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authormichaelt <what_is_it_to_do_anything@yahoo.com>2014-11-11 22:02:24 -0500
committermichaelt <what_is_it_to_do_anything@yahoo.com>2014-11-11 22:02:24 -0500
commit6c2fffdc8bc84879e103e6838e4f9fc762d50a2d (patch)
treea1cf38735800adf9757b1b609e9a6f75bf0b5941 /Pipes/Text
parent87f0d4d06a74aa59047a0bcb54eaf10acbfdf06a (diff)
downloadtext-pipes-6c2fffdc8bc84879e103e6838e4f9fc762d50a2d.tar.gz
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added eoflens to discriminate whether decoding was completed
Diffstat (limited to 'Pipes/Text')
-rw-r--r--Pipes/Text/Encoding.hs35
-rw-r--r--Pipes/Text/Tutorial.hs4
2 files changed, 37 insertions, 2 deletions
diff --git a/Pipes/Text/Encoding.hs b/Pipes/Text/Encoding.hs
index e00cd43..f26f168 100644
--- a/Pipes/Text/Encoding.hs
+++ b/Pipes/Text/Encoding.hs
@@ -12,6 +12,7 @@ module Pipes.Text.Encoding
12 -- $lenses 12 -- $lenses
13 Codec 13 Codec
14 , decode 14 , decode
15 , eof
15 -- * \'Viewing\' the Text in a byte stream 16 -- * \'Viewing\' the Text in a byte stream
16 -- $codecs 17 -- $codecs
17 , utf8 18 , utf8
@@ -88,9 +89,42 @@ type Codec
88 89
89-} 90-}
90 91
92
91decode :: ((b -> Constant b b) -> (a -> Constant b a)) -> a -> b 93decode :: ((b -> Constant b b) -> (a -> Constant b a)) -> a -> b
92decode codec a = getConstant (codec Constant a) 94decode codec a = getConstant (codec Constant a)
93 95
96{- | 'eof' tells you explicitly when decoding stops due to bad bytes or instead
97 reaches end-of-file happily. (Without it one just makes an explicit test
98 for emptiness of the resulting bytestring production using 'next')
99 Thus
100
101> decode (utf8 . eof) p = view (utf8 . eof) p = p^.utf8.eof
102
103 will be a text producer. If we hit undecodable bytes, the remaining
104 bytestring producer will be returned as a 'Left' value;
105 in the happy case, a 'Right' value is returned with the anticipated
106 return value for the original bytestring producer.
107 )
108
109-}
110
111eof :: Monad m => Lens' (Producer Text m (Producer ByteString m r))
112 (Producer Text m (Either (Producer ByteString m r) r))
113eof k p = fmap fromEither (k (toEither p)) where
114
115 fromEither = liftM (either id return)
116
117 toEither pp = do p <- pp
118 check p
119
120 check p = do e <- lift (next p)
121 case e of
122 Left r -> return (Right r)
123 Right (bs,pb) -> if B.null bs
124 then check pb
125 else return (Left (do yield bs
126 pb))
127
94 128
95{- $codecs 129{- $codecs
96 130
@@ -186,6 +220,7 @@ decodeStream = loop where
186 p') 220 p')
187{-# INLINABLE decodeStream#-} 221{-# INLINABLE decodeStream#-}
188 222
223
189{- $decoders 224{- $decoders
190 These are functions with the simple type: 225 These are functions with the simple type:
191 226
diff --git a/Pipes/Text/Tutorial.hs b/Pipes/Text/Tutorial.hs
index 07b8751..25f9e41 100644
--- a/Pipes/Text/Tutorial.hs
+++ b/Pipes/Text/Tutorial.hs
@@ -24,12 +24,12 @@ module Pipes.Text.Tutorial (
24 -- * Special types: @Producer Text m (Producer Text m r)@ and @FreeT (Producer Text m) m r@ 24 -- * Special types: @Producer Text m (Producer Text m r)@ and @FreeT (Producer Text m) m r@
25 -- $special 25 -- $special
26 ) where 26 ) where
27 27
28import Pipes 28import Pipes
29import Pipes.Text 29import Pipes.Text
30import Pipes.Text.IO 30import Pipes.Text.IO
31import Pipes.Text.Encoding 31import Pipes.Text.Encoding
32 32
33{- $intro 33{- $intro
34 This package provides @pipes@ utilities for /character streams/, 34 This package provides @pipes@ utilities for /character streams/,
35 realized as streams of 'Text' chunks. The individual chunks are uniformly /strict/, 35 realized as streams of 'Text' chunks. The individual chunks are uniformly /strict/,