From 9cf28251f67e91a97bb75a74ad1ed23bac609b0d Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sat, 20 Feb 2021 16:50:11 -0500
Subject: Zero node padding before passing to reader sinks

---
 src/n3.c     |  5 ++++-
 src/node.c   | 30 +++++++++++++++++++++++++++++-
 src/node.h   |  3 +++
 src/reader.c |  4 ++++
 src/stack.h  |  1 +
 5 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/src/n3.c b/src/n3.c
index a5299c38..bf65b038 100644
--- a/src/n3.c
+++ b/src/n3.c
@@ -1178,7 +1178,7 @@ 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;
@@ -1408,6 +1408,7 @@ read_base(SerdReader* reader, bool sparql, bool token)
 
   SerdNode* uri = NULL;
   TRY(st, read_IRIREF(reader, &uri));
+  serd_node_zero_pad(uri);
   TRY(st, serd_sink_write_base(reader->sink, uri));
 
   read_ws_star(reader);
@@ -1448,6 +1449,8 @@ read_prefixID(SerdReader* reader, bool sparql, bool token)
   SerdNode* uri = NULL;
   TRY(st, read_IRIREF(reader, &uri));
 
+  serd_node_zero_pad(name);
+  serd_node_zero_pad(uri);
   st = serd_sink_write_prefix(reader->sink, name, uri);
 
   if (!sparql) {
diff --git a/src/node.c b/src/node.c
index 522a939a..ed113bbd 100644
--- a/src/node.c
+++ b/src/node.c
@@ -109,6 +109,27 @@ serd_node_set(SerdNode** dst, const SerdNode* src)
   memcpy(*dst, src, size);
 }
 
+/**
+   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);
+
+  memset(buf + size, 0, padded_size - size);
+
+  if (node->flags & (SERD_HAS_DATATYPE | SERD_HAS_LANGUAGE)) {
+    serd_node_zero_pad(serd_node_meta(node));
+  }
+}
+
 SerdNode*
 serd_new_simple_node(SerdNodeType type, const SerdStringView str)
 {
@@ -206,7 +227,14 @@ serd_node_copy(const SerdNode* node)
   }
 
   const size_t size = serd_node_total_size(node);
-  SerdNode*    copy = (SerdNode*)calloc(1, size + 3);
+#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 5c6f790e..6bebdb6d 100644
--- a/src/node.h
+++ b/src/node.h
@@ -46,6 +46,9 @@ void
 serd_node_set(SerdNode* SERD_NONNULL* SERD_NONNULL dst,
               const SerdNode* SERD_NONNULL         src);
 
+void
+serd_node_zero_pad(SerdNode* SERD_NONNULL node);
+
 /// Create a new URI from a string, resolved against a base URI
 SerdNode* SERD_ALLOCATED
 serd_new_resolved_uri(SerdStringView string, SerdURIView base_uri);
diff --git a/src/reader.c b/src/reader.c
index 24240de8..f375be42 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -122,6 +122,10 @@ emit_statement(SerdReader* reader, ReadContext ctx, SerdNode* o)
     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);
+
   const SerdStatus st = serd_sink_write(
     reader->sink, *ctx.flags, ctx.subject, ctx.predicate, o, graph);
 
diff --git a/src/stack.h b/src/stack.h
index 4c53b4ae..62f3402b 100644
--- a/src/stack.h
+++ b/src/stack.h
@@ -85,6 +85,7 @@ 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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