From a2b2d9e18bffd3426123343c93c4f805e3ec5aad Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Thu, 12 Oct 2023 21:00:53 -0400
Subject: [PATCH] src/svgtiny_css.c: implement node_has_attribute_dashmatch()
 select handler

---
 src/svgtiny_css.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/src/svgtiny_css.c b/src/svgtiny_css.c
index 6e80847..5dbb83e 100644
--- a/src/svgtiny_css.c
+++ b/src/svgtiny_css.c
@@ -1,4 +1,5 @@
 #include <libcss/libcss.h>
+#include <strings.h> /* strncasecmp */
 
 #include "svgtiny.h"
 #include "svgtiny_internal.h"
@@ -26,6 +27,9 @@ static css_error node_has_attribute(void *pw, void *node,
 static css_error node_has_attribute_equal(void *pw, void *node,
 		const css_qname *qname, lwc_string *value,
 		bool *match);
+static css_error node_has_attribute_dashmatch(void *pw, void *node,
+		const css_qname *qname, lwc_string *value,
+		bool *match);
 
 
 /**
@@ -727,3 +731,90 @@ css_error node_has_attribute_equal(void *pw, void *node,
 
 	return CSS_OK;
 }
+
+
+/**
+ * Test the given node for an attribute with a specific value,
+ * possibly followed by a single hyphen
+ *
+ * This will return true (via the "match" pointer) if the libdom node
+ * has an attribute with the given name and value or with the given
+ * name and a value that is followed by exactly one hyphen. The
+ * comparison is case-sensitive. This corresponds to [attr|=value]
+ * in CSS.
+ *
+ * \param pw       Pointer to the current SVG parser state
+ * \param node     Libdom SVG node to test
+ * \param qname    Attribute name to check for
+ * \param value    Attribute value to check for
+ * \param match    Pointer to the test result
+ *
+ * \return Returns CSS_OK if successful and CSS_NOMEM if we cannot
+ *         intern the attribute name (which usually indicates memory
+ *         exhaustion)
+ */
+css_error node_has_attribute_dashmatch(void *pw, void *node,
+		const css_qname *qname, lwc_string *value,
+		bool *match)
+{
+	/* Implementation note: NetSurf always returns "no match" when
+	 * the value is empty (length zero). We allow it, because why
+	 * not? */
+
+	UNUSED(pw);
+	dom_string *name;
+	dom_string *attr_val;
+	dom_exception err;
+
+	const char *vdata;   /* to hold the data underlying "value" */
+	size_t vdata_len;
+	const char *avdata;  /* to hold the found attribute value data */
+	size_t avdata_len;
+
+	/* Intern the attribute name as a dom_string so we can
+	 * use dom_element_get_attribute() */
+	err = dom_string_create_interned(
+		(const uint8_t *) lwc_string_data(qname->name),
+		lwc_string_length(qname->name),
+		&name);
+	if (err != DOM_NO_ERR) {
+		return CSS_NOMEM;
+	}
+
+	err = dom_element_get_attribute((dom_node *)node, name, &attr_val);
+	if ((err != DOM_NO_ERR) || (attr_val == NULL)) {
+		/* There was an error getting the attribute's value or
+		 * the attribute doesn't exist. So, no match? */
+		dom_string_unref(name);
+		*match = false;
+		return CSS_OK;
+	}
+
+	/* Otherwise, we have the attribute value from the given node
+	 * and all we need to do is compare. */
+	dom_string_unref(name);
+	*match = dom_string_lwc_isequal(attr_val, value);
+	if (*match) {
+		/* Exact match, we're done */
+		dom_string_unref(attr_val);
+		return CSS_OK;
+	}
+
+	/* No exact match, try it with a hyphen on the end */
+	vdata = lwc_string_data(value);     /* needle */
+	vdata_len = lwc_string_length(value);
+	avdata = dom_string_data(attr_val); /* haystack */
+	avdata_len = dom_string_byte_length(attr_val);
+	dom_string_unref(attr_val);
+
+	if (avdata_len > vdata_len && avdata[vdata_len] == '-') {
+		if (strncasecmp(avdata, vdata, vdata_len) == 0) {
+			/* If there's a hyphen in the right position,
+			 * it suffices to compare the strings only up
+			 * to the hyphen */
+			*match = true;
+		}
+	}
+
+	return CSS_OK;
+}
-- 
2.44.2