From d7a4a379edeb88aeb4a1d84a5caced1fd7262017 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 13 Oct 2023 19:33:06 -0400
Subject: [PATCH] src/svgtiny_css.c: implement node_has_attribute_prefix()
 select handler

---
 src/svgtiny_css.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)

diff --git a/src/svgtiny_css.c b/src/svgtiny_css.c
index 3b03d91..95d3772 100644
--- a/src/svgtiny_css.c
+++ b/src/svgtiny_css.c
@@ -33,6 +33,9 @@ static css_error node_has_attribute_dashmatch(void *pw, void *node,
 static css_error node_has_attribute_includes(void *pw, void *node,
 		const css_qname *qname, lwc_string *word,
 		bool *match);
+static css_error node_has_attribute_prefix(void *pw, void *node,
+		const css_qname *qname, lwc_string *prefix,
+		bool *match);
 
 
 /**
@@ -911,3 +914,88 @@ css_error node_has_attribute_includes(void *pw, void *node,
 
 	return CSS_OK;
 }
+
+
+/**
+ * Test the given node for an attribute whose value begins with the
+ * given prefix
+ *
+ * This will return true (via the "match" pointer) if the libdom node
+ * has an attribute with the given name and whose value begins with
+ * the given prefix string. 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 prefix   Value prefix 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_prefix(void *pw, void *node,
+		const css_qname *qname, lwc_string *prefix,
+		bool *match)
+{
+	UNUSED(pw);
+	dom_string *name;
+	dom_string *attr_val;
+	dom_exception err;
+	const char *avdata; /* attribute value data */
+	size_t avdata_len; /* length of that attribute value data */
+	size_t prefixlen; /* length of "prefix" */
+
+	prefixlen = lwc_string_length(prefix);
+	if (prefixlen == 0) {
+		/* In this case, the spec says that "if 'val' is the
+		 * empty string, it will never represent anything." */
+		return CSS_OK;
+	}
+
+	/* 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 the first thing we want to do is check to see if the
+	 * whole thing matches the prefix. */
+	dom_string_unref(name);
+	*match = dom_string_lwc_isequal(attr_val, prefix);
+
+	/* If not, check to see if an, uh, prefix matches the
+	 * prefix */
+	if (*match == false) {
+		avdata = dom_string_data(attr_val);
+		avdata_len = dom_string_byte_length(attr_val);
+		if ((avdata_len >= prefixlen) &&
+				(strncasecmp(avdata,
+					lwc_string_data(prefix),
+					prefixlen) == 0)) {
+			/* Use strncasecmp to compare only the first
+			 * "n" characters, where "n" is the length of
+			 * the prefix. */
+			*match = true;
+		}
+	}
+
+	dom_string_unref(attr_val);
+
+	return CSS_OK;
+}
-- 
2.43.2