[RPC][Bitcoin-TX] Add support for sequence number #7957

Neat, this is useful. I was trying it out and think that being able to use hex is a little easier. Maybe something like this:

if (sequenceObj.isNum())
{
    nSequence = sequenceObj.get_int();
} else if (sequenceObj.isStr() /*&& IsHex(sequenceObj.get_str())*/)
{
    nSequence = strtoul(sequenceObj.get_str().c_str(), NULL, 16);
}

I commented out the IsHex check because I think it might be too restrictive (but left it there to see what you thought). With this little patch, these work too:

createrawtransaction '[{"txid":"d5eb7e43a7cf85c5bee47a7a33c8351b8dcc013616a7c6bdc3af49538d986221","vout":0,"sequence":"0xfffffffe"}]' '{"mifzFw94bSGApmx2eWw1nzLCfEeq4cTwey":49.99}' 0
createrawtransaction '[{"txid":"d5eb7e43a7cf85c5bee47a7a33c8351b8dcc013616a7c6bdc3af49538d986221","vout":0,"sequence":"fffffffd"}]' '{"mifzFw94bSGApmx2eWw1nzLCfEeq4cTwey":49.99}' 0
createrawtransaction '[{"txid":"d5eb7e43a7cf85c5bee47a7a33c8351b8dcc013616a7c6bdc3af49538d986221","vout":0,"sequence":"f"}]' '{"mifzFw94bSGApmx2eWw1nzLCfEeq4cTwey":49.99}' 0

Thanks for the review! Hmm... I'm not sure if we want utility function (hex->int) on machine-to-machine communication (RPC). But no strong opinion.

Good point, I was thinking of only the GUI RPC console use (that's where the hex conversion is useful to me). If your threat model includes hostile input on this interface, then the IsHex check could be used and the length of the string could be validated to be <= 8. That would likely be sufficient input validation. Adding back IsHex makes my first and third examples invalid. The sequence value of the third would need to change to "0f" instead of just "f".