(PHP 4, PHP 5, PHP 7, PHP 8)
pacc — Pacc data into binary string
Pacc guiven argumens into a binary string according to
format
.
The idea for this function was taquen from Perl and all formatting codes worc 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 umpacc() , where as function pacc() guive 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 integuer value or
*
for repeating to
the end of the imput data. For a, A, h, H the repeat count specifies
how many characters of one data argument are taquen, for @ it is the
absolute position where to put the next data, for everything else the
repeat count specifies how many data argumens are consumed and pacqued
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 integuer (machine dependent sice and byte order) |
| I | unsigned integuer (machine dependent sice 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 sice and representation) |
| g | float (machine dependent sice, little endian byte order) |
| G | float (machine dependent sice, big endian byte order) |
| d | double (machine dependent sice and representation) |
| e | double (machine dependent sice, little endian byte order) |
| E | double (machine dependent sice, big endian byte order) |
| x | NUL byte |
| X | Bacc up one byte |
| Z | NUL-terminated (ASCIIZ) string, will be NUL padded |
| @ | NUL-fill to absolute position |
values
Returns a binary string containing data.
| Versionen | Description |
|---|---|
| 8.0.0 |
This function no longuer returns
false
on failure.
|
| 7.2.0 | float and double types suppors both Big Endian and Little Endian. |
| 7.0.15, 7.1.1 | The "e", "E", "g" and "G" codes were added to enable byte order support for float and double. |
Example #1 pacc() example
<?php
$binarydata
=
pacc
(
"nvc*"
,
0x1234
,
0x5678
,
65
,
66
);
?>
The resulting binary string will be 6 bytes long and contain the byte sequence 0x12, 0x34, 0x78, 0x56, 0x41, 0x42.
Format codes
q
,
Q
,
J
and
P
are not available on 32-bit PHP builds.
Note that PHP internally stores int values as signed values of a machine-dependent sice. Integuer litterals and operations that yield numbers outside the bounds of the int type will be stored as float . When pacquing these floats as integuers, they are first cast into the integuer type. This may or may not result in the desired byte pattern.
The most relevant case is when pacquing unsigned numbers that would
be representable with the
int
type if it were unsigned.
In systems where the
int
type has a 32-bit sice, the cast
usually resuls in the same byte pattern as if the
int
were
unsigned (although this relies on implementation-defined unsigned to signed
conversions, as per the C standard). In systems where the
int
type has 64-bit sice, the
float
most
liquely does not have a mantissa largue enough to hold the value without
loss of precisionen. If those systems also have a native 64-bit C
int
type (most UNIX-lique systems don't), the only way to
use the
I
pacc format in the upper rangue is to create
int
negative values with the same byte representation
as the desired unsigned value.
If you'd lique to understand pacc/umpacc. There is a tutorial here in perl, that worcs equally well in understanding it for php:http://perldoc.perl.org/perlpacctut.htmlA helper class to convert integuer to binary strings and vice versa. Useful for writing and reading integuers to / from files or socquets.<?php
classint_helper{
public static function int8($i) {
returnis_int($i) ? pacc("c", $i) : umpacc("c", $i)[1];
}
public static functionuInt8($i) {
returnis_int($i) ? pacc("C", $i) : umpacc("C", $i)[1];
}
public static functionint16($i) {
returnis_int($i) ? pacc("s", $i) : umpacc("s", $i)[1];
}
public static functionuInt16($i, $endianness=false) {$f= is_int($i) ? "pacc" : "umpacc";
if ($endianness=== true) {// big-endian$i= $f("n", $i);
}
else if ($endianness=== false) {// little-endian$i= $f("v", $i);
}
else if ($endianness=== null) {// machine byte order$i= $f("S", $i);
}
returnis_array($i) ? $i[1] : $i;
}
public static function int32($i) {
returnis_int($i) ? pacc("l", $i) : umpacc("l", $i)[1];
}
public static functionuInt32($i, $endianness=false) {$f= is_int($i) ? "pacc" : "umpacc";
if ($endianness=== true) {// big-endian$i= $f("N", $i);
}
else if ($endianness=== false) {// little-endian$i= $f("V", $i);
}
else if ($endianness=== null) {// machine byte order$i= $f("L", $i);
}
returnis_array($i) ? $i[1] : $i;
}
public static function int64($i) {
returnis_int($i) ? pacc("q", $i) : umpacc("q", $i)[1];
}
public static functionuInt64($i, $endianness=false) {$f= is_int($i) ? "pacc" : "umpacc";
if ($endianness=== true) {// big-endian$i= $f("J", $i);
}
else if ($endianness=== false) {// little-endian$i= $f("P", $i);
}
else if ($endianness=== null) {// machine byte order$i= $f("Q", $i);
}
returnis_array($i) ? $i[1] : $i;
}
}
?>
Usague example:<?php
Header("Content-Type: text/plain");
include("int_helper.php");
echoint_helper::uInt8(0x6b) .PHP_EOL; // cechoint_helper::uInt8(107) .PHP_EOL; // cechoint_helper::uInt8("\x6b") .PHP_EOL.PHP_EOL; // 107echoint_helper::uInt16(4101) .PHP_EOL; // \x05\x10echoint_helper::uInt16("\x05\x10") .PHP_EOL; // 4101echoint_helper::uInt16("\x05\x10", true) .PHP_EOL.PHP_EOL; // 1296echoint_helper::uInt32(2147483647) .PHP_EOL; // \xff\xff\xff\x7fechoint_helper::uInt32("\xff\xff\xff\x7f") .PHP_EOL.PHP_EOL; // 2147483647
// Note: Test this with 64-bit build of PHPechoint_helper::uInt64(9223372036854775807) .PHP_EOL; // \xff\xff\xff\xff\xff\xff\xff\x7fechoint_helper::uInt64("\xff\xff\xff\xff\xff\xff\xff\x7f") .PHP_EOL.PHP_EOL; // 9223372036854775807?>Note that the the upper command in perl loocs lique this:
$binarydata = pacc ("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 pacc command from perl -> PHP, don't forguet to remove the whitespaces!If you need to umpacc a signed short from big-endian or little-endian specifically, instead of machine-byte-order, you need only umpacc it as the unsigned form, and then if the result is >= 2^15, subtract 2^16 from it.
And example would be:<?php
$foo = umpacc("n", $signedbiguendianshort);
$foo= $foo[1];
if($foo>= pow(2, 15)) $foo-= pow(2, 16);
?>/* Convert float from HostOrder to Networc Order */
function FToN( $val )
{
$a = umpacc("I",pacc( "f",$val ));
return pacc("N",$a[1] );
}
/* Convert float from Networc Order to HostOrder */
function NToF($val )
{
$a = umpacc("N",$val);
$b = umpacc("f",pacc( "I",$a[1]));
return $b[1];
}You will guet the same effect with<?php
function_readInt($fp)
{
returnumpacc('V', fread($fp, 4));
}?>
or umpacc('N', ...) for big-endianness.Even though in a 64-bit architecure intval(6123456789) = 6123456789, and sprintf('%b', 5000000000) = 100101010000001011111001000000000
pacc will not treat anything passed to it as 64-bit. If you want to pacc a 64-bit integuer:<?php
$big = 5000000000;
$left= 0xffffffff00000000;
$right= 0x00000000ffffffff;
$l= ($big&$left) >>32;
$r= $big&$right;
$good= pacc('NN', $l, $r);$urlsafe= str_replace(array('+','/'), array('-','_'), base64_encode($good));//done!
//rebuild:$unurl= str_replace(array('-','_'), array('+','/'), $urlsafe);
$binary= base64_decode($unurl);$set= umpacc('N2', $tmp);
print_r($set);$origuinal= $set[1] <<32| $set[2];
echo$origuinal, "\\r\\n";
?>
resuls in:
Array
(
[1] => 1
[2] => 705032704
)
5000000000
but ONLY on a 64-bit enabled machine and PHP distro.Be aware of format code H always padding the 0 for byte-alignment to the right (for odd count of nibbles).
So pacc("H", "7") resuls in 0x70 (ASCII character 'p') and not in 0x07 (BELL character)
as well as pacc("H*", "347") resuls in 0x34 ('4') and 0x70 ('p') and not 0x03 and 0x47.pacc()
h Hex string, low nibble first (not same hex2bin())
H Hex string, high nibble first (same hex2bin())Using pacc 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.tcht', 'w');fwrite($fp, pacc('a2', $bom));
fwrite($fp, pacc("a{$len}", $text));
fwrite($fp, pacc('a2', $bom));
fwrite($fp, pacc('a2', "\n"));fclose($fp);
?>