Added Text.PortableLines.ByteString.Lazy

I didn't implement a super-efficient algorithm, but copied the algorithm used in Text.PortableLines.ByteString.

Text/PortableLines/ByteString/Lazy.hs

@@ -0,0 +1,30 @@
+module Text.PortableLines.ByteString.Lazy
+    ( lines8
+    ) where
+
+import Prelude as P hiding (lines)
+
+import Data.ByteString.Lazy (ByteString)
+
+import qualified Data.ByteString.Lazy as L
+import qualified Data.ByteString.Lazy.Char8 as L8
+
+-- | Like the 'L8.lines' function from Data.ByteString.Lazy.Char8, but treat the
+-- @\"\\r\\n\"@ and @\"\\r\"@ sequences as newlines too, not just @\"\\n\"@.
+--
+-- Input is assumed to be in ASCII or an ASCII-compatible encoding (at least
+-- with respect to newline characters).  For example, UTF-8 is fine, but UTF-16
+-- is not.
+lines8 :: ByteString -> [ByteString]
+lines8 str | L.null str = []
+           | otherwise  = let (line, rest) = breakNewline8 str
+                           in line : lines8 rest
+
+breakNewline8 :: ByteString -> (ByteString, ByteString)
+breakNewline8 str =
+    case L.break (\c -> c == 13 || c == 10) str of
+        (line, rest) | L.null rest                -> (line, rest)
+                     | L.length rest >= 2 &&
+                       rest `L.index` 0 == 13 &&
+                       rest `L.index` 1 == 10     -> (line, L.drop 2 rest)
+                     | otherwise                  -> (line, L.tail rest)

portable-lines.cabal

@@ -33,6 +33,7 @@ cabal-version:       >=1.8
 library
     exposed-modules: Text.PortableLines
                    , Text.PortableLines.ByteString
+                   , Text.PortableLines.ByteString.Lazy
     build-depends: base == 4.*
                  , bytestring
     ghc-options: -Wall -O2