Add statement filter sink and serd-filter tool

3 files changed, 62 insertions, 0 deletions

diff --git a/include/serd/filter.h b/include/serd/filter.h
new file mode 100644
index 00000000..856df530
--- /dev/null
+++ b/include/serd/filter.h
@@ -0,0 +1,60 @@
+// Copyright 2011-2022 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#ifndef SERD_FILTER_H
+#define SERD_FILTER_H
+
+#include "serd/attributes.h"
+#include "serd/node.h"
+#include "serd/sink.h"
+#include "serd/world.h"
+#include "zix/attributes.h"
+
+#include <stdbool.h>
+
+SERD_BEGIN_DECLS
+
+/**
+   @defgroup serd_filter Filter
+   @ingroup serd_streaming
+   @{
+*/
+
+/**
+   Return a new sink that filters out statements that do not match a pattern.
+
+   The returned sink acts like `target` in all respects, except that some
+   statements may be dropped.
+
+   @param world The world to create the sink in.
+
+   @param target The target sink to pass the filtered data to.
+
+   @param subject The optional subject of the filter pattern.
+
+   @param predicate The optional predicate of the filter pattern.
+
+   @param object The optional object of the filter pattern.
+
+   @param graph The optional graph of the filter pattern.
+
+   @param inclusive If true, then only statements that match the pattern are
+   passed through.  Otherwise, only statements that do *not* match the pattern
+   are passed through.
+*/
+SERD_API SerdSink* ZIX_ALLOCATED
+serd_filter_new(const SerdWorld* ZIX_NONNULL world,
+                const SerdSink* ZIX_NONNULL  target,
+                const SerdNode* ZIX_NULLABLE subject,
+                const SerdNode* ZIX_NULLABLE predicate,
+                const SerdNode* ZIX_NULLABLE object,
+                const SerdNode* ZIX_NULLABLE graph,
+                bool                         inclusive);
+
+/**
+   @}
+*/
+
+SERD_END_DECLS
+
+#endif // SERD_FILTER_H
diff --git a/include/serd/serd.h b/include/serd/serd.h
index f874a0cc..77d1abf8 100644
--- a/include/serd/serd.h
+++ b/include/serd/serd.h
@@ -72,6 +72,7 @@
 #include "serd/canon.h"
 #include "serd/env.h"
 #include "serd/event.h"
+#include "serd/filter.h"
 #include "serd/sink.h"
 
 /**
diff --git a/include/serd/status.h b/include/serd/status.h
index c6047aff..5aedd5a6 100644
--- a/include/serd/status.h
+++ b/include/serd/status.h
@@ -39,6 +39,7 @@ typedef enum {
   SERD_BAD_URI,     ///< Invalid or unresolved URI
   SERD_BAD_DATA,    ///< Invalid data
   SERD_BAD_LITERAL, ///< Invalid literal
+  SERD_BAD_PATTERN, ///< Invalid statement pattern
 } SerdStatus;
 
 /// Return a string describing a status code