github.com/Bytom/bytom@v1.1.2-0.20210127130405-ae40204c0b09/blockchain/txbuilder/constraint.go (about)

     1  package txbuilder
     2  
     3  import (
     4  	"github.com/bytom/bytom/protocol/bc"
     5  	"github.com/bytom/bytom/protocol/vm"
     6  	"github.com/bytom/bytom/protocol/vm/vmutil"
     7  )
     8  
     9  // Constraint types express a constraint on an input of a proposed
    10  // transaction, and know how to turn that constraint into part of a
    11  // signature program in that input's witness.
    12  type constraint interface {
    13  	// Code produces bytecode expressing the constraint. The code, when
    14  	// executed, must consume nothing from the stack and leave a new
    15  	// boolean value on top of it.
    16  	code() []byte
    17  }
    18  
    19  // outpointConstraint requires the outputID (and therefore, the outpoint) being spent to equal the
    20  // given value.
    21  type outputIDConstraint bc.Hash
    22  
    23  func (o outputIDConstraint) code() []byte {
    24  	builder := vmutil.NewBuilder()
    25  	builder.AddData(bc.Hash(o).Bytes())
    26  	builder.AddOp(vm.OP_OUTPUTID)
    27  	builder.AddOp(vm.OP_EQUAL)
    28  	prog, _ := builder.Build() // error is impossible
    29  	return prog
    30  }
    31  
    32  // PayConstraint requires the transaction to include a given output
    33  // at the given index, optionally with the given refdatahash.
    34  type payConstraint struct {
    35  	Index int
    36  	bc.AssetAmount
    37  	Program []byte
    38  }
    39  
    40  func (p payConstraint) code() []byte {
    41  	builder := vmutil.NewBuilder()
    42  	builder.AddInt64(int64(p.Index))
    43  	builder.AddInt64(int64(p.Amount)).AddData(p.AssetId.Bytes()).AddInt64(1).AddData(p.Program)
    44  	builder.AddOp(vm.OP_CHECKOUTPUT)
    45  	prog, _ := builder.Build() // error is impossible
    46  	return prog
    47  }