Added sax-like parsers.

Author: ondrap

Data/JsonStream/Parser.hs

@@ -67,6 +67,9 @@ module Data.JsonStream.Parser (
   , filterI
   , takeI
   , toList
+    -- * SAX-like parsers
+  , arrayFound
+  , objectFound
 ) where
 
 import           Control.Applicative
@@ -222,6 +225,34 @@ array' valparse = Parser $ \tp ->
 arrayOf :: Parser a -> Parser a
 arrayOf valparse = array' (const valparse)
 
+-- | Generate start/end objects when an element is found, in between run a parser.
+-- The inner parser is not run if an array is not found.
+elemFound :: Element -> a -> a -> Parser a -> Parser a
+elemFound elsearch start end parser = Parser $ moreData handle
+  where
+    handle tok el _
+      | el == elsearch = Yield start (parseAndAppend (callParse parser tok))
+    handle tok _ _ = callParse ignoreVal tok
+
+    parseAndAppend (Failed err) = Failed err
+    parseAndAppend (Yield v np) = Yield v (parseAndAppend np)
+    parseAndAppend (MoreData (Parser np, ntp)) = MoreData (Parser (parseAndAppend . np), ntp)
+    parseAndAppend (Done ctx ntp) = Yield end (Done ctx ntp)
+
+-- | Generate start/end values when an array is found, in between run a parser.
+-- The inner parser is not run if an array is not found.
+objectFound :: a -> a -> Parser a -> Parser a
+objectFound = elemFound ObjectBegin
+
+-- | Generate start/end values when an object is found, in between run a parser.
+-- The inner parser is not run if an array is not found.
+--
+-- > >>> let test = "[[1,2,3],true,[],false,{\"key\":1}]" :: ByteString
+-- > >>> parseByteString (arrayOf (arrayFound 10 20 (1 .! integer))) test :: [Int]
+-- > [10,2,20,10,20]
+arrayFound :: a -> a -> Parser a -> Parser a
+arrayFound = elemFound ArrayBegin
+
 -- | Match nith item in an array.
 arrayWithIndexOf :: Int -> Parser a -> Parser a
 arrayWithIndexOf idx valparse = array' itemFn

test/ParserSpec.hs

@@ -105,6 +105,17 @@ specObjComb = describe "Object accesors" $ do
         msg = parseLazyByteString parser (BL.fromChunks test) :: [Int]
     msg `shouldBe` [1]
 
+  it "arrayFound generates events" $ do
+    let test = ["[[1,2,3],true,[],false,{\"key\":1}]"]
+        parser = arrayOf (arrayFound 10 20 (1 .! integer))
+        msg = parseLazyByteString parser (BL.fromChunks test) :: [Int]
+    msg `shouldBe` [10,2,20,10,20]
+
+  it "objectFound generates events" $ do
+    let test = ["[[1,2,3],true,[],false,{\"key\":1}]"]
+        parser = arrayOf (objectFound 10 20 ("key" .: integer))
+        msg = parseLazyByteString parser (BL.fromChunks test) :: [Int]
+    msg `shouldBe` [10,1,20]
 
 specEdge :: Spec
 specEdge = describe "Edge cases" $ do