1 files changed, 102 insertions, 0 deletions
diff --git a/src/filter.c b/src/filter.c
new file mode 100644
index 00000000..6d5e5a04
--- /dev/null
+++ b/src/filter.c
@@ -0,0 +1,102 @@
+/*
+  Copyright 2019-2020 David Robillard <d@drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "serd/serd.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+typedef struct {
+  const SerdSink* target;
+  SerdNode*       subject;
+  SerdNode*       predicate;
+  SerdNode*       object;
+  SerdNode*       graph;
+  bool            inclusive;
+} SerdFilterData;
+
+static void
+free_data(void* const handle)
+{
+  if (handle) {
+    SerdFilterData* data = (SerdFilterData*)handle;
+
+    serd_node_free(data->subject);
+    serd_node_free(data->predicate);
+    serd_node_free(data->object);
+    serd_node_free(data->graph);
+    free(data);
+  }
+}
+
+static SerdStatus
+serd_filter_on_event(void* const handle, const SerdEvent* const event)
+{
+  const SerdFilterData* const data = (SerdFilterData*)handle;
+
+  if (event->type == SERD_STATEMENT) {
+    const bool matches = serd_statement_matches(event->statement.statement,
+                                                data->subject,
+                                                data->predicate,
+                                                data->object,
+                                                data->graph);
+
+    if (data->inclusive == matches) {
+      // Emit statement with reset flags to avoid confusing the writer
+      SerdEvent out_event       = *event;
+      out_event.statement.flags = 0u;
+      return serd_sink_write_event(data->target, &out_event);
+    }
+
+    return SERD_SUCCESS; // Skip statement
+  }
+
+  return event->type == SERD_END ? SERD_SUCCESS
+                                 : serd_sink_write_event(data->target, event);
+}
+
+SerdSink*
+serd_filter_new(const SerdSink* const target,
+                const SerdNode* const subject,
+                const SerdNode* const predicate,
+                const SerdNode* const object,
+                const SerdNode* const graph,
+                const bool            inclusive)
+{
+  SerdFilterData* const data =
+    (SerdFilterData*)calloc(1, sizeof(SerdFilterData));
+
+  data->target    = target;
+  data->inclusive = inclusive;
+
+  if (subject && serd_node_type(subject) != SERD_VARIABLE) {
+    data->subject = serd_node_copy(subject);
+  }
+
+  if (predicate && serd_node_type(predicate) != SERD_VARIABLE) {
+    data->predicate = serd_node_copy(predicate);
+  }
+
+  if (object && serd_node_type(object) != SERD_VARIABLE) {
+    data->object = serd_node_copy(object);
+  }
+
+  if (graph && serd_node_type(graph) != SERD_VARIABLE) {
+    data->graph = serd_node_copy(graph);
+  }
+
+  return serd_sink_new(data, serd_filter_on_event, free_data);
+}