Methods needed for Covenants in Script

[jcramer]

I wanted to share two methods I used for the purpose of creating a Covenant type script contract. The LastWill contract is an example that uses this preimage data within the "refresh" scriptSig.

1. sigHashPreimageBufChunks(inIndex, prevOutScript, value, hashType) -->

[
    versionBuf,        // 4-bytes version    
    hPhSoBuf,          // 100-bytes (hashPrevouts, hashSequence, outpoint tx hash, outpoint vout)
    scriptCodeBuf,     // size varies 
    valueBuf,          // 8-bytes value
    nSequenceBuf,      // 4-bytes nSequence
    hashOutputs,       // 32-bytes hashOutputs
    tailBuf,           // 8-bytes nLockTime & sighash Type
]

2. sigHashPreimageBuf(inIndex, prevOutScript, value, hashType) --> sigHash preimage buf

[christroutner]

These look like they are only additive changes, which removes the risk of regression bugs. This should be safe to merge.

[jcramer]

@christroutner I will likely be adding some bits to this over the next few weeks. We want to have an option in the method to return the whole preimage, rather than the chunks.

[rkalis]

I like the idea of also being able to return the full preimage, but I think returning chunks is valuable too. Perhaps hPhSoBuf could be further broken up as well, in case someone might need it later on.

[jcramer]

Good idea, I can have it broken up to leave it up to the consumer to combine the chunks as they wish.

I'll add a method parameter asChunks or something set to false by default so an un-chunked preimage will be returned by default.