writes and builders for lossy Latin-1 encoding

  - this is useful for implementing protocols like HTTP

Blaze/ByteString/Builder/Char/Latin1.hs

@@ -0,0 +1,87 @@
+{-# OPTIONS_GHC -fno-warn-unused-imports #-} 
+-- ignore warning from 'import Data.Text.Encoding'
+
+-- |
+-- Module      : Blaze.ByteString.Builder.Char.Utf8
+-- Copyright   : (c) 2010 Jasper Van der Jeugt & Simon Meier
+-- License     : BSD3-style (see LICENSE)
+-- 
+-- Maintainer  : Simon Meier <iridcode@gmail.com>
+-- Stability   : experimental
+-- Portability : tested on GHC only
+--
+-- //Note:// This package is intended for low-level use like implementing
+-- protocols. If you need to //serialize// Unicode characters use one of the 
+-- UTF encodings (e.g. 'Blaze.ByteString.Builder.Char.UTF-8').
+--
+-- 'Write's and 'Builder's for serializing Unicode characters using the *lossy*
+-- Latin-1 (ISO 8859-1) encoding. Non-representable characters are dropped.
+--
+-- This corresponds to what the 'bytestring' package offer in
+-- 'Data.ByteString.Char8'.
+--
+module Blaze.ByteString.Builder.Char.Latin1
+    ( 
+      -- * Writing Latin-1 (ISO 8859-1) encodable characters to a buffer
+      writeChar
+
+      -- * Creating Builders from Latin-1 (ISO 8859-1) encodable characters
+    , fromChar
+    , fromString
+    , fromShow
+    , fromText
+    , fromLazyText
+    ) where
+
+import Foreign
+import Data.Char (ord)
+
+import qualified Data.Text               as TS
+import qualified Data.Text.Encoding      as TS -- imported for documentation links
+import qualified Data.Text.Lazy          as TL
+import qualified Data.Text.Lazy.Encoding as TS -- imported for documentation links
+
+import qualified Data.ByteString.Internal as S (c2w)
+
+import Blaze.ByteString.Builder.Internal
+
+-- | Write a UTF-8 encoded Unicode character to a buffer.
+--
+{-# INLINE writeChar #-}
+writeChar :: Char -> Write
+writeChar c0 = boundedWrite 1 (wio c0)
+  where
+    wio c | c < '\xFF' = writeN 1 $ \op -> poke op (S.c2w c)
+          | otherwise  = writeN 0 $ \_  -> return ()
+
+-- | /O(1)/. Serialize a Unicode character using the UTF-8 encoding.
+--
+fromChar :: Char -> Builder
+fromChar = fromWriteSingleton writeChar
+
+-- | /O(n)/. Serialize the Latin-1 encodable characters of a Unicode 'String'.
+--
+fromString :: String -> Builder
+fromString = fromWriteList writeChar
+
+-- | /O(n)/. Serialize a value by 'Show'ing it and Latin-1 encoding the
+-- encodable characters of the resulting 'String'.
+--
+fromShow :: Show a => a -> Builder
+fromShow = fromString . show
+
+-- | /O(n)/. Serialize the encodable characters of a strict Unicode 'TS.Text'
+-- value using the Latin-1 encoding.
+--
+{-# INLINE fromText #-}
+fromText :: TS.Text -> Builder
+fromText = fromString . TS.unpack
+
+
+
+-- | /O(n)/. Serialize the encodable characters of a lazy Unicode 'TS.Text'
+-- value using the Latin-1 encoding.
+--
+{-# INLINE fromLazyText #-}
+fromLazyText :: TL.Text -> Builder
+fromLazyText = fromString . TL.unpack