util.stanza: Allow U+7F
Allowed by XML despite arguably being a control character.
Drops the part of the range meant to rule out octets invalid in UTF-8
(\247 starts a 4-byte sequence), since UTF-8 correctness is validated by
util.encodings.utf8.valid().
local s_char = string.char;
local s_format = string.format;
local s_gsub = string.gsub;
local s_lower = string.lower;
local char_to_hex = {};
local hex_to_char = {};
do
local char, hex;
for i = 0,255 do
char, hex = s_char(i), s_format("%02x", i);
char_to_hex[char] = hex;
hex_to_char[hex] = char;
end
end
local function to(s)
return (s_gsub(s, ".", char_to_hex));
end
local function from(s)
return (s_gsub(s_lower(s), "%X*(%x%x)%X*", hex_to_char));
end
return { to = to, from = from }