Reuse the same rdf:type node for all "a" abbreviations

This reduces the stack space requirements for every type statement, at the cost
of adding a bit of constant bloat for the node in documents that do not contain
it.

3 files changed, 5 insertions, 3 deletions

diff --git a/src/read_turtle.c b/src/read_turtle.c
index d8a5de3e..03d1950f 100644
--- a/src/read_turtle.c
+++ b/src/read_turtle.c
@@ -581,9 +581,8 @@ read_verb(SerdReader* reader, SerdNode** const dest)
   if (node->length == 1 && serd_node_string(node)[0] == 'a' && next != ':' &&
       !is_PN_CHARS_BASE(next)) {
     serd_stack_pop_to(&reader->stack, orig_stack_size);
-    return ((*dest = push_node(reader, SERD_URI, NS_RDF "type", 47))
-              ? SERD_SUCCESS
-              : SERD_BAD_STACK);
+    *dest = reader->rdf_type;
+    return SERD_SUCCESS;
   }
 
   if ((st = read_PrefixedName(
diff --git a/src/reader.c b/src/reader.c
index 73509c6f..b7a64ce4 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -271,11 +271,13 @@ serd_reader_new(SerdWorld* const      world,
   me->rdf_first = push_node(me, SERD_URI, NS_RDF "first", 48);
   me->rdf_rest  = push_node(me, SERD_URI, NS_RDF "rest", 47);
   me->rdf_nil   = push_node(me, SERD_URI, NS_RDF "nil", 46);
+  me->rdf_type  = push_node(me, SERD_URI, NS_RDF "type", 47);
 
   // The initial stack size check should cover this
   assert(me->rdf_first);
   assert(me->rdf_rest);
   assert(me->rdf_nil);
+  assert(me->rdf_type);
 
   if (!(flags & SERD_READ_GLOBAL)) {
     me->bprefix[0]  = 'f';
diff --git a/src/reader.h b/src/reader.h
index 0bb3454b..9ec2e4ac 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -40,6 +40,7 @@ struct SerdReaderImpl {
   SerdNode*       rdf_first;
   SerdNode*       rdf_rest;
   SerdNode*       rdf_nil;
+  SerdNode*       rdf_type;
   SerdByteSource* source;
   SerdEnv*        env;
   SerdStack       stack;