From a31c0f7df8fea235633a2eb82fb8d89b85a2fd47 Mon Sep 17 00:00:00 2001
From: Bryan O'Sullivan <bos@serpentine.com>
Date: Fri, 23 Dec 2011 12:24:17 -0800
Subject: [PATCH] Improve ASCII encoding performance in a safer way.
---
Data/Text/Encoding.hs | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/Data/Text/Encoding.hs b/Data/Text/Encoding.hs
index e6a99e08..b0fd388e 100644
--- a/Data/Text/Encoding.hs
+++ b/Data/Text/Encoding.hs
@@ -153,8 +153,9 @@ encodeUtf8 (Text arr off len) = unsafePerformIO $ do
where
loop n1 m1 ptr = go n1 m1
where
+ offLen = off + len
go !n !m
- | n == off+len = return (PS fp 0 m)
+ | n == offLen = return (PS fp 0 m)
| otherwise = do
let poke8 k v = poke (ptr `plusPtr` k) (fromIntegral v :: Word8)
ensure k act
@@ -168,8 +169,17 @@ encodeUtf8 (Text arr off len) = unsafePerformIO $ do
{-# INLINE ensure #-}
case A.unsafeIndex arr n of
w| w <= 0x7F -> ensure 1 $ do
- poke8 m w
- go (n+1) (m+1)
+ poke (ptr `plusPtr` m) (fromIntegral w :: Word8)
+ -- A single ASCII octet is likely to start a run of
+ -- them. We see better performance when we
+ -- special-case this assumption.
+ let ascii !t !u
+ | t == offLen || u == size || v >= 0x80 = go t u
+ | otherwise = do
+ poke (ptr `plusPtr` u) (fromIntegral v :: Word8)
+ ascii (t+1) (u+1)
+ where v = A.unsafeIndex arr t
+ ascii (n+1) (m+1)
| w <= 0x7FF -> ensure 2 $ do
poke8 m $ (w `shiftR` 6) + 0xC0
poke8 (m+1) $ (w .&. 0x3f) + 0x80
--
GitLab