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inidb.go
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inidb.go
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// Copyright (c) 2016 Company 0, LLC.
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
// inidb package uses a regular ini file as a database. Ini sections are
// considered tables. Individual entries are considered records and are
// key = value pairs.
//
// The package assumes that the user will create a single inidb per directory.
package inidb
import (
"errors"
"fmt"
"io/ioutil"
"os"
"path"
"strings"
"sync"
"time"
"github.com/vaughan0/go-ini"
)
const (
auto = "# This file is autogenerated, DO NOT EDIT!"
)
var (
ErrNotFound = errors.New("record not found")
ErrCreated = errors.New("database created")
)
// INIDB is an opaque structure that contains the database context.
type INIDB struct {
mtx sync.Mutex // mutex for this structure
filename string // inidb full path
depth int // max journal files that are kept
dirty bool // like your mom
created bool // db was created
tables ini.File // ini sections
}
// New returns a new INIDB context. Depth contains the maximum number of files
// that are retained. Create indicates if the database should be created if it
// doesn't exist. If depth is negative there is no limit. If the ini file does
// not exist it returns an error.
// The inidb package assumes there is only one inidb per directory. DO NOT
// CREATE MULTIPLE INIDBS IN A SINGLE DIRECTORY.
func New(filename string, create bool, depth int) (*INIDB, error) {
i := INIDB{
filename: filename,
depth: depth,
}
_, err := os.Stat(path.Dir(filename))
if os.IsNotExist(err) && create {
err = os.MkdirAll(path.Dir(filename), 0700)
if err != nil {
return nil, fmt.Errorf("could not create directory: %v",
err)
}
} else if err != nil {
return nil, fmt.Errorf("could not create lock %v: %v",
path.Dir(filename), err)
}
i.tables, err = ini.LoadFile(filename)
i.tables.Section("") // default always exists
if os.IsNotExist(err) && create {
// save empty file
i.created = true
i.dirty = true
err2 := i.Save()
if err2 != nil {
return nil, err2
}
err = ErrCreated // indicate we just created it
} else if err != nil {
return nil, fmt.Errorf("could not open %v: %v", filename, err)
}
return &i, err
}
// Save flushes current in memory database back to disk. The process is as
// follows:
// 1. Check if the database is dirty and abort process if it isn't
// 2. Create temporary file that contains all memory tables and records
// 3. Backup original file
// 4. Rename temporary file to the original file name
// This creates a running log of flushes.
//
// NOTE: currently there is no file count limiter.
func (i *INIDB) Save() error {
i.mtx.Lock()
defer i.mtx.Unlock()
if !i.dirty {
return nil
}
f, err := ioutil.TempFile(path.Dir(i.filename), path.Base(i.filename))
if err != nil {
return fmt.Errorf("could not create temporary file: %v", err)
}
// save all records
fmt.Fprintf(f, "%v\n", auto)
for tk, tv := range i.tables {
if tk != "" {
fmt.Fprintf(f, "[%v]\n", tk)
}
for rk, rv := range tv {
fmt.Fprintf(f, "%v = %v\n", rk, rv)
}
fmt.Fprintf(f, "\n")
}
f.Close()
// backup original
if !i.created {
backup := fmt.Sprintf("%v.%v",
i.filename,
time.Now().Format("20060102.150405.000000000"))
err = os.Rename(i.filename, backup)
if err != nil {
return fmt.Errorf("could not rename original file: %v",
err)
}
}
// rename new one
err = os.Rename(f.Name(), i.filename)
if err != nil {
return fmt.Errorf("could not rename new file: %v", err)
}
i.dirty = false
return i.prune()
}
func (i *INIDB) prune() error {
if i.depth < 0 {
return nil
}
d, err := ioutil.ReadDir(path.Dir(i.filename))
if err != nil {
return fmt.Errorf("could not read directory %v: %v",
path.Dir(i.filename), err)
}
// create prune list
pl := make([]string, 0, len(d))
find := path.Base(i.filename) + "."
for _, v := range d {
if !strings.HasPrefix(v.Name(), find) {
continue
}
pl = append(pl, v.Name())
}
// actually prune
if len(pl)-i.depth < 0 {
return nil
}
for _, v := range pl[:len(pl)-i.depth] {
_ = os.Remove(path.Join(path.Dir(i.filename), v))
}
return nil
}
// Get returns a record from table. If the record does not exist ErrNotFound
// is returned.
func (i *INIDB) Get(table string, key string) (string, error) {
i.mtx.Lock()
defer i.mtx.Unlock()
value, ok := i.tables.Get(table, key)
if !ok {
return "", ErrNotFound
}
return value, nil
}
// Set creates/overwrites a record in table. If table does not exist
// ErrNotFound is returned.
func (i *INIDB) Set(table, key, value string) error {
i.mtx.Lock()
defer i.mtx.Unlock()
s, ok := i.tables[table]
if !ok {
return ErrNotFound
}
s[key] = value
i.dirty = true
return nil
}
// Del remove a record from a table.
func (i *INIDB) Del(table, key string) error {
i.mtx.Lock()
defer i.mtx.Unlock()
s, ok := i.tables[table]
if !ok {
return ErrNotFound
}
delete(s, key)
i.dirty = true
return nil
}
// NewTable creates a new table.
func (i *INIDB) NewTable(table string) {
i.mtx.Lock()
defer i.mtx.Unlock()
i.tables.Section(table)
}
// DelTable deletes an entire table including all records.
func (i *INIDB) DelTable(table string) error {
i.mtx.Lock()
defer i.mtx.Unlock()
_, ok := i.tables[table]
if !ok {
return ErrNotFound
}
delete(i.tables, table)
i.dirty = true
return nil
}
// Records returns a copy of all records in the given table.
func (i *INIDB) Records(table string) map[string]string {
i.mtx.Lock()
defer i.mtx.Unlock()
t := make(map[string]string)
for k, v := range i.tables[table] {
t[k] = v
}
return t
}
// Tables returns a copy of all tables in the inidb.
func (i *INIDB) Tables() []string {
i.mtx.Lock()
defer i.mtx.Unlock()
tables := make([]string, 0, len(i.tables))
for k := range i.tables {
tables = append(tables, k)
}
return tables
}