webdav/prop.go - net - Git at Google

 // Copyright 2015 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 (
 	"bytes"
 	"encoding/xml"
 	"fmt"
 	"io"
 	"mime"
 	"net/http"
 	"os"
 	"path/filepath"
 	"strconv"

 	"golang.org/x/net/context"
 )

 // Proppatch describes a property update instruction as defined in RFC 4918.
 // See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPPATCH
 type Proppatch struct {
 	// Remove specifies whether this patch removes properties. If it does not
 	// remove them, it sets them.
 	Remove bool
 	// Props contains the properties to be set or removed.
 	Props []Property
 }

 // Propstat describes a XML propstat element as defined in RFC 4918.
 // See http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat
 type Propstat struct {
 	// Props contains the properties for which Status applies.
 	Props []Property

 	// Status defines the HTTP status code of the properties in Prop.
 	// Allowed values include, but are not limited to the WebDAV status
 	// code extensions for HTTP/1.1.
 	// http://www.webdav.org/specs/rfc4918.html#status.code.extensions.to.http11
 	Status int

 	// XMLError contains the XML representation of the optional error element.
 	// XML content within this field must not rely on any predefined
 	// namespace declarations or prefixes. If empty, the XML error element
 	// is omitted.
 	XMLError string

 	// ResponseDescription contains the contents of the optional
 	// responsedescription field. If empty, the XML element is omitted.
 	ResponseDescription string
 }

 // makePropstats returns a slice containing those of x and y whose Props slice
 // is non-empty. If both are empty, it returns a slice containing an otherwise
 // zero Propstat whose HTTP status code is 200 OK.
 func makePropstats(x, y Propstat) []Propstat {
 	pstats := make([]Propstat, 0, 2)
 	if len(x.Props) != 0 {
 		pstats = append(pstats, x)
 	}
 	if len(y.Props) != 0 {
 		pstats = append(pstats, y)
 	}
 	if len(pstats) == 0 {
 		pstats = append(pstats, Propstat{
 			Status: http.StatusOK,
 		})
 	}
 	return pstats
 }

 // DeadPropsHolder holds the dead properties of a resource.
 //
 // Dead properties are those properties that are explicitly defined. In
 // comparison, live properties, such as DAV:getcontentlength, are implicitly
 // defined by the underlying resource, and cannot be explicitly overridden or
 // removed. See the Terminology section of
 // http://www.webdav.org/specs/rfc4918.html#rfc.section.3
 //
 // There is a whitelist of the names of live properties. This package handles
 // all live properties, and will only pass non-whitelisted names to the Patch
 // method of DeadPropsHolder implementations.
 type DeadPropsHolder interface {
 	// DeadProps returns a copy of the dead properties held.
 	DeadProps() (map[xml.Name]Property, error)

 	// Patch patches the dead properties held.
 	//
 	// Patching is atomic; either all or no patches succeed. It returns (nil,
 	// non-nil) if an internal server error occurred, otherwise the Propstats
 	// collectively contain one Property for each proposed patch Property. If
 	// all patches succeed, Patch returns a slice of length one and a Propstat
 	// element with a 200 OK HTTP status code. If none succeed, for reasons
 	// other than an internal server error, no Propstat has status 200 OK.
 	//
 	// For more details on when various HTTP status codes apply, see
 	// http://www.webdav.org/specs/rfc4918.html#PROPPATCH-status
 	Patch([]Proppatch) ([]Propstat, error)
 }

 // liveProps contains all supported, protected DAV: properties.
 var liveProps = map[xml.Name]struct {
 	// findFn implements the propfind function of this property. If nil,
 	// it indicates a hidden property.
 	findFn func(context.Context, FileSystem, LockSystem, string, os.FileInfo) (string, error)
 	// dir is true if the property applies to directories.
 	dir bool
 }{
 	{Space: "DAV:", Local: "resourcetype"}: {
 		findFn: findResourceType,
 		dir:    true,
 	},
 	{Space: "DAV:", Local: "displayname"}: {
 		findFn: findDisplayName,
 		dir:    true,
 	},
 	{Space: "DAV:", Local: "getcontentlength"}: {
 		findFn: findContentLength,
 		dir:    false,
 	},
 	{Space: "DAV:", Local: "getlastmodified"}: {
 		findFn: findLastModified,
 		// http://webdav.org/specs/rfc4918.html#PROPERTY_getlastmodified
 		// suggests that getlastmodified should only apply to GETable
 		// resources, and this package does not support GET on directories.
 		//
 		// Nonetheless, some WebDAV clients expect child directories to be
 		// sortable by getlastmodified date, so this value is true, not false.
 		// See golang.org/issue/15334.
 		dir: true,
 	},
 	{Space: "DAV:", Local: "creationdate"}: {
 		findFn: nil,
 		dir:    false,
 	},
 	{Space: "DAV:", Local: "getcontentlanguage"}: {
 		findFn: nil,
 		dir:    false,
 	},
 	{Space: "DAV:", Local: "getcontenttype"}: {
 		findFn: findContentType,
 		dir:    false,
 	},
 	{Space: "DAV:", Local: "getetag"}: {
 		findFn: findETag,
 		// findETag implements ETag as the concatenated hex values of a file's
 		// modification time and size. This is not a reliable synchronization
 		// mechanism for directories, so we do not advertise getetag for DAV
 		// collections.
 		dir: false,
 	},

 	// TODO: The lockdiscovery property requires LockSystem to list the
 	// active locks on a resource.
 	{Space: "DAV:", Local: "lockdiscovery"}: {},
 	{Space: "DAV:", Local: "supportedlock"}: {
 		findFn: findSupportedLock,
 		dir:    true,
 	},
 }

 // TODO(nigeltao) merge props and allprop?

 // Props returns the status of the properties named pnames for resource name.
 //
 // Each Propstat has a unique status and each property name will only be part
 // of one Propstat element.
 func props(ctx context.Context, fs FileSystem, ls LockSystem, name string, pnames []xml.Name) ([]Propstat, error) {
 	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
 	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
 	fi, err := f.Stat()
 	if err != nil {
 		return nil, err
 	}
 	isDir := fi.IsDir()

 	var deadProps map[xml.Name]Property
 	if dph, ok := f.(DeadPropsHolder); ok {
 		deadProps, err = dph.DeadProps()
 		if err != nil {
 			return nil, err
 		}
 	}

 	pstatOK := Propstat{Status: http.StatusOK}
 	pstatNotFound := Propstat{Status: http.StatusNotFound}
 	for _, pn := range pnames {
 		// If this file has dead properties, check if they contain pn.
 		if dp, ok := deadProps[pn]; ok {
 			pstatOK.Props = append(pstatOK.Props, dp)
 			continue
 		}
 		// Otherwise, it must either be a live property or we don't know it.
 		if prop := liveProps[pn]; prop.findFn != nil && (prop.dir || !isDir) {
 			innerXML, err := prop.findFn(ctx, fs, ls, name, fi)
 			if err != nil {
 				return nil, err
 			}
 			pstatOK.Props = append(pstatOK.Props, Property{
 				XMLName:  pn,
 				InnerXML: []byte(innerXML),
 			})
 		} else {
 			pstatNotFound.Props = append(pstatNotFound.Props, Property{
 				XMLName: pn,
 			})
 		}
 	}
 	return makePropstats(pstatOK, pstatNotFound), nil
 }

 // Propnames returns the property names defined for resource name.
 func propnames(ctx context.Context, fs FileSystem, ls LockSystem, name string) ([]xml.Name, error) {
 	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
 	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
 	fi, err := f.Stat()
 	if err != nil {
 		return nil, err
 	}
 	isDir := fi.IsDir()

 	var deadProps map[xml.Name]Property
 	if dph, ok := f.(DeadPropsHolder); ok {
 		deadProps, err = dph.DeadProps()
 		if err != nil {
 			return nil, err
 		}
 	}

 	pnames := make([]xml.Name, 0, len(liveProps)+len(deadProps))
 	for pn, prop := range liveProps {
 		if prop.findFn != nil && (prop.dir || !isDir) {
 			pnames = append(pnames, pn)
 		}
 	}
 	for pn := range deadProps {
 		pnames = append(pnames, pn)
 	}
 	return pnames, nil
 }

 // Allprop returns the properties defined for resource name and the properties
 // named in include.
 //
 // Note that RFC 4918 defines 'allprop' to return the DAV: properties defined
 // within the RFC plus dead properties. Other live properties should only be
 // returned if they are named in 'include'.
 //
 // See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPFIND
 func allprop(ctx context.Context, fs FileSystem, ls LockSystem, name string, include []xml.Name) ([]Propstat, error) {
 	pnames, err := propnames(ctx, fs, ls, name)
 	if err != nil {
 		return nil, err
 	}
 	// Add names from include if they are not already covered in pnames.
 	nameset := make(map[xml.Name]bool)
 	for _, pn := range pnames {
 		nameset[pn] = true
 	}
 	for _, pn := range include {
 		if !nameset[pn] {
 			pnames = append(pnames, pn)
 		}
 	}
 	return props(ctx, fs, ls, name, pnames)
 }

 // Patch patches the properties of resource name. The return values are
 // constrained in the same manner as DeadPropsHolder.Patch.
 func patch(ctx context.Context, fs FileSystem, ls LockSystem, name string, patches []Proppatch) ([]Propstat, error) {
 	conflict := false
 loop:
 	for _, patch := range patches {
 		for _, p := range patch.Props {
 			if _, ok := liveProps[p.XMLName]; ok {
 				conflict = true
 				break loop
 			}
 		}
 	}
 	if conflict {
 		pstatForbidden := Propstat{
 			Status:   http.StatusForbidden,
 			XMLError: `<D:cannot-modify-protected-property xmlns:D="DAV:"/>`,
 		}
 		pstatFailedDep := Propstat{
 			Status: StatusFailedDependency,
 		}
 		for _, patch := range patches {
 			for _, p := range patch.Props {
 				if _, ok := liveProps[p.XMLName]; ok {
 					pstatForbidden.Props = append(pstatForbidden.Props, Property{XMLName: p.XMLName})
 				} else {
 					pstatFailedDep.Props = append(pstatFailedDep.Props, Property{XMLName: p.XMLName})
 				}
 			}
 		}
 		return makePropstats(pstatForbidden, pstatFailedDep), nil
 	}

 	f, err := fs.OpenFile(ctx, name, os.O_RDWR, 0)
 	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
 	if dph, ok := f.(DeadPropsHolder); ok {
 		ret, err := dph.Patch(patches)
 		if err != nil {
 			return nil, err
 		}
 		// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat says that
 		// "The contents of the prop XML element must only list the names of
 		// properties to which the result in the status element applies."
 		for _, pstat := range ret {
 			for i, p := range pstat.Props {
 				pstat.Props[i] = Property{XMLName: p.XMLName}
 			}
 		}
 		return ret, nil
 	}
 	// The file doesn't implement the optional DeadPropsHolder interface, so
 	// all patches are forbidden.
 	pstat := Propstat{Status: http.StatusForbidden}
 	for _, patch := range patches {
 		for _, p := range patch.Props {
 			pstat.Props = append(pstat.Props, Property{XMLName: p.XMLName})
 		}
 	}
 	return []Propstat{pstat}, nil
 }

 func escapeXML(s string) string {
 	for i := 0; i < len(s); i++ {
 		// As an optimization, if s contains only ASCII letters, digits or a
 		// few special characters, the escaped value is s itself and we don't
 		// need to allocate a buffer and convert between string and []byte.
 		switch c := s[i]; {
 		case c == ' ' || c == '_' ||
 			('+' <= c && c <= '9') || // Digits as well as + , - . and /
 			('A' <= c && c <= 'Z') ||
 			('a' <= c && c <= 'z'):
 			continue
 		}
 		// Otherwise, go through the full escaping process.
 		var buf bytes.Buffer
 		xml.EscapeText(&buf, []byte(s))
 		return buf.String()
 	}
 	return s
 }

 func findResourceType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	if fi.IsDir() {
 		return `<D:collection xmlns:D="DAV:"/>`, nil
 	}
 	return "", nil
 }

 func findDisplayName(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	if slashClean(name) == "/" {
 		// Hide the real name of a possibly prefixed root directory.
 		return "", nil
 	}
 	return escapeXML(fi.Name()), nil
 }

 func findContentLength(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	return strconv.FormatInt(fi.Size(), 10), nil
 }

 func findLastModified(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	return fi.ModTime().Format(http.TimeFormat), nil
 }

 func findContentType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
 	if err != nil {
 		return "", err
 	}
 	defer f.Close()
 	// This implementation is based on serveContent's code in the standard net/http package.
 	ctype := mime.TypeByExtension(filepath.Ext(name))
 	if ctype != "" {
 		return ctype, nil
 	}
 	// Read a chunk to decide between utf-8 text and binary.
 	var buf [512]byte
 	n, err := io.ReadFull(f, buf[:])
 	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
 		return "", err
 	}
 	ctype = http.DetectContentType(buf[:n])
 	// Rewind file.
 	_, err = f.Seek(0, os.SEEK_SET)
 	return ctype, err
 }

 func findETag(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	// The Apache http 2.4 web server by default concatenates the
 	// modification time and size of a file. We replicate the heuristic
 	// with nanosecond granularity.
 	return fmt.Sprintf(`"%x%x"`, fi.ModTime().UnixNano(), fi.Size()), nil
 }

 func findSupportedLock(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
 	return `` +
 		`<D:lockentry xmlns:D="DAV:">` +
 		`<D:lockscope><D:exclusive/></D:lockscope>` +
 		`<D:locktype><D:write/></D:locktype>` +
 		`</D:lockentry>`, nil
 }
	// Copyright 2015 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 (
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"mime"
	"net/http"
	"os"
	"path/filepath"
	"strconv"

	"golang.org/x/net/context"
	)

	// Proppatch describes a property update instruction as defined in RFC 4918.
	// See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPPATCH
	type Proppatch struct {
	// Remove specifies whether this patch removes properties. If it does not
	// remove them, it sets them.
	Remove bool
	// Props contains the properties to be set or removed.
	Props []Property
	}

	// Propstat describes a XML propstat element as defined in RFC 4918.
	// See http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat
	type Propstat struct {
	// Props contains the properties for which Status applies.
	Props []Property

	// Status defines the HTTP status code of the properties in Prop.
	// Allowed values include, but are not limited to the WebDAV status
	// code extensions for HTTP/1.1.
	// http://www.webdav.org/specs/rfc4918.html#status.code.extensions.to.http11
	Status int

	// XMLError contains the XML representation of the optional error element.
	// XML content within this field must not rely on any predefined
	// namespace declarations or prefixes. If empty, the XML error element
	// is omitted.
	XMLError string

	// ResponseDescription contains the contents of the optional
	// responsedescription field. If empty, the XML element is omitted.
	ResponseDescription string
	}

	// makePropstats returns a slice containing those of x and y whose Props slice
	// is non-empty. If both are empty, it returns a slice containing an otherwise
	// zero Propstat whose HTTP status code is 200 OK.
	func makePropstats(x, y Propstat) []Propstat {
	pstats := make([]Propstat, 0, 2)
	if len(x.Props) != 0 {
	pstats = append(pstats, x)
	}
	if len(y.Props) != 0 {
	pstats = append(pstats, y)
	}
	if len(pstats) == 0 {
	pstats = append(pstats, Propstat{
	Status: http.StatusOK,
	})
	}
	return pstats
	}

	// DeadPropsHolder holds the dead properties of a resource.
	//
	// Dead properties are those properties that are explicitly defined. In
	// comparison, live properties, such as DAV:getcontentlength, are implicitly
	// defined by the underlying resource, and cannot be explicitly overridden or
	// removed. See the Terminology section of
	// http://www.webdav.org/specs/rfc4918.html#rfc.section.3
	//
	// There is a whitelist of the names of live properties. This package handles
	// all live properties, and will only pass non-whitelisted names to the Patch
	// method of DeadPropsHolder implementations.
	type DeadPropsHolder interface {
	// DeadProps returns a copy of the dead properties held.
	DeadProps() (map[xml.Name]Property, error)

	// Patch patches the dead properties held.
	//
	// Patching is atomic; either all or no patches succeed. It returns (nil,
	// non-nil) if an internal server error occurred, otherwise the Propstats
	// collectively contain one Property for each proposed patch Property. If
	// all patches succeed, Patch returns a slice of length one and a Propstat
	// element with a 200 OK HTTP status code. If none succeed, for reasons
	// other than an internal server error, no Propstat has status 200 OK.
	//
	// For more details on when various HTTP status codes apply, see
	// http://www.webdav.org/specs/rfc4918.html#PROPPATCH-status
	Patch([]Proppatch) ([]Propstat, error)
	}

	// liveProps contains all supported, protected DAV: properties.
	var liveProps = map[xml.Name]struct {
	// findFn implements the propfind function of this property. If nil,
	// it indicates a hidden property.
	findFn func(context.Context, FileSystem, LockSystem, string, os.FileInfo) (string, error)
	// dir is true if the property applies to directories.
	dir bool
	}{
	{Space: "DAV:", Local: "resourcetype"}: {
	findFn: findResourceType,
	dir: true,
	},
	{Space: "DAV:", Local: "displayname"}: {
	findFn: findDisplayName,
	dir: true,
	},
	{Space: "DAV:", Local: "getcontentlength"}: {
	findFn: findContentLength,
	dir: false,
	},
	{Space: "DAV:", Local: "getlastmodified"}: {
	findFn: findLastModified,
	// http://webdav.org/specs/rfc4918.html#PROPERTY_getlastmodified
	// suggests that getlastmodified should only apply to GETable
	// resources, and this package does not support GET on directories.
	//
	// Nonetheless, some WebDAV clients expect child directories to be
	// sortable by getlastmodified date, so this value is true, not false.
	// See golang.org/issue/15334.
	dir: true,
	},
	{Space: "DAV:", Local: "creationdate"}: {
	findFn: nil,
	dir: false,
	},
	{Space: "DAV:", Local: "getcontentlanguage"}: {
	findFn: nil,
	dir: false,
	},
	{Space: "DAV:", Local: "getcontenttype"}: {
	findFn: findContentType,
	dir: false,
	},
	{Space: "DAV:", Local: "getetag"}: {
	findFn: findETag,
	// findETag implements ETag as the concatenated hex values of a file's
	// modification time and size. This is not a reliable synchronization
	// mechanism for directories, so we do not advertise getetag for DAV
	// collections.
	dir: false,
	},

	// TODO: The lockdiscovery property requires LockSystem to list the
	// active locks on a resource.
	{Space: "DAV:", Local: "lockdiscovery"}: {},
	{Space: "DAV:", Local: "supportedlock"}: {
	findFn: findSupportedLock,
	dir: true,
	},
	}

	// TODO(nigeltao) merge props and allprop?

	// Props returns the status of the properties named pnames for resource name.
	//
	// Each Propstat has a unique status and each property name will only be part
	// of one Propstat element.
	func props(ctx context.Context, fs FileSystem, ls LockSystem, name string, pnames []xml.Name) ([]Propstat, error) {
	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
	if err != nil {
	return nil, err
	}
	defer f.Close()
	fi, err := f.Stat()
	if err != nil {
	return nil, err
	}
	isDir := fi.IsDir()

	var deadProps map[xml.Name]Property
	if dph, ok := f.(DeadPropsHolder); ok {
	deadProps, err = dph.DeadProps()
	if err != nil {
	return nil, err
	}
	}

	pstatOK := Propstat{Status: http.StatusOK}
	pstatNotFound := Propstat{Status: http.StatusNotFound}
	for _, pn := range pnames {
	// If this file has dead properties, check if they contain pn.
	if dp, ok := deadProps[pn]; ok {
	pstatOK.Props = append(pstatOK.Props, dp)
	continue
	}
	// Otherwise, it must either be a live property or we don't know it.
	if prop := liveProps[pn]; prop.findFn != nil && (prop.dir \|\| !isDir) {
	innerXML, err := prop.findFn(ctx, fs, ls, name, fi)
	if err != nil {
	return nil, err
	}
	pstatOK.Props = append(pstatOK.Props, Property{
	XMLName: pn,
	InnerXML: []byte(innerXML),
	})
	} else {
	pstatNotFound.Props = append(pstatNotFound.Props, Property{
	XMLName: pn,
	})
	}
	}
	return makePropstats(pstatOK, pstatNotFound), nil
	}

	// Propnames returns the property names defined for resource name.
	func propnames(ctx context.Context, fs FileSystem, ls LockSystem, name string) ([]xml.Name, error) {
	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
	if err != nil {
	return nil, err
	}
	defer f.Close()
	fi, err := f.Stat()
	if err != nil {
	return nil, err
	}
	isDir := fi.IsDir()

	var deadProps map[xml.Name]Property
	if dph, ok := f.(DeadPropsHolder); ok {
	deadProps, err = dph.DeadProps()
	if err != nil {
	return nil, err
	}
	}

	pnames := make([]xml.Name, 0, len(liveProps)+len(deadProps))
	for pn, prop := range liveProps {
	if prop.findFn != nil && (prop.dir \|\| !isDir) {
	pnames = append(pnames, pn)
	}
	}
	for pn := range deadProps {
	pnames = append(pnames, pn)
	}
	return pnames, nil
	}

	// Allprop returns the properties defined for resource name and the properties
	// named in include.
	//
	// Note that RFC 4918 defines 'allprop' to return the DAV: properties defined
	// within the RFC plus dead properties. Other live properties should only be
	// returned if they are named in 'include'.
	//
	// See http://www.webdav.org/specs/rfc4918.html#METHOD_PROPFIND
	func allprop(ctx context.Context, fs FileSystem, ls LockSystem, name string, include []xml.Name) ([]Propstat, error) {
	pnames, err := propnames(ctx, fs, ls, name)
	if err != nil {
	return nil, err
	}
	// Add names from include if they are not already covered in pnames.
	nameset := make(map[xml.Name]bool)
	for _, pn := range pnames {
	nameset[pn] = true
	}
	for _, pn := range include {
	if !nameset[pn] {
	pnames = append(pnames, pn)
	}
	}
	return props(ctx, fs, ls, name, pnames)
	}

	// Patch patches the properties of resource name. The return values are
	// constrained in the same manner as DeadPropsHolder.Patch.
	func patch(ctx context.Context, fs FileSystem, ls LockSystem, name string, patches []Proppatch) ([]Propstat, error) {
	conflict := false
	loop:
	for _, patch := range patches {
	for _, p := range patch.Props {
	if _, ok := liveProps[p.XMLName]; ok {
	conflict = true
	break loop
	}
	}
	}
	if conflict {
	pstatForbidden := Propstat{
	Status: http.StatusForbidden,
	XMLError: `<D:cannot-modify-protected-property xmlns:D="DAV:"/>`,
	}
	pstatFailedDep := Propstat{
	Status: StatusFailedDependency,
	}
	for _, patch := range patches {
	for _, p := range patch.Props {
	if _, ok := liveProps[p.XMLName]; ok {
	pstatForbidden.Props = append(pstatForbidden.Props, Property{XMLName: p.XMLName})
	} else {
	pstatFailedDep.Props = append(pstatFailedDep.Props, Property{XMLName: p.XMLName})
	}
	}
	}
	return makePropstats(pstatForbidden, pstatFailedDep), nil
	}

	f, err := fs.OpenFile(ctx, name, os.O_RDWR, 0)
	if err != nil {
	return nil, err
	}
	defer f.Close()
	if dph, ok := f.(DeadPropsHolder); ok {
	ret, err := dph.Patch(patches)
	if err != nil {
	return nil, err
	}
	// http://www.webdav.org/specs/rfc4918.html#ELEMENT_propstat says that
	// "The contents of the prop XML element must only list the names of
	// properties to which the result in the status element applies."
	for _, pstat := range ret {
	for i, p := range pstat.Props {
	pstat.Props[i] = Property{XMLName: p.XMLName}
	}
	}
	return ret, nil
	}
	// The file doesn't implement the optional DeadPropsHolder interface, so
	// all patches are forbidden.
	pstat := Propstat{Status: http.StatusForbidden}
	for _, patch := range patches {
	for _, p := range patch.Props {
	pstat.Props = append(pstat.Props, Property{XMLName: p.XMLName})
	}
	}
	return []Propstat{pstat}, nil
	}

	func escapeXML(s string) string {
	for i := 0; i < len(s); i++ {
	// As an optimization, if s contains only ASCII letters, digits or a
	// few special characters, the escaped value is s itself and we don't
	// need to allocate a buffer and convert between string and []byte.
	switch c := s[i]; {
	case c == ' ' \|\| c == '_' \|\|
	('+' <= c && c <= '9') \|\| // Digits as well as + , - . and /
	('A' <= c && c <= 'Z') \|\|
	('a' <= c && c <= 'z'):
	continue
	}
	// Otherwise, go through the full escaping process.
	var buf bytes.Buffer
	xml.EscapeText(&buf, []byte(s))
	return buf.String()
	}
	return s
	}

	func findResourceType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	if fi.IsDir() {
	return `<D:collection xmlns:D="DAV:"/>`, nil
	}
	return "", nil
	}

	func findDisplayName(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	if slashClean(name) == "/" {
	// Hide the real name of a possibly prefixed root directory.
	return "", nil
	}
	return escapeXML(fi.Name()), nil
	}

	func findContentLength(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	return strconv.FormatInt(fi.Size(), 10), nil
	}

	func findLastModified(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	return fi.ModTime().Format(http.TimeFormat), nil
	}

	func findContentType(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	f, err := fs.OpenFile(ctx, name, os.O_RDONLY, 0)
	if err != nil {
	return "", err
	}
	defer f.Close()
	// This implementation is based on serveContent's code in the standard net/http package.
	ctype := mime.TypeByExtension(filepath.Ext(name))
	if ctype != "" {
	return ctype, nil
	}
	// Read a chunk to decide between utf-8 text and binary.
	var buf [512]byte
	n, err := io.ReadFull(f, buf[:])
	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
	return "", err
	}
	ctype = http.DetectContentType(buf[:n])
	// Rewind file.
	_, err = f.Seek(0, os.SEEK_SET)
	return ctype, err
	}

	func findETag(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	// The Apache http 2.4 web server by default concatenates the
	// modification time and size of a file. We replicate the heuristic
	// with nanosecond granularity.
	return fmt.Sprintf(`"%x%x"`, fi.ModTime().UnixNano(), fi.Size()), nil
	}

	func findSupportedLock(ctx context.Context, fs FileSystem, ls LockSystem, name string, fi os.FileInfo) (string, error) {
	return `` +
	`<D:lockentry xmlns:D="DAV:">` +
	`<D:lockscope><D:exclusive/></D:lockscope>` +
	`<D:locktype><D:write/></D:locktype>` +
	`</D:lockentry>`, nil
	}