update vendor

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

vendor/github.com/containerd/continuity/syscallx/syscall_unix.go

@@ -0,0 +1,26 @@
+// +build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package syscallx
+
+import "syscall"
+
+// Readlink returns the destination of the named symbolic link.
+func Readlink(path string, buf []byte) (n int, err error) {
+	return syscall.Readlink(path, buf)
+}

vendor/github.com/containerd/continuity/syscallx/syscall_windows.go

@@ -0,0 +1,112 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package syscallx
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+type reparseDataBuffer struct {
+	ReparseTag        uint32
+	ReparseDataLength uint16
+	Reserved          uint16
+
+	// GenericReparseBuffer
+	reparseBuffer byte
+}
+
+type mountPointReparseBuffer struct {
+	SubstituteNameOffset uint16
+	SubstituteNameLength uint16
+	PrintNameOffset      uint16
+	PrintNameLength      uint16
+	PathBuffer           [1]uint16
+}
+
+type symbolicLinkReparseBuffer struct {
+	SubstituteNameOffset uint16
+	SubstituteNameLength uint16
+	PrintNameOffset      uint16
+	PrintNameLength      uint16
+	Flags                uint32
+	PathBuffer           [1]uint16
+}
+
+const (
+	_IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003
+	_SYMLINK_FLAG_RELATIVE      = 1
+)
+
+// Readlink returns the destination of the named symbolic link.
+func Readlink(path string, buf []byte) (n int, err error) {
+	fd, err := syscall.CreateFile(syscall.StringToUTF16Ptr(path), syscall.GENERIC_READ, 0, nil, syscall.OPEN_EXISTING,
+		syscall.FILE_FLAG_OPEN_REPARSE_POINT|syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
+	if err != nil {
+		return -1, err
+	}
+	defer syscall.CloseHandle(fd)
+
+	rdbbuf := make([]byte, syscall.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
+	var bytesReturned uint32
+	err = syscall.DeviceIoControl(fd, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
+	if err != nil {
+		return -1, err
+	}
+
+	rdb := (*reparseDataBuffer)(unsafe.Pointer(&rdbbuf[0]))
+	var s string
+	switch rdb.ReparseTag {
+	case syscall.IO_REPARSE_TAG_SYMLINK:
+		data := (*symbolicLinkReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
+		p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
+		s = syscall.UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
+		if data.Flags&_SYMLINK_FLAG_RELATIVE == 0 {
+			if len(s) >= 4 && s[:4] == `\??\` {
+				s = s[4:]
+				switch {
+				case len(s) >= 2 && s[1] == ':': // \??\C:\foo\bar
+					// do nothing
+				case len(s) >= 4 && s[:4] == `UNC\`: // \??\UNC\foo\bar
+					s = `\\` + s[4:]
+				default:
+					// unexpected; do nothing
+				}
+			} else {
+				// unexpected; do nothing
+			}
+		}
+	case _IO_REPARSE_TAG_MOUNT_POINT:
+		data := (*mountPointReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
+		p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
+		s = syscall.UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
+		if len(s) >= 4 && s[:4] == `\??\` { // \??\C:\foo\bar
+			if len(s) < 48 || s[:11] != `\??\Volume{` {
+				s = s[4:]
+			}
+		} else {
+			// unexpected; do nothing
+		}
+	default:
+		// the path is not a symlink or junction but another type of reparse
+		// point
+		return -1, syscall.ENOENT
+	}
+	n = copy(buf, []byte(s))
+
+	return n, nil
+}