Though I would like to clarify that maybe my wording was a bit confusing. By “string of bits”, I did not mean the term as it is typically used in programming language environments, but rather a raw binary sequence, e.g., the first 24 bits of an IP address, therefore allocating 3 bytes of memory for storing the NID.
Comment on Is the bitwise AND of subnet masks and IP addresses redundant?
DmMacniel@feddit.org 1 week ago
But why do we need the bitwise AND for that, specifically? I understand the idea, but would it not be easier to only parse the IP address string of bits only for the first n bits and then disregard the remainder (the host identifier)?
Essentially it boils down to:
bit operations are stupid fast, String operations are super slow.
ricdeh@lemmy.world 1 week ago
DmMacniel@feddit.org 1 week ago
but rather a raw binary sequence, e.g., the first 24 bits of an IP address, therefore allocating 3 bytes of memory for storing the NID.
That would require dynamic memory allocation, since you can never know what CIDR your stack encounters. It could be a nibble, a byte, a byte and a nibble, …, 4 bytes. So you would allocate a int32/int64 anyway to be on the safe side.
ricdeh@lemmy.world 1 week ago
Yep, I agree. Though one could make a hypothetical argument for expanding the array dynamically when needed. Of course, due to the varying sizes of NIDs resulting from CIDR (which you correctly mentioned), you would need to have a second array that can store the length of each NID, with 5 bits per element, leaving you with 3 bits “saved” per IP address.
That can end up wasting more memory than the 32-bit per NID approach, e.g., when the host identifier is smaller than 5 bits. And there’s the slowness of memory allocation and copying from one array to another that comes on-top of that.
I think that it is theoretically possible to deploy a NID-extracting and tracking program that is a tiny bit more memory efficient than the 32-bit implementation, but would probably come at a performance overhead and depend on you knowing the range of your expected IP addresses really well. So, not useful at all, lol
Anyway, thanks for your contributions.
DmMacniel@feddit.org 1 week ago
sure thing buddy, and never feel discouraged to ask “stupid questions”, it’s how we learn after all :)
ricdeh@lemmy.world 1 week ago
Okay, that makes sense. Thank you.