github.com/bhojpur/cache@v0.0.4/pkg/file/types/shard_io.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  	"encoding/json"
    25  	"errors"
    26  	"fmt"
    27  	"io/ioutil"
    28  	"path/filepath"
    29  
    30  	"github.com/bhojpur/cache/pkg/file/common"
    31  )
    32  
    33  // ErrInvalidShard is returned when a shard's hash is not valid when loading from memory.
    34  var ErrInvalidShard = errors.New("shard from memory is not valid")
    35  
    36  // WriteShardToMemory writes a shard to memory.
    37  func (shard *Shard) WriteShardToMemory() error {
    38  	bytes := shard.Serialize()
    39  
    40  	// Create a dir to store the shards
    41  	err := common.CreateDirIfDoesNotExist("data/shards")
    42  	if err != nil {
    43  		return err
    44  	}
    45  
    46  	// Create the filename of the hash
    47  	shardHashString := (*shard).Hash.String()[0:8]
    48  	filename := fmt.Sprintf("data/shards/shard_%s.json", shardHashString)
    49  
    50  	err = ioutil.WriteFile(filepath.FromSlash(filename), bytes, 0644)
    51  	if err != nil {
    52  		return err
    53  	}
    54  
    55  	return nil
    56  }
    57  
    58  // ReadShardFromMemory reads a shard from memory.
    59  func ReadShardFromMemory(hash string) (*Shard, error) {
    60  	// Read the file from memory
    61  	data, err := ioutil.ReadFile(fmt.Sprintf("data/shards/shard_%s.json", hash))
    62  	if err != nil {
    63  		return nil, err
    64  	}
    65  
    66  	buffer := &Shard{} // Init a shard buffer
    67  
    68  	// Read into the buffer
    69  	err = json.Unmarshal(data, buffer)
    70  	if err != nil {
    71  		return nil, err
    72  	}
    73  
    74  	if (*buffer).Validate() == false {
    75  		return nil, ErrInvalidShard
    76  	}
    77  
    78  	return buffer, nil // Return the shard pointer
    79  }