Upgrade for SegWit

[JornC]

With SegWit being merged, and its release in clients and subsequent activation on the network looming around the corner, adapting some shred of it into this block explorer is becoming a strong desire.

Some pointers:

• Display witness root
• Highlight witness commitment in the Coinbase tx (for blocks that have segwit txns)

And optionally:

• Display 'cost' and 'vsize'

[JornC]

FTR

yoghurt [22:46]
@roasbeef: heyho, any suggestions for this: http://srv2.yogh.io/#block:last block explorer with regards to upgrading it for segwit, perchance?

roasbeef [22:46]
yeah I'll take a peak [22:46]
smartbits had a nice one (better than the rest) for segnet, but seems they haven't upgraded their testnet node [22:47]
one suggestion is to also display the witness root [22:47]
it's in the op_return of the coinbase tx, ​iff​ there are witness txns in the block [22:48]
code to locate it looks like: https://github.com/Roasbeef/btcd/blob/2fdd75f73301f56650c1a39ded5138109f6d6ea2/blockchain/merkle.go#L157 [22:48]
the salient bytes are: https://github.com/Roasbeef/btcd/blob/2fdd75f73301f56650c1a39ded5138109f6d6ea2/blockchain/merkle.go#L30 [22:50]
the coinbase tx has the witness nonce in its witness stack, which is just all zeroes atm, but will change in future soft-forks to add more comtiments

yoghurt [22:52]
thanks @roasbeef, I can definitely work with that :+1:

[22:53]
yoghurt: you'll also want to display cost: https://github.com/Roasbeef/btcd/blob/segwit-final/blockchain/cost.go#L52 [22:53]
and "vsize" for transactions: https://github.com/Roasbeef/btcd/blob/segwit-final/blockchain/cost.go#L39 [22:53]
after segwit "vsize" is used to calculate sufficient tx fees, and priority