/
mapdb.go
182 lines (146 loc) · 2.84 KB
/
mapdb.go
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package mapdb
import (
"encoding/json"
"errors"
"io/ioutil"
"os"
"path/filepath"
"sort"
"time"
"github.com/0xef53/kvmrun/internal/flock"
)
var (
MIN_VALUE = 200
MAX_VALUE = 65000
ErrNoAvailableValues = errors.New("no available values")
)
type DB struct {
file string
lockfile string
}
func New(fname string) *DB {
return &DB{
file: fname,
lockfile: fname + ".lock",
}
}
func (db *DB) Get(key string) (int, error) {
if err := os.MkdirAll(filepath.Dir(db.file), 0755); err != nil {
return -1, err
}
lock, err := flock.NewLocker(db.lockfile)
if err != nil {
return -1, err
}
defer lock.Release()
if err := lock.Acquire(time.Second * 10); err != nil {
return -1, err
}
var m map[string]int
if b, err := ioutil.ReadFile(db.file); err == nil {
if err := json.Unmarshal(b, &m); err != nil {
return -1, err
}
} else {
if os.IsNotExist(err) {
m = make(map[string]int)
} else {
return -1, err
}
}
if v, ok := m[key]; ok {
return v, nil
}
values := make([]int, 0, len(m))
for _, v := range m {
values = append(values, v)
}
if x, err := getVacantValue(values); err == nil {
m[key] = x
} else {
return -1, err
}
if err := db.save(m); err != nil {
return -1, err
}
return m[key], nil
}
func (db *DB) Delete(key string) (int, error) {
lock, err := flock.NewLocker(db.lockfile)
if err != nil {
return -1, err
}
defer lock.Release()
if err := lock.Acquire(time.Second * 10); err != nil {
return -1, err
}
var m map[string]int
if b, err := ioutil.ReadFile(db.file); err == nil {
if err := json.Unmarshal(b, &m); err != nil {
return -1, err
}
} else {
if os.IsNotExist(err) {
return -1, nil
} else {
return -1, err
}
}
if v, ok := m[key]; ok {
delete(m, key)
if err := db.save(m); err != nil {
return -1, err
}
return v, nil
}
return -1, nil
}
func (db *DB) save(m map[string]int) error {
b, err := json.MarshalIndent(m, "", " ")
if err != nil {
return err
}
return ioutil.WriteFile(db.file, b, 0644)
}
func getVacantValue(values []int) (int, error) {
if len(values) == 0 {
return MIN_VALUE, nil
}
tmp := make([]int, 0, len(values))
contains := func(x int) bool {
for _, v := range tmp {
if v == x {
return true
}
}
return false
}
// Exclude out-of-bounds values
for _, v := range values {
if v >= MIN_VALUE && v <= MAX_VALUE && !contains(v) {
tmp = append(tmp, v)
}
}
switch {
case len(tmp) == 1:
if tmp[0] == MIN_VALUE {
return tmp[0] + 1, nil
} else {
return MIN_VALUE, nil
}
case len(tmp) > 1:
sort.Ints(tmp)
if tmp[0] == MIN_VALUE {
for idx := 0; idx < len(tmp)-1; idx++ {
if tmp[idx]+1 != tmp[idx+1] {
return tmp[idx] + 1, nil
}
}
if tmp[len(tmp)-1] == MAX_VALUE {
return -1, ErrNoAvailableValues
}
return tmp[len(tmp)-1] + 1, nil
}
}
return MIN_VALUE, nil
}