Core Function Pack
From Sputnik Wiki
Pack( <expression>, <expressions> )
Contents |
Description
Pack data into a binary array
expression
The format string to use.
expressions
One or more expressions to convert.
Return Value
Success: Returns a binary variable which contains the array of bytes.
Failure: Returns empty array.
Remarks
To access the binary data in the variable you will need to either request elements from index id, cycle through all elements in a loop or use the Unpack function to convert the binary array into something useful.
Its worth noting you can cycle through a Binary variable like this :
$binary = Pack("z0", "Hello World!"); Foreach ($binary as $i) { println( "Byte: " . $i . " | Hex: " . Hex($i) . " | Char: " . Chr($i) ); }
Control Specifiers
| Character | Description |
| ^ | Switch to big endian encoding |
| _ | Switch to little endian encoding |
| % | Switch to host (native) encoding |
| ! | Aligns the next data type to its natural boundary, for example for a double that would be 8 bytes, for a 32-bit int, that would be 4 bytes. For strings this is set to 4. |
| N | A number between 1 and 9, indicates a repeat count (process N items with the following datatype |
| [N] | For numbers larger than 9, use brackets, for example [20] |
| * | Repeat the next data type until the arguments are exhausted |
Data Encoding
Warning - The pack for $variables is designed to create the bytes of the arrays elements such as array of ints however it does not unpack to a $variable instead you must unpack it as the base type you packed it to such as Int32.
| Character | Description |
| s | Int16 |
| S | UInt16 |
| i | Int32 |
| I | UInt32 |
| l | Int64 |
| L | UInt64 |
| f | float |
| d | double |
| b | byte |
| c | 1-byte signed character |
| C | 1-byte unsigned character |
| h | Hex string to convert to bytes (For Pack) |
| h | 2 Char Lowercase Hexstring of a byte (For Unpack) |
| H | 2 Char Uppercase Hexstring of a byte (For Unpack) |
| z8 | string encoded as UTF8 with 1-byte null terminator |
| z6 | string encoded as UTF16 with 2-byte null terminator |
| z7 | string encoded as UTF7 with 1-byte null terminator |
| zb | string encoded as BigEndianUnicode with 2-byte null terminator |
| z3 | string encoded as UTF32 with 4-byte null terminator |
| z4 | string encoded as UTF32 big endian with 4-byte null terminator |
| z0 | ASCII string without a null terminator |
| z1 | ASCII string with 1-byte terminator |
| $ab | A $variable containing an array of Byte values |
| $as | A $variable containing an array of Int16 values |
| $aS | A $variable containing an array of UInt16 values |
| $ai | A $variable containing an array of Int32 values |
| $aI | A $variable containing an array of UInt32 values |
| $al | A $variable containing an array of Int64 values |
| $aL | A $variable containing an array of UInt64 values |
| $af | A $variable containing an array of Float values |
| $ad | A $variable containing an array of Double values |
| x | null byte |
Example
Converting an array of Ints into bytes then back into an array of ints again:
$oldArray = array(100, 200, 300, 400); // Create an array // Pack the array into bytes with each element converted to Int32 $binary = Pack('$ai', $oldArray); // NOTICE '' was used instead of ""? This is vital when packing variables or else it will fail Foreach ($binary as $i) { println( "Byte: " . $i ); // Prints the bytes just for looksee } $newArray = Unpack('*i', $binary); // Unpack All the Int32s into an array println("Old Array : " . $oldArray); println("New Array : " . $newArray);
Same as above but this time packing a float and a double as well :
$oldArray = array(100, 200, 300, 400); // Create an array // Pack the array into bytes with each element converted to Int32 $binary = Pack('$aifd', $oldArray, (float)777, (double)1337.42); // NOTICE '' was used instead of ""? This is vital when packing variables or else it will fail Foreach ($binary as $i) { println( "Byte: " . $i ); // Prints the bytes just for looksee } $newArray = Unpack('4ifd', $binary); // Unpack 4 Int32s, 1 float and 1 double into an array println("Old Array : " . $oldArray); println("New Array : " . $newArray); foreach ($newArray as $i) { println("Value: " . $i ); }
Of course we could set how many Ints to decode dynamically example:
$oldArray = array(100, 200, 300, 400); // Create an array // Pack the array into bytes with each element converted to Int32 $binary = Pack('$aifd', $oldArray, (float)777, (double)1337.42); // NOTICE '' was used instead of ""? This is vital when packing variables or else it will fail Foreach ($binary as $i) { println( "Byte: " . $i ); // Prints the bytes just for looksee } $newArray = Unpack(UBound($oldArray) . 'ifd', $binary); // Unpack 4 Int32s, 1 float and 1 double into an array println("Old Array : " . $oldArray); println("New Array : " . $newArray); foreach ($newArray as $i) { println("Value: " . $i ); }
Convert a string into a binary array and back again:
$arr = Pack("z0", "Hello World!"); foreach ($arr as $i) { println($i); } $str = Unpack("z0", $arr); println($str);
Convert a dobule into a binary array and back again:
$arr = Pack("d", 777.42); foreach ($arr as $i) { println($i); } $str = Unpack("d", $arr); println($str);
Convert a int into a binary array and back again:
$arr = Pack("d", (int)777); foreach ($arr as $i) { println($i); } $str = Unpack("d", $arr); println($str);
Convert a string into a hex and back again:
$hex = Join(Unpack("*H", Pack("z0", "Hello World!")), ''); println("Hex String: " . $hex); $str = Unpack("z0", Pack("h", $hex)); println("Normal String: " . $str);
Convert a string into a hex and back again (alternative 1):
$hex = Unpack("*H", "Hello World!", 1); println("Hex String: " . $hex); $str = Unpack("z0", Pack("h", $hex)); println("Normal String: " . $str);
Convert a string into a hex and back again (alternative 2):
$hex = Unpack("*H", "Hello World!", 1); println("Hex String: " . $hex); $hex =~ s/([\dA-Fa-f][\dA-Fa-f])/Chr(Dec($1))/ego; println("Normal String: " . $hex);
To pack two integers in big endian format, you would use this:
$bytes = Pack ("^ii", 1234, 4542);
More Examples:
; The following means: ; Little endian encoding of a Int16, followed by an aligned ; int32 value. $r = Pack("_s!i", 0x7b, 0x12345678); foreach ($r as $i) { print(Hex($i) . " "); } // Prints 7B 0 0 0 80 56 34 12 $bytes = Pack("CCCC", 65, 66, 67, 68); foreach ($bytes as $i) { print(Chr($i) . " "); } // Prints 4-byte sequence for "ABCD" $bytes = Pack("4C", 65, 66, 67, 68); foreach ($bytes as $i) { print(Chr($i) . " "); } // Prints 4-byte sequence for "ABCD" $bytes = Pack("*C", 65, 66, 67, 68); foreach ($bytes as $i) { print(Chr($i) . " "); } // Prints 4-byte sequence for "ABCD" $bytes = Pack("^ii", 0x1234abcd, 0x7fadb007); foreach ($bytes as $i) { print(Hex($i) . " "); } println(""); // Result: 12 34 ab cd 7f ad b0 07 // Encode 3 integers as big-endian, but only provides two as arguments, // this defaults to zero for the last value. $bytes = Pack("^iii", 0x1234abcd, 0x7fadb007); foreach ($bytes as $i) { print(Hex($i) . " "); } println(""); // Result: 12 34 ab cd 7f ad b0 07 00 00 00 00 // Encode as little endian, pack 1 short, align, 1 int $bytes = Pack("_s!i", 0x7b, 0x12345678); foreach ($bytes as $i) { print(Hex($i) . " "); } println(""); // Result: 7b 00 00 00 78 56 34 12 // Encode a string in utf-8 with a null terminator $bytes = Pack("z8", "hello"); foreach ($bytes as $i) { print(Hex($i) . " "); } println(""); // Result: 68 65 6c 6c 6f 00 00 00 00 // Little endian encoding, for Int16, followed by an aligned // Int32 $bytes = Pack("_s!i", 0x7b, 0x12345678); foreach ($bytes as $i) { print(Hex($i) . " "); } println(""); // Result: 7b 00 00 00 78 56 34 12
