hval: routines for attribute escaping

We'll use HTML attributes + anchor links to link to filenames
in coming commits.

1 files changed, 33 insertions, 2 deletions

diff --git a/lib/PublicInbox/Hval.pm b/lib/PublicInbox/Hval.pm
index 53810b33..95a0f709 100644
--- a/lib/PublicInbox/Hval.pm
+++ b/lib/PublicInbox/Hval.pm
@@ -9,8 +9,8 @@ use warnings;
 use Encode qw(find_encoding);
 use PublicInbox::MID qw/mid_clean mid_escape/;
 use base qw/Exporter/;
-our @EXPORT_OK = qw/ascii_html obfuscate_addrs to_filename src_escape/;
-
+our @EXPORT_OK = qw/ascii_html obfuscate_addrs to_filename src_escape
+                to_attr from_attr/;
 my $enc_ascii = find_encoding('us-ascii');
 
 sub new {
@@ -122,4 +122,35 @@ sub to_filename ($) {
         $s
 }
 
+# convert a filename (or any string) to HTML attribute
+
+my %ESCAPES = map { chr($_) => sprintf('::%02x', $_) } (0..255);
+$ESCAPES{'/'} = ':'; # common
+
+sub to_attr ($) {
+        my ($str) = @_;
+
+        # git would never do this to us:
+        return if index($str, '//') >= 0;
+
+        my $first = '';
+        if ($str =~ s/\A([^A-Ya-z])//ms) { # start with a letter
+                  $first = sprintf('Z%02x', ord($1));
+        }
+        $str =~ s/([^A-Za-z0-9_\.\-])/$ESCAPES{$1}/egms;
+        $first . $str;
+}
+
+# reverse the result of to_attr
+sub from_attr ($) {
+        my ($str) = @_;
+        my $first = '';
+        if ($str =~ s/\AZ([a-f0-9]{2})//ms) {
+                $first = chr(hex($1));
+        }
+        $str =~ s!::([a-f0-9]{2})!chr(hex($1))!egms;
+        $str =~ tr!:!/!;
+        $first . $str;
+}
+
 1;