compressed_data = $data;
$this->compressed_size = strlen($data);
}
/**
* Decode the GZIP stream
*
* @return bool Successfulness
*/
public function parse()
{
if ($this->compressed_size >= $this->min_compressed_size) {
$len = 0;
// Check ID1, ID2, and CM
if (substr($this->compressed_data, 0, 3) !== "\x1F\x8B\x08") {
return false;
}
// Get the FLG (FLaGs)
$this->flags = ord($this->compressed_data[3]);
// FLG bits above (1 << 4) are reserved
if ($this->flags > 0x1F) {
return false;
}
// Advance the pointer after the above
$this->position += 4;
// MTIME
$mtime = substr($this->compressed_data, $this->position, 4);
// Reverse the string if we're on a big-endian arch because l is the only signed long and is machine endianness
if (current((array) unpack('S', "\x00\x01")) === 1) {
$mtime = strrev($mtime);
}
$this->MTIME = current((array) unpack('l', $mtime));
$this->position += 4;
// Get the XFL (eXtra FLags)
$this->XFL = ord($this->compressed_data[$this->position++]);
// Get the OS (Operating System)
$this->OS = ord($this->compressed_data[$this->position++]);
// Parse the FEXTRA
if ($this->flags & 4) {
// Read subfield IDs
$this->SI1 = $this->compressed_data[$this->position++];
$this->SI2 = $this->compressed_data[$this->position++];
// SI2 set to zero is reserved for future use
if ($this->SI2 === "\x00") {
return false;
}
// Get the length of the extra field
$len = current((array) unpack('v', substr($this->compressed_data, $this->position, 2)));
$this->position += 2;
// Check the length of the string is still valid
$this->min_compressed_size += $len + 4;
if ($this->compressed_size >= $this->min_compressed_size) {
// Set the extra field to the given data
$this->extra_field = substr($this->compressed_data, $this->position, $len);
$this->position += $len;
} else {
return false;
}
}
// Parse the FNAME
if ($this->flags & 8) {
// Get the length of the filename
$len = strcspn($this->compressed_data, "\x00", $this->position);
// Check the length of the string is still valid
$this->min_compressed_size += $len + 1;
if ($this->compressed_size >= $this->min_compressed_size) {
// Set the original filename to the given string
$this->filename = substr($this->compressed_data, $this->position, $len);
$this->position += $len + 1;
} else {
return false;
}
}
// Parse the FCOMMENT
if ($this->flags & 16) {
// Get the length of the comment
$len = strcspn($this->compressed_data, "\x00", $this->position);
// Check the length of the string is still valid
$this->min_compressed_size += $len + 1;
if ($this->compressed_size >= $this->min_compressed_size) {
// Set the original comment to the given string
$this->comment = substr($this->compressed_data, $this->position, $len);
$this->position += $len + 1;
} else {
return false;
}
}
// Parse the FHCRC
if ($this->flags & 2) {
// Check the length of the string is still valid
$this->min_compressed_size += $len + 2;
if ($this->compressed_size >= $this->min_compressed_size) {
// Read the CRC
$crc = current((array) unpack('v', substr($this->compressed_data, $this->position, 2)));
// Check the CRC matches
if ((crc32(substr($this->compressed_data, 0, $this->position)) & 0xFFFF) === $crc) {
$this->position += 2;
} else {
return false;
}
} else {
return false;
}
}
// Decompress the actual data
if (($data = gzinflate(substr($this->compressed_data, $this->position, -8))) === false) {
return false;
}
$this->data = $data;
$this->position = $this->compressed_size - 8;
// Check CRC of data
$crc = current((array) unpack('V', substr($this->compressed_data, $this->position, 4)));
$this->position += 4;
/*if (extension_loaded('hash') && sprintf('%u', current(unpack('V', hash('crc32b', $this->data)))) !== sprintf('%u', $crc))
{
return false;
}*/
// Check ISIZE of data
$isize = current((array) unpack('V', substr($this->compressed_data, $this->position, 4)));
$this->position += 4;
if (sprintf('%u', strlen($this->data) & 0xFFFFFFFF) !== sprintf('%u', $isize)) {
return false;
}
// Wow, against all odds, we've actually got a valid gzip string
return true;
}
return false;
}
}
class_alias('SimplePie\Gzdecode', 'SimplePie_gzdecode');