/**
* Encodes a stdClass instance.
*
* @param \stdClass $data The EMV TLV data structure.
*
* @return string Returns a string representing the encoded EMV TLV data
* structure.
*/
protected function encodeObject(\stdClass $data)
{
if (!isset($data->tag, $data->value) || !in_array(strlen($data->tag), array(2, 4, 6))) {
return '';
}
$value = (string) $data->value;
if (Tag::isConstructed(hexdec(substr($data->tag, 0, 2)))) {
$value = $this->encode($data->value);
}
$length = strlen($value) / 2;
/*
* ISO/IEC 7816-4:2013, sect. 5.2.2.2: "ISO/IEC 7816 supports length
* fields [...] up to five bytes."
*
* This means that the value field can be made of 4294967295 (FFFFFFFF)
* bytes at most.
*
* If the length excesses this value, bail out.
*/
if ($length > 4294967295.0) {
return '';
}
$bytes = $length < 128 ? 1 : ($length < 256 ? 2 : ($length < 65536 ? 3 : ($length < 16777216 ? 4 : 5)));
if ($bytes === 1) {
$length = sprintf('%02X', $length);
} else {
$length = sprintf('%032b', $length);
$length = str_split($length, 8);
$length = array_map(function ($bits) {
return sprintf('%02X', bindec($bits));
}, $length);
$length = array_filter($length, function ($bits) {
return '00' !== $bits;
});
$length = implode('', $length);
$length = strval(79 + $bytes) . $length;
}
return sprintf('%s%s%s', $data->tag, $length, $value);
}
/**
* Decodes a list of bytes representing some EMV TLV-encoded data.
*
* @param int[] $bytes The list of bytes.
*
* @return \stdClass[] Returns a list of \stdClass instances containing the
* parsed EMV TLV-encoded data. May contain nested lists of objects.
*/
protected function decodeTlv($bytes)
{
$tree = array();
$extent = count($bytes);
$cursor = 0;
while ($cursor < $extent) {
// Tag
// -----------------------------------------------------------------
if (!isset($bytes[$cursor])) {
break;
}
$tag = array($bytes[$cursor]);
// Is the tag valid? No? Move the cursor forward and skip any
// remaining computation.
if (!Tag::isValid($tag[0])) {
/**
* Trigger an error? Throw an exception? Log something? No! To
* be really useful such a message should include the original
* EMV-TLV data block, which we cannot disclose inside the log
* files because of PCI DSS requirements.
*/
$cursor++;
continue;
}
$tagIsConstructed = Tag::isConstructed($tag[0]);
if (Tag::isMultiByte($tag[0])) {
// Two-byte tag
// -------------------------------------------------------------
$cursor++;
if (!isset($bytes[$cursor])) {
break;
}
$tag[] = $bytes[$cursor];
if (!Tag::isLast($bytes[$cursor])) {
// Three-byte tag
// -------------------------------------------------------------
$cursor++;
if (!isset($bytes[$cursor])) {
break;
}
$tag[] = $bytes[$cursor];
}
}
$tag = array_map(function ($byte) {
return sprintf('%02X', $byte);
}, $tag);
$tag = implode('', $tag);
$cursor++;
// Length
// -----------------------------------------------------------------
if (!isset($bytes[$cursor])) {
break;
}
$length = $bytes[$cursor];
if (!Length::isValid($length)) {
/**
* Trigger an error? Throw an exception? Log something? No! To
* be really useful such a message should include the original
* EMV TLV data block, which we cannot disclose inside the log
* files because of PCI DSS requirements.
*/
break;
}
$length = Length::getLength($length);
if (Length::isMultiByte($bytes[$cursor])) {
$length_cursor = 0;
$length_extent = $length;
$length = array();
while ($length_cursor < $length_extent) {
$cursor++;
if (!isset($bytes[$cursor])) {
break;
}
$length[] = $bytes[$cursor] << ($length_extent - $length_cursor - 1) * 8;
$length_cursor++;
}
if (!isset($bytes[$cursor])) {
break;
}
$length_output = 0;
foreach ($length as $length_part) {
$length_output = $length_output | $length_part;
}
$length = $length_output;
}
$cursor++;
// Value
// -----------------------------------------------------------------
if (!isset($bytes[$cursor])) {
break;
}
$value = array_slice($bytes, $cursor, $length);
if ($tagIsConstructed) {
$value = $this->decodeTlv($value);
} else {
$value = array_map(function ($byte) {
return sprintf('%02x', $byte);
}, $value);
$value = implode('', $value);
}
$cursor += $length;
// All together now!
// -----------------------------------------------------------------
$leaf = new \stdClass();
$leaf->name = Tag::getName($tag);
$leaf->length = $length;
$leaf->value = $value;
// Add it to the output, now!
// -----------------------------------------------------------------
$tree[$tag] = $leaf;
}
return $tree;
}
