in reply to Locating a specified number of contiguous 0 bits within a large bitstring efficiently.

You could do it fairly efficiently with a regex, giving 8 alternations which represent the 8 possible start positions within a byte. For example, matching 12 contiguous zeros might be done using something along the lines of 
/
    \x00        [\x00\x10\x20\x30..\xf0]
|   [\x00\\x01] [\x00\x20\x40\x60..\xe0]
...
    [\x00-\x7f] \x00 [\x00\x08\x10\x18..\xf8]
/x

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(That's approx off the top of my head. It probably includes errors and endian mistakes. You'd want to write a function that generates it automatically.)

Dave.

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Re^2: Locating a specified number of contiguous 0 bits within a large bitstring efficiently.
by BrowserUk (Patriarch) on Jun 07, 2013 at 03:20 UTC

    Any thoughts on how to convert $-[0] byte position at which the match is found to a bit position?

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      I guess just see how many high bits are zero in the byte at position $-[0] ?

      Dave.

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