/
log.go
109 lines (98 loc) · 2.04 KB
/
log.go
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package db
import (
"encoding/json"
"fmt"
"os"
"syscall"
)
type Entry struct {
Command string
Key string
Value string
Term int
}
type Log struct {
data []byte
Entries []Entry
fd int
filename string
file *os.File
}
func (log *Log) load() {
err := json.Unmarshal(log.data, &log.Entries)
if err != nil {
fmt.Println("Error unmarshalling initial data into map: ", err)
}
}
func (log *Log) mmap(size int) {
fmt.Println("mmapping log file: ", size)
data, err := syscall.Mmap(log.fd, 0, size, syscall.PROT_WRITE|syscall.PROT_READ, syscall.MAP_SHARED)
if err != nil {
fmt.Println("Error mmapping: ", err)
}
log.data = data
}
func (log *Log) resize(size int) {
fmt.Println("Resizing log file: ", size)
err := syscall.Ftruncate(log.fd, int64(size))
if err != nil {
fmt.Println("Error resizing log file: ", err)
}
}
func (log *Log) open() {
fmt.Println("Getting log file descriptor")
f, err := os.OpenFile(log.filename, os.O_CREATE|os.O_RDWR, 0)
if err != nil {
fmt.Println("Could not open log file: ", err)
}
log.fd = int(f.Fd())
log.file = f
}
func (log *Log) extend(size int) {
log.file.Close()
log.open()
log.resize(size)
log.mmap(size)
}
func (log *Log) SetEntries(entries []Entry) {
log.Entries = entries
b, err := json.Marshal(log.Entries)
if err != nil {
fmt.Println("Error marshalling log: ", err)
}
if len(b) > len(log.data) {
log.extend(len(b))
}
copy(log.data, b)
}
func (log *Log) AppendEntry(entry Entry) {
log.Entries = append(log.Entries, entry)
b, err := json.Marshal(log.Entries)
if err != nil {
fmt.Println("Error marshalling log: ", err)
}
if len(b) > len(log.data) {
log.extend(len(b))
}
copy(log.data, b)
}
func initLog(filename string) *Log {
var data []byte
var entries []Entry
var fd int
var file *os.File
log := &Log{data, entries, fd, filename, file}
log.open()
f, err := os.Stat(filename)
if err != nil {
fmt.Println("Could not stat file: ", err)
}
size := int(f.Size())
if size == 0 {
size = 10
log.resize(size)
}
log.mmap(size)
log.load()
return log
}