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How to convert bits from python to php?

I have this hex code F0C2CA89012A04008C0000000000000000000000 from the device. This hex code shows the value of the water drops.

In my python code

msg = F0C2CA89012A04008C0000000000000000000000
msg_counters = bytes.fromhex(msg)[5:20] 
# output: b'*x04x00x8cx00x00x00x00x00x00x00x00x00x00x00'      
msg_counters_int = int.from_bytes(msg_counters)
# output: 218157641024778742068286256301735936    
bin_string = '{:0120b}'.format(msg_counters_int)
print(bin_string)

this print the value of bits. These bits shows the value of water

001010100000010000000000100011000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

00101 = 5
01000 = 8
00010 = 2

I’m trying to convert the code to PHP and I’m stuck in int.from_bytes from python. I don’t know how to convert the value.
In my PHP code

$a = hex2bin("F0C2CA89012A04008C0000000000000000000000");
$b = substr($a, 5, 20);
// output: b"*x04x00Œx00x00x00x00x00x00x00x00x00x00x00"

I tried to use unpack functionality but it doesn’t show the correct value

Tags:

2

Answers


  1. 0

    To convert this Python code into PHP, you need to handle hexadecimal string manipulation, byte slicing, and integer conversion. Here’s how you can achieve the equivalent in PHP:

    Python Code

    msg = "F0C2CA89012A04008C0000000000000000000000"
msg_counters = bytes.fromhex(msg)[5:20]
msg_counters_int = int.from_bytes(msg_counters)
bin_string = '{:0120b}'.format(msg_counters_int)
print(bin_string)

    Equivalent PHP Code

    <?php
$msg = "F0C2CA89012A04008C0000000000000000000000";

// Convert hex string to binary data
$msg_counters = hex2bin(substr($msg, 5, 30)); // Get the binary data from hex string

// Convert binary data to integer
$msg_counters_int = gmp_init(bin2hex($msg_counters), 16); // GMP for handling large integers

// Convert integer to binary string with leading zeros
$bin_string = str_pad(gmp_strval($msg_counters_int, 2), 120, '0', STR_PAD_LEFT);

echo $bin_string;
?>

    Explanation:

    1. Hex to Binary Conversion:

      • hex2bin(substr($msg, 5, 30)) converts the relevant part of the hexadecimal string to binary data. substr($msg, 5, 30) extracts the substring starting from the 6th character (index 5) and with a length of 30 characters.

    2. Binary to Integer Conversion:

      • bin2hex($msg_counters) converts binary data to hexadecimal.
      • gmp_init(bin2hex($msg_counters), 16) initializes a GMP (GNU Multiple Precision) number from the hexadecimal string, since PHP’s integer type might not handle very large numbers.

    3. Integer to Binary String:

      • gmp_strval($msg_counters_int, 2) converts the GMP number to a binary string.
      • str_pad(..., 120, '0', STR_PAD_LEFT) ensures the binary string has leading zeros to match the 120-bit length.

    This PHP code snippet provides an equivalent result to the Python code, converting the specified segment of a hexadecimal string into a binary string with leading zeros.

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  2. 0

    Here is an alternative solution that doesn’t rely on the GMP extension, but on the standard base_convert() function. For every byte, the two hex digits are extracted from the input string and converted to base 2:

    function getBits(string $msg, int $from, int $to)
{
    $bits = '';
    for($i=$from; $i<$to; $i++)
    {
        $s = base_convert(substr($msg, 2*$i, 2), 16, 2);
        $bits .= str_pad($s, 8, '0', STR_PAD_LEFT);
    }
    return $bits;
}

echo getBits('F0C2CA89012A04008C0000000000000000000000', 5, 20);

    Output:

    001010100000010000000000100011000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
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