We’re collecting data from a partner’s IoT devices and the data comes encoded in a hex string like
1C000000010028 which contains binary data:
- Byte 0 bit 0 Boolean
- Byte 0 bit 1 Boolean
- Byte 0 bit 2 Boolean
- Byte 0 bit 3 Boolean
- Byte 0 bits 4-7 UInt4
- Bytes 1-2 bits 0-15 UInt16
- Byte 3 bits 0-7 UInt8
- Bytes 4-5 bits 0-15 UInt16
- Byte 6 bits 0-7 UInt8
I have never worked with this kind of data and am wondering how to decode / unpack this in PHP. I was guessing that https://www.php.net/manual/de/function.unpack.php would be my friend but I just don’t get it. Any help would be much appreciated, thanks!
They say that the input is a hex string like ‘1C000000010028’.
$code = '1C000000010028';
To use unpack() the data must be a string with binaryData. You can convert it with hex2bin.
$binaryData = hex2bin($code); // "x1cx00x00x00x01x00x28"
Now you could use unpack.
$arr = unpack('Cbyte_0/vUInt16_0/Cbyte_1/vUInt16_1/Cbyte_2',$binaryData); /* $arr = array ( 'byte_0' => 28, 'UInt16_0' => 0, 'byte_1' => 0, 'UInt16_1' => 1, 'byte_2' => 40, ) */
Individual data types such as Boolean and UInt4 are not included in the pack/unpack formats. To get this data you have to work with the bit operators.
Just one example of this:
$byte_0bit2 = (bool)($arr['byte_0'] & 0b00000100);
This can lead to further questions, the answers of which can be found here on Stackoverflow.