Got Money, Got Paid

Finally!

Anyway, I haven't mad a blog post in waaaaaaaaaaaaaay too long. Anyway, the bit that I'm working on now is to resolve the issue of sequence number wrap-around. The way that I'm implementing it will (hopefully) have the benefit of automating the calculation of SND.NXT and a buffer of octets that need to be retransmitted based off of the send/sent segments, and SND.UNA.

Essentially, it's a continuous list with an offset. Less simple than it would originally appear due to the way slices work. Here's a quick example:

Example:
>>> from segmentBuffer import *
>>> sb = segmentBuffer(base=10, max=15)
>>> sb += range(8)
>>> sb[10] # The first item is at [10]
0
>>> sb[11] # The second item is at [11]
1
>>> sb # However, the items are in the proper order
[0, 1, 2, 3, 4, 5, 6, 7]
>>> sb[10:] # And are properly sliced
[0, 1, 2, 3, 4, 5, 6, 7]
>>> sb[10:2] # And the slices wrap-around at max
[0, 1, 2, 3, 4, 5, 6]
>>> sb[2:10] # And slices stop when it hits a gap.
[7]
>>> sb == sb[10:] # Truth works just fine.
True
>>> sb += 2 # The offset is incremented easily
>>> sb # Notice that the first two items are deleted
[2, 3, 4, 5, 6, 7]
>>> len(sb) # The length indeed goes down 8->2
6
>>> sb += range(100,200)
>>> len(sb) # Adding 100 items keeps the correct length
15
>>> sb # Only items up to the limit are added
[2, 3, 4, 5, 6, 7, 100, 101, 102, 103, 104, 105, 106, 107, 108]
>>> sb2 = sb + range(300,400)
>>> sb is sb2 # Addition operator returns a new object.
False
>>> sb2 += 3 # The other object can be incremented
>>> [i for i in sb if i not in sb2]
[2, 3, 4] # Just an example to show the difference
>>> sb[12:15] # This shows that the items were taken off the front
[2, 3, 4]
>>> sb[12:2]
[2, 3, 4, 5, 6]
>>> sb2[12:2] # The indexes for the remaining items do not change
[5, 6] # Although the deleted items are gone.
>>> sb
[2, 3, 4, 5, 6, 7, 100, 101, 102, 103, 104, 105, 106, 107, 108]
>>> sb2
[5, 6, 7, 100, 101, 102, 103, 104, 105, 106, 107, 108]

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