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package core
import (
"bufio"
"encoding/binary"
"encoding/json"
"fmt"
"os"
bolt "go.etcd.io/bbolt"
)
type Header struct {
MagicNumber int
Signature string
FilesystemSize int
TableSize int
}
type Node struct {
BlockStart int
BlockEnd int
BlockSum string
PrevNodeSum string
}
func ReadHeader(partition string) (Header, error) {
_, exist := os.Stat(partition)
if os.IsNotExist(exist) {
return Header{}, fmt.Errorf("Cannot find partition %s", partition)
}
part, err := os.Open(partition)
if err != nil {
return Header{}, err
}
defer part.Close()
header := Header{}
reader := bufio.NewReader(part)
MagicNumber := make([]byte, 2)
Signature := make([]byte, 302)
FileSystemSize := make([]byte, 4)
TableSize := make([]byte, 4)
_, err = reader.Read(MagicNumber)
MagicNum := binary.BigEndian.Uint16(MagicNumber)
if MagicNum != 0xACAB { // The Silliest of magic numbers
return Header{}, err
}
header.MagicNumber = int(MagicNum)
_, err = reader.Read(Signature)
if err != nil {
return Header{}, err
}
_, err = reader.Read(FileSystemSize)
if err != nil {
return Header{}, err
}
_, err = reader.Read(TableSize)
if err != nil {
return Header{}, err
}
header.Signature = string(Signature)
header.FilesystemSize = int(binary.BigEndian.Uint16(FileSystemSize))
header.TableSize = int(binary.BigEndian.Uint16(TableSize))
return header, nil
}
func OpenDB() (*bolt.DB, error) {
_, exist := os.Stat("my.db") // TODO: use configuration file for db path
if os.IsNotExist(exist) {
os.Create("my.db")
}
db, err := bolt.Open("my.db", 0777, nil)
if err != nil {
return nil, err
}
return db, nil
}
func AddNode(node Node, db *bolt.DB) error {
var err error
var deferDB bool
if db == nil {
db, err = OpenDB()
if err != nil {
return err
}
deferDB = true
}
err = db.Update(func(tx *bolt.Tx) error {
nodes, err := tx.CreateBucketIfNotExists([]byte("Nodes"))
if err != nil {
return err
}
if buf, err := json.Marshal(node); err != nil {
return err
} else if err := nodes.Put([]byte(node.PrevNodeSum), buf); err != nil {
return err
}
return nil
})
if deferDB {
defer db.Close()
}
return err
}
func GetNode(checksum string, db *bolt.DB) (Node, error) {
var err error
var deferDB bool
if db == nil {
db, err = OpenDB()
if err != nil {
return Node{}, err
}
deferDB = true
}
var node Node
err = db.View(func(tx *bolt.Tx) error {
nodes := tx.Bucket([]byte("Nodes"))
app := nodes.Get([]byte(checksum))
err := json.Unmarshal(app, &node)
return err
})
if deferDB {
defer db.Close()
}
return node, err
}
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