diff options
Diffstat (limited to 'compiler/utils/StringBuffer.hs')
| -rw-r--r-- | compiler/utils/StringBuffer.hs | 40 |
1 files changed, 39 insertions, 1 deletions
diff --git a/compiler/utils/StringBuffer.hs b/compiler/utils/StringBuffer.hs index fcc344554b..d75e537fca 100644 --- a/compiler/utils/StringBuffer.hs +++ b/compiler/utils/StringBuffer.hs @@ -6,7 +6,7 @@ Buffers for scanning string input stored in external arrays. -} -{-# LANGUAGE CPP, MagicHash, UnboxedTuples #-} +{-# LANGUAGE BangPatterns, CPP, MagicHash, UnboxedTuples #-} {-# OPTIONS_GHC -O #-} -- We always optimise this, otherwise performance of a non-optimised -- compiler is severely affected @@ -32,6 +32,7 @@ module StringBuffer stepOn, offsetBytes, byteDiff, + atLine, -- * Conversion lexemeToString, @@ -240,6 +241,43 @@ byteDiff s1 s2 = cur s2 - cur s1 atEnd :: StringBuffer -> Bool atEnd (StringBuffer _ l c) = l == c +-- | Computes a 'StringBuffer' which points to the first character of the +-- wanted line. Lines begin at 1. +atLine :: Int -> StringBuffer -> Maybe StringBuffer +atLine line sb@(StringBuffer buf len _) = + inlinePerformIO $ + withForeignPtr buf $ \p -> do + p' <- skipToLine line len p + if p' == nullPtr + then return Nothing + else + let + delta = p' `minusPtr` p + in return $ Just (sb { cur = delta + , len = len - delta + }) + +skipToLine :: Int -> Int -> Ptr Word8 -> IO (Ptr Word8) +skipToLine !line !len !op0 = go 1 op0 + where + !opend = op0 `plusPtr` len + + go !i_line !op + | op >= opend = pure nullPtr + | i_line == line = pure op + | otherwise = do + w <- peek op :: IO Word8 + case w of + 10 -> go (i_line + 1) (plusPtr op 1) + 13 -> do + -- this is safe because a 'StringBuffer' is + -- guaranteed to have 3 bytes sentinel values. + w' <- peek (plusPtr op 1) :: IO Word8 + case w' of + 10 -> go (i_line + 1) (plusPtr op 2) + _ -> go (i_line + 1) (plusPtr op 1) + _ -> go i_line (plusPtr op 1) + -- ----------------------------------------------------------------------------- -- Conversion |