Use a fixed-size reader stack

This improves performance, and makes the reader more suitable for embedded or
network-facing applications, at the cost of requiring the user to specify a
maximum stack size.

7 files changed, 219 insertions, 180 deletions

diff --git a/src/n3.c b/src/n3.c
index 37976f58..190d7239 100644
--- a/src/n3.c
+++ b/src/n3.c
@@ -41,7 +41,7 @@ fancy_syntax(const SerdReader* reader)
 }
 
 static SerdStatus
-read_collection(SerdReader* reader, ReadContext ctx, Ref* dest);
+read_collection(SerdReader* reader, ReadContext ctx, SerdNode** dest);
 
 static SerdStatus
 read_predicateObjectList(SerdReader* reader, ReadContext ctx, bool* ate_dot);
@@ -60,7 +60,7 @@ read_HEX(SerdReader* reader)
 
 // Read UCHAR escape, initial \ is already eaten by caller
 static inline SerdStatus
-read_UCHAR(SerdReader* reader, Ref dest, uint32_t* char_code)
+read_UCHAR(SerdReader* reader, SerdNode* dest, uint32_t* char_code)
 {
 	const int b      = peek_byte(reader);
 	unsigned  length = 0;
@@ -99,9 +99,9 @@ read_UCHAR(SerdReader* reader, Ref dest, uint32_t* char_code)
 	} else {
 		r_err(reader, SERD_ERR_BAD_SYNTAX,
 		      "unicode character 0x%X out of range\n", code);
-		push_bytes(reader, dest, replacement_char, 3);
 		*char_code = 0xFFFD;
-		return SERD_SUCCESS;
+		const SerdStatus st = push_bytes(reader, dest, replacement_char, 3);
+		return st ? st : SERD_SUCCESS;
 	}
 
 	// Build output in buf
@@ -130,42 +130,35 @@ read_UCHAR(SerdReader* reader, Ref dest, uint32_t* char_code)
 		break;
 	}
 
-	push_bytes(reader, dest, buf, size);
 	*char_code = code;
-	return SERD_SUCCESS;
+	return push_bytes(reader, dest, buf, size);
 }
 
 // Read ECHAR escape, initial \ is already eaten by caller
 static inline SerdStatus
-read_ECHAR(SerdReader* reader, Ref dest, SerdNodeFlags* flags)
+read_ECHAR(SerdReader* reader, SerdNode* dest, SerdNodeFlags* flags)
 {
 	const int c = peek_byte(reader);
 	switch (c) {
 	case 't':
 		eat_byte_safe(reader, 't');
-		push_byte(reader, dest, '\t');
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, '\t');
 	case 'b':
 		eat_byte_safe(reader, 'b');
-		push_byte(reader, dest, '\b');
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, '\b');
 	case 'n':
 		*flags |= SERD_HAS_NEWLINE;
 		eat_byte_safe(reader, 'n');
-		push_byte(reader, dest, '\n');
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, '\n');
 	case 'r':
 		*flags |= SERD_HAS_NEWLINE;
 		eat_byte_safe(reader, 'r');
-		push_byte(reader, dest, '\r');
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, '\r');
 	case 'f':
 		eat_byte_safe(reader, 'f');
-		push_byte(reader, dest, '\f');
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, '\f');
 	case '\\': case '"': case '\'':
-		push_byte(reader, dest, eat_byte_safe(reader, c));
-		return SERD_SUCCESS;
+		return push_byte(reader, dest, eat_byte_safe(reader, c));
 	default:
 		return SERD_ERR_BAD_SYNTAX;
 	}
@@ -208,21 +201,21 @@ read_utf8_bytes(SerdReader* reader, uint8_t bytes[4], uint32_t* size, uint8_t c)
 }
 
 static SerdStatus
-read_utf8_character(SerdReader* reader, Ref dest, uint8_t c)
+read_utf8_character(SerdReader* reader, SerdNode* dest, uint8_t c)
 {
 	uint32_t   size     = 0;
 	uint8_t    bytes[4] = {0, 0, 0, 0};
 	SerdStatus st       = read_utf8_bytes(reader, bytes, &size, c);
 	if (st) {
 		push_bytes(reader, dest, replacement_char, 3);
-	} else {
-		push_bytes(reader, dest, bytes, size);
+		return st;
 	}
-	return st;
+
+	return push_bytes(reader, dest, bytes, size);
 }
 
 static SerdStatus
-read_utf8_code(SerdReader* reader, Ref dest, uint32_t* code, uint8_t c)
+read_utf8_code(SerdReader* reader, SerdNode* dest, uint32_t* code, uint8_t c)
 {
 	uint32_t   size     = 0;
 	uint8_t    bytes[4] = {0, 0, 0, 0};
@@ -232,15 +225,17 @@ read_utf8_code(SerdReader* reader, Ref dest, uint32_t* code, uint8_t c)
 		return st;
 	}
 
-	push_bytes(reader, dest, bytes, size);
-	*code = parse_counted_utf8_char(bytes, size);
+	if (!(st = push_bytes(reader, dest, bytes, size))) {
+		*code = parse_counted_utf8_char(bytes, size);
+	}
+
 	return st;
 }
 
 // Read one character (possibly multi-byte)
 // The first byte, c, has already been eaten by caller
 static inline SerdStatus
-read_character(SerdReader* reader, Ref dest, SerdNodeFlags* flags, uint8_t c)
+read_character(SerdReader* reader, SerdNode* dest, SerdNodeFlags* flags, uint8_t c)
 {
 	if (!(c & 0x80)) {
 		switch (c) {
@@ -253,6 +248,7 @@ read_character(SerdReader* reader, Ref dest, SerdNodeFlags* flags, uint8_t c)
 		default:
 			break;
 		}
+
 		return push_byte(reader, dest, c);
 	}
 	return read_utf8_character(reader, dest, c);
@@ -314,7 +310,7 @@ eat_delim(SerdReader* reader, const char delim)
 // Initial triple quotes are already eaten by caller
 static SerdStatus
 read_STRING_LITERAL_LONG(SerdReader*    reader,
-                         Ref            ref,
+                         SerdNode*      ref,
                          SerdNodeFlags* flags,
                          uint8_t        q)
 {
@@ -357,7 +353,7 @@ read_STRING_LITERAL_LONG(SerdReader*    reader,
 // Initial quote is already eaten by caller
 static SerdStatus
 read_STRING_LITERAL(SerdReader*    reader,
-                    Ref            ref,
+                    SerdNode*      ref,
                     SerdNodeFlags* flags,
                     uint8_t        q)
 {
@@ -397,7 +393,7 @@ read_STRING_LITERAL(SerdReader*    reader,
 }
 
 static SerdStatus
-read_String(SerdReader* reader, Ref node, SerdNodeFlags* flags)
+read_String(SerdReader* reader, SerdNode* node, SerdNodeFlags* flags)
 {
 	const int q1 = peek_byte(reader);
 	eat_byte_safe(reader, q1);
@@ -438,7 +434,7 @@ is_PN_CHARS_BASE(const uint32_t c)
 }
 
 static SerdStatus
-read_PN_CHARS_BASE(SerdReader* reader, Ref dest)
+read_PN_CHARS_BASE(SerdReader* reader, SerdNode* dest)
 {
 	uint32_t   code = 0;
 	const int  c    = peek_byte(reader);
@@ -468,7 +464,7 @@ is_PN_CHARS(const uint32_t c)
 }
 
 static SerdStatus
-read_PN_CHARS(SerdReader* reader, Ref dest)
+read_PN_CHARS(SerdReader* reader, SerdNode* dest)
 {
 	uint32_t   code = 0;
 	const int  c    = peek_byte(reader);
@@ -488,7 +484,7 @@ read_PN_CHARS(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_PERCENT(SerdReader* reader, Ref dest)
+read_PERCENT(SerdReader* reader, SerdNode* dest)
 {
 	push_byte(reader, dest, eat_byte_safe(reader, '%'));
 	const uint8_t h1 = read_HEX(reader);
@@ -501,7 +497,7 @@ read_PERCENT(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_PN_LOCAL_ESC(SerdReader* reader, Ref dest)
+read_PN_LOCAL_ESC(SerdReader* reader, SerdNode* dest)
 {
 	eat_byte_safe(reader, '\\');
 
@@ -537,7 +533,7 @@ read_PN_LOCAL_ESC(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_PLX(SerdReader* reader, Ref dest)
+read_PLX(SerdReader* reader, SerdNode* dest)
 {
 	const int c = peek_byte(reader);
 	switch (c) {
@@ -551,7 +547,7 @@ read_PLX(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_PN_LOCAL(SerdReader* reader, Ref dest, bool* ate_dot)
+read_PN_LOCAL(SerdReader* reader, SerdNode* dest, bool* ate_dot)
 {
 	int        c                      = peek_byte(reader);
 	SerdStatus st                     = SERD_SUCCESS;
@@ -580,10 +576,9 @@ read_PN_LOCAL(SerdReader* reader, Ref dest, bool* ate_dot)
 		trailing_unescaped_dot = (c == '.');
 	}
 
-	SerdNode* const n = deref(reader, dest);
 	if (trailing_unescaped_dot) {
 		// Ate trailing dot, pop it from stack/node and inform caller
-		--n->n_bytes;
+		--dest->n_bytes;
 		serd_stack_pop(&reader->stack, 1);
 		*ate_dot = true;
 	}
@@ -593,7 +588,7 @@ read_PN_LOCAL(SerdReader* reader, Ref dest, bool* ate_dot)
 
 // Read the remainder of a PN_PREFIX after some initial characters
 static SerdStatus
-read_PN_PREFIX_tail(SerdReader* reader, Ref dest)
+read_PN_PREFIX_tail(SerdReader* reader, SerdNode* dest)
 {
 	int c = 0;
 	while ((c = peek_byte(reader))) {  // Middle: (PN_CHARS | '.')*
@@ -604,8 +599,7 @@ read_PN_PREFIX_tail(SerdReader* reader, Ref dest)
 		}
 	}
 
-	const SerdNode* const n = deref(reader, dest);
-	if (serd_node_string(n)[n->n_bytes - 1] == '.' &&
+	if (serd_node_string(dest)[dest->n_bytes - 1] == '.' &&
 	    read_PN_CHARS(reader, dest)) {
 		return r_err(reader, SERD_ERR_BAD_SYNTAX, "prefix ends with `.'\n");
 	}
@@ -614,7 +608,7 @@ read_PN_PREFIX_tail(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_PN_PREFIX(SerdReader* reader, Ref dest)
+read_PN_PREFIX(SerdReader* reader, SerdNode* dest)
 {
 	if (!read_PN_CHARS_BASE(reader, dest)) {
 		return read_PN_PREFIX_tail(reader, dest);
@@ -623,14 +617,16 @@ read_PN_PREFIX(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_LANGTAG(SerdReader* reader, Ref* dest)
+read_LANGTAG(SerdReader* reader, SerdNode** dest)
 {
 	int c = peek_byte(reader);
 	if (!is_alpha(c)) {
 		return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected `%c'\n", c);
 	}
 
-	*dest = push_node(reader, SERD_LITERAL, "", 0);
+	if (!(*dest = push_node(reader, SERD_LITERAL, "", 0))) {
+		return SERD_ERR_OVERFLOW;
+	}
 
 	SerdStatus st = SERD_SUCCESS;
 	TRY(st, push_byte(reader, *dest, eat_byte_safe(reader, c)));
@@ -647,7 +643,7 @@ read_LANGTAG(SerdReader* reader, Ref* dest)
 }
 
 static SerdStatus
-read_IRIREF_scheme(SerdReader* reader, Ref dest)
+read_IRIREF_scheme(SerdReader* reader, SerdNode* dest)
 {
 	int c = peek_byte(reader);
 	if (!is_alpha(c)) {
@@ -675,7 +671,7 @@ read_IRIREF_scheme(SerdReader* reader, Ref dest)
 }
 
 static SerdStatus
-read_IRIREF(SerdReader* reader, Ref* dest)
+read_IRIREF(SerdReader* reader, SerdNode** dest)
 {
 	if (!eat_byte_check(reader, '<')) {
 		return SERD_ERR_BAD_SYNTAX;
@@ -747,7 +743,7 @@ read_IRIREF(SerdReader* reader, Ref* dest)
 }
 
 static SerdStatus
-read_PrefixedName(SerdReader* reader, Ref dest, bool read_prefix, bool* ate_dot)
+read_PrefixedName(SerdReader* reader, SerdNode* dest, bool read_prefix, bool* ate_dot)
 {
 	SerdStatus st = SERD_SUCCESS;
 	if (read_prefix && ((st = read_PN_PREFIX(reader, dest)) > SERD_FAILURE)) {
@@ -764,7 +760,7 @@ read_PrefixedName(SerdReader* reader, Ref dest, bool read_prefix, bool* ate_dot)
 }
 
 static SerdStatus
-read_0_9(SerdReader* reader, Ref str, bool at_least_one)
+read_0_9(SerdReader* reader, SerdNode* str, bool at_least_one)
 {
 	unsigned   count = 0;
 	SerdStatus st    = SERD_SUCCESS;
@@ -779,8 +775,8 @@ read_0_9(SerdReader* reader, Ref str, bool at_least_one)
 
 static SerdStatus
 read_number(SerdReader*    reader,
-            Ref*           dest,
-            Ref*           datatype,
+            SerdNode**     dest,
+            SerdNode**     datatype,
             SerdNodeFlags* flags,
             bool*          ate_dot)
 {
@@ -793,9 +789,12 @@ read_number(SerdReader*    reader,
 	SerdStatus st          = SERD_SUCCESS;
 	int        c           = peek_byte(reader);
 	bool       has_decimal = false;
-	if (c == '-' || c == '+') {
+	if (!*dest) {
+		return SERD_ERR_OVERFLOW;
+	} else if (c == '-' || c == '+') {
 		push_byte(reader, *dest, eat_byte_safe(reader, c));
 	}
+
 	if ((c = peek_byte(reader)) == '.') {
 		has_decimal = true;
 		// decimal case 2 (e.g. '.0' or `-.0' or `+.0')
@@ -847,20 +846,26 @@ read_number(SerdReader*    reader,
 }
 
 static SerdStatus
-read_iri(SerdReader* reader, Ref* dest, bool* ate_dot)
+read_iri(SerdReader* reader, SerdNode** dest, bool* ate_dot)
 {
 	switch (peek_byte(reader)) {
 	case '<':
 		return read_IRIREF(reader, dest);
 	default:
-		*dest = push_node(reader, SERD_CURIE, "", 0);
+		if (!(*dest = push_node(reader, SERD_CURIE, "", 0))) {
+			return SERD_ERR_OVERFLOW;
+		}
 		return read_PrefixedName(reader, *dest, true, ate_dot);
 	}
 }
 
 static SerdStatus
-read_literal(SerdReader* reader, Ref* dest,
-             Ref* datatype, Ref* lang, SerdNodeFlags* flags, bool* ate_dot)
+read_literal(SerdReader*    reader,
+             SerdNode**     dest,
+             SerdNode**     datatype,
+             SerdNode**     lang,
+             SerdNodeFlags* flags,
+             bool*          ate_dot)
 {
 	*dest = push_node(reader, SERD_LITERAL, "", 0);
 
@@ -897,7 +902,7 @@ read_literal(SerdReader* reader, Ref* dest,
 }
 
 static SerdStatus
-read_verb(SerdReader* reader, Ref* dest)
+read_verb(SerdReader* reader, SerdNode** dest)
 {
 	if (peek_byte(reader) == '<') {
 		return read_IRIREF(reader, dest);
@@ -906,11 +911,13 @@ read_verb(SerdReader* reader, Ref* dest)
 	/* Either a qname, or "a".  Read the prefix first, and if it is in fact
 	   "a", produce that instead.
 	*/
-	*dest = push_node(reader, SERD_CURIE, "", 0);
+	if (!(*dest = push_node(reader, SERD_CURIE, "", 0))) {
+		return SERD_ERR_OVERFLOW;
+	}
 
 	SerdStatus st      = read_PN_PREFIX(reader, *dest);
 	bool       ate_dot = false;
-	SerdNode*  node    = deref(reader, *dest);
+	SerdNode*  node    = *dest;
 	const int  next    = peek_byte(reader);
 	if (!st && node->n_bytes == 1 &&
 	    serd_node_string(node)[0] == 'a' &&
@@ -929,12 +936,12 @@ read_verb(SerdReader* reader, Ref* dest)
 }
 
 static SerdStatus
-read_BLANK_NODE_LABEL(SerdReader* reader, Ref* dest, bool* ate_dot)
+read_BLANK_NODE_LABEL(SerdReader* reader, SerdNode** dest, bool* ate_dot)
 {
 	eat_byte_safe(reader, '_');
 	eat_byte_check(reader, ':');
 
-	const Ref ref = *dest =
+	SerdNode* n = *dest =
 	    push_node(reader,
 	              SERD_BLANK,
 	              reader->bprefix ? reader->bprefix : "",
@@ -942,23 +949,22 @@ read_BLANK_NODE_LABEL(SerdReader* reader, Ref* dest, bool* ate_dot)
 
 	int c = peek_byte(reader);  // First: (PN_CHARS | '_' | [0-9])
 	if (is_digit(c) || c == '_') {
-		push_byte(reader, ref, eat_byte_safe(reader, c));
-	} else if (read_PN_CHARS(reader, ref)) {
-		*dest = pop_node(reader, *dest);
+		push_byte(reader, n, eat_byte_safe(reader, c));
+	} else if (read_PN_CHARS(reader, n)) {
+		*dest = pop_node(reader, n);
 		return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid name start\n");
 	}
 
 	while ((c = peek_byte(reader))) {  // Middle: (PN_CHARS | '.')*
 		if (c == '.') {
-			push_byte(reader, ref, eat_byte_safe(reader, c));
-		} else if (read_PN_CHARS(reader, ref)) {
+			push_byte(reader, n, eat_byte_safe(reader, c));
+		} else if (read_PN_CHARS(reader, n)) {
 			break;
 		}
 	}
 
-	SerdNode* n   = deref(reader, ref);
-	char*     buf = serd_node_buffer(n);
-	if (buf[n->n_bytes - 1] == '.' && read_PN_CHARS(reader, ref)) {
+	char* buf = serd_node_buffer(n);
+	if (buf[n->n_bytes - 1] == '.' && read_PN_CHARS(reader, n)) {
 		// Ate trailing dot, pop it from stack/node and inform caller
 		--n->n_bytes;
 		serd_stack_pop(&reader->stack, 1);
@@ -972,7 +978,7 @@ read_BLANK_NODE_LABEL(SerdReader* reader, Ref* dest, bool* ate_dot)
 				reader->seen_genid = true;
 			} else if (reader->seen_genid &&
 			           buf[reader->bprefix_len] == 'B') {
-				*dest = pop_node(reader, *dest);
+				*dest = pop_node(reader, n);
 				return r_err(
 					reader, SERD_ERR_ID_CLASH,
 					"found both `b' and `B' blank IDs, prefix required\n");
@@ -982,24 +988,24 @@ read_BLANK_NODE_LABEL(SerdReader* reader, Ref* dest, bool* ate_dot)
 	return SERD_SUCCESS;
 }
 
-static Ref
+static SerdNode*
 read_blankName(SerdReader* reader)
 {
 	eat_byte_safe(reader, '=');
 	if (eat_byte_check(reader, '=') != '=') {
 		r_err(reader, SERD_ERR_BAD_SYNTAX, "expected `='\n");
-		return 0;
+		return NULL;
 	}
 
-	Ref  subject = 0;
-	bool ate_dot = false;
+	SerdNode* subject = 0;
+	bool      ate_dot = false;
 	read_ws_star(reader);
 	read_iri(reader, &subject, &ate_dot);
 	return subject;
 }
 
 static SerdStatus
-read_anon(SerdReader* reader, ReadContext ctx, bool subject, Ref* dest)
+read_anon(SerdReader* reader, ReadContext ctx, bool subject, SerdNode** dest)
 {
 	const SerdStatementFlags old_flags = *ctx.flags;
 	bool                     empty     = false;
@@ -1038,7 +1044,7 @@ read_anon(SerdReader* reader, ReadContext ctx, bool subject, Ref* dest)
 		}
 		read_ws_star(reader);
 		if (reader->sink->end) {
-			reader->sink->end(reader->sink->handle, deref(reader, *dest));
+			reader->sink->end(reader->sink->handle, *dest);
 		}
 		*ctx.flags = old_flags;
 	}
@@ -1062,10 +1068,9 @@ read_object(SerdReader* reader, ReadContext* ctx, bool emit, bool* ate_dot)
 	SerdStatus ret = SERD_FAILURE;
 
 	bool      simple   = (ctx->subject != 0);
-	SerdNode* node     = NULL;
-	Ref       o        = 0;
-	Ref       datatype = 0;
-	Ref       lang     = 0;
+	SerdNode* o        = 0;
+	SerdNode* datatype = 0;
+	SerdNode* lang     = 0;
 	uint32_t  flags    = 0;
 	const int c        = peek_byte(reader);
 	if (!fancy_syntax(reader)) {
@@ -1105,15 +1110,17 @@ read_object(SerdReader* reader, ReadContext* ctx, bool emit, bool* ate_dot)
 		/* Either a boolean literal, or a qname.  Read the prefix first, and if
 		   it is in fact a "true" or "false" literal, produce that instead.
 		*/
-		o = push_node(reader, SERD_CURIE, "", 0);
+		if (!(o = push_node(reader, SERD_CURIE, "", 0))) {
+			return SERD_ERR_OVERFLOW;
+		}
+
 		while (!read_PN_CHARS_BASE(reader, o)) {}
-		node = deref(reader, o);
-		if ((node->n_bytes == 4 &&
-		     !memcmp(serd_node_string(node), "true", 4)) ||
-		    (node->n_bytes == 5 &&
-		     !memcmp(serd_node_string(node), "false", 5))) {
+		if ((o->n_bytes == 4 &&
+		     !memcmp(serd_node_string(o), "true", 4)) ||
+		    (o->n_bytes == 5 &&
+		     !memcmp(serd_node_string(o), "false", 5))) {
 			flags      = flags | SERD_HAS_DATATYPE;
-			node->type = SERD_LITERAL;
+			o->type = SERD_LITERAL;
 			datatype   = push_node(
 				reader, SERD_URI, XSD_BOOLEAN, XSD_BOOLEAN_LEN);
 			ret = SERD_SUCCESS;
@@ -1129,7 +1136,7 @@ read_object(SerdReader* reader, ReadContext* ctx, bool emit, bool* ate_dot)
 	}
 
 	if (!ret && simple && o) {
-		deref(reader, o)->flags = flags;
+		o->flags = flags;
 	}
 
 	if (!ret && emit && simple) {
@@ -1204,7 +1211,11 @@ read_predicateObjectList(SerdReader* reader, ReadContext ctx, bool* ate_dot)
 }
 
 static SerdStatus
-end_collection(SerdReader* reader, ReadContext ctx, Ref n1, Ref n2, SerdStatus st)
+end_collection(SerdReader* reader,
+               ReadContext ctx,
+               SerdNode*   n1,
+               SerdNode*   n2,
+               SerdStatus  st)
 {
 	pop_node(reader, n2);
 	pop_node(reader, n1);
@@ -1217,7 +1228,7 @@ end_collection(SerdReader* reader, ReadContext ctx, Ref n1, Ref n2, SerdStatus s
 }
 
 static SerdStatus
-read_collection(SerdReader* reader, ReadContext ctx, Ref* dest)
+read_collection(SerdReader* reader, ReadContext ctx, SerdNode** dest)
 {
 	SerdStatus st = SERD_SUCCESS;
 	eat_byte_safe(reader, '(');
@@ -1238,10 +1249,14 @@ read_collection(SerdReader* reader, ReadContext ctx, Ref* dest)
 
 	/* The order of node allocation here is necessarily not in stack order,
 	   so we create two nodes and recycle them throughout. */
-	Ref n1   = push_node_padded(reader, genid_size(reader), SERD_BLANK, "", 0);
-	Ref n2   = 0;
-	Ref node = n1;
-	Ref rest = 0;
+	SerdNode* n1   = push_node_padded(reader, genid_size(reader), SERD_BLANK, "", 0);
+	SerdNode* n2   = 0;
+	SerdNode* node = n1;
+	SerdNode* rest = 0;
+
+	if (!n1) {
+		return SERD_ERR_OVERFLOW;
+	}
 
 	ctx.subject = *dest;
 	while (!peek_delim(reader, ')')) {
@@ -1276,7 +1291,7 @@ read_collection(SerdReader* reader, ReadContext ctx, Ref* dest)
 }
 
 static SerdStatus
-read_subject(SerdReader* reader, ReadContext ctx, Ref* dest, int* s_type)
+read_subject(SerdReader* reader, ReadContext ctx, SerdNode** dest, int* s_type)
 {
 	SerdStatus st      = SERD_SUCCESS;
 	bool       ate_dot = false;
@@ -1303,7 +1318,7 @@ read_subject(SerdReader* reader, ReadContext ctx, Ref* dest, int* s_type)
 }
 
 static SerdStatus
-read_labelOrSubject(SerdReader* reader, Ref* dest)
+read_labelOrSubject(SerdReader* reader, SerdNode** dest)
 {
 	bool ate_dot = false;
 	switch (peek_byte(reader)) {
@@ -1356,10 +1371,10 @@ read_base(SerdReader* reader, bool sparql, bool token)
 
 	read_ws_star(reader);
 
-	Ref uri = 0;
+	SerdNode* uri = NULL;
 	TRY(st, read_IRIREF(reader, &uri));
 	if (reader->sink->base) {
-		TRY(st, reader->sink->base(reader->sink->handle, deref(reader, uri)));
+		TRY(st, reader->sink->base(reader->sink->handle, uri));
 	}
 	pop_node(reader, uri);
 
@@ -1382,8 +1397,10 @@ read_prefixID(SerdReader* reader, bool sparql, bool token)
 	}
 
 	read_ws_star(reader);
-	Ref  name = push_node(reader, SERD_LITERAL, "", 0);
-	if ((st = read_PN_PREFIX(reader, name)) > SERD_FAILURE) {
+	SerdNode* name = push_node(reader, SERD_LITERAL, "", 0);
+	if (!name) {
+		return SERD_ERR_OVERFLOW;
+	} else if ((st = read_PN_PREFIX(reader, name)) > SERD_FAILURE) {
 		return st;
 	}
 
@@ -1393,13 +1410,11 @@ read_prefixID(SerdReader* reader, bool sparql, bool token)
 	}
 
 	read_ws_star(reader);
-	Ref uri = 0;
+	SerdNode* uri = NULL;
 	TRY(st, read_IRIREF(reader, &uri));
 
 	if (reader->sink->prefix) {
-		st = reader->sink->prefix(reader->sink->handle,
-		                          deref(reader, name),
-		                          deref(reader, uri));
+		st = reader->sink->prefix(reader->sink->handle, name, uri);
 	}
 	pop_node(reader, uri);
 	pop_node(reader, name);
@@ -1469,13 +1484,11 @@ read_wrappedGraph(SerdReader* reader, ReadContext* ctx)
 }
 
 static int
-tokcmp(SerdReader* reader, Ref ref, const char* tok, size_t n)
+tokcmp(SerdNode* node, const char* tok, size_t n)
 {
-	SerdNode* node = deref(reader, ref);
-	if (!node || node->n_bytes != n) {
-		return -1;
-	}
-	return serd_strncasecmp(serd_node_string(node), tok, n);
+	return ((!node || node->n_bytes != n)
+	        ? -1
+	        : serd_strncasecmp(serd_node_string(node), tok, n));
 }
 
 SerdStatus
@@ -1516,11 +1529,11 @@ read_n3_statement(SerdReader* reader)
 			return st;
 		}
 
-		if (!tokcmp(reader, ctx.subject, "base", 4)) {
+		if (!tokcmp(ctx.subject, "base", 4)) {
 			st = read_base(reader, true, false);
-		} else if (!tokcmp(reader, ctx.subject, "prefix", 6)) {
+		} else if (!tokcmp(ctx.subject, "prefix", 6)) {
 			st = read_prefixID(reader, true, false);
-		} else if (!tokcmp(reader, ctx.subject, "graph", 5)) {
+		} else if (!tokcmp(ctx.subject, "graph", 5)) {
 			read_ws_star(reader);
 			TRY(st, read_labelOrSubject(reader, &ctx.graph));
 			read_ws_star(reader);
diff --git a/src/reader.c b/src/reader.c
index 95031e0c..bb71be83 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -41,9 +41,8 @@ r_err(SerdReader* reader, SerdStatus st, const char* fmt, ...)
 }
 
 void
-set_blank_id(SerdReader* reader, Ref ref, size_t buf_size)
+set_blank_id(SerdReader* reader, SerdNode* node, size_t buf_size)
 {
-	SerdNode*   node   = deref(reader, ref);
 	char*       buf    = (char*)(node + 1);
 	const char* prefix = reader->bprefix ? (const char*)reader->bprefix : "";
 
@@ -57,21 +56,28 @@ genid_size(SerdReader* reader)
 	return reader->bprefix_len + 1 + 10 + 1;  // + "b" + UINT32_MAX + \0
 }
 
-Ref
+SerdNode*
 blank_id(SerdReader* reader)
 {
-	Ref ref = push_node_padded(reader, genid_size(reader), SERD_BLANK, "", 0);
-	set_blank_id(reader, ref, genid_size(reader));
+	SerdNode* ref = push_node_padded(
+		reader, genid_size(reader), SERD_BLANK, "", 0);
+	if (ref) {
+		set_blank_id(reader, ref, genid_size(reader));
+	}
 	return ref;
 }
 
-Ref
+SerdNode*
 push_node_padded(SerdReader* reader, size_t maxlen,
                  SerdType type, const char* str, size_t n_bytes)
 {
 	void* mem = serd_stack_push_aligned(
 		&reader->stack, sizeof(SerdNode) + maxlen + 1, sizeof(SerdNode));
 
+	if (!mem) {
+		return NULL;
+	}
+
 	SerdNode* const node = (SerdNode*)mem;
 	node->n_bytes = n_bytes;
 	node->flags   = 0;
@@ -85,41 +91,34 @@ push_node_padded(SerdReader* reader, size_t maxlen,
 		reader->allocs, sizeof(reader->allocs) * (++reader->n_allocs));
 	reader->allocs[reader->n_allocs - 1] = (mem - reader->stack.buf);
 #endif
-	return (Ref)((char*)node - reader->stack.buf);
+	return node;
 }
 
-Ref
+SerdNode*
 push_node(SerdReader* reader, SerdType type, const char* str, size_t n_bytes)
 {
 	return push_node_padded(reader, n_bytes, type, str, n_bytes);
 }
 
 SerdNode*
-deref(SerdReader* reader, const Ref ref)
-{
-	return ref ? (SerdNode*)(reader->stack.buf + ref) : NULL;
-}
-
-Ref
-pop_node(SerdReader* reader, Ref ref)
+pop_node(SerdReader* reader, const SerdNode* node)
 {
-	if (ref && ref != reader->rdf_first && ref != reader->rdf_rest
-	    && ref != reader->rdf_nil) {
+	if (node && node != reader->rdf_first && node != reader->rdf_rest
+	    && node != reader->rdf_nil) {
 #ifdef SERD_STACK_CHECK
-		SERD_STACK_ASSERT_TOP(reader, ref);
+		SERD_STACK_ASSERT_TOP(reader, node);
 		--reader->n_allocs;
 #endif
-		SerdNode* const node = deref(reader, ref);
-		char* const     top  = reader->stack.buf + reader->stack.size;
+		char* const top = reader->stack.buf + reader->stack.size;
 		serd_stack_pop_aligned(&reader->stack, (size_t)(top - (char*)node));
 	}
-	return 0;
+	return NULL;
 }
 
 SerdStatus
-emit_statement(SerdReader* reader, ReadContext ctx, Ref o)
+emit_statement(SerdReader* reader, ReadContext ctx, SerdNode* o)
 {
-	SerdNode* graph = deref(reader, ctx.graph);
+	SerdNode* graph = ctx.graph;
 	if (!graph && reader->default_graph) {
 		graph = reader->default_graph;
 	}
@@ -130,9 +129,9 @@ emit_statement(SerdReader* reader, ReadContext ctx, Ref o)
 	        : reader->sink->statement(reader->sink->handle,
 	                                  *ctx.flags,
 	                                  graph,
-	                                  deref(reader, ctx.subject),
-	                                  deref(reader, ctx.predicate),
-	                                  deref(reader, o));
+	                                  ctx.subject,
+	                                  ctx.predicate,
+	                                  o);
 
 	*ctx.flags &= SERD_ANON_CONT|SERD_LIST_CONT;  // Preserve only cont flags
 	return st;
@@ -159,14 +158,17 @@ serd_reader_read_document(SerdReader* reader)
 }
 
 SerdReader*
-serd_reader_new(SerdWorld* world, SerdSyntax syntax, const SerdSink* sink)
+serd_reader_new(SerdWorld*      world,
+                SerdSyntax      syntax,
+                const SerdSink* sink,
+                size_t          stack_size)
 {
 	SerdReader* me = (SerdReader*)calloc(1, sizeof(SerdReader));
 
 	me->world         = world;
 	me->sink          = sink;
 	me->default_graph = NULL;
-	me->stack         = serd_stack_new(SERD_PAGE_SIZE);
+	me->stack         = serd_stack_new(stack_size);
 	me->syntax        = syntax;
 	me->next_id       = 1;
 	me->strict        = true;
diff --git a/src/reader.h b/src/reader.h
index d3d27f39..4925dbda 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -41,18 +41,13 @@
 #    define SERD_STACK_ASSERT_TOP(reader, ref)
 #endif
 
-/* Reference to a node in the stack (we can not use pointers since the
-   stack may be reallocated, invalidating any pointers to elements).
-*/
-typedef size_t Ref;
-
 typedef struct {
-	Ref                 graph;
-	Ref                 subject;
-	Ref                 predicate;
-	Ref                 object;
-	Ref                 datatype;
-	Ref                 lang;
+	SerdNode*           graph;
+	SerdNode*           subject;
+	SerdNode*           predicate;
+	SerdNode*           object;
+	SerdNode*           datatype;
+	SerdNode*           lang;
 	SerdStatementFlags* flags;
 } ReadContext;
 
@@ -61,9 +56,9 @@ struct SerdReaderImpl {
 	const SerdSink*   sink;
 	SerdErrorSink     error_sink;
 	void*             error_handle;
-	Ref               rdf_first;
-	Ref               rdf_rest;
-	Ref               rdf_nil;
+	SerdNode*         rdf_first;
+	SerdNode*         rdf_rest;
+	SerdNode*         rdf_nil;
 	SerdNode*         default_graph;
 	SerdByteSource    source;
 	SerdStack         stack;
@@ -75,8 +70,8 @@ struct SerdReaderImpl {
 	bool              strict;     ///< True iff strict parsing
 	bool              seen_genid;
 #ifdef SERD_STACK_CHECK
-	Ref*              allocs;     ///< Stack of push offsets
-	size_t            n_allocs;   ///< Number of stack pushes
+	SerdNode**        allocs; ///< Stack of push offsets
+	size_t            n_allocs; ///< Number of stack pushes
 #endif
 };
 
@@ -84,27 +79,25 @@ SERD_LOG_FUNC(3, 4)
 SerdStatus
 r_err(SerdReader* reader, SerdStatus st, const char* fmt, ...);
 
-Ref push_node_padded(SerdReader* reader,
+SerdNode* push_node_padded(SerdReader* reader,
                      size_t      maxlen,
                      SerdType    type,
                      const char* str,
                      size_t      n_bytes);
 
-Ref push_node(SerdReader* reader,
-              SerdType    type,
-              const char* str,
-              size_t      n_bytes);
-
-size_t genid_size(SerdReader* reader);
-Ref    blank_id(SerdReader* reader);
-void   set_blank_id(SerdReader* reader, Ref ref, size_t buf_size);
+SerdNode* push_node(SerdReader* reader,
+                    SerdType    type,
+                    const char* str,
+                    size_t      n_bytes);
 
-SerdNode* deref(SerdReader* reader, Ref ref);
+size_t    genid_size(SerdReader* reader);
+SerdNode* blank_id(SerdReader* reader);
+void      set_blank_id(SerdReader* reader, SerdNode* node, size_t buf_size);
 
-Ref pop_node(SerdReader* reader, Ref ref);
+SerdNode* pop_node(SerdReader* reader, const SerdNode* node);
 
 SerdStatus
-emit_statement(SerdReader* reader, ReadContext ctx, Ref o);
+emit_statement(SerdReader* reader, ReadContext ctx, SerdNode* o);
 
 SerdStatus read_n3_statement(SerdReader* reader);
 SerdStatus read_nquadsDoc(SerdReader* reader);
@@ -154,25 +147,33 @@ eat_string(SerdReader* reader, const char* str, unsigned n)
 }
 
 static inline SerdStatus
-push_byte(SerdReader* reader, Ref ref, const int c)
+push_byte(SerdReader* reader, SerdNode* node, const int c)
 {
 	assert(c != EOF);
 	SERD_STACK_ASSERT_TOP(reader, ref);
 
-	char* const     s    = (char*)serd_stack_push(&reader->stack, 1);
-	SerdNode* const node = (SerdNode*)(reader->stack.buf + ref);
+	char* const s = (char*)serd_stack_push(&reader->stack, 1);
+	if (!s) {
+		return SERD_ERR_OVERFLOW;
+	}
+
 	++node->n_bytes;
 	*(s - 1) = (uint8_t)c;
 	*s       = '\0';
 	return SERD_SUCCESS;
 }
 
-static inline void
-push_bytes(SerdReader* reader, Ref ref, const uint8_t* bytes, unsigned len)
+static inline SerdStatus
+push_bytes(SerdReader* reader, SerdNode* ref, const uint8_t* bytes, unsigned len)
 {
+	if (reader->stack.buf_size < reader->stack.size + len) {
+		return SERD_ERR_OVERFLOW;
+	}
+
 	for (unsigned i = 0; i < len; ++i) {
 		push_byte(reader, ref, bytes[i]);
 	}
+	return SERD_SUCCESS;
 }
 
 #endif // SERD_READER_H
diff --git a/src/serdi.c b/src/serdi.c
index ef620c3c..fcb4274e 100644
--- a/src/serdi.c
+++ b/src/serdi.c
@@ -25,8 +25,10 @@
 #include <io.h>
 #endif
 
+#include <limits.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #define SERDI_ERROR(msg)       fprintf(stderr, "serdi: " msg)
@@ -98,6 +100,7 @@ print_usage(const char* name, bool error)
 	fprintf(os, "  -f           Keep full URIs in input (don't qualify).\n");
 	fprintf(os, "  -h           Display this help and exit.\n");
 	fprintf(os, "  -i SYNTAX    Input syntax: turtle/ntriples/trig/nquads.\n");
+	fprintf(os, "  -k BYTES     Parser stack size.\n");
 	fprintf(os, "  -l           Lax (non-strict) parsing.\n");
 	fprintf(os, "  -o SYNTAX    Output syntax: turtle/ntriples/nquads.\n");
 	fprintf(os, "  -p PREFIX    Add PREFIX to blank node IDs.\n");
@@ -140,6 +143,7 @@ main(int argc, char** argv)
 	bool           full_uris     = false;
 	bool           lax           = false;
 	bool           quiet         = false;
+	size_t         stack_size    = 4194304;
 	const char*    add_prefix    = NULL;
 	const char*    chop_prefix   = NULL;
 	const char*    root_uri      = NULL;
@@ -174,6 +178,17 @@ main(int argc, char** argv)
 			} else if (!(input_syntax = get_syntax(argv[a]))) {
 				return print_usage(argv[0], true);
 			}
+		} else if (argv[a][1] == 'k') {
+			if (++a == argc) {
+				return missing_arg(argv[0], 'k');
+			}
+			char*      endptr = NULL;
+			const long size   = strtol(argv[a], &endptr, 10);
+			if (size <= 0 || size == LONG_MAX || *endptr != '\0') {
+				SERDI_ERRORF("invalid stack size `%s'\n", argv[a]);
+				return 1;
+			}
+			stack_size = (size_t)size;
 		} else if (argv[a][1] == 'o') {
 			if (++a == argc) {
 				return missing_arg(argv[0], 'o');
@@ -262,8 +277,8 @@ main(int argc, char** argv)
 	                                     (SerdWriteFunc)fwrite,
 	                                     out_fd);
 
-	SerdReader* reader =
-		serd_reader_new(world, input_syntax, serd_writer_get_sink(writer));
+	SerdReader* reader = serd_reader_new(
+		world, input_syntax, serd_writer_get_sink(writer), stack_size);
 
 	serd_reader_set_strict(reader, !lax);
 	if (quiet) {
diff --git a/src/stack.h b/src/stack.h
index 8943370c..174c6378 100644
--- a/src/stack.h
+++ b/src/stack.h
@@ -66,8 +66,7 @@ serd_stack_push(SerdStack* stack, size_t n_bytes)
 {
 	const size_t new_size = stack->size + n_bytes;
 	if (stack->buf_size < new_size) {
-		stack->buf_size += (stack->buf_size >> 1); // *= 1.5
-		stack->buf = (char*)realloc(stack->buf, stack->buf_size);
+		return NULL;
 	}
 	char* const ret = (stack->buf + stack->size);
 	stack->size = new_size;
@@ -85,12 +84,16 @@ static inline void*
 serd_stack_push_aligned(SerdStack* stack, size_t n_bytes, size_t align)
 {
 	// Push one byte to ensure space for a pad count
-	serd_stack_push(stack, 1);
+	if (!serd_stack_push(stack, 1)) {
+		return NULL;
+	}
 
 	// Push padding if necessary
 	const size_t pad = align - stack->size % align;
 	if (pad > 0) {
-		serd_stack_push(stack, pad);
+		if (!serd_stack_push(stack, pad)) {
+			return NULL;
+		}
 	}
 
 	// Set top of stack to pad count so we can properly pop later
diff --git a/src/string.c b/src/string.c
index 9a6b4ff6..c755ff97 100644
--- a/src/string.c
+++ b/src/string.c
@@ -42,6 +42,7 @@ serd_strerror(SerdStatus status)
 	case SERD_ERR_ID_CLASH:   return "Blank node ID clash";
 	case SERD_ERR_BAD_CURIE:  return "Invalid CURIE";
 	case SERD_ERR_INTERNAL:   return "Internal error";
+	case SERD_ERR_OVERFLOW:   return "Stack overflow";
 	default:                  break;
 	}
 	return "Unknown error";  // never reached
diff --git a/src/writer.c b/src/writer.c
index 9d7a6790..827f7264 100644
--- a/src/writer.c
+++ b/src/writer.c
@@ -804,6 +804,10 @@ serd_writer_write_statement(SerdWriter*        writer,
 	if (flags & (SERD_ANON_S_BEGIN|SERD_ANON_O_BEGIN)) {
 		WriteContext* ctx = (WriteContext*)serd_stack_push(
 			&writer->anon_stack, sizeof(WriteContext));
+		if (!ctx) {
+			return SERD_ERR_OVERFLOW;
+		}
+
 		*ctx = writer->context;
 		WriteContext new_context = {
 			serd_node_copy(graph), serd_node_copy(subject), NULL };
@@ -876,7 +880,7 @@ serd_writer_new(SerdWorld*     world,
 	writer->env          = env;
 	writer->root_node    = NULL;
 	writer->root_uri     = SERD_URI_NULL;
-	writer->anon_stack   = serd_stack_new(4 * sizeof(WriteContext));
+	writer->anon_stack   = serd_stack_new(SERD_PAGE_SIZE);
 	writer->context      = context;
 	writer->list_subj    = NULL;
 	writer->empty        = true;