If you'd like to understand pack/unpack. There is a tutorial here in perl, that works equally well in understanding it for php:
http://perldoc.perl.org/perlpacktut.html
(PHP 4, PHP 5, PHP 7)
pack — Pack data into binary string
Pack given arguments into a binary string according to
format.
The idea for this function was taken from Perl and all formatting codes work the same as in Perl. However, there are some formatting codes that are missing such as Perl's "u" format code.
Note that the distinction between signed and unsigned values only affects the function unpack(), where as function pack() gives the same result for signed and unsigned format codes.
format
The format string consists of format codes
followed by an optional repeater argument. The repeater argument can
be either an integer value or * for repeating to
the end of the input data. For a, A, h, H the repeat count specifies
how many characters of one data argument are taken, for @ it is the
absolute position where to put the next data, for everything else the
repeat count specifies how many data arguments are consumed and packed
into the resulting binary string.
Currently implemented formats are:
| Code | Description |
|---|---|
| a | NUL-padded string |
| A | SPACE-padded string |
| h | Hex string, low nibble first |
| H | Hex string, high nibble first |
| c | signed char |
| C | unsigned char |
| s | signed short (always 16 bit, machine byte order) |
| S | unsigned short (always 16 bit, machine byte order) |
| n | unsigned short (always 16 bit, big endian byte order) |
| v | unsigned short (always 16 bit, little endian byte order) |
| i | signed integer (machine dependent size and byte order) |
| I | unsigned integer (machine dependent size and byte order) |
| l | signed long (always 32 bit, machine byte order) |
| L | unsigned long (always 32 bit, machine byte order) |
| N | unsigned long (always 32 bit, big endian byte order) |
| V | unsigned long (always 32 bit, little endian byte order) |
| q | signed long long (always 64 bit, machine byte order) |
| Q | unsigned long long (always 64 bit, machine byte order) |
| J | unsigned long long (always 64 bit, big endian byte order) |
| P | unsigned long long (always 64 bit, little endian byte order) |
| f | float (machine dependent size and representation) |
| d | double (machine dependent size and representation) |
| x | NUL byte |
| X | Back up one byte |
| Z | NUL-padded string (new in PHP 5.5) |
| @ | NUL-fill to absolute position |
args
Returns a binary string containing data.
| Version | Description |
|---|---|
| 5.6.3 | The "q", "Q", "J" and "P" codes were added to enable working with 64-bit numbers. |
| 5.5.0 | The "Z" code was added with equivalent functionality to "a" for Perl compatibility. |
Example #1 pack() example
<?php
$binarydata = pack("nvc*", 0x1234, 0x5678, 65, 66);
?>
The resulting binary string will be 6 bytes long and contain the byte sequence 0x12, 0x34, 0x78, 0x56, 0x41, 0x42.
Note that PHP internally stores integer values as signed values of a machine-dependent size (C type long). Integer literals and operations that yield numbers outside the bounds of the integer type will be stored as float. When packing these floats as integers, they are first cast into the integer type. This may or may not result in the desired byte pattern.
The most relevant case is when packing unsigned numbers that would be representable with the integer type if it were unsigned. In systems where the integer type has a 32-bit size, the cast usually results in the same byte pattern as if the integer were unsigned (although this relies on implementation-defined unsigned to signed conversions, as per the C standard). In systems where the integer type has 64-bit size, the float most likely does not have a mantissa large enough to hold the value without loss of precision. If those systems also have a native 64-bit C int type (most UNIX-like systems don't), the only way to use the I pack format in the upper range is to create integer negative values with the same byte representation as the desired unsigned value.
If you'd like to understand pack/unpack. There is a tutorial here in perl, that works equally well in understanding it for php:
http://perldoc.perl.org/perlpacktut.html
If you need to unpack a signed short from big-endian or little-endian specifically, instead of machine-byte-order, you need only unpack it as the unsigned form, and then if the result is >= 2^15, subtract 2^16 from it.
And example would be:
<?php
$foo = unpack("n", $signedbigendianshort);
$foo = $foo[1];
if($foo >= pow(2, 15)) $foo -= pow(2, 16);
?>
Note that the the upper command in perl looks like this:
$binarydata = pack ("n v c*", 0x1234, 0x5678, 65, 66);
In PHP it seems that no whitespaces are allowed in the first parameter. So if you want to convert your pack command from perl -> PHP, don't forget to remove the whitespaces!
Coder's example is basically an explanation of bindec() and decbin(), not pack() and unpack().
Here's some code to convert a string binary expression into its binary-string equivalent and vice versa.
(Would be even simpler if pack/unpack offered a 'b' format code....)
<?php
function bin2bstr($input)
// Convert a binary expression (e.g., "100111") into a binary-string
{
if (!is_string($input)) return null; // Sanity check
// Pack into a string
return pack('H*', base_convert($input, 2, 16));
}
function bstr2bin($input)
// Binary representation of a binary-string
{
if (!is_string($input)) return null; // Sanity check
// Unpack as a hexadecimal string
$value = unpack('H*', $input);
// Output binary representation
return base_convert($value[1], 16, 2);
}
// Returns string(3) "ABC"
var_dump(bin2bstr('01000001 01000010 01000011'));
// Returns string(24) "010000010100001001000011"
var_dump(bstr2bin('ABC'));
?>
<?PHP
function ntohs($port) {
$b=pack("N", $port);
return substr($b,2,2);
}
?>
I've spent a number of hours (n>=2) finding how to do this,
it works like the c function 'ntohs', used for eg the socks5 proxy protocol.
Even though in a 64-bit architecure intval(6123456789) = 6123456789, and sprintf('%b', 5000000000) = 100101010000001011111001000000000
pack will not treat anything passed to it as 64-bit. If you want to pack a 64-bit integer:
<?php
$big = 5000000000;
$left = 0xffffffff00000000;
$right = 0x00000000ffffffff;
$l = ($big & $left) >>32;
$r = $big & $right;
$good = pack('NN', $l, $r);
$urlsafe = str_replace(array('+','/'), array('-','_'), base64_encode($good));
//done!
//rebuild:
$unurl = str_replace(array('-','_'), array('+','/'), $urlsafe);
$binary = base64_decode($unurl);
$set = unpack('N2', $tmp);
print_r($set);
$original = $set[1] << 32 | $set[2];
echo $original, "\\r\\n";
?>
results in:
Array
(
[1] => 1
[2] => 705032704
)
5000000000
but ONLY on a 64-bit enabled machine and PHP distro.
You will get the same effect with
<?php
function _readInt($fp)
{
return unpack('V', fread($fp, 4));
}
?>
or unpack('N', ...) for big-endianness.
Using pack to write Arabic char(s) to a file.
<?php
$text = "㔆㘆㘆";
$text = mb_convert_encoding($text, "UCS-2BE", "HTML-ENTITIES");
$len = mb_strlen($text);
$bom = mb_convert_encoding("", "unicode", "HTML-ENTITIES");
$fp = fopen('text.txt', 'w');
fwrite($fp, pack('a2', $bom));
fwrite($fp, pack("a{$len}", $text));
fwrite($fp, pack('a2', $bom));
fwrite($fp, pack('a2', "\n"));
fclose($fp);
?>
/* Convert float from HostOrder to Network Order */
function FToN( $val )
{
$a = unpack("I",pack( "f",$val ));
return pack("N",$a[1] );
}
/* Convert float from Network Order to HostOrder */
function NToF($val )
{
$a = unpack("N",$val);
$b = unpack("f",pack( "I",$a[1]));
return $b[1];
}
Be aware of format code H always padding the 0 for byte-alignment to the right (for odd count of nibbles).
So pack("H", "7") results in 0x70 (ASCII character 'p') and not in 0x07 (BELL character)
as well as pack("H*", "347") results in 0x34 ('4') and 0x70 ('p') and not 0x03 and 0x47.
These two functions allow conversion between binary string and signed integer with possibility to give the bit length.
Usage:
<?php
echo si2bin(-10, 32);
11111111111111111111111111110110
echo si2bin(10, 32);
00000000000000000000000000001010
echo bin2si("11111111111111111111111111110110", 32);
-10
echo bin2si("00000000000000000000000000001010", 32);
10
// signed integer to binary
function si2bin($si, $bits=32)
{
if ($si >= -pow(2,$bits-1) and $si <= pow(2,$bits-1) )
{
if ($si >= 0) // positive or zero
{
$bin = base_convert($si,10,2);
// pad to $bits bit
$bin_length = strlen($bin);
if ($bin_length < $bits) $bin = str_repeat ( "0", $bits-$bin_length).$bin;
}
else // negative
{
$si = -$si-pow(2,$bits);
$bin = base_convert($si,10,2);
$bin_length = strlen($bin);
if ($bin_length > $bits) $bin = str_repeat ( "1", $bits-$bin_length).$bin;
}
return $bin;
}
}
// binary to signed integer
function bin2si($bin,$bits=32)
{
if (strlen($bin)==$bits)
{
if (substr($bin,0,1) == 0) // positive or zero
{
$si = base_convert($bin,2,10);
}
else // negative
{
$si = base_convert($bin,2,10);
$si = -(pow(2,$bits)-$si);
}
return $si;
}
}
?>
This is how I used pack to convert base2 to base64 since base_convert doesn't support base64
The base conversions don't work for long strings, which is why I convert 1 byte at a time
Hope this helps someone
function base2to64($base2) {
if ($remainbits = strlen($base2)%8) $base2 .= str_repeat('0',8-$remainbits);
$base64 = NULL;
for ($i=0;$i<strlen($base2);$i+=8) $base16 .= sprintf('%02x',bindec(sprintf('%08d',substr($base2,$i,8))));
return base64_encode(pack('H*',$base16));
}
function base64to2($base64) {
list($base16) = unpack('H*0',base64_decode($base64));
$base2 = NULL;
for ($i=0;$i<strlen($base16);$i++) $base2 .= sprintf('%04d',base_convert(substr($base16,$i,1),16,2));
return $base2;
}
a cool function to converrt numbers to Persian numbers(utf-8)
origin: http://www.farsiweb.info/jalali/jalali.phps
function farsinum($str)
{
$ret = "";
for ($i = 0; $i < strlen($str); ++$i) {
$c = $str[$i];
if( $c >= '0' && $c <= '9' )
$out .= pack("C*", 0xDB, 0xB0 + $c);
else
$ret .= $c;
}
return $ret;
}
Array pack:
<?php
function pack_array($v,$a) {
return call_user_func_array(pack,array_merge(array($v),(array)$a));
}
?>
You can use pack to strip the byte order mark (BOM) from a file.
For example, strip the UTF-8 BOM:
<?php
// Strips the UTF-8 mark: (hex value: EF BB BF)
function trimUTF8BOM($data){
if(substr($data, 0, 3) == pack('CCC', 239, 187, 191)) {
return substr($data, 3);
}
return $data;
}
?>
This function could be easily adjusted to match any byte order mark. Have a look at wikipedia for a full list of hex codes for each specific encoding.
- Gerard
If you're bugged by http://bugs.php.net/bug.php?id=5889 then you can try this:
Use igbinary-serialize if you don't mind a little overhead.
Or intarray (by the same person) if you don't mind using a slightly experimental package which may have problems sharing data between differently byte/bit ordered architectures.
I don't believe it would be too difficult to shove a serialize function and unserialize function in there if you rip out the code from igbinary for storing numeric arrays with the correct endianess. Looking at `igbinary_serialize32` and `igbinary_unserialize32` in igbinary.c it should be very easy to copy that functionality to intarray.c.
Take away the "<<0" though, that's just stupid :P
Ref: http://opensource.dynamoid.com/
When trying to create a ZIP file using the pack function - I experienced trouble with the "a" code - It converted all chars correct from the std. ASCII charset but not more language specific like ÆøÅ.
It seems that ZIP files do not use the same HEX for these as everything else does.
The fix was a quick workaround but you'll probably get the picture:
function UniHex($str) {
// æ ø å Æ Ø Å
//These are simply one HEX code being replaced by another to correct the issue
$except = array("E6"=>"91","F8"=>"9B","E5"=>"86","C6"=>"92","D8"=>"9D", "C5"=>"8F");
for($i = 0; $i < strlen($str); $i++) {
$hex = bin2hex(substr($str, $i, 1));
if ($except[strtoupper($hex)])
$hex = $except[strtoupper($hex)];
$return .= $hex;
}
return $return;
}
And then i replaced an "a100" code with "H".strlen(uniHex($mystring))
This is like i said a quick workaround, but if you find the real reason for this i'd be happy to see it
How to convert an integer to raw data, specifying the amount of bytes to convert to (will be padded with 0's):
public function toRaw($int, $bytes = 4)
{
$hex = dechex($int);
if (strlen($hex) % 2 != 0)
$hex = '0'. $hex;
$arr = str_split($hex, 2);
while (count($arr) < $bytes)
array_unshift($arr, 0);
$arr = array_map('hexdec', $arr);
$arr = array_map('chr', $arr);
return join('', array_reverse($arr));
}