Remove SerdString from public API in favour of more expressive (and not necessarily inline with data payload) SerdNode.

git-svn-id: http://svn.drobilla.net/serd/trunk@53 490d8e77-9747-427b-9fa3-0b8f29cee8a0

8 files changed, 367 insertions, 294 deletions

diff --git a/serd/serd.h b/serd/serd.h
index 6b27ff18..17f00a80 100644
--- a/serd/serd.h
+++ b/serd/serd.h
@@ -15,7 +15,7 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-/* @file
+/** @file
  * Public Serd API.
  */
 
@@ -112,7 +112,7 @@ typedef enum {
  * @{
  */
 
-/** A chunk of memory (unterminated string). */
+/** An unterminated string fragment. */
 typedef struct {
 	const uint8_t* buf;  ///< Start of chunk
 	size_t         len;  ///< Length of chunk in bytes
@@ -163,38 +163,21 @@ size_t
 serd_uri_serialise(const SerdURI* uri, SerdSink sink, void* stream);
 
 /** @} */
-/** @name SerdString
- * @brief A measured UTF-8 string.
+/** @name SerdNode
+ * @brief An RDF node.
  * @{
  */
 
-/** Measured UTF-8 string. */
+/** A syntactic RDF node. */
 typedef struct {
-	size_t  n_bytes;  ///< Size in bytes including trailing null byte
-	size_t  n_chars;  ///< Length in characters
-	uint8_t buf[];    ///< Buffer
-} SerdString;
+	SerdType       type;
+	size_t         n_bytes;  ///< Size in bytes including trailing null byte
+	size_t         n_chars;  ///< Length in characters
+	const uint8_t* buf;      ///< Buffer
+} SerdNode;
 
-/** Create a new UTF-8 string from @a utf8. */
-SERD_API
-SerdString*
-serd_string_new(const uint8_t* utf8);
-
-/** Copy @a string. */
-SERD_API
-SerdString*
-serd_string_copy(const SerdString* str);
+static const SerdNode SERD_NODE_NULL = { 0, 0, 0, 0 };
 
-/** Free @a str. */
-SERD_API
-void
-serd_string_free(SerdString* str);
-
-/** Serialise @a uri to a string. */
-SERD_API
-SerdString*
-serd_string_new_from_uri(const SerdURI* uri,
-                         SerdURI*       out);
 
 /** @} */
 /** @name SerdEnv
@@ -215,17 +198,17 @@ serd_env_free(SerdEnv env);
 /** Add namespace @a uri to @a ns using prefix @a name. */
 SERD_API
 void
-serd_env_add(SerdEnv           env,
-             const SerdString* name,
-             const SerdString* uri);
+serd_env_add(SerdEnv         env,
+             const SerdNode* name,
+             const SerdNode* uri);
 
 /** Expand @a qname. */
 SERD_API
 bool
-serd_env_expand(const SerdEnv     env,
-                const SerdString* qname,
-                SerdChunk*        uri_prefix,
-                SerdChunk*        uri_suffix);
+serd_env_expand(const SerdEnv   env,
+                const SerdNode* qname,
+                SerdChunk*      uri_prefix,
+                SerdChunk*      uri_suffix);
 
 /** @} */
 /** @name SerdReader
@@ -234,31 +217,30 @@ serd_env_expand(const SerdEnv     env,
  */
 
 /** Sink for base URI changes. */
-typedef bool (*SerdBaseSink)(void*             handle,
-                             const SerdString* uri);
+typedef bool (*SerdBaseSink)(void*           handle,
+                             const SerdNode* uri);
 
 /** Sink for namespace definitions. */
-typedef bool (*SerdPrefixSink)(void*             handle,
-                               const SerdString* name,
-                               const SerdString* uri);
+typedef bool (*SerdPrefixSink)(void*           handle,
+                               const SerdNode* name,
+                               const SerdNode* uri);
 
 /** Sink for statements. */
-typedef bool (*SerdStatementSink)(
-	void*             handle,
-	const SerdString* graph,     SerdType graph_type,
-	const SerdString* subject,   SerdType subject_type,
-	const SerdString* predicate, SerdType predicate_type,
-	const SerdString* object,    SerdType object_type,
-	const SerdString* object_lang,
-	const SerdString* object_datatype);
+typedef bool (*SerdStatementSink)(void*           handle,
+                                  const SerdNode* graph,
+                                  const SerdNode* subject,
+                                  const SerdNode* predicate,
+                                  const SerdNode* object,
+                                  const SerdNode* object_datatype,
+                                  const SerdNode* object_lang);
 
 /** Sink for anonymous node end markers.
  * This is called to indicate that the anonymous node with the given
  * @a value will no longer be referred to by any future statements
  * (i.e. the anonymous serialisation of the node is finished).
  */
-typedef bool (*SerdEndSink)(void*             handle,
-                            const SerdString* value);
+typedef bool (*SerdEndSink)(void*           handle,
+                            const SerdNode* node);
 
 /** Create a new RDF reader. */
 SERD_API
@@ -317,27 +299,26 @@ serd_writer_set_base_uri(SerdWriter     writer,
 /** Set the current output base URI. */
 SERD_API
 void
-serd_writer_set_prefix(SerdWriter        writer,
-                       const SerdString* name,
-                       const SerdString* uri);
+serd_writer_set_prefix(SerdWriter      writer,
+                       const SerdNode* name,
+                       const SerdNode* uri);
 
 /** Write a statement. */
 SERD_API
 bool
-serd_writer_write_statement(
-	SerdWriter        writer,
-	const SerdString* graph,     SerdType graph_type,
-	const SerdString* subject,   SerdType subject_type,
-	const SerdString* predicate, SerdType predicate_type,
-	const SerdString* object,    SerdType object_type,
-	const SerdString* object_datatype,
-	const SerdString* object_lang);
+serd_writer_write_statement(SerdWriter      writer,
+                            const SerdNode* graph,
+                            const SerdNode* subject,
+                            const SerdNode* predicate,
+                            const SerdNode* object,
+                            const SerdNode* object_datatype,
+                            const SerdNode* object_lang);
 
 /** Mark the end of an anonymous node's description. */
 SERD_API
 bool
-serd_writer_end_anon(SerdWriter        writer,
-                     const SerdString* subject);
+serd_writer_end_anon(SerdWriter      writer,
+                     const SerdNode* node);
 
 /** Finish a write. */
 SERD_API
diff --git a/src/env.c b/src/env.c
index 9d8b6235..87356ad6 100644
--- a/src/env.c
+++ b/src/env.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -20,7 +20,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "serd/serd.h"
+#include "serd_internal.h"
 
 typedef struct {
 	SerdString* name;
@@ -72,29 +72,29 @@ serd_env_find(SerdEnv        env,
 
 SERD_API
 void
-serd_env_add(SerdEnv           env,
-             const SerdString* name,
-             const SerdString* uri)
+serd_env_add(SerdEnv         env,
+             const SerdNode* name,
+             const SerdNode* uri)
 {
 	assert(name && uri);
 	SerdPrefix* const prefix = serd_env_find(env, name->buf, name->n_chars);
 	if (prefix) {
 		serd_string_free(prefix->uri);
-		prefix->uri = serd_string_copy(uri);
+		prefix->uri = serd_string_new_from_node(uri);
 	} else {
 		env->prefixes = realloc(env->prefixes,
 		                        (++env->n_prefixes) * sizeof(SerdPrefix));
-		env->prefixes[env->n_prefixes - 1].name   = serd_string_copy(name);
-		env->prefixes[env->n_prefixes - 1].uri = serd_string_copy(uri);
+		env->prefixes[env->n_prefixes - 1].name = serd_string_new_from_node(name);
+		env->prefixes[env->n_prefixes - 1].uri  = serd_string_new_from_node(uri);
 	}
 }
 
 SERD_API
 bool
-serd_env_expand(const SerdEnv     env,
-                const SerdString* qname,
-                SerdChunk*        uri_prefix,
-                SerdChunk*        uri_suffix)
+serd_env_expand(const SerdEnv   env,
+                const SerdNode* qname,
+                SerdChunk*      uri_prefix,
+                SerdChunk*      uri_suffix)
 {
 	const uint8_t* const colon = memchr(qname->buf, ':', qname->n_bytes);
 	if (!colon) {
@@ -102,7 +102,7 @@ serd_env_expand(const SerdEnv     env,
 	}
 
 	const size_t            name_len = colon - qname->buf;
-	const SerdPrefix* const prefix = serd_env_find(env, qname->buf, name_len);
+	const SerdPrefix* const prefix   = serd_env_find(env, qname->buf, name_len);
 	if (prefix) {
 		uri_prefix->buf = prefix->uri->buf;
 		uri_prefix->len = prefix->uri->n_bytes - 1;
diff --git a/src/reader.c b/src/reader.c
index 0dfdbedc..35067403 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -34,7 +34,7 @@
 #define STACK_PAGE_SIZE 4096
 #define READ_BUF_LEN    4096
 #ifndef NDEBUG
-#define STACK_DEBUG       1
+#define STACK_DEBUG     1
 #endif
 
 typedef struct {
@@ -60,7 +60,7 @@ typedef struct {
 	const Node* predicate;
 } ReadContext;
 
-static const Node SERD_NODE_NULL = { 0, 0, 0, 0 };
+static const Node INTERNAL_NODE_NULL = { 0, 0, 0, 0 };
 
 struct SerdReaderImpl {
 	void*             handle;
@@ -269,18 +269,42 @@ pop_string(SerdReader reader, Ref ref)
 	}
 }
 
+static inline SerdNode
+public_node_from_ref(SerdReader reader, SerdType type, Ref ref)
+{
+	if (!ref) {
+		return SERD_NODE_NULL;
+	}
+	const SerdString* str    = deref(reader, ref);
+	const SerdNode    public = { type, str->n_bytes, str->n_chars, str->buf };
+	return public;
+}
+
+static inline SerdNode
+public_node(SerdReader reader, const Node* private)
+{
+	return public_node_from_ref(reader, private->type, private->value);
+}
+
+	
 static inline bool
 emit_statement(SerdReader reader,
                const Node* g, const Node* s, const Node* p, const Node* o)
 {
 	assert(s->value && p->value && o->value);
-	return reader->statement_sink(
-		reader->handle,
-		g ? deref(reader, g->value) : NULL, g ? g->type : 0,
-		deref(reader, s->value), s->type,
-		deref(reader, p->value), p->type,
-		deref(reader, o->value), o->type,
-		deref(reader, o->datatype), deref(reader, o->lang));
+	const SerdNode graph           = g ? public_node(reader, g) : SERD_NODE_NULL;
+	const SerdNode subject         = public_node(reader, s);
+	const SerdNode predicate       = public_node(reader, p);
+	const SerdNode object          = public_node(reader, o);
+	const SerdNode object_datatype = public_node_from_ref(reader, SERD_URI, o->datatype);
+	const SerdNode object_lang     = public_node_from_ref(reader, SERD_LITERAL, o->lang);
+	return reader->statement_sink(reader->handle,
+	                              &graph,
+	                              &subject,
+	                              &predicate,
+	                              &object,
+	                              &object_datatype,
+	                              &object_lang);
 }
 
 static bool read_collection(SerdReader reader, ReadContext ctx, Node* dest);
@@ -891,7 +915,7 @@ static bool
 read_literal(SerdReader reader, Node* dest)
 {
 	Ref           str      = 0;
-	Node          datatype = SERD_NODE_NULL;
+	Node          datatype = INTERNAL_NODE_NULL;
 	const uint8_t c        = peek_byte(reader);
 	if (c == '-' || c == '+' || is_digit(c)) {
 		return read_number(reader, dest);
@@ -1000,7 +1024,8 @@ read_blank(SerdReader reader, ReadContext ctx, Node* dest)
 		read_ws_star(reader);
 		eat_byte(reader, ']');
 		if (reader->end_sink) {
-			reader->end_sink(reader->handle, deref(reader, dest->value));
+			const SerdNode end = public_node(reader, dest);
+			reader->end_sink(reader->handle, &end);
 		}
 		return true;
 	case '(':
@@ -1040,7 +1065,7 @@ read_object(SerdReader reader, ReadContext ctx)
 	uint8_t       pre[6];
 	bool          ret  = false;
 	bool          emit = (ctx.subject != 0);
-	Node          o    = SERD_NODE_NULL;
+	Node          o    = INTERNAL_NODE_NULL;
 	const uint8_t c    = peek_byte(reader);
 	switch (c) {
 	case ')':
@@ -1122,7 +1147,7 @@ read_predicateObjectList(SerdReader reader, ReadContext ctx)
 	if (reader->eof) {
 		return false;
 	}
-	Node predicate = SERD_NODE_NULL;
+	Node predicate = INTERNAL_NODE_NULL;
 	TRY_RET(read_verb(reader, &predicate));
 	TRY_THROW(read_ws_plus(reader));
 	ctx.predicate = &predicate;
@@ -1207,7 +1232,7 @@ read_collection(SerdReader reader, ReadContext ctx, Node* dest)
 static Node
 read_subject(SerdReader reader, ReadContext ctx)
 {
-	Node    subject = SERD_NODE_NULL;
+	Node    subject = INTERNAL_NODE_NULL;
 	switch (peek_byte(reader)) {
 	case '[': case '(': case '_':
 		read_blank(reader, ctx, &subject);
@@ -1244,7 +1269,8 @@ read_base(SerdReader reader)
 	TRY_RET(read_ws_plus(reader));
 	Ref uri;
 	TRY_RET(uri = read_uriref(reader));
-	reader->base_sink(reader->handle, deref(reader, uri));
+	const SerdNode uri_node = public_node_from_ref(reader, SERD_URI, uri);
+	reader->base_sink(reader->handle, &uri_node);
 	pop_string(reader, uri);
 	return true;
 }
@@ -1266,9 +1292,9 @@ read_prefixID(SerdReader reader)
 	read_ws_star(reader);
 	Ref uri = 0;
 	TRY_THROW(uri = read_uriref(reader));
-	ret = reader->prefix_sink(reader->handle,
-	                          deref(reader, name),
-	                          deref(reader, uri));
+	const SerdNode name_node = public_node_from_ref(reader, SERD_LITERAL, name);
+	const SerdNode uri_node  = public_node_from_ref(reader, SERD_URI, uri);
+	ret = reader->prefix_sink(reader->handle, &name_node, &uri_node);
 	pop_string(reader, uri);
 except:
 	pop_string(reader, name);
@@ -1352,7 +1378,7 @@ serd_reader_new(SerdSyntax        syntax,
 
 	memset(reader->read_buf, '\0', READ_BUF_LEN * 2);
 
-	/* Read into the second page of the buffer.  Occasionally readahead
+	/* Read into the second page of the buffer. Occasionally readahead
 	   will move the read_head to before this point when readahead causes
 	   a page fault.
 	*/
diff --git a/src/serd_internal.h b/src/serd_internal.h
index 49db82d5..1b601e12 100644
--- a/src/serd_internal.h
+++ b/src/serd_internal.h
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef SERD_INTERNAL_H
@@ -30,7 +30,7 @@ typedef struct {
 	size_t   size;      ///< Conceptual size of stack in buf
 } SerdStack;
 
-/** An offset to start the stack at.  Note 0 is reserved for NULL. */
+/** An offset to start the stack at. Note 0 is reserved for NULL. */
 #define SERD_STACK_BOTTOM sizeof(void*)
 
 static inline SerdStack
@@ -99,4 +99,27 @@ is_digit(const uint8_t c)
 	return in_range(c, '0', '9');
 }
 
+/** Measured UTF-8 string. */
+typedef struct {
+	size_t  n_bytes;  ///< Size in bytes including trailing null byte
+	size_t  n_chars;  ///< Length in characters
+	uint8_t buf[];    ///< Buffer
+} SerdString;
+
+#if 0
+/** Create a new UTF-8 string from @a utf8. */
+SerdString*
+serd_string_new(const uint8_t* utf8);
+
+/** Copy @a string. */
+SerdString*
+serd_string_copy(const SerdString* str);
+#endif
+
+void
+serd_string_free(SerdString* str);
+
+SerdString*
+serd_string_new_from_node(const SerdNode* node);
+
 #endif // SERD_INTERNAL_H
diff --git a/src/serdi.c b/src/serdi.c
index d8b88dd0..810de74c 100644
--- a/src/serdi.c
+++ b/src/serdi.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -21,103 +21,174 @@
 
 #include "serd/serd.h"
 
+// #define URI_DEBUG 1
+
 typedef struct {
-	SerdWriter  writer;
-	SerdEnv     env;
-	SerdString* base_uri_str;
-	SerdURI     base_uri;
+	SerdWriter writer;
+	SerdEnv    env;
+	SerdNode   base_uri_node;
+	SerdURI    base_uri;
 } State;
 
-static bool
-event_base(void*             handle,
-           const SerdString* uri_str)
+static size_t
+serd_uri_string_length(const SerdURI* uri)
 {
-	State* const state = (State*)handle;
+	size_t len = uri->path_base.len;
+
+#define ADD_LEN(field, n_delims) \
+	if ((field).len) { len += (field).len + (n_delims); }
+
+	ADD_LEN(uri->path,      1);  // + possible leading `/'
+	ADD_LEN(uri->scheme,    1);  // + trailing `:'
+	ADD_LEN(uri->authority, 2);  // + leading `//'
+	ADD_LEN(uri->query,     1);  // + leading `?'
+	ADD_LEN(uri->fragment,  1);  // + leading `#'
+
+	return len;
+}
+
+static size_t
+string_sink(const void* buf, size_t len, void* stream)
+{
+	uint8_t** ptr = (uint8_t**)stream;
+	memcpy(*ptr, buf, len);
+	*ptr += len;
+	return len;
+}
+
+static SerdNode
+serd_node_new_uri(const SerdURI* uri, SerdURI* out)
+{
+	const size_t len = serd_uri_string_length(uri);
+	uint8_t*     buf = malloc(len + 1);
+
+	SerdNode node = { SERD_URI, len + 1, len, buf };  // FIXME: UTF-8
+
+	uint8_t*     ptr        = buf;
+	const size_t actual_len = serd_uri_serialise(uri, string_sink, &ptr);
+
+	buf[actual_len] = '\0';
+	node.n_bytes    = actual_len + 1;
+	node.n_chars    = actual_len;
+
+	// FIXME: double parse
+	if (!serd_uri_parse(buf, out)) {
+		fprintf(stderr, "error parsing URI\n");
+		return SERD_NODE_NULL;
+	}
 
-	SerdURI uri;
-	if (!serd_uri_parse(uri_str->buf, &uri)) {
+	#ifdef URI_DEBUG
+	fwrite("URI: `'", 1, 6, stderr);
+	fwrite(node.buf, 1, node.n_bytes - 1, stderr);
+	fwrite("'\n", 1, 2, stderr);
+	#endif
+
+	return node;
+}
+
+static uint8_t*
+copy_string(const uint8_t* str, size_t* n_bytes)
+{
+	const size_t   len = strlen((const char*)str);
+	uint8_t* const ret = malloc(len + 1);
+	memcpy(ret, str, len + 1);
+	*n_bytes = len + 1;
+	return ret;
+}
+
+#if 0
+static SerdNode
+serd_node_copy(const SerdNode* node)
+{
+	SerdNode copy = *node;
+	uint8_t* buf  = malloc(copy.n_bytes);
+	memcpy(buf, node->buf, copy.n_bytes);
+	copy.buf = buf;
+	return copy;
+}
+
+static void
+serd_node_free(SerdNode* node)
+{
+	free((uint8_t*)node->buf);  // FIXME: const cast
+}
+#endif
+
+static bool
+event_base(void*           handle,
+           const SerdNode* uri_node)
+{
+	State* const state         = (State*)handle;
+	SerdNode     base_uri_node = *uri_node;
+	SerdURI      base_uri;
+	if (!serd_uri_parse(uri_node->buf, &base_uri)) {
 		return false;
 	}
 
-	SerdURI     base_uri = SERD_URI_NULL;
-	SerdString* base_uri_str;
-	if (!uri.scheme.len) {
-		// URI has no scheme (relative by definition), resolve
+	if (!base_uri.scheme.len) {  // URI has no scheme, resolve relative URI
 		SerdURI abs_base_uri;
-		if (!serd_uri_resolve(&uri, &state->base_uri, &abs_base_uri)) {
+		if (!serd_uri_resolve(&base_uri, &state->base_uri, &abs_base_uri)) {
 			fprintf(stderr, "error: failed to resolve new base URI\n");
 			return false;
 		}
-		base_uri_str = serd_string_new_from_uri(&abs_base_uri, &base_uri);
-		// FIXME: double parse
-		serd_uri_parse(base_uri_str->buf, &base_uri);
+		base_uri_node = serd_node_new_uri(&abs_base_uri, &base_uri);
 	} else {
-		// Absolute URI, use literally as new base URI
-		base_uri_str = serd_string_copy(uri_str);
-		// FIXME: double parse
-		serd_uri_parse(base_uri_str->buf, &base_uri);
+		SerdURI new_base_uri;
+		base_uri_node = serd_node_new_uri(&base_uri, &new_base_uri);
+		base_uri      = new_base_uri;
 	}
 
-	// Replace the old base URI
-	serd_string_free(state->base_uri_str);
-	state->base_uri_str     = base_uri_str;
-	state->base_uri         = base_uri;
+	state->base_uri_node = base_uri_node;
+	state->base_uri      = base_uri;
 	serd_writer_set_base_uri(state->writer, &base_uri);
-
 	return true;
 }
 
 static bool
-event_prefix(void*             handle,
-             const SerdString* name,
-             const SerdString* uri_string)
+event_prefix(void*           handle,
+             const SerdNode* name,
+             const SerdNode* uri_node)
 {
 	State* const state = (State*)handle;
-	if (!serd_uri_string_has_scheme(uri_string->buf)) {
+	if (!serd_uri_string_has_scheme(uri_node->buf)) {
 		SerdURI uri;
-		if (!serd_uri_parse(uri_string->buf, &uri)) {
+		if (!serd_uri_parse(uri_node->buf, &uri)) {
 			return false;
 		}
 		SerdURI abs_uri;
 		if (!serd_uri_resolve(&uri, &state->base_uri, &abs_uri)) {
 			return false;
 		}
-		SerdURI     new_abs_uri;
-		SerdString* abs_uri_string = serd_string_new_from_uri(&abs_uri, &new_abs_uri);
-		serd_env_add(state->env, name, abs_uri_string);
-		serd_string_free(abs_uri_string);
+		SerdURI  base_uri;
+		SerdNode base_uri_node = serd_node_new_uri(&abs_uri, &base_uri);
+		serd_env_add(state->env, name, &base_uri_node);
 	} else {
-		serd_env_add(state->env, name, uri_string);
+		serd_env_add(state->env, name, uri_node);
 	}
-	serd_writer_set_prefix(state->writer, name, uri_string);
-
+	serd_writer_set_prefix(state->writer, name, uri_node);
 	return true;
 }
 
 static bool
-event_statement(void*             handle,
-                const SerdString* graph,     SerdType graph_type,
-                const SerdString* subject,   SerdType subject_type,
-                const SerdString* predicate, SerdType predicate_type,
-                const SerdString* object,    SerdType object_type,
-                const SerdString* object_datatype,
-                const SerdString* object_lang)
+event_statement(void*           handle,
+                const SerdNode* graph,
+                const SerdNode* subject,
+                const SerdNode* predicate,
+                const SerdNode* object,
+                const SerdNode* object_datatype,
+                const SerdNode* object_lang)
 {
-	State* const state = (State*)handle;
-	return serd_writer_write_statement(state->writer,
-	                                   graph,     graph_type,
-	                                   subject,   subject_type,
-	                                   predicate, predicate_type,
-	                                   object,    object_type,
-	                                   object_datatype, object_lang);
+	return serd_writer_write_statement(
+		((State*)handle)->writer,
+		graph, subject, predicate, object, object_datatype, object_lang);
 }
 
 static bool
-event_end(void*             handle,
-          const SerdString* subject)
+event_end(void*           handle,
+          const SerdNode* node)
 {
 	State* const state = (State*)handle;
-	return serd_writer_end_anon(state->writer, subject);
+	return serd_writer_end_anon(state->writer, node);
 }
 
 int
@@ -184,20 +255,23 @@ main(int argc, char** argv)
 		}
 	}
 
-	SerdString* base_uri_str = NULL;
-	SerdURI     base_uri;
+	uint8_t* base_uri_str     = NULL;
+	size_t   base_uri_n_bytes = 0;
+	SerdURI  base_uri;
 	if (a < argc) {  // Base URI given on command line
 		const uint8_t* const in_base_uri = (const uint8_t*)argv[a++];
 		if (!serd_uri_parse((const uint8_t*)in_base_uri, &base_uri)) {
 			fprintf(stderr, "invalid base URI `%s'\n", argv[2]);
 			return 1;
 		}
-		base_uri_str = serd_string_new(in_base_uri);
+		base_uri_str = copy_string(in_base_uri, &base_uri_n_bytes);
 	} else {  // Use input file URI
-		base_uri_str = serd_string_new(in_filename);
+		base_uri_str = copy_string(in_filename, &base_uri_n_bytes);
 	}
 
-	serd_uri_parse(base_uri_str->buf, &base_uri);
+	if (!serd_uri_parse(base_uri_str, &base_uri)) {
+		fprintf(stderr, "invalid base URI `%s'\n", base_uri_str);
+	}
 
 	if (!in_fd) {
 		in_fd  = fopen((const char*)in_filename,  "r");
@@ -216,10 +290,15 @@ main(int argc, char** argv)
 		? SERD_STYLE_ASCII
 		: SERD_STYLE_ABBREVIATED;
 
+	const SerdNode base_uri_node = { SERD_URI,
+	                                 base_uri_n_bytes,
+	                                 base_uri_n_bytes - 1,
+	                                 base_uri_str };
+
 	State state = {
 		serd_writer_new(output_syntax, output_style,
 		                env, &base_uri, file_sink, out_fd),
-		env, base_uri_str, base_uri
+		env, base_uri_node, base_uri
 	};
 
 	SerdReader reader = serd_reader_new(
@@ -233,7 +312,7 @@ main(int argc, char** argv)
 	serd_writer_free(state.writer);
 
 	serd_env_free(state.env);
-	serd_string_free(state.base_uri_str);
+	free(base_uri_str);
 
 	if (success) {
 		return 0;
diff --git a/src/string.c b/src/string.c
index 0f5d2430..77346676 100644
--- a/src/string.c
+++ b/src/string.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -20,8 +20,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "serd/serd.h"
+#include "serd_internal.h"
 
+#if 0
 static inline size_t
 utf8_strlen(const uint8_t* utf8, size_t* out_n_bytes)
 {
@@ -38,20 +39,37 @@ utf8_strlen(const uint8_t* utf8, size_t* out_n_bytes)
 	}
 	return n_chars;
 }
+#endif
 
+static SerdString*
+serd_string_new_measured(const uint8_t* utf8, size_t n_bytes, size_t n_chars)
+{
+	SerdString* const str = malloc(sizeof(SerdString) + n_bytes);
+	str->n_bytes = n_bytes;
+	str->n_chars = n_chars;
+	memcpy(str->buf, utf8, n_bytes);
+	return str;
+}
+
+#if 0
 SERD_API
 SerdString*
 serd_string_new(const uint8_t* utf8)
 {
 	size_t n_bytes;
 	size_t n_chars = utf8_strlen(utf8, &n_bytes);
-	SerdString* const str = malloc(sizeof(SerdString) + n_bytes);
-	str->n_bytes = n_bytes;
-	str->n_chars = n_chars;
-	memcpy(str->buf, utf8, str->n_bytes);
-	return str;
+	return serd_string_new_measured(utf8, n_bytes, n_chars);
+}
+#endif
+
+SERD_API
+SerdString*
+serd_string_new_from_node(const SerdNode* node)
+{
+	return serd_string_new_measured(node->buf, node->n_bytes, node->n_chars);
 }
 
+#if 0
 SERD_API
 SerdString*
 serd_string_copy(const SerdString* s)
@@ -63,6 +81,7 @@ serd_string_copy(const SerdString* s)
 	}
 	return NULL;
 }
+#endif
 
 SERD_API
 void
diff --git a/src/uri.c b/src/uri.c
index 6fb6d42e..3c62c01f 100644
--- a/src/uri.c
+++ b/src/uri.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -338,55 +338,3 @@ serd_uri_serialise(const SerdURI* uri, SerdSink sink, void* stream)
 	}
 	return write_size;
 }
-
-
-static size_t
-serd_uri_string_length(const SerdURI* uri)
-{
-	size_t len = uri->path_base.len;
-
-#define ADD_LEN(field, n_delims) \
-	if ((field).len) { len += (field).len + (n_delims); }
-
-	ADD_LEN(uri->path,      1);  // + possible leading `/'
-	ADD_LEN(uri->scheme,    1);  // + trailing `:'
-	ADD_LEN(uri->authority, 2);  // + leading `//'
-	ADD_LEN(uri->query,     1);  // + leading `?'
-	ADD_LEN(uri->fragment,  1);  // + leading `#'
-
-	return len;
-}
-
-static size_t
-string_sink(const void* buf, size_t len, void* stream)
-{
-	uint8_t** ptr = (uint8_t**)stream;
-	memcpy(*ptr, buf, len);
-	*ptr += len;
-	return len;
-}
-
-SERD_API
-SerdString*
-serd_string_new_from_uri(const SerdURI* uri, SerdURI* out)
-{
-	const size_t len = serd_uri_string_length(uri);
-	SerdString*  str = malloc(sizeof(SerdString) + len + 1);
-	str->n_bytes = len + 1;
-	str->n_chars = len;  // FIXME: UTF-8
-
-	uint8_t* ptr = str->buf;
-	const size_t actual_len = serd_uri_serialise(uri, string_sink, &ptr);
-
-	str->buf[actual_len] = '\0';
-	str->n_bytes = actual_len + 1;
-	str->n_chars = str->n_bytes - 1;  // FIXME: UTF-8
-
-	#ifdef URI_DEBUG
-	fwrite("URI: `'", 1, 6, stderr);
-	fwrite(str->buf, 1, str->n_bytes - 1, stderr);
-	fwrite("'\n", 1, 2, stderr);
-	#endif
-
-	return str;
-}
diff --git a/src/writer.c b/src/writer.c
index 194d26dd..1de08a4c 100644
--- a/src/writer.c
+++ b/src/writer.c
@@ -8,11 +8,11 @@
  *
  * Serd is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for details.
  *
  * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>
@@ -22,12 +22,14 @@
 #include "serd_internal.h"
 
 typedef struct {
-	const SerdString* graph;
-	const SerdString* subject;
-	const SerdString* predicate;
+	SerdNode graph;
+	SerdNode subject;
+	SerdNode predicate;
 } WriteContext;
 
-static const WriteContext WRITE_CONTEXT_NULL = { 0, 0, 0 };
+static const WriteContext WRITE_CONTEXT_NULL = {
+	{ 0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, 0}
+};
 
 struct SerdWriterImpl {
 	SerdSyntax   syntax;
@@ -162,15 +164,14 @@ serd_writer_write_delim(SerdWriter writer, const uint8_t delim)
 }
 
 static bool
-write_node(SerdWriter        writer,
-           SerdType          type,
-           const SerdString* str,
-           const SerdString* datatype,
-           const SerdString* lang)
+write_node(SerdWriter      writer,
+           const SerdNode* node,
+           const SerdNode* datatype,
+           const SerdNode* lang)
 {
 	SerdChunk uri_prefix;
 	SerdChunk uri_suffix;
-	switch (type) {
+	switch (node->type) {
 	case SERD_ANON_BEGIN:
 		if (writer->syntax != SERD_NTRIPLES) {
 			++writer->indent;
@@ -178,8 +179,8 @@ write_node(SerdWriter        writer,
 			WriteContext* ctx = (WriteContext*)serd_stack_push(
 				&writer->anon_stack, sizeof(WriteContext));
 			*ctx = writer->context;
-			writer->context.subject   = str;
-			writer->context.predicate = 0;
+			writer->context.subject   = *node;
+			writer->context.predicate = SERD_NODE_NULL;
 			break;
 		}
 	case SERD_ANON:
@@ -188,13 +189,13 @@ write_node(SerdWriter        writer,
 		}  // else fall through
 	case SERD_BLANK_ID:
 		writer->sink("_:", 2, writer->stream);
-		writer->sink(str->buf, str->n_bytes - 1, writer->stream);
+		writer->sink(node->buf, node->n_bytes - 1, writer->stream);
 		break;
 	case SERD_CURIE:
 		switch (writer->syntax) {
 		case SERD_NTRIPLES:
-			if (!serd_env_expand(writer->env, str, &uri_prefix, &uri_suffix)) {
-				fprintf(stderr, "error: undefined namespace prefix `%s'\n", str->buf);
+			if (!serd_env_expand(writer->env, node, &uri_prefix, &uri_suffix)) {
+				fprintf(stderr, "error: undefined namespace prefix `%s'\n", node->buf);
 				return false;
 			}
 			writer->sink("<", 1, writer->stream);
@@ -203,25 +204,25 @@ write_node(SerdWriter        writer,
 			writer->sink(">", 1, writer->stream);
 			break;
 		case SERD_TURTLE:
-			writer->sink(str->buf, str->n_bytes - 1, writer->stream);
+			writer->sink(node->buf, node->n_bytes - 1, writer->stream);
 		}
 		break;
 	case SERD_LITERAL:
 		writer->sink("\"", 1, writer->stream);
-		write_text(writer, WRITE_STRING, str->buf, str->n_bytes - 1, '"');
+		write_text(writer, WRITE_STRING, node->buf, node->n_bytes - 1, '"');
 		writer->sink("\"", 1, writer->stream);
-		if (lang) {
+		if (lang->buf) {
 			writer->sink("@", 1, writer->stream);
 			writer->sink(lang->buf, lang->n_bytes - 1, writer->stream);
-		} else if (datatype) {
+		} else if (datatype->buf) {
 			writer->sink("^^", 2, writer->stream);
-			write_node(writer, SERD_URI, datatype, NULL, NULL);
+			write_node(writer, datatype, NULL, NULL);
 		}
 		break;
 	case SERD_URI:
-		if (!serd_uri_string_has_scheme(str->buf)) {
+		if (!serd_uri_string_has_scheme(node->buf)) {
 			SerdURI uri;
-			if (serd_uri_parse(str->buf, &uri)) {
+			if (serd_uri_parse(node->buf, &uri)) {
 				SerdURI abs_uri;
 				if (serd_uri_resolve(&uri, &writer->base_uri, &abs_uri)) {
 					writer->sink("<", 1, writer->stream);
@@ -232,7 +233,7 @@ write_node(SerdWriter        writer,
 			}
 		} else {
 			writer->sink("<", 1, writer->stream);
-			write_text(writer, WRITE_URI, str->buf, str->n_bytes - 1, '>');
+			write_text(writer, WRITE_URI, node->buf, node->n_bytes - 1, '>');
 			writer->sink(">", 1, writer->stream);
 			return true;
 		}
@@ -243,23 +244,22 @@ write_node(SerdWriter        writer,
 
 SERD_API
 bool
-serd_writer_write_statement(
-	SerdWriter        writer,
-	const SerdString* graph,     SerdType graph_type,
-	const SerdString* subject,   SerdType subject_type,
-	const SerdString* predicate, SerdType predicate_type,
-	const SerdString* object,    SerdType object_type,
-	const SerdString* object_datatype,
-	const SerdString* object_lang)
+serd_writer_write_statement(SerdWriter      writer,
+                            const SerdNode* graph,
+                            const SerdNode* subject,
+                            const SerdNode* predicate,
+                            const SerdNode* object,
+                            const SerdNode* object_datatype,
+                            const SerdNode* object_lang)
 {
 	assert(subject && predicate && object);
 	switch (writer->syntax) {
 	case SERD_NTRIPLES:
-		write_node(writer, subject_type, subject, NULL, NULL);
+		write_node(writer, subject, NULL, NULL);
 		writer->sink(" ", 1, writer->stream);
-		write_node(writer, predicate_type, predicate, NULL, NULL);
+		write_node(writer, predicate, NULL, NULL);
 		writer->sink(" ", 1, writer->stream);
-		if (!write_node(writer, object_type, object, object_datatype, object_lang)) {
+		if (!write_node(writer, object, object_datatype, object_lang)) {
 			return false;
 		}
 		writer->sink(" .\n", 3, writer->stream);
@@ -267,27 +267,26 @@ serd_writer_write_statement(
 	case SERD_TURTLE:
 		break;
 	}
-	
-	if (subject == writer->context.subject) {
-		if (predicate == writer->context.predicate) {  // Abbreviate S P
+	if (subject->buf == writer->context.subject.buf) {
+		if (predicate->buf == writer->context.predicate.buf) {  // Abbreviate S P
 			++writer->indent;
 			serd_writer_write_delim(writer, ',');
-			write_node(writer, object_type, object, object_datatype, object_lang);
+			write_node(writer, object, object_datatype, object_lang);
 			--writer->indent;
 		} else {  // Abbreviate S
-			if (writer->context.predicate) {
+			if (writer->context.predicate.buf) {
 				serd_writer_write_delim(writer, ';');
 			} else {
 				++writer->indent;
 				serd_writer_write_delim(writer, '\n');
 			}
-			write_node(writer, predicate_type, predicate, NULL, NULL);
-			writer->context.predicate = predicate;
+			write_node(writer, predicate, NULL, NULL);
+			writer->context.predicate = *predicate;
 			writer->sink(" ", 1, writer->stream);
-			write_node(writer, object_type, object, object_datatype, object_lang);
+			write_node(writer, object, object_datatype, object_lang);
 		}
 	} else {
-		if (writer->context.subject) {
+		if (writer->context.subject.buf) {
 			if (writer->indent > 0) {
 				--writer->indent;
 			}
@@ -297,41 +296,39 @@ serd_writer_write_statement(
 			}
 		}
 
-		if (subject_type == SERD_ANON_BEGIN) {
+		if (subject->type == SERD_ANON_BEGIN) {
 			writer->sink("[ ", 2, writer->stream);
 			++writer->indent;
 			WriteContext* ctx = (WriteContext*)serd_stack_push(
 				&writer->anon_stack, sizeof(WriteContext));
 			*ctx = writer->context;
-			writer->context.subject   = subject;
-			writer->context.predicate = 0;
 		} else {
-			write_node(writer, subject_type, subject, NULL, NULL);
+			write_node(writer, subject, NULL, NULL);
 			++writer->indent;
-			if (subject_type != SERD_ANON_BEGIN && subject_type != SERD_ANON) {
+			if (subject->type != SERD_ANON_BEGIN && subject->type != SERD_ANON) {
 				serd_writer_write_delim(writer, '\n');
 			}
 		}
 
-		writer->context.subject   = subject;
-		writer->context.predicate = 0;
+		writer->context.subject   = *subject;
+		writer->context.predicate = SERD_NODE_NULL;
 
-		write_node(writer, predicate_type, predicate, NULL, NULL);
-		writer->context.predicate = predicate;
+		write_node(writer, predicate, NULL, NULL);
+		writer->context.predicate = *predicate;
 		writer->sink(" ", 1, writer->stream);
 
-		write_node(writer, object_type, object, object_datatype, object_lang);
+		write_node(writer, object, object_datatype, object_lang);
 	}
 
-	const WriteContext new_context = { graph, subject, predicate };
+	const WriteContext new_context = { *graph, *subject, *predicate };
 	writer->context = new_context;
 	return true;
 }
 
 SERD_API
 bool
-serd_writer_end_anon(SerdWriter        writer,
-                     const SerdString* subject)
+serd_writer_end_anon(SerdWriter      writer,
+                     const SerdNode* node)
 {
 	if (writer->syntax == SERD_NTRIPLES) {
 		return true;
@@ -346,8 +343,8 @@ serd_writer_end_anon(SerdWriter        writer,
 	writer->sink("]", 1, writer->stream);
 	writer->context = *anon_stack_top(writer);
 	serd_stack_pop(&writer->anon_stack, sizeof(WriteContext));
-	if (!writer->context.subject) {  // End of anonymous subject
-		writer->context.subject = subject;
+	if (!writer->context.subject.buf) {  // End of anonymous subject
+		writer->context.subject = *node;
 	}
 	return true;
 }
@@ -356,7 +353,7 @@ SERD_API
 void
 serd_writer_finish(SerdWriter writer)
 {
-	if (writer->context.subject) {
+	if (writer->context.subject.buf) {
 		writer->sink(" .\n", 3, writer->stream);
 	}
 }
@@ -391,7 +388,7 @@ serd_writer_set_base_uri(SerdWriter     writer,
 {
 	writer->base_uri = *uri;
 	if (writer->syntax != SERD_NTRIPLES) {
-		if (writer->context.graph || writer->context.subject) {
+		if (writer->context.graph.buf || writer->context.subject.buf) {
 			writer->sink(" .\n\n", 4, writer->stream);
 			writer->context = WRITE_CONTEXT_NULL;
 		}
@@ -404,12 +401,12 @@ serd_writer_set_base_uri(SerdWriter     writer,
 
 SERD_API
 void
-serd_writer_set_prefix(SerdWriter        writer,
-                       const SerdString* name,
-                       const SerdString* uri)
+serd_writer_set_prefix(SerdWriter      writer,
+                       const SerdNode* name,
+                       const SerdNode* uri)
 {
 	if (writer->syntax != SERD_NTRIPLES) {
-		if (writer->context.graph || writer->context.subject) {
+		if (writer->context.graph.buf || writer->context.subject.buf) {
 			writer->sink(" .\n\n", 4, writer->stream);
 			writer->context = WRITE_CONTEXT_NULL;
 		}