From a339e2422fcffe41e515aff7eee3f501ca70f311 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 13 May 2018 00:48:31 +0200
Subject: Zero node padding before passing to reader sinks

---
 src/n3.c     |  9 ++++++---
 src/node.c   | 25 +++++++++++++++++++++++++
 src/node.h   |  1 +
 src/reader.c |  5 +++++
 src/stack.h  |  1 +
 5 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/src/n3.c b/src/n3.c
index a95a85b7..712c3cc7 100644
--- a/src/n3.c
+++ b/src/n3.c
@@ -1044,10 +1044,10 @@ read_object(SerdReader* reader, ReadContext* ctx, bool emit, bool* ate_dot)
 		o->flags = flags;
 	}
 
-	if (ret && emit && simple) {
+	if (ret && emit && simple && o) {
 		ret = emit_statement(reader, *ctx, o);
 	} else if (ret && !emit) {
-		ctx->object   = o;
+		ctx->object = o;
 		return true;
 	}
 
@@ -1255,6 +1255,7 @@ read_base(SerdReader* reader, bool sparql, bool token)
 	if (!uri) {
 		return false;
 	} else if (reader->sink->base) {
+		serd_node_zero_pad(uri);
 		reader->sink->base(reader->sink->handle, uri);
 	}
 
@@ -1289,12 +1290,14 @@ read_prefixID(SerdReader* reader, bool sparql, bool token)
 	}
 
 	read_ws_star(reader);
-	const SerdNode* uri = read_IRIREF(reader);
+	SerdNode* uri = read_IRIREF(reader);
 	if (!uri) {
 		return false;
 	}
 
 	if (reader->sink->prefix) {
+		serd_node_zero_pad(name);
+		serd_node_zero_pad(uri);
 		ret = !reader->sink->prefix(reader->sink->handle, name, uri);
 	}
 	if (!sparql) {
diff --git a/src/node.c b/src/node.c
index e6dfd451..8f32c536 100644
--- a/src/node.c
+++ b/src/node.c
@@ -210,6 +210,24 @@ serd_node_new_uri(const char* str)
 	return serd_node_new_simple(SERD_URI, str);
 }
 
+/**
+   Zero node padding.
+
+   This is used for nodes which live in re-used stack memory during reading,
+   which must be normalized before being passed to a sink so comparison will
+   work correctly.
+*/
+void
+serd_node_zero_pad(SerdNode* node)
+{
+	char*        buf         = serd_node_buffer(node);
+	const size_t size        = node->n_bytes;
+	const size_t padded_size = serd_node_pad_size(node->n_bytes);
+	if (padded_size > size) {
+		memset(buf + size, 0, padded_size - size);
+	}
+}
+
 SerdNode*
 serd_node_copy(const SerdNode* node)
 {
@@ -218,6 +236,13 @@ serd_node_copy(const SerdNode* node)
 	}
 
 	const size_t size = serd_node_total_size(node);
+#ifndef NDEBUG
+	const size_t unpadded_size = node->n_bytes;
+	const size_t padded_size   = serd_node_pad_size(node->n_bytes);
+	for (size_t i = 0; i < padded_size - unpadded_size; ++i) {
+		assert(serd_node_buffer_c(node)[unpadded_size + i] == '\0');
+	}
+#endif
 	SerdNode*    copy = (SerdNode*)calloc(1, size + 3);
 	memcpy(copy, node, size);
 	return copy;
diff --git a/src/node.h b/src/node.h
index 1dbb10d0..47d73a32 100644
--- a/src/node.h
+++ b/src/node.h
@@ -41,6 +41,7 @@ serd_node_buffer_c(const SerdNode* node)
 
 SerdNode* serd_node_malloc(size_t n_bytes, SerdNodeFlags flags, SerdType type);
 void      serd_node_set(SerdNode** dst, const SerdNode* src);
+void      serd_node_zero_pad(SerdNode* node);
 SerdNode* serd_node_new_resolved_uri_i(const char* str, const SerdURI* base);
 
 #endif  // SERD_NODE_H
diff --git a/src/reader.c b/src/reader.c
index e6629305..5d8d1dbd 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -118,6 +118,11 @@ emit_statement(SerdReader* reader, ReadContext ctx, SerdNode* o)
 	if (!graph && reader->default_graph) {
 		graph = reader->default_graph;
 	}
+
+	/* Zero the pad of the object node on the top of the stack.  Lower nodes
+	   (subject and predicate) were already zeroed by subsequent pushes. */
+	serd_node_zero_pad(o);
+
 	bool ret = !reader->sink->statement ||
 		!reader->sink->statement(
 			reader->sink->handle, *ctx.flags, graph,
diff --git a/src/stack.h b/src/stack.h
index 24641461..5c84df37 100644
--- a/src/stack.h
+++ b/src/stack.h
@@ -82,6 +82,7 @@ static inline void
 serd_stack_pop_to(SerdStack* stack, size_t n_bytes)
 {
 	assert(stack->size >= n_bytes);
+	memset(stack->buf + n_bytes, 0, stack->size - n_bytes);
 	stack->size = n_bytes;
 }
 
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