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/*
*
* 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 (
"errors"
)
const counterLen = 12
var (
errInvalidCounter = errors.New("invalid counter")
)
// Counter is a 96-bit, little-endian counter.
type Counter struct {
value [counterLen]byte
invalid bool
overflowLen int
}
// Value returns the current value of the counter as a byte slice.
func (c *Counter) Value() ([]byte, error) {
if c.invalid {
return nil, errInvalidCounter
}
return c.value[:], nil
}
// Inc increments the counter and checks for overflow.
func (c *Counter) Inc() {
// If the counter is already invalid, there is no need to increase it.
if c.invalid {
return
}
i := 0
for ; i < c.overflowLen; i++ {
c.value[i]++
if c.value[i] != 0 {
break
}
}
if i == c.overflowLen {
c.invalid = true
}
}
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