Bool
== Integer
0     = [Word8
0]
    | Bool
otherwise  = if Word8 -> Int -> Bool
forall a. Bits a => a -> Int -> Bool
testBit ([Word8] -> Word8
forall a. [a] -> a
head [Word8]
nints) Int
7 then [Word8]
nints else Word8
0xff Word8 -> [Word8] -> [Word8]
forall a. a -> [a] -> [a]
: [Word8]
nints
    where
        uints :: [Word8]
uints = Integer -> [Word8]
bytesOfUInt (Integer -> Integer
forall a. Num a => a -> a
abs Integer
i)
        nints :: [Word8]
nints = [Word8] -> [Word8]
forall a. [a] -> [a]
reverse ([Word8] -> [Word8]) -> [Word8] -> [Word8]
forall a b. (a -> b) -> a -> b
$ [Word8] -> [Word8]
forall a. (Num a, Eq a) => [a] -> [a]
plusOne ([Word8] -> [Word8]) -> [Word8] -> [Word8]
forall a b. (a -> b) -> a -> b
$ [Word8] -> [Word8]
forall a. [a] -> [a]
reverse ([Word8] -> [Word8]) -> [Word8] -> [Word8]
forall a b. (a -> b) -> a -> b
$ (Word8 -> Word8) -> [Word8] -> [Word8]
forall a b. (a -> b) -> [a] -> [b]
map Word8 -> Word8
forall a. Bits a => a -> a
complement ([Word8] -> [Word8]) -> [Word8] -> [Word8]
forall a b. (a -> b) -> a -> b
$ [Word8]
uints
        plusOne :: [a] -> [a]
plusOne []     = [a
1]
        plusOne (a
x:[a]
xs) = if a
x a -> a -> Bool
forall a. Eq a => a -> a -> Bool
== a
0xff then a
0 a -> [a] -> [a]
forall a. a -> [a] -> [a]
: [a] -> [a]
plusOne [a]
xs else (a
xa -> a -> a
forall a. Num a => a -> a -> a
+a
1) a -> [a] -> [a]
forall a. a -> [a] -> [a]
: [a]
xs

{- ASN1 often uses a particular kind of 7-bit encoding of integers like
   in the case of long tags or encoding of integer component of OID's.
   Use this function for such an encoding. Assumes a positive integer.

   Here is the description of the algorithm of the above encoding:

   1. The integer is chunked up into 7-bit groups. Each of these 7bit
      chunks are encoded as a single octet.

   2. All the octets except the last one has its 8th bit set.
-}
putVarEncodingIntegral :: (Bits i, Integral i) => i -> ByteString
putVarEncodingIntegral :: i -> ByteString
putVarEncodingIntegral i
i = ByteString -> ByteString
B.reverse (ByteString -> ByteString) -> ByteString -> ByteString
forall a b. (a -> b) -> a -> b
$ ((i, Bool) -> Maybe (Word8, (i, Bool))) -> (i, Bool) -> ByteString
forall a. (a -> Maybe (Word8, a)) -> a -> ByteString
B.unfoldr (i, Bool) -> Maybe (Word8, (i, Bool))
forall a a.
(Integral a, Bits a, Bits a, Num a) =>
(a, Bool) -> Maybe (a, (a, Bool))
genOctets (i
i,Bool
True)
    where genOctets :: (a, Bool) -> Maybe (a, (a, Bool))
genOctets (a
x,Bool
first)
            | a
x a -> a -> Bool
forall a. Ord a => a -> a -> Bool
> a
0     =
                let out :: a
out = a -> a
forall a b. (Integral a, Num b) => a -> b
fromIntegral (a
x a -> a -> a
forall a. Bits a => a -> a -> a
.&. a
0x7F) a -> a -> a
forall a. Bits a => a -> a -> a
.|. (if Bool
first then a
0 else a
0x80) in
                (a, (a, Bool)) -> Maybe (a, (a, Bool))
forall a. a -> Maybe a
Just (a
out, (a -> Int -> a
forall a. Bits a => a -> Int -> a
shiftR a
x Int
7, Bool
False))
            | Bool
otherwise = Maybe (a, (a, Bool))
forall a. Maybe a
Nothing