php hex: how to convert from xml - php

Question

Good day). A hex question.
This is a piece of imported xml data:
<?xml version=\x221.0\x22 encoding=\x22UTF-8\x22?>
\x0A<issues>\x0A\x09<issue id=\x225863\x22 found=\x221\x22>\xD0\x9F\xD0\xBE \xD0\xBD\xD0\xBE\xD0\xBC\xD0\xB5\xD1\x80\xD1\x83 \xD1\x81\xD1\x87\xD0\xB
5\xD1\x82\xD0\xB0 19479 \xD0\xBD\xD0\xB0\xD0\xB9\xD0\xB4\xD0\xB5\xD0\xBD\xD0\xBE:\x0A\xD0\x97\xD0\xB0\xD0\xBA\xD0\xB0\xD0\xB7 \xD0\xBF\xD0\xBE\xD0\xBA\xD1\x83\xD0\xBF\xD0\xB0\xD1\x82\xD0\xB5\xD0\xBB\xD1\x8F
0000015597 \xD0\xBE\xD1
Seems to be hex, but i can't find matching parser from standart libraries.
Is there any ?
I tried preg_replace_callback:
$source = preg_replace_callback('/\\\\x([a-f0-9]+)/mi',
function($m)
{
return chr('0x'.$m[1]);
}, $source);
Output is still little dirty:
<?xml version="1.0" encoding="UTF-8"?>
<issues>
<issue id="5863" found="1">По номеру сч�\xB
5та найдено:
Ответственный:Максим\xD
0�йко Евгений
частное лицо (Саф\x
D1�онов Антон )
So is there a solution to correctly parse it ?

Answer 1

You have got some kind of transport encoding here that you first need to decode to obtain the XML document.
Your regex looks like that you've perhaps already found out that all binary values below x20 (Space) (often control characters) but also above x7D are encoded for transport.
The problem your regex pattern has, that it does not include these control characters which have been encoded for transport as part of the pattern to match the encoding sequences "\xHH". As the original transport encoding is unknown, a more stable pattern with the decoding problem you describe would be to optionally allow control characters between each of these characters:
/\\\\[\x00-\x1f]*x[\x00-\x1f]*([A-F0-9])[\x00-\x1f]*([A-F0-9])/m
`----------´ `----------´ `----------´
With the matching groups you then build the binary value similar to what you already do, the only difference here is that I use the hex2bin function:
$source = preg_replace_callback(
'/\\\\[\x00-\x1f]*x[\x00-\x1f]*([A-F0-9])[\x00-\x1f]*([A-F0-9])/m',
function($matches)
{
$hex = $matches[1].$matches[2];
return hex2bin($hex);
}, $source);
This then is more stable. Alternatively depending from where you fetch the input, you could also use a read filter chain on the input. Considering the XML is from a standard PHP stream represented by $file:
$buffer = file_get_contents("php://filter/read=filter.controlchars/decode.hexsequences/resource=" . $file);
having two registered read filters:
filter.controlchars - removes control characters (\x00-\x1F) from the stream
decode.hexsequences - decode the hexadecimal sequences you have
would make $buffer the data you're interested. This requires some work to setup those filters, however they then can be used (and swapped) whenever you need them:
stream_filter_register('filter.controlchars', 'ControlCharsFilter');
stream_filter_register('decode.hexsequences', 'HexDecodeFilter');
This needs the filter-classes to be defined, here I use an abstract base class with two concrete classes, one for the removal filter and one for the decode filter:
abstract class ReadFilter extends php_user_filter {
function filter($in, $out, &$consumed, $closing) {
while ($bucket = stream_bucket_make_writeable($in)) {
$bucket->data = $this->apply($bucket->data);
$consumed += $bucket->datalen;
stream_bucket_append($out, $bucket);
}
return PSFS_PASS_ON;
}
abstract function apply($string);
}
class ControlCharsFilter extends ReadFilter {
function apply($string) {
return preg_replace('~[\x00-\x1f]+~', '', $string);
}
}
class HexDecodeFilter extends ReadFilter {
function apply($string) {
return preg_replace_callback(
'/\\\\x([A-F0-9]{2})/i', 'self::decodeHexMatches'
, $string
);
}
private static function decodeHexMatches($matches) {
return hex2bin($matches[1]);
}
}
The code of a stand-alone example as gist https://gist.github.com/hakre/d34239bb237c50e728fd and as online demo: http://3v4l.org/IO6Ll

Answer 2

The problem are the linebreaks (e.x. between \xB and 5). So you get an invalid HEX code. A fix would be to remove new lines. But this probably also removes new lines which should be kept. Except they are also hex encoded. Then a simple
str_replace(array("\r\n", "\n"), null, $source);
should do the trick.