github.com/bhojpur/cache@v0.0.4/pkg/file/types/sharddb.go (about)

     1  package types
     2  
     3  // Copyright (c) 2018 Bhojpur Consulting Private Limited, India. All rights reserved.
     4  
     5  // Permission is hereby granted, free of charge, to any person obtaining a copy
     6  // of this software and associated documentation files (the "Software"), to deal
     7  // in the Software without restriction, including without limitation the rights
     8  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     9  // copies of the Software, and to permit persons to whom the Software is
    10  // furnished to do so, subject to the following conditions:
    11  
    12  // The above copyright notice and this permission notice shall be included in
    13  // all copies or substantial portions of the Software.
    14  
    15  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    16  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    17  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    18  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    19  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    20  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    21  // THE SOFTWARE.
    22  
    23  import (
    24  	"errors"
    25  
    26  	"github.com/bhojpur/cache/pkg/file/crypto"
    27  )
    28  
    29  // errNilDBLabel is returned when a nil label is given.
    30  var ErrNilDBLabel = errors.New("label for creating a shard database header must not be nil")
    31  
    32  // shardDB is the database that holds the locations of each shard of a (larger) file.
    33  type shardDB struct {
    34  	header   DatabaseHeader        // Database header
    35  	shardMap map[shardID]shardData // Shard data map
    36  
    37  	hash crypto.Hash // Hash of the entire database
    38  }
    39  
    40  // generateShardDB constructs a new shard database.
    41  func generateShardDB(shards []Shard, nodes []NodeID) (shardDB, error) {
    42  	if len(shards) != len(nodes) {
    43  		return shardDB{}, errors.New("shard count and node count do not match")
    44  	}
    45  
    46  	// Construct the map
    47  	shardMap := make(map[shardID]shardData)
    48  
    49  	// Generate and add shard data to the map
    50  	for i, shard := range shards {
    51  		id, data := generateShardEntry(shard, i, nodes[i]) // Generate the pair
    52  		shardMap[id] = data                                // Put the data in the map
    53  	}
    54  
    55  	// Construct the database
    56  	sharddb := shardDB{
    57  		header:   NewDatabaseHeader(""), // Generate and set the header
    58  		shardMap: shardMap,              // Set the shardMap
    59  	}
    60  
    61  	return sharddb, nil
    62  }