SignBlock produces a SignedBlock from a Block. It invokes its callback once for each position in [0..N) where N is the number of pubkeys in the previous block's NextPredicate, until a quorum of signatures is obtained. Any callback returning an error will cause SignBlock to return with an error. A c
(b *UnsignedBlock, prev *BlockHeader, f func(int) (interface{}, error))
| 37 | // skipped silently. If too many callbacks do this, SignBlock will |
| 38 | // return ErrTooFewSignatures. |
| 39 | func SignBlock(b *UnsignedBlock, prev *BlockHeader, f func(int) (interface{}, error)) (*Block, error) { |
| 40 | sb := &Block{UnsignedBlock: b} |
| 41 | if b.Height == 1 { |
| 42 | // Block at height 1 does not require a signature. |
| 43 | return sb, nil |
| 44 | } |
| 45 | if prev == nil { |
| 46 | return nil, errors.New("must supply previous blockheader to Sign") |
| 47 | } |
| 48 | pred := prev.NextPredicate |
| 49 | if pred == nil { |
| 50 | return nil, errors.New("no next predicate in previous blockheader") |
| 51 | } |
| 52 | if pred.Version != 1 { |
| 53 | return nil, errors.New("unknown predicate version") |
| 54 | } |
| 55 | sb.Arguments = make([]interface{}, len(pred.Pubkeys)) |
| 56 | q := pred.Quorum |
| 57 | if q > 0 && f == nil { |
| 58 | return nil, errors.New("no signature function provided") |
| 59 | } |
| 60 | for i := 0; q > 0 && i < len(pred.Pubkeys); i++ { |
| 61 | arg, err := f(i) |
| 62 | if err != nil { |
| 63 | return nil, errors.Wrapf(err, "getting signature %d for block %d", i, b.Height) |
| 64 | } |
| 65 | if arg == nil { |
| 66 | continue |
| 67 | } |
| 68 | if sig, ok := arg.([]byte); ok { |
| 69 | if len(sig) > 0 { |
| 70 | sb.Arguments[i] = sig |
| 71 | q-- |
| 72 | } |
| 73 | continue |
| 74 | } |
| 75 | return nil, errors.New("non-signature in block arguments") |
| 76 | } |
| 77 | if q > 0 { |
| 78 | return nil, ErrTooFewSignatures |
| 79 | } |
| 80 | return sb, nil |
| 81 | } |
| 82 | |
| 83 | // MarshalText fulfills the json.Marshaler interface. |
| 84 | // This guarantees that blocks will get deserialized correctly |