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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package webdav
import (
"container/heap"
"errors"
"strconv"
"strings"
"sync"
"time"
)
var (
// ErrConfirmationFailed is returned by a LockSystem's Confirm method.
ErrConfirmationFailed = errors.New("webdav: confirmation failed")
// ErrForbidden is returned by a LockSystem's Unlock method.
ErrForbidden = errors.New("webdav: forbidden")
// ErrLocked is returned by a LockSystem's Create, Refresh and Unlock methods.
ErrLocked = errors.New("webdav: locked")
// ErrNoSuchLock is returned by a LockSystem's Refresh and Unlock methods.
ErrNoSuchLock = errors.New("webdav: no such lock")
)
// Condition can match a WebDAV resource, based on a token or ETag.
// Exactly one of Token and ETag should be non-empty.
type Condition struct {
Not bool
Token string
ETag string
}
// LockSystem manages access to a collection of named resources. The elements
// in a lock name are separated by slash ('/', U+002F) characters, regardless
// of host operating system convention.
type LockSystem interface {
// Confirm confirms that the caller can claim all of the locks specified by
// the given conditions, and that holding the union of all of those locks
// gives exclusive access to all of the named resources. Up to two resources
// can be named. Empty names are ignored.
//
// Exactly one of release and err will be non-nil. If release is non-nil,
// all of the requested locks are held until release is called. Calling
// release does not unlock the lock, in the WebDAV UNLOCK sense, but once
// Confirm has confirmed that a lock claim is valid, that lock cannot be
// Confirmed again until it has been released.
//
// If Confirm returns ErrConfirmationFailed then the Handler will continue
// to try any other set of locks presented (a WebDAV HTTP request can
// present more than one set of locks). If it returns any other non-nil
// error, the Handler will write a "500 Internal Server Error" HTTP status.
Confirm(now time.Time, name0, name1 string, conditions ...Condition) (release func(), err error)
// Create creates a lock with the given depth, duration, owner and root
// (name). The depth will either be negative (meaning infinite) or zero.
//
// If Create returns ErrLocked then the Handler will write a "423 Locked"
// HTTP status. If it returns any other non-nil error, the Handler will
// write a "500 Internal Server Error" HTTP status.
//
// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.10.6 for
// when to use each error.
//
// The token returned identifies the created lock. It should be an absolute
// URI as defined by RFC 3986, Section 4.3. In particular, it should not
// contain whitespace.
Create(now time.Time, details LockDetails) (token string, err error)
// Refresh refreshes the lock with the given token.
//
// If Refresh returns ErrLocked then the Handler will write a "423 Locked"
// HTTP Status. If Refresh returns ErrNoSuchLock then the Handler will write
// a "412 Precondition Failed" HTTP Status. If it returns any other non-nil
// error, the Handler will write a "500 Internal Server Error" HTTP status.
//
// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.10.6 for
// when to use each error.
Refresh(now time.Time, token string, duration time.Duration) (LockDetails, error)
// Unlock unlocks the lock with the given token.
//
// If Unlock returns ErrForbidden then the Handler will write a "403
// Forbidden" HTTP Status. If Unlock returns ErrLocked then the Handler
// will write a "423 Locked" HTTP status. If Unlock returns ErrNoSuchLock
// then the Handler will write a "409 Conflict" HTTP Status. If it returns
// any other non-nil error, the Handler will write a "500 Internal Server
// Error" HTTP status.
//
// See http://www.webdav.org/specs/rfc4918.html#rfc.section.9.11.1 for
// when to use each error.
Unlock(now time.Time, token string) error
}
// LockDetails are a lock's metadata.
type LockDetails struct {
// Root is the root resource name being locked. For a zero-depth lock, the
// root is the only resource being locked.
Root string
// Duration is the lock timeout. A negative duration means infinite.
Duration time.Duration
// OwnerXML is the verbatim <owner> XML given in a LOCK HTTP request.
//
// TODO: does the "verbatim" nature play well with XML namespaces?
// Does the OwnerXML field need to have more structure? See
// https://codereview.appspot.com/175140043/#msg2
OwnerXML string
// ZeroDepth is whether the lock has zero depth. If it does not have zero
// depth, it has infinite depth.
ZeroDepth bool
}
// NewMemLS returns a new in-memory LockSystem.
func NewMemLS() LockSystem {
return &memLS{
byName: make(map[string]*memLSNode),
byToken: make(map[string]*memLSNode),
gen: uint64(time.Now().Unix()),
}
}
type memLS struct {
mu sync.Mutex
byName map[string]*memLSNode
byToken map[string]*memLSNode
gen uint64
// byExpiry only contains those nodes whose LockDetails have a finite
// Duration and are yet to expire.
byExpiry byExpiry
}
func (m *memLS) nextToken() string {
m.gen++
return strconv.FormatUint(m.gen, 10)
}
func (m *memLS) collectExpiredNodes(now time.Time) {
for len(m.byExpiry) > 0 {
if now.Before(m.byExpiry[0].expiry) {
break
}
m.remove(m.byExpiry[0])
}
}
func (m *memLS) Confirm(now time.Time, name0, name1 string, conditions ...Condition) (func(), error) {
m.mu.Lock()
defer m.mu.Unlock()
m.collectExpiredNodes(now)
var n0, n1 *memLSNode
if name0 != "" {
if n0 = m.lookup(slashClean(name0), conditions...); n0 == nil {
return nil, ErrConfirmationFailed
}
}
if name1 != "" {
if n1 = m.lookup(slashClean(name1), conditions...); n1 == nil {
return nil, ErrConfirmationFailed
}
}
// Don't hold the same node twice.
if n1 == n0 {
n1 = nil
}
if n0 != nil {
m.hold(n0)
}
if n1 != nil {
m.hold(n1)
}
return func() {
m.mu.Lock()
defer m.mu.Unlock()
if n1 != nil {
m.unhold(n1)
}
if n0 != nil {
m.unhold(n0)
}
}, nil
}
// lookup returns the node n that locks the named resource, provided that n
// matches at least one of the given conditions and that lock isn't held by
// another party. Otherwise, it returns nil.
//
// n may be a parent of the named resource, if n is an infinite depth lock.
func (m *memLS) lookup(name string, conditions ...Condition) (n *memLSNode) {
// TODO: support Condition.Not and Condition.ETag.
for _, c := range conditions {
n = m.byToken[c.Token]
if n == nil || n.held {
continue
}
if name == n.details.Root {
return n
}
if n.details.ZeroDepth {
continue
}
if n.details.Root == "/" || strings.HasPrefix(name, n.details.Root+"/") {
return n
}
}
return nil
}
func (m *memLS) hold(n *memLSNode) {
if n.held {
panic("webdav: memLS inconsistent held state")
}
n.held = true
if n.details.Duration >= 0 && n.byExpiryIndex >= 0 {
heap.Remove(&m.byExpiry, n.byExpiryIndex)
}
}
func (m *memLS) unhold(n *memLSNode) {
if !n.held {
panic("webdav: memLS inconsistent held state")
}
n.held = false
if n.details.Duration >= 0 {
heap.Push(&m.byExpiry, n)
}
}
func (m *memLS) Create(now time.Time, details LockDetails) (string, error) {
m.mu.Lock()
defer m.mu.Unlock()
m.collectExpiredNodes(now)
details.Root = slashClean(details.Root)
if !m.canCreate(details.Root, details.ZeroDepth) {
return "", ErrLocked
}
n := m.create(details.Root)
n.token = m.nextToken()
m.byToken[n.token] = n
n.details = details
if n.details.Duration >= 0 {
n.expiry = now.Add(n.details.Duration)
heap.Push(&m.byExpiry, n)
}
return n.token, nil
}
func (m *memLS) Refresh(now time.Time, token string, duration time.Duration) (LockDetails, error) {
m.mu.Lock()
defer m.mu.Unlock()
m.collectExpiredNodes(now)
n := m.byToken[token]
if n == nil {
return LockDetails{}, ErrNoSuchLock
}
if n.held {
return LockDetails{}, ErrLocked
}
if n.byExpiryIndex >= 0 {
heap.Remove(&m.byExpiry, n.byExpiryIndex)
}
n.details.Duration = duration
if n.details.Duration >= 0 {
n.expiry = now.Add(n.details.Duration)
heap.Push(&m.byExpiry, n)
}
return n.details, nil
}
func (m *memLS) Unlock(now time.Time, token string) error {
m.mu.Lock()
defer m.mu.Unlock()
m.collectExpiredNodes(now)
n := m.byToken[token]
if n == nil {
return ErrNoSuchLock
}
if n.held {
return ErrLocked
}
m.remove(n)
return nil
}
func (m *memLS) canCreate(name string, zeroDepth bool) bool {
return walkToRoot(name, func(name0 string, first bool) bool {
n := m.byName[name0]
if n == nil {
return true
}
if first {
if n.token != "" {
// The target node is already locked.
return false
}
if !zeroDepth {
// The requested lock depth is infinite, and the fact that n exists
// (n != nil) means that a descendent of the target node is locked.
return false
}
} else if n.token != "" && !n.details.ZeroDepth {
// An ancestor of the target node is locked with infinite depth.
return false
}
return true
})
}
func (m *memLS) create(name string) (ret *memLSNode) {
walkToRoot(name, func(name0 string, first bool) bool {
n := m.byName[name0]
if n == nil {
n = &memLSNode{
details: LockDetails{
Root: name0,
},
byExpiryIndex: -1,
}
m.byName[name0] = n
}
n.refCount++
if first {
ret = n
}
return true
})
return ret
}
func (m *memLS) remove(n *memLSNode) {
delete(m.byToken, n.token)
n.token = ""
walkToRoot(n.details.Root, func(name0 string, first bool) bool {
x := m.byName[name0]
x.refCount--
if x.refCount == 0 {
delete(m.byName, name0)
}
return true
})
if n.byExpiryIndex >= 0 {
heap.Remove(&m.byExpiry, n.byExpiryIndex)
}
}
func walkToRoot(name string, f func(name0 string, first bool) bool) bool {
for first := true; ; first = false {
if !f(name, first) {
return false
}
if name == "/" {
break
}
name = name[:strings.LastIndex(name, "/")]
if name == "" {
name = "/"
}
}
return true
}
type memLSNode struct {
// details are the lock metadata. Even if this node's name is not explicitly locked,
// details.Root will still equal the node's name.
details LockDetails
// token is the unique identifier for this node's lock. An empty token means that
// this node is not explicitly locked.
token string
// refCount is the number of self-or-descendent nodes that are explicitly locked.
refCount int
// expiry is when this node's lock expires.
expiry time.Time
// byExpiryIndex is the index of this node in memLS.byExpiry. It is -1
// if this node does not expire, or has expired.
byExpiryIndex int
// held is whether this node's lock is actively held by a Confirm call.
held bool
}
type byExpiry []*memLSNode
func (b *byExpiry) Len() int {
return len(*b)
}
func (b *byExpiry) Less(i, j int) bool {
return (*b)[i].expiry.Before((*b)[j].expiry)
}
func (b *byExpiry) Swap(i, j int) {
(*b)[i], (*b)[j] = (*b)[j], (*b)[i]
(*b)[i].byExpiryIndex = i
(*b)[j].byExpiryIndex = j
}
func (b *byExpiry) Push(x interface{}) {
n := x.(*memLSNode)
n.byExpiryIndex = len(*b)
*b = append(*b, n)
}
func (b *byExpiry) Pop() interface{} {
i := len(*b) - 1
n := (*b)[i]
(*b)[i] = nil
n.byExpiryIndex = -1
*b = (*b)[:i]
return n
}
const infiniteTimeout = -1
// parseTimeout parses the Timeout HTTP header, as per section 10.7. If s is
// empty, an infiniteTimeout is returned.
func parseTimeout(s string) (time.Duration, error) {
if s == "" {
return infiniteTimeout, nil
}
if i := strings.IndexByte(s, ','); i >= 0 {
s = s[:i]
}
s = strings.TrimSpace(s)
if s == "Infinite" {
return infiniteTimeout, nil
}
const pre = "Second-"
if !strings.HasPrefix(s, pre) {
return 0, errInvalidTimeout
}
s = s[len(pre):]
if s == "" || s[0] < '0' || '9' < s[0] {
return 0, errInvalidTimeout
}
n, err := strconv.ParseInt(s, 10, 64)
if err != nil || 1<<32-1 < n {
return 0, errInvalidTimeout
}
return time.Duration(n) * time.Second, nil
}
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