wire: add bitcoin network magic for default SigNet

[starius]

Added constant wire.SigNet, added it to stringer for BitcoinNet type.

Added a test in chaincfg to compare calculated magic value with the constant.

[Roasbeef]

Approved CI.

[Roasbeef]

Is this documented anywhere? Doesn't seem to be in the OG BIP.

[starius]

I copied the constant from https://en.bitcoin.it/wiki/Protocol_documentation#Common_structures
The constant is equal to chaincfg.SigNetParams.Net, this is checked in new test TestSigNetMagic.

[guggero]

It should also be equal to CustomSignetParams(DefaultSignetChallenge, nil).Net, or:

	challengeLength := byte(len(DefaultSignetChallenge))
	hashDouble := chainhash.DoubleHashB(
		append([]byte{challengeLength}, challenge...),
	)
	net := binary.LittleEndian.Uint32(hashDouble[0:4])

Perhaps we can add a simple test case for it?

[guggero]

Ah, I guess that's what we're doing with TestSigNetMagic, so never mind.

[coveralls]

Pull Request Test Coverage Report for Build 12011166502

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 57.236%

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Totals
Change from base Build 11941199528:	0.002%
Covered Lines:	29883
Relevant Lines:	52210

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💛 - Coveralls

[guggero]

Just one clarification request, otherwise LGTM 🎉

[guggero]

It should also be equal to CustomSignetParams(DefaultSignetChallenge, nil).Net, or:

	challengeLength := byte(len(DefaultSignetChallenge))
	hashDouble := chainhash.DoubleHashB(
		append([]byte{challengeLength}, challenge...),
	)
	net := binary.LittleEndian.Uint32(hashDouble[0:4])

Perhaps we can add a simple test case for it?

[guggero]

I know this is probably the way it's called in most places (signet (default)), though I think we could make it a bit more obvious that this is only one of many possible signets, we could add something like: // SigNet represents the public default SigNet. For custom signets, see CustomSignetParams`.

[starius]

Thanks! Fixed.

[guggero]

Ah, I guess that's what we're doing with TestSigNetMagic, so never mind.