Make nodes opaque

6 files changed, 242 insertions, 199 deletions

diff --git a/src/env.c b/src/env.c
index f1bfd2d7..6abcef72 100644
--- a/src/env.c
+++ b/src/env.c
@@ -20,14 +20,14 @@
 #include <string.h>
 
 typedef struct {
-	SerdNode name;
-	SerdNode uri;
+	SerdNode* name;
+	SerdNode* uri;
 } SerdPrefix;
 
 struct SerdEnvImpl {
 	SerdPrefix* prefixes;
 	size_t      n_prefixes;
-	SerdNode    base_uri_node;
+	SerdNode*   base_uri_node;
 	SerdURI     base_uri;
 };
 
@@ -47,11 +47,11 @@ void
 serd_env_free(SerdEnv* env)
 {
 	for (size_t i = 0; i < env->n_prefixes; ++i) {
-		serd_node_free(&env->prefixes[i].name);
-		serd_node_free(&env->prefixes[i].uri);
+		serd_node_free(env->prefixes[i].name);
+		serd_node_free(env->prefixes[i].uri);
 	}
 	free(env->prefixes);
-	serd_node_free(&env->base_uri_node);
+	serd_node_free(env->base_uri_node);
 	free(env);
 }
 
@@ -63,7 +63,7 @@ serd_env_get_base_uri(const SerdEnv* env,
 	if (out) {
 		*out = env->base_uri;
 	}
-	return &env->base_uri_node;
+	return env->base_uri_node;
 }
 
 SERD_API
@@ -76,13 +76,13 @@ serd_env_set_base_uri(SerdEnv*        env,
 	}
 
 	// Resolve base URI and create a new node and URI for it
-	SerdURI  base_uri;
-	SerdNode base_uri_node = serd_node_new_uri_from_node(
+	SerdURI   base_uri;
+	SerdNode* base_uri_node = serd_node_new_uri_from_node(
 		uri, &env->base_uri, &base_uri);
 
-	if (base_uri_node.buf) {
+	if (base_uri_node) {
 		// Replace the current base URI
-		serd_node_free(&env->base_uri_node);
+		serd_node_free(env->base_uri_node);
 		env->base_uri_node = base_uri_node;
 		env->base_uri      = base_uri;
 		return SERD_SUCCESS;
@@ -96,7 +96,7 @@ serd_env_find(const SerdEnv* env,
               size_t         name_len)
 {
 	for (size_t i = 0; i < env->n_prefixes; ++i) {
-		const SerdNode* const prefix_name = &env->prefixes[i].name;
+		const SerdNode* const prefix_name = env->prefixes[i].name;
 		if (prefix_name->n_bytes == name_len) {
 			if (!memcmp(serd_node_get_string(prefix_name), name, name_len)) {
 				return &env->prefixes[i];
@@ -114,9 +114,9 @@ serd_env_add(SerdEnv*        env,
 	const char*       name_str = serd_node_get_string(name);
 	SerdPrefix* const prefix   = serd_env_find(env, name_str, name->n_bytes);
 	if (prefix) {
-		SerdNode old_prefix_uri = prefix->uri;
+		SerdNode* old_prefix_uri = prefix->uri;
 		prefix->uri = serd_node_copy(uri);
-		serd_node_free(&old_prefix_uri);
+		serd_node_free(old_prefix_uri);
 	} else {
 		env->prefixes = (SerdPrefix*)realloc(
 			env->prefixes, (++env->n_prefixes) * sizeof(SerdPrefix));
@@ -131,20 +131,20 @@ serd_env_set_prefix(SerdEnv*        env,
                     const SerdNode* name,
                     const SerdNode* uri)
 {
-	if (!name->buf || uri->type != SERD_URI) {
+	if (!name || uri->type != SERD_URI) {
 		return SERD_ERR_BAD_ARG;
 	} else if (serd_uri_string_has_scheme(serd_node_get_string(uri))) {
 		// Set prefix to absolute URI
 		serd_env_add(env, name, uri);
 	} else {
 		// Resolve relative URI and create a new node and URI for it
-		SerdURI  abs_uri;
-		SerdNode abs_uri_node = serd_node_new_uri_from_node(
+		SerdURI   abs_uri;
+		SerdNode* abs_uri_node = serd_node_new_uri_from_node(
 			uri, &env->base_uri, &abs_uri);
 
 		// Set prefix to resolved (absolute) URI
-		serd_env_add(env, name, &abs_uri_node);
-		serd_node_free(&abs_uri_node);
+		serd_env_add(env, name, abs_uri_node);
+		serd_node_free(abs_uri_node);
 	}
 	return SERD_SUCCESS;
 }
@@ -155,10 +155,14 @@ serd_env_set_prefix_from_strings(SerdEnv*    env,
                                  const char* name,
                                  const char* uri)
 {
-	const SerdNode name_node = serd_node_from_string(SERD_LITERAL, name);
-	const SerdNode uri_node  = serd_node_from_string(SERD_URI, uri);
+	SerdNode* name_node = serd_node_new_string(SERD_LITERAL, name);
+	SerdNode* uri_node  = serd_node_new_string(SERD_URI, uri);
 
-	return serd_env_set_prefix(env, &name_node, &uri_node);
+	const SerdStatus st = serd_env_set_prefix(env, name_node, uri_node);
+
+	serd_node_free(name_node);
+	serd_node_free(uri_node);
+	return st;
 }
 
 static inline bool
@@ -184,13 +188,13 @@ is_name(const char* buf, size_t len)
 
 SERD_API
 bool
-serd_env_qualify(const SerdEnv*  env,
-                 const SerdNode* uri,
-                 SerdNode*       prefix,
-                 SerdSlice*      suffix)
+serd_env_qualify(const SerdEnv*   env,
+                 const SerdNode*  uri,
+                 const SerdNode** prefix,
+                 SerdSlice*       suffix)
 {
 	for (size_t i = 0; i < env->n_prefixes; ++i) {
-		const SerdNode* const prefix_uri = &env->prefixes[i].uri;
+		const SerdNode* const prefix_uri = env->prefixes[i].uri;
 		if (uri->n_bytes >= prefix_uri->n_bytes) {
 			const char* prefix_str = serd_node_get_string(prefix_uri);
 			const char* uri_str    = serd_node_get_string(uri);
@@ -224,8 +228,8 @@ serd_env_expand(const SerdEnv*  env,
 	const size_t            name_len = colon - str;
 	const SerdPrefix* const prefix   = serd_env_find(env, str, name_len);
 	if (prefix) {
-		uri_prefix->buf = serd_node_get_string(&prefix->uri);
-		uri_prefix->len = prefix->uri.n_bytes;
+		uri_prefix->buf = serd_node_get_string(prefix->uri);
+		uri_prefix->len = prefix->uri->n_bytes;
 		uri_suffix->buf = colon + 1;
 		uri_suffix->len = curie->n_bytes - (colon - str) - 1;
 		return SERD_SUCCESS;
@@ -234,7 +238,7 @@ serd_env_expand(const SerdEnv*  env,
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_env_expand_node(const SerdEnv*  env,
                      const SerdNode* node)
 {
@@ -243,12 +247,13 @@ serd_env_expand_node(const SerdEnv*  env,
 		SerdSlice prefix;
 		SerdSlice suffix;
 		if (serd_env_expand(env, node, &prefix, &suffix)) {
-			return SERD_NODE_NULL;
+			return NULL;
 		}
 		const size_t len = prefix.len + suffix.len;
-		char*        buf = (char*)malloc(len + 1);
-		SerdNode     ret = { buf, len, 0, SERD_URI };
-		snprintf((char*)buf, ret.n_bytes + 1, "%s%s", prefix.buf, suffix.buf);
+		SerdNode*    ret = serd_node_malloc(len, 0, SERD_URI);
+		char*        buf = serd_node_buffer(ret);
+		snprintf(buf, len + 1, "%s%s", prefix.buf, suffix.buf);
+		ret->n_bytes = len;
 		return ret;
 	}
 	case SERD_URI: {
@@ -256,7 +261,7 @@ serd_env_expand_node(const SerdEnv*  env,
 		return serd_node_new_uri_from_node(node, &env->base_uri, &ignored);
 	}
 	default:
-		return SERD_NODE_NULL;
+		return NULL;
 	}
 }
 
@@ -267,6 +272,6 @@ serd_env_foreach(const SerdEnv* env,
                  void*          handle)
 {
 	for (size_t i = 0; i < env->n_prefixes; ++i) {
-		func(handle, &env->prefixes[i].name, &env->prefixes[i].uri);
+		func(handle, env->prefixes[i].name, env->prefixes[i].uri);
 	}
 }
diff --git a/src/node.c b/src/node.c
index 65a2172b..e7e18533 100644
--- a/src/node.c
+++ b/src/node.c
@@ -31,52 +31,79 @@
 #    endif
 #endif
 
+SerdNode*
+serd_node_malloc(size_t n_bytes, SerdNodeFlags flags, SerdType type)
+{
+	SerdNode* node = (SerdNode*)calloc(1, sizeof(SerdNode) + n_bytes + 1);
+	node->n_bytes = 0;
+	node->flags   = flags;
+	node->type    = type;
+	return node;
+}
+
 char*
 serd_node_buffer(SerdNode* node)
 {
 	return (char*)(node + 1);
 }
 
+void
+serd_node_set(SerdNode** dst, const SerdNode* src)
+{
+	if (src) {
+		if (!(*dst) || (*dst)->n_bytes < src->n_bytes) {
+			(*dst) = (SerdNode*)realloc(*dst, sizeof(SerdNode) + src->n_bytes + 1);
+		}
+
+		memcpy(*dst, src, sizeof(SerdNode) + src->n_bytes + 1);
+	} else if (*dst) {
+		(*dst)->type = SERD_NOTHING;
+	}
+}
+
 SERD_API
-SerdNode
-serd_node_from_string(SerdType type, const char* str)
+SerdNode*
+serd_node_new_string(SerdType type, const char* str)
 {
 	if (!str) {
-		return SERD_NODE_NULL;
+		return NULL;
 	}
 
-	uint32_t       flags   = 0;
-	const size_t   n_bytes = serd_strlen(str, &flags);
-	const SerdNode ret     = { str, n_bytes, flags, type };
-	return ret;
+	uint32_t     flags   = 0;
+	const size_t n_bytes = serd_strlen(str, &flags);
+	SerdNode*    node    = serd_node_malloc(n_bytes, flags, type);
+	memcpy(serd_node_buffer(node), str, n_bytes);
+	node->n_bytes = n_bytes;
+	return node;
 }
 
 SERD_API
-SerdNode
-serd_node_from_substring(SerdType type, const char* str, const size_t len)
+SerdNode*
+serd_node_new_substring(SerdType type, const char* str, const size_t len)
 {
 	if (!str) {
-		return SERD_NODE_NULL;
+		return NULL;
 	}
 
-	uint32_t       flags   = 0;
-	const size_t   n_bytes = serd_substrlen(str, len, &flags);
-	const SerdNode ret     = { str, n_bytes, flags, type };
-	return ret;
+	uint32_t     flags   = 0;
+	const size_t n_bytes = serd_substrlen(str, len, &flags);
+	SerdNode*    node    = serd_node_malloc(n_bytes, flags, type);
+	memcpy(serd_node_buffer(node), str, n_bytes);
+	node->n_bytes = n_bytes;
+	return node;
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_copy(const SerdNode* node)
 {
-	if (!node || !node->buf) {
-		return SERD_NODE_NULL;
+	if (!node) {
+		return NULL;
 	}
 
-	SerdNode copy = *node;
-	char* buf  = (char*)malloc(copy.n_bytes + 1);
-	memcpy(buf, node->buf, copy.n_bytes + 1);
-	copy.buf = buf;
+	const size_t size = sizeof(SerdNode) + node->n_bytes + 1;
+	SerdNode*    copy = (SerdNode*)malloc(size);
+	memcpy(copy, node, size);
 	return copy;
 }
 
@@ -84,12 +111,11 @@ SERD_API
 bool
 serd_node_equals(const SerdNode* a, const SerdNode* b)
 {
-	return (a == b)
-		|| (a->type == b->type
-		    && a->n_bytes == b->n_bytes
-		    && ((a->buf == b->buf) || !memcmp((const char*)a->buf,
-		                                      (const char*)b->buf,
-		                                      a->n_bytes + 1)));
+	return (a == b) ||
+	       (a && b && a->type == b->type && a->n_bytes == b->n_bytes &&
+	        !memcmp(serd_node_get_string(a),
+	                serd_node_get_string(b),
+	                a->n_bytes));
 }
 
 static size_t
@@ -119,7 +145,7 @@ string_sink(const void* buf, size_t len, void* stream)
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_uri_from_node(const SerdNode* uri_node,
                             const SerdURI*  base,
                             SerdURI*        out)
@@ -127,18 +153,18 @@ serd_node_new_uri_from_node(const SerdNode* uri_node,
 	const char* uri_str = serd_node_get_string(uri_node);
 	return (uri_node->type == SERD_URI && uri_str)
 		? serd_node_new_uri_from_string(uri_str, base, out)
-		: SERD_NODE_NULL;
+		: NULL;
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_uri_from_string(const char*    str,
                               const SerdURI* base,
                               SerdURI*       out)
 {
 	if (!str || str[0] == '\0') {
 		// Empty URI => Base URI, or nothing if no base is given
-		return base ? serd_node_new_uri(base, NULL, out) : SERD_NODE_NULL;
+		return base ? serd_node_new_uri(base, NULL, out) : NULL;
 	}
 
 	SerdURI uri;
@@ -166,7 +192,7 @@ is_uri_path_char(const char c)
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_file_uri(const char* path,
                        const char* hostname,
                        SerdURI*    out,
@@ -201,16 +227,18 @@ serd_node_new_file_uri(const char* path,
 	}
 	serd_buffer_sink_finish(&buffer);
 
+	SerdNode* node = serd_node_new_substring(
+		SERD_URI, (const char*)buffer.buf, buffer.len);
 	if (out) {
-		serd_uri_parse((const char*)buffer.buf, out);
+		serd_uri_parse(serd_node_buffer(node), out);
 	}
 
-	return serd_node_from_substring(
-		SERD_URI, (const char*)buffer.buf, buffer.len);
+	free(buffer.buf);
+	return node;
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_uri(const SerdURI* uri, const SerdURI* base, SerdURI* out)
 {
 	SerdURI abs_uri = *uri;
@@ -219,23 +247,22 @@ serd_node_new_uri(const SerdURI* uri, const SerdURI* base, SerdURI* out)
 	}
 
 	const size_t len        = serd_uri_string_length(&abs_uri);
-	char*        buf        = (char*)malloc(len + 1);
-	SerdNode     node       = { buf, len, 0, SERD_URI };
-	char*        ptr        = buf;
+	SerdNode*    node       = serd_node_malloc(len, 0, SERD_URI);
+	char*        ptr        = serd_node_buffer(node);
 	const size_t actual_len = serd_uri_serialise(&abs_uri, string_sink, &ptr);
 
-	buf[actual_len] = '\0';
-	node.n_bytes    = actual_len;
+	serd_node_buffer(node)[actual_len] = '\0';
+	node->n_bytes = actual_len;
 
 	if (out) {
-		serd_uri_parse(buf, out);  // TODO: cleverly avoid double parse
+		serd_uri_parse(serd_node_buffer(node), out);  // TODO: avoid double parse
 	}
 
 	return node;
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_relative_uri(const SerdURI* uri,
                            const SerdURI* base,
                            const SerdURI* root,
@@ -243,17 +270,16 @@ serd_node_new_relative_uri(const SerdURI* uri,
 {
 	const size_t uri_len    = serd_uri_string_length(uri);
 	const size_t base_len   = serd_uri_string_length(base);
-	char*        buf        = (char*)malloc(uri_len + base_len + 1);
-	SerdNode     node       = { buf, 0, 0, SERD_URI };
-	char*        ptr        = buf;
+	SerdNode*    node       = serd_node_malloc(uri_len + base_len, 0, SERD_URI);
+	char*        ptr        = serd_node_buffer(node);
 	const size_t actual_len = serd_uri_serialise_relative(
 		uri, base, root, string_sink, &ptr);
 
-	buf[actual_len] = '\0';
-	node.n_bytes    = actual_len;
+	serd_node_buffer(node)[actual_len] = '\0';
+	node->n_bytes = actual_len;
 
 	if (out) {
-		serd_uri_parse(buf, out);  // TODO: cleverly avoid double parse
+		serd_uri_parse(serd_node_buffer(node), out);  // TODO: avoid double parse
 	}
 
 	return node;
@@ -267,18 +293,19 @@ serd_digits(double abs)
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_decimal(double d, unsigned frac_digits)
 {
 	if (isnan(d) || isinf(d)) {
-		return SERD_NODE_NULL;
+		return NULL;
 	}
 
-	const double   abs_d      = fabs(d);
-	const unsigned int_digits = serd_digits(abs_d);
-	char*          buf        = (char*)calloc(int_digits + frac_digits + 3, 1);
-	SerdNode       node       = { buf, 0, 0, SERD_LITERAL };
-	const double   int_part   = floor(abs_d);
+	const double    abs_d      = fabs(d);
+	const unsigned  int_digits = serd_digits(abs_d);
+	const size_t    len        = int_digits + frac_digits + 3;
+	SerdNode* const node       = serd_node_malloc(len, 0, SERD_LITERAL);
+	char* const     buf        = serd_node_buffer(node);
+	const double    int_part   = floor(abs_d);
 
 	// Point s to decimal point location
 	char* s = buf + int_digits;
@@ -294,13 +321,14 @@ serd_node_new_decimal(double d, unsigned frac_digits)
 		*t-- = '0' + (dec % 10);
 	} while ((dec /= 10) > 0);
 
+
 	*s++ = '.';
 
 	// Write fractional part (right to left)
 	double frac_part = fabs(d - int_part);
 	if (frac_part < DBL_EPSILON) {
 		*s++ = '0';
-		node.n_bytes = (s - buf);
+		node->n_bytes = (s - buf);
 	} else {
 		uint64_t frac = frac_part * pow(10.0, (int)frac_digits) + 0.5;
 		s += frac_digits - 1;
@@ -309,7 +337,7 @@ serd_node_new_decimal(double d, unsigned frac_digits)
 		// Skip trailing zeros
 		for (; i < frac_digits - 1 && !(frac % 10); ++i, --s, frac /= 10) {}
 
-		node.n_bytes = (s - buf) + 1;
+		node->n_bytes = (s - buf) + 1;
 
 		// Write digits from last trailing zero to decimal point
 		for (; i < frac_digits; ++i) {
@@ -322,13 +350,13 @@ serd_node_new_decimal(double d, unsigned frac_digits)
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_integer(int64_t i)
 {
 	int64_t        abs_i  = (i < 0) ? -i : i;
 	const unsigned digits = serd_digits(abs_i);
-	char*          buf    = (char*)calloc(digits + 2, 1);
-	SerdNode       node   = { (const char*)buf, 0, 0, SERD_LITERAL };
+	SerdNode*      node   = serd_node_malloc(digits + 2, 0, SERD_LITERAL);
+	char*          buf    = serd_node_buffer(node);
 
 	// Point s to the end
 	char* s = buf + digits - 1;
@@ -337,7 +365,7 @@ serd_node_new_integer(int64_t i)
 		++s;
 	}
 
-	node.n_bytes = (s - buf) + 1;
+	node->n_bytes = (s - buf) + 1;
 
 	// Write integer part (right to left)
 	do {
@@ -369,12 +397,12 @@ encode_chunk(uint8_t out[4], const uint8_t in[3], size_t n_in)
 }
 
 SERD_API
-SerdNode
+SerdNode*
 serd_node_new_blob(const void* buf, size_t size, bool wrap_lines)
 {
 	const size_t len  = ((size + 2) / 3) * 4 + (wrap_lines ? (size / 57) : 0);
-	uint8_t*     str  = (uint8_t*)calloc(1, len + 2);
-	SerdNode     node = { (const char*)str, len, 0, SERD_LITERAL };
+	SerdNode*    node = serd_node_malloc(len + 1, 0, SERD_LITERAL);
+	uint8_t*     str  = (uint8_t*)serd_node_buffer(node);
 	for (size_t i = 0, j = 0; i < size; i += 3, j += 4) {
 		uint8_t in[4] = { 0, 0, 0, 0 };
 		size_t  n_in  = MIN(3, size - i);
@@ -382,11 +410,12 @@ serd_node_new_blob(const void* buf, size_t size, bool wrap_lines)
 
 		if (wrap_lines && i > 0 && (i % 57) == 0) {
 			str[j++] = '\n';
-			node.flags |= SERD_HAS_NEWLINE;
+			node->flags |= SERD_HAS_NEWLINE;
 		}
 
 		encode_chunk(str + j, in, n_in);
 	}
+	node->n_bytes = len + 1;
 	return node;
 }
 
@@ -401,7 +430,7 @@ SERD_API
 const char*
 serd_node_get_string(const SerdNode* node)
 {
-	return node ? node->buf : NULL;
+	return node ? (const char*)(node + 1) : NULL;
 }
 
 SERD_API
@@ -422,8 +451,5 @@ SERD_API
 void
 serd_node_free(SerdNode* node)
 {
-	if (node && node->buf) {
-		free((char*)node->buf);
-		node->buf = NULL;
-	}
+	free(node);
 }
diff --git a/src/reader.c b/src/reader.c
index 7e2fa4ec..cedf84cf 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -40,9 +40,9 @@ void
 set_blank_id(SerdReader* reader, Ref ref, size_t buf_size)
 {
 	SerdNode*   node   = deref(reader, ref);
+	char*       buf    = (char*)(node + 1);
 	const char* prefix = reader->bprefix ? (const char*)reader->bprefix : "";
-	node->n_bytes = snprintf(
-		(char*)node->buf, buf_size, "%sb%u", prefix, reader->next_id++);
+	node->n_bytes = snprintf(buf, buf_size, "%sb%u", prefix, reader->next_id++);
 }
 
 size_t
@@ -83,7 +83,6 @@ push_node_padded(SerdReader* reader, size_t maxlen,
 	node->n_bytes = n_bytes;
 	node->flags   = 0;
 	node->type    = type;
-	node->buf     = NULL;
 
 	char* buf = (char*)(node + 1);
 	memcpy(buf, str, n_bytes + 1);
@@ -105,12 +104,7 @@ push_node(SerdReader* reader, SerdType type, const char* str, size_t n_bytes)
 SerdNode*
 deref(SerdReader* reader, const Ref ref)
 {
-	if (ref) {
-		SerdNode* node = (SerdNode*)(reader->stack.buf + ref);
-		node->buf = (char*)node + sizeof(SerdNode);
-		return node;
-	}
-	return NULL;
+	return ref ? (SerdNode*)(reader->stack.buf + ref) : NULL;
 }
 
 Ref
@@ -133,8 +127,8 @@ bool
 emit_statement(SerdReader* reader, ReadContext ctx, Ref o, Ref d, Ref l)
 {
 	SerdNode* graph = deref(reader, ctx.graph);
-	if (!graph && reader->default_graph.buf) {
-		graph = &reader->default_graph;
+	if (!graph && reader->default_graph) {
+		graph = reader->default_graph;
 	}
 	bool ret = !reader->statement_sink ||
 		!reader->statement_sink(
@@ -179,7 +173,7 @@ serd_reader_new(SerdSyntax        syntax,
 	me->prefix_sink      = prefix_sink;
 	me->statement_sink   = statement_sink;
 	me->end_sink         = end_sink;
-	me->default_graph    = SERD_NODE_NULL;
+	me->default_graph    = NULL;
 	me->stack            = serd_stack_new(SERD_PAGE_SIZE);
 	me->syntax           = syntax;
 	me->next_id          = 1;
@@ -216,7 +210,7 @@ serd_reader_free(SerdReader* reader)
 	pop_node(reader, reader->rdf_nil);
 	pop_node(reader, reader->rdf_rest);
 	pop_node(reader, reader->rdf_first);
-	serd_node_free(&reader->default_graph);
+	serd_node_free(reader->default_graph);
 
 #ifdef SERD_STACK_CHECK
 	free(reader->allocs);
@@ -256,7 +250,7 @@ void
 serd_reader_set_default_graph(SerdReader*     reader,
                               const SerdNode* graph)
 {
-	serd_node_free(&reader->default_graph);
+	serd_node_free(reader->default_graph);
 	reader->default_graph = serd_node_copy(graph);
 }
 
diff --git a/src/serd_internal.h b/src/serd_internal.h
index 6c273b6c..5be89a12 100644
--- a/src/serd_internal.h
+++ b/src/serd_internal.h
@@ -44,6 +44,16 @@
 
 static const uint8_t replacement_char[] = { 0xEF, 0xBF, 0xBD };
 
+struct SerdNodeImpl {
+	size_t        n_bytes;  /**< Size in bytes (not including null) */
+	SerdNodeFlags flags;    /**< Node flags (e.g. string properties) */
+	SerdType      type;     /**< Node type */
+};
+
+static const SerdNode SERD_NODE_NULL = { 0, 0, SERD_NOTHING };
+
+SerdNode* serd_node_malloc(size_t n_bytes, SerdNodeFlags flags, SerdType type);
+void      serd_node_set(SerdNode** dst, const SerdNode* src);
 char*     serd_node_buffer(SerdNode* node);
 
 /* File and Buffer Utilities */
@@ -520,7 +530,7 @@ struct SerdReaderImpl {
 	Ref               rdf_first;
 	Ref               rdf_rest;
 	Ref               rdf_nil;
-	SerdNode          default_graph;
+	SerdNode*         default_graph;
 	SerdByteSource    source;
 	SerdStack         stack;
 	SerdSyntax        syntax;
diff --git a/src/serdi.c b/src/serdi.c
index 419d3d06..571e2208 100644
--- a/src/serdi.c
+++ b/src/serdi.c
@@ -221,8 +221,8 @@ main(int argc, char** argv)
 			: SERD_NQUADS);
 	}
 
-	SerdURI  base_uri = SERD_URI_NULL;
-	SerdNode base     = SERD_NODE_NULL;
+	SerdURI   base_uri = SERD_URI_NULL;
+	SerdNode* base     = NULL;
 	if (a < argc) {  // Base URI given on command line
 		base = serd_node_new_uri_from_string(
 			(const char*)argv[a], NULL, &base_uri);
@@ -231,7 +231,7 @@ main(int argc, char** argv)
 	}
 
 	FILE*    out_fd = stdout;
-	SerdEnv* env    = serd_env_new(&base);
+	SerdEnv* env    = serd_env_new(base);
 
 	int output_style = 0;
 	if (output_syntax == SERD_NTRIPLES || ascii) {
@@ -270,10 +270,11 @@ main(int argc, char** argv)
 		serd_writer_set_error_sink(writer, quiet_error_sink, NULL);
 	}
 
-	SerdNode root = serd_node_from_string(SERD_URI, root_uri);
-	serd_writer_set_root_uri(writer, &root);
+	SerdNode* root = serd_node_new_string(SERD_URI, root_uri);
+	serd_writer_set_root_uri(writer, root);
 	serd_writer_chop_blank_prefix(writer, chop_prefix);
 	serd_reader_add_blank_prefix(reader, add_prefix);
+	serd_node_free(root);
 
 	SerdStatus status = SERD_SUCCESS;
 	if (!from_file) {
@@ -292,7 +293,7 @@ main(int argc, char** argv)
 	serd_writer_finish(writer);
 	serd_writer_free(writer);
 	serd_env_free(env);
-	serd_node_free(&base);
+	serd_node_free(base);
 
 	if (from_file) {
 		fclose(in_fd);
diff --git a/src/writer.c b/src/writer.c
index d40e4024..2190d51f 100644
--- a/src/writer.c
+++ b/src/writer.c
@@ -22,16 +22,12 @@
 #include <string.h>
 
 typedef struct {
-	SerdNode graph;
-	SerdNode subject;
-	SerdNode predicate;
+	SerdNode* graph;
+	SerdNode* subject;
+	SerdNode* predicate;
 } WriteContext;
 
-static const WriteContext WRITE_CONTEXT_NULL = {
-	{ 0, 0, 0, SERD_NOTHING },
-	{ 0, 0, 0, SERD_NOTHING },
-	{ 0, 0, 0, SERD_NOTHING }
-};
+static const WriteContext WRITE_CONTEXT_NULL = { NULL, NULL, NULL };
 
 typedef enum {
 	SEP_NONE,
@@ -82,7 +78,7 @@ struct SerdWriterImpl {
 	SerdSyntax    syntax;
 	SerdStyle     style;
 	SerdEnv*      env;
-	SerdNode      root_node;
+	SerdNode*     root_node;
 	SerdURI       root_uri;
 	SerdURI       base_uri;
 	SerdStack     anon_stack;
@@ -90,7 +86,7 @@ struct SerdWriterImpl {
 	SerdErrorSink error_sink;
 	void*         error_handle;
 	WriteContext  context;
-	SerdNode      list_subj;
+	SerdNode*     list_subj;
 	unsigned      list_depth;
 	unsigned      indent;
 	uint8_t*      bprefix;
@@ -142,18 +138,23 @@ anon_stack_top(SerdWriter* writer)
 	                       + writer->anon_stack.size - sizeof(WriteContext));
 }
 
-static void
-copy_node(SerdNode* dst, const SerdNode* src)
-{
-	if (src) {
-		dst->buf = (char*)realloc((char*)dst->buf, src->n_bytes + 1);
-		dst->n_bytes = src->n_bytes;
-		dst->flags   = src->flags;
-		dst->type    = src->type;
-		memcpy((char*)dst->buf, src->buf, src->n_bytes + 1);
-	} else {
-		dst->type = SERD_NOTHING;
+static inline SerdNode*
+ctx(SerdWriter* writer, const Field field)
+{
+	SerdNode* node = NULL;
+	switch (field) {
+	case FIELD_SUBJECT:
+		node = writer->context.subject;
+		break;
+	case FIELD_PREDICATE:
+		node = writer->context.predicate;
+		break;
+	case FIELD_GRAPH:
+		node = writer->context.graph;
+	default: break;
 	}
+
+	return node && node->type ? node : NULL;
 }
 
 static inline size_t
@@ -394,22 +395,26 @@ write_sep(SerdWriter* writer, const Sep sep)
 static SerdStatus
 reset_context(SerdWriter* writer, bool graph)
 {
-	if (graph) {
-		writer->context.graph.type = SERD_NOTHING;
+	if (graph && writer->context.graph) {
+		writer->context.graph->type = SERD_NOTHING;
+	}
+	if (writer->context.subject) {
+		writer->context.subject->type = SERD_NOTHING;
+	}
+	if (writer->context.predicate) {
+		writer->context.predicate->type = SERD_NOTHING;
 	}
-	writer->context.subject.type   = SERD_NOTHING;
-	writer->context.predicate.type = SERD_NOTHING;
-	writer->empty                  = false;
+	writer->empty = false;
 	return SERD_SUCCESS;
 }
 
 static SerdStatus
 free_context(SerdWriter* writer)
 {
-	serd_node_free(&writer->context.graph);
-	serd_node_free(&writer->context.subject);
-	serd_node_free(&writer->context.predicate);
-	return reset_context(writer, true);
+	serd_node_free(writer->context.graph);
+	serd_node_free(writer->context.subject);
+	serd_node_free(writer->context.predicate);
+	return SERD_SUCCESS;
 }
 
 static bool
@@ -475,8 +480,8 @@ write_uri_node(SerdWriter* const        writer,
                const Field              field,
                const SerdStatementFlags flags)
 {
-	SerdNode  prefix;
-	SerdSlice suffix;
+	const SerdNode* prefix;
+	SerdSlice       suffix;
 
 	if (is_inline_start(writer, field, flags)) {
 		++writer->indent;
@@ -493,7 +498,7 @@ write_uri_node(SerdWriter* const        writer,
 		return sink("()", 2, writer) == 2;
 	} else if (has_scheme && (writer->style & SERD_STYLE_CURIED) &&
 	           serd_env_qualify(writer->env, node, &prefix, &suffix)) {
-		write_uri_from_node(writer, &prefix);
+		write_uri_from_node(writer, prefix);
 		sink(":", 1, writer);
 		write_uri(writer, suffix.buf, suffix.len);
 		return true;
@@ -578,7 +583,7 @@ write_blank(SerdWriter* const        writer,
 			return write_sep(writer, SEP_ANON_BEGIN);
 		} else if (field == FIELD_SUBJECT && (flags & SERD_LIST_S_BEGIN)) {
 			assert(writer->list_depth == 0);
-			copy_node(&writer->list_subj, node);
+			serd_node_set(&writer->list_subj, node);
 			++writer->list_depth;
 			++writer->indent;
 			return write_sep(writer, SEP_LIST_BEGIN);
@@ -644,7 +649,7 @@ write_pred(SerdWriter* writer, SerdStatementFlags flags, const SerdNode* pred)
 {
 	write_node(writer, pred, NULL, NULL, FIELD_PREDICATE, flags);
 	write_sep(writer, SEP_P_O);
-	copy_node(&writer->context.predicate, pred);
+	serd_node_set(&writer->context.predicate, pred);
 }
 
 static bool
@@ -677,9 +682,8 @@ serd_writer_write_statement(SerdWriter*        writer,
                             const SerdNode*    datatype,
                             const SerdNode*    lang)
 {
-	if (!subject || !predicate || !object
-	    || !subject->buf || !predicate->buf || !object->buf
-	    || !is_resource(subject) || !is_resource(predicate)) {
+	if (!subject || !predicate || !object ||
+	    !is_resource(subject) || !is_resource(predicate)) {
 		return SERD_ERR_BAD_ARG;
 	}
 
@@ -706,13 +710,13 @@ serd_writer_write_statement(SerdWriter*        writer,
 		break;
 	}
 
-	if ((graph && !serd_node_equals(graph, &writer->context.graph)) ||
-	    (!graph && writer->context.graph.type)) {
+	if ((graph && !serd_node_equals(graph, writer->context.graph)) ||
+	    (!graph && ctx(writer, FIELD_GRAPH))) {
 		writer->indent = 0;
-		if (writer->context.subject.type) {
+		if (ctx(writer, FIELD_SUBJECT)) {
 			write_sep(writer, SEP_END_S);
 		}
-		if (writer->context.graph.type) {
+		if (ctx(writer, FIELD_GRAPH)) {
 			write_sep(writer, SEP_GRAPH_END);
 		}
 
@@ -721,23 +725,23 @@ serd_writer_write_statement(SerdWriter*        writer,
 			TRY(write_node(writer, graph, datatype, lang, FIELD_GRAPH, flags));
 			++writer->indent;
 			write_sep(writer, SEP_GRAPH_BEGIN);
-			copy_node(&writer->context.graph, graph);
+			serd_node_set(&writer->context.graph, graph);
 		}
 	}
 
 	if ((flags & SERD_LIST_CONT)) {
 		if (write_list_obj(writer, flags, predicate, object, datatype, lang)) {
 			// Reached end of list
-			if (--writer->list_depth == 0 && writer->list_subj.type) {
+			if (--writer->list_depth == 0 && writer->list_subj) {
 				reset_context(writer, false);
-				serd_node_free(&writer->context.subject);
+				serd_node_free(writer->context.subject);
 				writer->context.subject = writer->list_subj;
-				writer->list_subj       = SERD_NODE_NULL;
+				writer->list_subj = NULL;
 			}
 			return SERD_SUCCESS;
 		}
-	} else if (serd_node_equals(subject, &writer->context.subject)) {
-		if (serd_node_equals(predicate, &writer->context.predicate)) {
+	} else if (serd_node_equals(subject, writer->context.subject)) {
+		if (serd_node_equals(predicate, writer->context.predicate)) {
 			// Abbreviate S P
 			if (!(flags & SERD_ANON_O_BEGIN)) {
 				++writer->indent;
@@ -749,14 +753,14 @@ serd_writer_write_statement(SerdWriter*        writer,
 			}
 		} else {
 			// Abbreviate S
-			Sep sep = writer->context.predicate.type ? SEP_END_P : SEP_S_P;
+			Sep sep = ctx(writer, FIELD_PREDICATE) ? SEP_END_P : SEP_S_P;
 			write_sep(writer, sep);
 			write_pred(writer, flags, predicate);
 			write_node(writer, object, datatype, lang, FIELD_OBJECT, flags);
 		}
 	} else {
 		// No abbreviation
-		if (writer->context.subject.type) {
+		if (ctx(writer, FIELD_SUBJECT)) {
 			assert(writer->indent > 0);
 			--writer->indent;
 			if (serd_stack_is_empty(&writer->anon_stack)) {
@@ -775,7 +779,7 @@ serd_writer_write_statement(SerdWriter*        writer,
 		}
 
 		reset_context(writer, false);
-		copy_node(&writer->context.subject, subject);
+		serd_node_set(&writer->context.subject, subject);
 
 		if (!(flags & SERD_LIST_S_BEGIN)) {
 			write_pred(writer, flags, predicate);
@@ -789,15 +793,15 @@ serd_writer_write_statement(SerdWriter*        writer,
 			&writer->anon_stack, sizeof(WriteContext));
 		*ctx = writer->context;
 		WriteContext new_context = {
-			serd_node_copy(graph), serd_node_copy(subject), SERD_NODE_NULL };
+			serd_node_copy(graph), serd_node_copy(subject), NULL };
 		if ((flags & SERD_ANON_S_BEGIN)) {
 			new_context.predicate = serd_node_copy(predicate);
 		}
 		writer->context = new_context;
 	} else {
-		copy_node(&writer->context.graph, graph);
-		copy_node(&writer->context.subject, subject);
-		copy_node(&writer->context.predicate, predicate);
+		serd_node_set(&writer->context.graph, graph);
+		serd_node_set(&writer->context.subject, subject);
+		serd_node_set(&writer->context.predicate, predicate);
 	}
 
 	return SERD_SUCCESS;
@@ -821,10 +825,10 @@ serd_writer_end_anon(SerdWriter*     writer,
 	free_context(writer);
 	writer->context = *anon_stack_top(writer);
 	serd_stack_pop(&writer->anon_stack, sizeof(WriteContext));
-	const bool is_subject = serd_node_equals(node, &writer->context.subject);
+	const bool is_subject = serd_node_equals(node, writer->context.subject);
 	if (is_subject) {
-		copy_node(&writer->context.subject, node);
-		writer->context.predicate.type = SERD_NOTHING;
+		serd_node_set(&writer->context.subject, node);
+		writer->context.predicate->type = SERD_NOTHING;
 	}
 	return SERD_SUCCESS;
 }
@@ -833,15 +837,17 @@ SERD_API
 SerdStatus
 serd_writer_finish(SerdWriter* writer)
 {
-	if (writer->context.subject.type) {
+	if (ctx(writer, FIELD_SUBJECT)) {
 		write_sep(writer, SEP_END_S);
 	}
-	if (writer->context.graph.type) {
+	if (ctx(writer, FIELD_GRAPH)) {
 		write_sep(writer, SEP_GRAPH_END);
 	}
 	serd_byte_sink_flush(&writer->byte_sink);
-	writer->indent = 0;
-	return free_context(writer);
+	free_context(writer);
+	writer->indent  = 0;
+	writer->context = WRITE_CONTEXT_NULL;
+	return SERD_SUCCESS;
 }
 
 SERD_API
@@ -858,12 +864,12 @@ serd_writer_new(SerdSyntax     syntax,
 	writer->syntax       = syntax;
 	writer->style        = style;
 	writer->env          = env;
-	writer->root_node    = SERD_NODE_NULL;
+	writer->root_node    = NULL;
 	writer->root_uri     = SERD_URI_NULL;
 	writer->base_uri     = base_uri ? *base_uri : SERD_URI_NULL;
 	writer->anon_stack   = serd_stack_new(4 * sizeof(WriteContext));
 	writer->context      = context;
-	writer->list_subj    = SERD_NODE_NULL;
+	writer->list_subj    = NULL;
 	writer->empty        = true;
 	writer->byte_sink    = serd_byte_sink_new(
 		ssink, stream, (style & SERD_STYLE_BULK) ? SERD_PAGE_SIZE : 1);
@@ -904,7 +910,7 @@ serd_writer_set_base_uri(SerdWriter*     writer,
 		serd_env_get_base_uri(writer->env, &writer->base_uri);
 
 		if (writer->syntax == SERD_TURTLE || writer->syntax == SERD_TRIG) {
-			if (writer->context.graph.type || writer->context.subject.type) {
+			if (ctx(writer, FIELD_GRAPH) || ctx(writer, FIELD_SUBJECT)) {
 				sink(" .\n\n", 4, writer);
 				reset_context(writer, true);
 			}
@@ -923,12 +929,13 @@ SerdStatus
 serd_writer_set_root_uri(SerdWriter*     writer,
                          const SerdNode* uri)
 {
-	serd_node_free(&writer->root_node);
-	if (uri && uri->buf) {
+	serd_node_free(writer->root_node);
+	if (uri) {
 		writer->root_node = serd_node_copy(uri);
-		serd_uri_parse(serd_node_get_string(uri), &writer->root_uri);
+		serd_uri_parse(serd_node_get_string(writer->root_node),
+		               &writer->root_uri);
 	} else {
-		writer->root_node = SERD_NODE_NULL;
+		writer->root_node = NULL;
 		writer->root_uri  = SERD_URI_NULL;
 	}
 	return SERD_SUCCESS;
@@ -942,7 +949,7 @@ serd_writer_set_prefix(SerdWriter*     writer,
 {
 	if (!serd_env_set_prefix(writer->env, name, uri)) {
 		if (writer->syntax == SERD_TURTLE || writer->syntax == SERD_TRIG) {
-			if (writer->context.graph.type || writer->context.subject.type) {
+			if (ctx(writer, FIELD_GRAPH) || ctx(writer, FIELD_SUBJECT)) {
 				sink(" .\n\n", 4, writer);
 				reset_context(writer, true);
 			}
@@ -966,7 +973,7 @@ serd_writer_free(SerdWriter* writer)
 	serd_stack_free(&writer->anon_stack);
 	free(writer->bprefix);
 	serd_byte_sink_free(&writer->byte_sink);
-	serd_node_free(&writer->root_node);
+	serd_node_free(writer->root_node);
 	free(writer);
 }