Re^6: Using pack to evaluate text strings as hexadecimal values

Perhaps I am missing something. Why would it be "impossible" to have a format item "Y" (where "Y" is some unused format character, finding which may be the real problem) such that

  pack("Y4", 32);       # produces "0020"
  unpack("Y4", "0020"); # produces 32
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There are many format characters, v among them, that pack integers into strings and unpack strings into integers. I believe the only practical difference between "Y" and "v" is the contents of the string. The one produced by "v" may be unsuitable for display, the one produced by "Y" would be both displayable and, when displayed, indicative of the bits in the integer from which it was produced.

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Re^7: Using pack to evaluate text strings as hexadecimal values
by BrowserUk (Patriarch) on Mar 22, 2011 at 13:58 UTC

Actually, now you put it that way, I'm wrong. It could work and would be useful. It would be a departure from the norm of converting numerics to and from their binary representation.

There are some issues as to what should happen if you specified pack 'Y4', 100000; or pack 'Y4', 32.0 but actually that perhaps suggests a way around the lack of remaining letters that also has an existing precedent.

To skip a complex structure--say consisting of 2 shorts and float--the syntax is X[vvf], meaning skip enough bytes to cover 2 shorts and a float. Ie. 2+2+4 = 8 bytes.

To get your hexified numeric, the syntax could be pack 'H[v]', 32, meaning treat the number as a a 16-bit int and hexify it; thereby producing your 4 bytes of output.

The nice thing is that this then extends naturally to pack 'H[V]', 32; to produce 8-bytes of hex. And pack 'H[Q]', 123456789012345; and even pack 'H[f]', 1234.56e78; and so on.

And once that is accepted, this further extends to the other bain of pack/unpack; binary. With 'B[v] b[V} B[d]' etc. And a quick peruse of the docs suggest that 'O' isn't currently used, so maybe 'O[v] O[Q]' might be useful also.

Now all you've got to do is: knock up the patch; get it by p5p; and wait for it to make it into a build :)

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