80 lines
2.2 KiB
HTML
80 lines
2.2 KiB
HTML
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<h2>Comments</h2>
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<pre><code>-- Single line comment
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{- Multi-line
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comment -}</code></pre>
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<h2>Strings and characters</h2>
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<pre><code>'a'
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'\n'
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'\^A'
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'\^]'
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'\NUL'
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'\23'
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'\o75'
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'\xFE'
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"Here is a backslant \\ as well as \137, \
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\a numeric escape character, and \^X, a control character."</code></pre>
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<h2>Numbers</h2>
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<pre><code>42
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123.456
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123.456e-789
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1e+3
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0o74
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0XAF</code></pre>
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<h2>Full example</h2>
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<pre><code>hGetLine h =
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wantReadableHandle_ "Data.ByteString.hGetLine" h $
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\ h_@Handle__{haByteBuffer} -> do
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flushCharReadBuffer h_
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buf <- readIORef haByteBuffer
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if isEmptyBuffer buf
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then fill h_ buf 0 []
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else haveBuf h_ buf 0 []
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where
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fill h_@Handle__{haByteBuffer,haDevice} buf len xss =
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len `seq` do
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(r,buf') <- Buffered.fillReadBuffer haDevice buf
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if r == 0
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then do writeIORef haByteBuffer buf{ bufR=0, bufL=0 }
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if len > 0
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then mkBigPS len xss
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else ioe_EOF
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else haveBuf h_ buf' len xss
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haveBuf h_@Handle__{haByteBuffer}
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buf@Buffer{ bufRaw=raw, bufR=w, bufL=r }
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len xss =
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do
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off <- findEOL r w raw
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let new_len = len + off - r
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xs <- mkPS raw r off
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-- if eol == True, then off is the offset of the '\n'
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-- otherwise off == w and the buffer is now empty.
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if off /= w
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then do if (w == off + 1)
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then writeIORef haByteBuffer buf{ bufL=0, bufR=0 }
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else writeIORef haByteBuffer buf{ bufL = off + 1 }
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mkBigPS new_len (xs:xss)
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else do
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fill h_ buf{ bufL=0, bufR=0 } new_len (xs:xss)
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-- find the end-of-line character, if there is one
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findEOL r w raw
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| r == w = return w
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| otherwise = do
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c <- readWord8Buf raw r
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if c == fromIntegral (ord '\n')
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then return r -- NB. not r+1: don't include the '\n'
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else findEOL (r+1) w raw
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mkPS :: RawBuffer Word8 -> Int -> Int -> IO ByteString
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mkPS buf start end =
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create len $ \p ->
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withRawBuffer buf $ \pbuf -> do
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copyBytes p (pbuf `plusPtr` start) len
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where
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len = end - start</code></pre>
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