github.com/letsencrypt/trillian@v1.1.2-0.20180615153820-ae375a99d36a/storage/suffix.go (about)

     1  // Copyright 2017 Google Inc. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package storage
    16  
    17  import (
    18  	"encoding/base64"
    19  )
    20  
    21  // Suffix represents the tail of a NodeID. It is the path within the subtree.
    22  // The portion of the path that extends beyond the subtree is not part of this suffix.
    23  type Suffix struct {
    24  	// bits is the number of bits in the node ID suffix.
    25  	// TODO(gdbelvin): make bits an integer.
    26  	Bits byte
    27  	// path is the suffix itself.
    28  	Path []byte
    29  }
    30  
    31  // String returns a string that represents Suffix.
    32  // This is a base64 encoding of the following format:
    33  // [ 1 byte for depth || path bytes ]
    34  func (s Suffix) String() string {
    35  	r := make([]byte, 1, 1+(len(s.Path)))
    36  	r[0] = s.Bits
    37  	r = append(r, s.Path...)
    38  	return base64.StdEncoding.EncodeToString(r)
    39  }
    40  
    41  // ParseSuffix converts a suffix string back into a Suffix.
    42  func ParseSuffix(s string) (Suffix, error) {
    43  	b, err := base64.StdEncoding.DecodeString(s)
    44  	if err != nil {
    45  		return Suffix{}, err
    46  	}
    47  
    48  	return Suffix{
    49  		Bits: byte(b[0]),
    50  		Path: b[1:],
    51  	}, nil
    52  }