Source: utils.go in package google.golang.org/grpc/credentials/alts/internal/conn

* * Copyright 2018 gRPC authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http:www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. *


package conn

import core "google.golang.org/grpc/credentials/alts/internal"

NewOutCounter returns an outgoing counter initialized to the starting sequence number for the client/server side of a connection.

func NewOutCounter(s core.Side, overflowLen int) (c Counter) {
	c.overflowLen = overflowLen

Server counters in ALTS record have the little-endian high bit set.

		c.value[counterLen-1] = 0x80
	}
	return
}

NewInCounter returns an incoming counter initialized to the starting sequence number for the client/server side of a connection. This is used in ALTS record to check that incoming counters are as expected, since ALTS record guarantees that messages are unwrapped in the same order that the peer wrapped them.

func NewInCounter(s core.Side, overflowLen int) (c Counter) {
	c.overflowLen = overflowLen

Server counters in ALTS record have the little-endian high bit set.

		c.value[counterLen-1] = 0x80
	}
	return
}

CounterFromValue creates a new counter given an initial value.

func CounterFromValue(value []byte, overflowLen int) (c Counter) {
	c.overflowLen = overflowLen
	copy(c.value[:], value)
	return
}

CounterSide returns the connection side (client/server) a sequence counter is associated with.

func CounterSide(c []byte) core.Side {
	if c[counterLen-1]&0x80 == 0x80 {
		return core.ServerSide
	}
	return core.ClientSide