[gs-commits] mupdf 1.16.1.43 Optimise memory use in fz_xml.

commit be5481469972dec2e893ca5ab5ec7a34fae89428
Author: Robin Watts <[email protected]>
Date:   Fri Sep 27 00:30:37 2019 +0100

    Optimise memory use in fz_xml.
    
    Store one less pointer; tail is only used during creation, at a
    time when 'next' isn't being used. Remove it and use next instead.
    
    Move names to the end of the structures, so the structures can be
    truncated to the actual size required. This has the extra
    benefit of no longer restricting us to 40 chars for a tag or
    attribute name.

diff --git a/source/fitz/xml.c b/source/fitz/xml.c
index 12decb4..ac38a9c 100644
--- a/source/fitz/xml.c
+++ b/source/fitz/xml.c
@@ -77,9 +77,9 @@ struct parser
 
 struct attribute
 {
-	char name[40];
 	char *value;
 	struct attribute *next;
+	char name[1];
 };
 
 struct fz_xml_doc_s
@@ -90,10 +90,10 @@ struct fz_xml_doc_s
 
 struct fz_xml_s
 {
-	char name[40];
 	char *text;
 	struct attribute *atts;
-	fz_xml *up, *down, *tail, *prev, *next;
+	fz_xml *up, *down, *prev, *next;
+	char name[1];
 };
 
 static void xml_indent(int n)
@@ -344,15 +344,15 @@ static void xml_emit_open_tag(fz_context *ctx, struct parser *parser, char *a, c
 {
 	fz_xml *head, *tail;
 	char *ns;
+	size_t size;
 
 	/* skip namespace prefix */
 	for (ns = a; ns < b - 1; ++ns)
 		if (*ns == ':')
 			a = ns + 1;
 
-	head = fz_pool_alloc(ctx, parser->pool, sizeof *head);
-	if (b - a > sizeof(head->name) - 1)
-		b = a + sizeof(head->name) - 1;
+	size = offsetof(fz_xml, name) + b-a+1;
+	head = fz_pool_alloc(ctx, parser->pool, size);
 	memcpy(head->name, a, b - a);
 	head->name[b - a] = 0;
 
@@ -363,15 +363,18 @@ static void xml_emit_open_tag(fz_context *ctx, struct parser *parser, char *a, c
 	head->prev = NULL;
 	head->next = NULL;
 
+	/* During construction, we use head->next to mean "the
+	 * tail of the children. When we close the tag, we
+	 * rewrite it to be NULL. */
 	if (!parser->head->down) {
 		parser->head->down = head;
-		parser->head->tail = head;
+		parser->head->next = head;
 	}
 	else {
-		tail = parser->head->tail;
+		tail = parser->head->next;
 		tail->next = head;
 		head->prev = tail;
-		parser->head->tail = head;
+		parser->head->next = head;
 	}
 
 	parser->head = head;
@@ -382,10 +385,10 @@ static void xml_emit_att_name(fz_context *ctx, struct parser *parser, char *a, c
 {
 	fz_xml *head = parser->head;
 	struct attribute *att;
+	size_t size;
 
-	att = fz_pool_alloc(ctx, parser->pool, sizeof *att);
-	if (b - a > sizeof(att->name) - 1)
-		b = a + sizeof(att->name) - 1;
+	size = offsetof(struct attribute, name) + b-a+1;
+	att = fz_pool_alloc(ctx, parser->pool, size);
 	memcpy(att->name, a, b - a);
 	att->name[b - a] = 0;
 	att->value = NULL;
@@ -417,6 +420,7 @@ static void xml_emit_att_value(fz_context *ctx, struct parser *parser, char *a,
 static void xml_emit_close_tag(fz_context *ctx, struct parser *parser)
 {
 	parser->depth--;
+	parser->head->next = NULL;
 	if (parser->head->up)
 		parser->head = parser->head->up;
 }

http://git.ghostscript.com/?p=mupdf.git;a=commit;h=be5481469972dec2e893ca5ab5ec7a34fae89428

--
MuPDF library
Artifex Software, Inc.