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authordefanor <defanor@uberspace.net>2018-02-22 00:51:57 +0300
committerdefanor <defanor@uberspace.net>2018-02-22 00:51:57 +0300
commit906669784eebc833366c1a6d348eacca7d5cc964 (patch)
tree3aac3c24b72a101ef12b6bbc89fcb7aadd5286c1 /Redland/Util.hs
parentb52e6bf3822150fbca9a6aadd3ce73dcdf7ed0ad (diff)
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Add a few statements and streams functions
Diffstat (limited to 'Redland/Util.hs')
-rw-r--r--Redland/Util.hs108
1 files changed, 87 insertions, 21 deletions
diff --git a/Redland/Util.hs b/Redland/Util.hs
index 0472dde..3d34206 100644
--- a/Redland/Util.hs
+++ b/Redland/Util.hs
@@ -11,7 +11,8 @@ Utility functions based on mid-level bindings.
module Redland.Util where
import Foreign
-import Control.Exception
+import Control.Monad
+import Data.Maybe
import Redland.LowLevel
import Redland.MidLevel
@@ -30,6 +31,19 @@ withHash world factory l f =
f hash
+-- * RDF Graph (librdf_model)
+
+withStatements :: ForeignPtr RedlandWorld
+ -> ForeignPtr RedlandModel
+ -> Triple
+ -> ([Triple] -> IO a)
+ -> IO a
+withStatements world model t f =
+ withNew (tripleToStatement world t) $ \statement ->
+ withNew (modelFindStatements model statement) $
+ streamToList >=> f
+
+
-- * RDF term (librdf_node)
data Node = BlankNode String
@@ -47,28 +61,29 @@ redlandNodeToNode rn = do
(_, True, _) -> LiteralNode <$> nodeGetLiteralValue rn
_ -> ResourceNode <$> (nodeGetURI rn >>= uriAsString)
+nodeToRedlandNode :: ForeignPtr RedlandWorld
+ -> Node
+ -> Initializer RedlandNode
+nodeToRedlandNode world (BlankNode s) = nodeFromBlankIdentifier world (Just s)
+nodeToRedlandNode world (LiteralNode s) = nodeFromLiteral world s Nothing False
+nodeToRedlandNode world (ResourceNode s) =
+ withNew (redlandURI world s) $ nodeFromURI world
+
-- * Parsers
-- | Tries different parsers until one of them succeeds.
-tryParseStringIntoModel :: ForeignPtr RedlandWorld
- -> [String]
- -- ^ parsers to try
- -> ForeignPtr RedlandModel
- -> ForeignPtr RedlandURI
- -- ^ base URI
- -> String
- -- ^ string to parse
- -> IO ()
-tryParseStringIntoModel world (parser:parsers) model uri str =
- handle tryNext $
- withNew (redlandParser world (Just parser) Nothing Nothing) $ \parser ->
- parseStringIntoModel parser str uri model
- where
- tryNext :: RedlandException -> IO ()
- tryNext (OperationException _) = tryParseStringIntoModel world parsers model uri str
- tryNext e = throw e
-tryParseStringIntoModel world [] model uri str = throw ParseFailure
+guessingParseStringIntoModel :: ForeignPtr RedlandWorld
+ -> ForeignPtr RedlandModel
+ -> ForeignPtr RedlandURI
+ -- ^ base URI
+ -> String
+ -- ^ string to parse
+ -> IO ()
+guessingParseStringIntoModel world model uri str = do
+ parser <- parserGuessName2 world Nothing (Just str) Nothing
+ withNew (redlandParser world parser Nothing Nothing) $ \p ->
+ parseStringIntoModel p str uri model
-- * Querying
@@ -85,8 +100,7 @@ withQuery :: ForeignPtr RedlandWorld
-> IO a
withQuery world model ql qs bURI f =
withNew (redlandQuery world ql Nothing qs bURI) $ \query ->
- withNew (modelQueryExecute model query) $ \results ->
- queryResultsToList results >>= f
+ withNew (modelQueryExecute model query) $ queryResultsToList >=> f
-- * Query results
@@ -112,6 +126,58 @@ queryResultsToList qr = do
pure (name, val)
+-- * RDF Triple (librdf_statement)
+
+data Triple = Triple { subject :: Maybe Node
+ , predicate :: Maybe Node
+ , object :: Maybe Node
+ } deriving (Eq, Show)
+
+statementToTriple :: ForeignPtr RedlandStatement
+ -> IO Triple
+statementToTriple statement = do
+ s <- componentToTriple statementGetSubject
+ p <- componentToTriple statementGetPredicate
+ o <- componentToTriple statementGetObject
+ pure $ Triple s p o
+ where
+ componentToTriple :: (ForeignPtr RedlandStatement ->
+ IO (Maybe (ForeignPtr RedlandNode)))
+ -> IO (Maybe Node)
+ componentToTriple f = do
+ c <- f statement
+ case c of
+ Just c' -> Just <$> redlandNodeToNode c'
+ Nothing -> pure Nothing
+
+tripleToStatement :: ForeignPtr RedlandWorld
+ -> Triple
+ -> Initializer RedlandStatement
+tripleToStatement world (Triple s p o) = do
+ statement <- redlandStatement world
+ let maybeSet f mn = case mn of
+ Just n -> withNew (nodeToRedlandNode world n) $ \n' ->
+ f statement (Just n')
+ Nothing -> pure ()
+ maybeSet statementSetSubject s
+ maybeSet statementSetPredicate p
+ maybeSet statementSetObject o
+ pure statement
+
+-- * Stream of triples (librdf_statement)
+
+streamToList :: ForeignPtr RedlandStream -> IO [Triple]
+streamToList stream = do
+ done <- streamEnd stream
+ if done
+ then pure []
+ else do
+ triple <- streamGetObject stream >>= statementToTriple
+ next <- streamNext stream
+ rest <- if next then streamToList stream else pure []
+ pure (triple : rest)
+
+
-- * Other
-- | Initializes world, storage, model, and base URI at once.