woodpecker/vendor/github.com/djherbis/fscache/fs.go

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2016-04-13 00:27:24 +00:00
package fscache
import (
"bytes"
"crypto/md5"
"crypto/rand"
"encoding/base64"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
"time"
"gopkg.in/djherbis/atime.v1"
"gopkg.in/djherbis/stream.v1"
)
// FileSystem is used as the source for a Cache.
type FileSystem interface {
// Stream FileSystem
stream.FileSystem
// Reload should look through the FileSystem and call the suplied fn
// with the key/filename pairs that are found.
Reload(func(key, name string)) error
// RemoveAll should empty the FileSystem of all files.
RemoveAll() error
// AccessTimes takes a File.Name() and returns the last time the file was read,
// and the last time it was written to.
// It will be used to check expiry of a file, and must be concurrent safe
// with modifications to the FileSystem (writes, reads etc.)
AccessTimes(name string) (rt, wt time.Time, err error)
}
type stdFs struct {
root string
}
// NewFs returns a FileSystem rooted at directory dir.
// Dir is created with perms if it doesn't exist.
func NewFs(dir string, mode os.FileMode) (FileSystem, error) {
return &stdFs{root: dir}, os.MkdirAll(dir, mode)
}
func (fs *stdFs) Reload(add func(key, name string)) error {
files, err := ioutil.ReadDir(fs.root)
if err != nil {
return err
}
addfiles := make(map[string]struct {
os.FileInfo
key string
})
for _, f := range files {
if strings.HasSuffix(f.Name(), ".key") {
continue
}
key, err := fs.getKey(f.Name())
if err != nil {
return err
}
fi, ok := addfiles[key]
if !ok || fi.ModTime().Before(f.ModTime()) {
if ok {
fs.Remove(fi.Name())
}
addfiles[key] = struct {
os.FileInfo
key string
}{
FileInfo: f,
key: key,
}
} else {
fs.Remove(f.Name())
}
}
for _, f := range addfiles {
path, err := filepath.Abs(filepath.Join(fs.root, f.Name()))
if err != nil {
return err
}
add(f.key, path)
}
return nil
}
func (fs *stdFs) Create(name string) (stream.File, error) {
name, err := fs.makeName(name)
if err != nil {
return nil, err
}
return fs.create(name)
}
func (fs *stdFs) create(name string) (stream.File, error) {
return os.OpenFile(filepath.Join(fs.root, name), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
}
func (fs *stdFs) Open(name string) (stream.File, error) {
return os.Open(name)
}
func (fs *stdFs) Remove(name string) error {
os.Remove(fmt.Sprintf("%s.key", name))
return os.Remove(name)
}
func (fs *stdFs) RemoveAll() error {
return os.RemoveAll(fs.root)
}
func (fs *stdFs) AccessTimes(name string) (rt, wt time.Time, err error) {
fi, err := os.Stat(name)
if err != nil {
return rt, wt, err
}
return atime.Get(fi), fi.ModTime(), nil
}
const (
saltSize = 8
maxShort = 20
shortPrefix = "s"
longPrefix = "l"
)
func salt() string {
buf := bytes.NewBufferString("")
enc := base64.NewEncoder(base64.URLEncoding, buf)
io.CopyN(enc, rand.Reader, saltSize)
return buf.String()
}
func tob64(s string) string {
buf := bytes.NewBufferString("")
enc := base64.NewEncoder(base64.URLEncoding, buf)
enc.Write([]byte(s))
enc.Close()
return buf.String()
}
func fromb64(s string) string {
buf := bytes.NewBufferString(s)
dec := base64.NewDecoder(base64.URLEncoding, buf)
out := bytes.NewBufferString("")
io.Copy(out, dec)
return out.String()
}
func (fs *stdFs) makeName(key string) (string, error) {
b64key := tob64(key)
// short name
if len(b64key) < maxShort {
return fmt.Sprintf("%s%s%s", shortPrefix, salt(), b64key), nil
}
// long name
hash := md5.Sum([]byte(key))
name := fmt.Sprintf("%s%s%x", longPrefix, salt(), hash[:])
f, err := fs.create(fmt.Sprintf("%s.key", name))
if err != nil {
return "", err
}
_, err = f.Write([]byte(key))
f.Close()
return name, err
}
func (fs *stdFs) getKey(name string) (string, error) {
// short name
if strings.HasPrefix(name, shortPrefix) {
return fromb64(strings.TrimPrefix(name, shortPrefix)[saltSize:]), nil
}
// long name
f, err := fs.Open(filepath.Join(fs.root, fmt.Sprintf("%s.key", name)))
if err != nil {
return "", err
}
defer f.Close()
key, err := ioutil.ReadAll(f)
if err != nil {
return "", err
}
return string(key), nil
}