gitee.com/ks-custle/core-gm@v0.0.0-20230922171213-b83bdd97b62c/grpc/credentials/alts/internal/conn/counter.go (about)

     1  /*
     2   *
     3   * Copyright 2018 gRPC authors.
     4   *
     5   * Licensed under the Apache License, Version 2.0 (the "License");
     6   * you may not use this file except in compliance with the License.
     7   * You may obtain a copy of the License at
     8   *
     9   *     http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   */
    18  
    19  package conn
    20  
    21  import (
    22  	"errors"
    23  )
    24  
    25  const counterLen = 12
    26  
    27  var (
    28  	errInvalidCounter = errors.New("invalid counter")
    29  )
    30  
    31  // Counter is a 96-bit, little-endian counter.
    32  type Counter struct {
    33  	value       [counterLen]byte
    34  	invalid     bool
    35  	overflowLen int
    36  }
    37  
    38  // Value returns the current value of the counter as a byte slice.
    39  func (c *Counter) Value() ([]byte, error) {
    40  	if c.invalid {
    41  		return nil, errInvalidCounter
    42  	}
    43  	return c.value[:], nil
    44  }
    45  
    46  // Inc increments the counter and checks for overflow.
    47  func (c *Counter) Inc() {
    48  	// If the counter is already invalid, there is no need to increase it.
    49  	if c.invalid {
    50  		return
    51  	}
    52  	i := 0
    53  	for ; i < c.overflowLen; i++ {
    54  		c.value[i]++
    55  		if c.value[i] != 0 {
    56  			break
    57  		}
    58  	}
    59  	if i == c.overflowLen {
    60  		c.invalid = true
    61  	}
    62  }