[PATCHv7 6/9] gitweb: gravatar url cache

@@ -1515,6 +1515,27 @@ sub format_subject_html {
 	}
 }
 
+# Rather than recomputing the url for an email multiple times, we cache it
+# after the first hit. This gives a visible benefit in views where the avatar
+# for the same email is used repeatedly (e.g. shortlog).
+# The cache is shared by all avatar engines (currently gravatar only), which
+# are free to use it as preferred. Since only one avatar engine is used for any
+# given page, there's no risk for cache conflicts.
+our %avatar_cache = ();
+
+# Compute the gravatar url for a given email, if it's not in the cache already.
+# Gravatar stores only the part of the URL before the size, since that's the
+# one computationally more expensive. This also allows reuse of the cache for
+# different sizes (for this particular engine).
+sub gravatar_url {
+	my $email = lc shift;
+	my $size = shift;
+	$avatar_cache{$email} ||=
+		"http://www.gravatar.com/avatar.php?gravatar_id=" .
+			Digest::MD5::md5_hex($email) . "&size=";
+	return $avatar_cache{$email} . $size;
+}
+
 # Insert an avatar for the given $email at the given $size if the feature
 # is enabled.
 sub git_get_avatar {

@@ -1524,15 +1545,18 @@ sub git_get_avatar {
 	my $size = $avatar_size{$opts{'size'}} || $avatar_size{'default'};
 	my $url = "";
 	if ($git_avatar eq 'gravatar') {
-		$url = "http://www.gravatar.com/avatar.php?gravatar_id=" .
-			Digest::MD5::md5_hex(lc $email) . "&size=$size";
+		$url = gravatar_url($email, $size);
 	}
 	# Currently only gravatars are supported, but other forms such as
 	# picons can be added by putting an else up here and defining $url
 	# as needed. If no variant puts something in $url, we assume avatars
 	# are completely disabled/unavailable.
 	if ($url) {
-		return $pre_white . "<img width=\"$size\" class=\"avatar\" src=\"$url\" />" . $post_white;
+		return $pre_white .
+		       "<img width=\"$size\" " .
+		            "class=\"avatar\" " .
+		            "src=\"$url\" " .
+		       "/>" . $post_white;
 	} else {
 		return "";
 	}