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dannym@lemmy.escapebigtech.info ⁨11⁩ ⁨months⁩ ago

Please don’t. Use regex to find something that looks like an IP then build a real parser. This is madness

Just parse [0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3} using regex (for v4) and then have some code check that all the octets are valid (and store the IP as a u32)

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Emma_Gold_Man@lemmy.dbzer0.com ⁨11⁩ ⁨months⁩ ago
And dupe check. 0.0.0.0 and 000.000.000.000 may both be valid, but they resolve the same

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- azertyfun@sh.itjust.works ⁨11⁩ ⁨months⁩ ago
  Fuck that, if for whatever reason I’m writing an IP validator by hand I’m disallowing leading zeros. Parsers are very inconsistent, some will parse 010 as 10, others as 0o10 == 8 (you can try that right now with a POSIX ping). Talk about a footgun.
  
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  - stringere@reddthat.com ⁨11⁩ ⁨months⁩ ago
    
    some will parse 010 as 10, others as 0o10 == 8
    
    …and that’s me in the fetal position, thanks.
    
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- dannym@lemmy.escapebigtech.info ⁨11⁩ ⁨months⁩ ago
  Definitely, tho if you store it as a u32 that is fixed magically. Because 1.2.3.4 and 1.02.003.04 both map to the same number.
  
  What I mean by storing it as a u32 is to convert it to a number, similar to how the IP gets sent over the wire, so for v4:
  
  octet[3] | octet[2] << 8 | octet[1] << 16 | octet[0] << 24
  
  or in more human terms:
  
  (fourth octet) + (first octet * 256^3) + (second octet * 256^2) + (third octet * 256)
  
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  - p1mrx@sh.itjust.works ⁨11⁩ ⁨months⁩ ago
    
    Because 1.2.3.4 and 1.02.003.04 both map to the same number.
    
    But 10.20.30.40 and 010.020.030.040 map to different numbers. It’s often best to reject IPv4 addresses with leading zeroes to avoid the decimal vs. octal ambiguity.
    
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  - Emma_Gold_Man@lemmy.dbzer0.com ⁨11⁩ ⁨months⁩ ago
    True enough for database or dictionary storage, but a lot of times things get implemented in arrays where you still wind up with two copies of the same uint32.
    
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