neoneo-go/pkg/core/interop/callback/syscall.go

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package callback
import (
"errors"
"github.com/nspcc-dev/neo-go/pkg/core/interop"
"github.com/nspcc-dev/neo-go/pkg/vm"
"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
)
// SyscallCallback represents callback for a syscall.
type SyscallCallback struct {
desc *interop.Function
}
var _ Callback = (*SyscallCallback)(nil)
// ArgCount implements Callback interface.
func (p *SyscallCallback) ArgCount() int {
return p.desc.ParamCount
}
// LoadContext implements Callback interface.
func (p *SyscallCallback) LoadContext(v *vm.VM, args []stackitem.Item) {
for i := len(args) - 1; i >= 0; i-- {
v.Estack().PushVal(args[i])
}
}
// CreateFromSyscall creates callback from syscall.
func CreateFromSyscall(ic *interop.Context, v *vm.VM) error {
id := uint32(v.Estack().Pop().BigInt().Int64())
f := ic.GetFunction(id)
if f == nil {
return errors.New("syscall not found")
}
if f.DisallowCallback {
return errors.New("syscall is not allowed to be used in a callback")
}
v.Estack().PushVal(stackitem.NewInterop(&SyscallCallback{f}))
return nil
}