add check for len == power of 2 #47

Job	Run time
tests (A-B tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/...	1m 19s
tests (C-[a-m] tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFin...	2m 6s
tests (C-[n-o] tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFin...	7m 30s
tests (C-[p-z] tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFin...	45s
tests (D-I tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/...	2m 40s
tests (J-N tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/...	2m 4s
tests (O-R tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/...	1m 34s
tests (S tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/XD...	1m 26s
tests (T-Z tests, go run build/ci.go test -coverage $(go list ./... \| grep "github.com/XinFinOrg/...	1m 47s
devnet_build_push	0s
tag_build	0s
devnet_terraform_apply	0s
devnet_send_notification	0s
	21m 11s

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