distribution/storagedriver/inmemory/mfs.go
2014-12-08 21:08:07 -08:00

330 lines
5.8 KiB
Go

package inmemory
import (
"fmt"
"io"
"path"
"sort"
"strings"
"time"
)
var (
errExists = fmt.Errorf("exists")
errNotExists = fmt.Errorf("exists")
errIsNotDir = fmt.Errorf("notdir")
errIsDir = fmt.Errorf("isdir")
)
type node interface {
name() string
path() string
isdir() bool
modtime() time.Time
}
// dir is the central type for the memory-based storagedriver. All operations
// are dispatched from a root dir.
type dir struct {
common
// TODO(stevvooe): Use sorted slice + search.
children map[string]node
}
var _ node = &dir{}
func (d *dir) isdir() bool {
return true
}
// add places the node n into dir d.
func (d *dir) add(n node) {
if d.children == nil {
d.children = make(map[string]node)
}
d.children[n.name()] = n
d.mod = time.Now()
}
// find searches for the node, given path q in dir. If the node is found, it
// will be returned. If the node is not found, the closet existing parent. If
// the node is found, the returned (node).path() will match q.
func (d *dir) find(q string) node {
q = strings.Trim(q, "/")
i := strings.Index(q, "/")
if q == "" {
return d
}
if i == 0 {
panic("shouldn't happen, no root paths")
}
var component string
if i < 0 {
// No more path components
component = q
} else {
component = q[:i]
}
child, ok := d.children[component]
if !ok {
// Node was not found. Return p and the current node.
return d
}
if child.isdir() {
// traverse down!
q = q[i+1:]
return child.(*dir).find(q)
}
return child
}
func (d *dir) list(p string) ([]string, error) {
n := d.find(p)
if n.path() != p {
return nil, errNotExists
}
if !n.isdir() {
return nil, errIsNotDir
}
var children []string
for _, child := range n.(*dir).children {
children = append(children, child.path())
}
sort.Strings(children)
return children, nil
}
// mkfile or return the existing one. returns an error if it exists and is a
// directory. Essentially, this is open or create.
func (d *dir) mkfile(p string) (*file, error) {
n := d.find(p)
if n.path() == p {
if n.isdir() {
return nil, errIsDir
}
return n.(*file), nil
}
dirpath, filename := path.Split(p)
// Make any non-existent directories
n, err := d.mkdirs(dirpath)
if err != nil {
return nil, err
}
dd := n.(*dir)
n = &file{
common: common{
p: path.Join(dd.path(), filename),
mod: time.Now(),
},
}
dd.add(n)
return n.(*file), nil
}
// mkdirs creates any missing directory entries in p and returns the result.
func (d *dir) mkdirs(p string) (*dir, error) {
if p == "" {
p = "/"
}
n := d.find(p)
if !n.isdir() {
// Found something there
return nil, errIsNotDir
}
if n.path() == p {
return n.(*dir), nil
}
dd := n.(*dir)
relative := strings.Trim(strings.TrimPrefix(p, n.path()), "/")
if relative == "" {
return dd, nil
}
components := strings.Split(relative, "/")
for _, component := range components {
d, err := dd.mkdir(component)
if err != nil {
// This should actually never happen, since there are no children.
return nil, err
}
dd = d
}
return dd, nil
}
// mkdir creates a child directory under d with the given name.
func (d *dir) mkdir(name string) (*dir, error) {
if name == "" {
return nil, fmt.Errorf("invalid dirname")
}
_, ok := d.children[name]
if ok {
return nil, errExists
}
child := &dir{
common: common{
p: path.Join(d.path(), name),
mod: time.Now(),
},
}
d.add(child)
d.mod = time.Now()
return child, nil
}
func (d *dir) move(src, dst string) error {
dstDirname, _ := path.Split(dst)
dp, err := d.mkdirs(dstDirname)
if err != nil {
return err
}
srcDirname, srcFilename := path.Split(src)
sp := d.find(srcDirname)
if sp.path() != srcDirname {
return errNotExists
}
s, ok := sp.(*dir).children[srcFilename]
if !ok {
return errNotExists
}
delete(sp.(*dir).children, srcFilename)
switch n := s.(type) {
case *dir:
n.p = dst
case *file:
n.p = dst
}
dp.add(s)
return nil
}
func (d *dir) delete(p string) error {
dirname, filename := path.Split(p)
parent := d.find(dirname)
if dirname != parent.path() {
return errNotExists
}
if _, ok := parent.(*dir).children[filename]; !ok {
return errNotExists
}
delete(parent.(*dir).children, filename)
return nil
}
// dump outputs a primitive directory structure to stdout.
func (d *dir) dump(indent string) {
fmt.Println(indent, d.name()+"/")
for _, child := range d.children {
if child.isdir() {
child.(*dir).dump(indent + "\t")
} else {
fmt.Println(indent, child.name())
}
}
}
func (d *dir) String() string {
return fmt.Sprintf("&dir{path: %v, children: %v}", d.p, d.children)
}
// file stores actual data in the fs tree. It acts like an open, seekable file
// where operations are conducted through ReadAt and WriteAt. Use it with
// SectionReader for the best effect.
type file struct {
common
data []byte
}
var _ node = &file{}
func (f *file) isdir() bool {
return false
}
func (f *file) truncate() {
f.data = f.data[:0]
}
func (f *file) sectionReader(offset int64) io.Reader {
return io.NewSectionReader(f, offset, int64(len(f.data))-offset)
}
func (f *file) ReadAt(p []byte, offset int64) (n int, err error) {
return copy(p, f.data[offset:]), nil
}
func (f *file) WriteAt(p []byte, offset int64) (n int, err error) {
off := int(offset)
if cap(f.data) < off+len(p) {
data := make([]byte, len(f.data), off+len(p))
copy(data, f.data)
f.data = data
}
f.data = f.data[:off+len(p)]
return copy(f.data[off:off+len(p)], p), nil
}
func (f *file) String() string {
return fmt.Sprintf("&file{path: %q}", f.p)
}
// common provides shared fields and methods for node implementations.
type common struct {
p string
mod time.Time
}
func (c *common) name() string {
_, name := path.Split(c.p)
return name
}
func (c *common) path() string {
return c.p
}
func (c *common) modtime() time.Time {
return c.mod
}