如何根据动态值移动二进制字符串 - PHP

Question

I have a binary string of 336 in 0 and 1 form. I am getting a value from a variable. Let's say the string is 010101010001111 and variable value is 3, then I want a string like this: 111010101010001.

Is it possible? How can it be done in PHP?

Any help would be highly appreciated.

Answer 1

You have to do a bit of bit manipulation here,

$string = '010101010001111';
$decVal = bindec($string);
$variable = 3;
$result = decbin(($decVal >> $variable) | (($decVal << (strlen($string) - $variable)) & ~(~0 << strlen($string))));
echo $result;

Live Demo: https://3v4l.org/lSCLq

The overall idea is like this:

1. Convert binary string to decimal value.

   $decVal = bindec($string); // 010101010001111 --> 10895
   

2. Right shift $decVal value by $variable positions.

   $decVal >> $variable  // 010101010001111 --> 000010101010001
   

3. Left shift $decVal value by strlen($string) - $variable positions

   $decVal << (strlen($string) - $variable) // 010101010001111 --> 010101010001111000000000000
   

4. AND the output of step# 3 with ...0000000000111111111111111

   (($decVal << (strlen($string) - $variable)) & ~(~0 << strlen($string))) // 010101010001111000000000000 & ...0000000000111111111111111 --> ...0000000000111000000000000
   

5. OR the output of step# 2 and step# 4 to achieve the desired result

   ($decVal >> $variable) | (($decVal << (strlen($string) - $variable)) & ~(($decVal | ~0) << strlen($string))) // 000010101010001 | ...0000000000111000000000000--> 111010101010001
   

6. Finally, display the output of step# 5 in binary string representation.

   $result = decbin(...);
   echo $result;