Vendor continuity

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

vendor/github.com/stevvooe/continuity/driver.go

@@ -0,0 +1,158 @@
+package continuity
+
+import (
+	"errors"
+	"os"
+	"strconv"
+)
+
+// Driver provides all of the system-level functions in a common interface.
+// The context should call these with full paths and should never use the `os`
+// package or any other package to access resources on the filesystem. This
+// mechanism let's us carefully control access to the context and maintain
+// path and resource integrity. It also gives us an interface to reason about
+// direct resource access.
+//
+// Implementations don't need to do much other than meet the interface. For
+// example, it is not required to wrap os.FileInfo to return correct paths for
+// the call to Name().
+type Driver interface {
+	Open(path string) (*os.File, error)
+	Stat(path string) (os.FileInfo, error)
+	Lstat(path string) (os.FileInfo, error)
+	Readlink(p string) (string, error)
+	Mkdir(path string, mode os.FileMode) error
+	Remove(path string) error
+
+	Link(oldname, newname string) error
+	Lchmod(path string, mode os.FileMode) error
+	Lchown(path, uid, gid string) error
+	Symlink(oldname, newname string) error
+
+	// TODO(aaronl): These methods might move outside the main Driver
+	// interface in the future as more platforms are added.
+	Mknod(path string, mode os.FileMode, major int, minor int) error
+	Mkfifo(path string, mode os.FileMode) error
+
+	// NOTE(stevvooe): We may want to actually include the path manipulation
+	// functions here, as well. They have been listed below to make the
+	// discovery process easier.
+
+	// Join(path ...string) string
+	// IsAbs(string) bool
+	// Abs(string) (string, error)
+	// Rel(base, target string) (string, error)
+	// Walk(string, filepath.WalkFunc) error
+}
+
+func NewSystemDriver() (Driver, error) {
+	// TODO(stevvooe): Consider having this take a "hint" path argument, which
+	// would be the context root. The hint could be used to resolve required
+	// filesystem support when assembling the driver to use.
+	return &driver{}, nil
+}
+
+// XAttrDriver should be implemented on operation systems and filesystems that
+// have xattr support for regular files and directories.
+type XAttrDriver interface {
+	// Getxattr returns all of the extended attributes for the file at path.
+	// Typically, this takes a syscall call to Listxattr and Getxattr.
+	Getxattr(path string) (map[string][]byte, error)
+
+	// Setxattr sets all of the extended attributes on file at path, following
+	// any symbolic links, if necessary. All attributes on the target are
+	// replaced by the values from attr. If the operation fails to set any
+	// attribute, those already applied will not be rolled back.
+	Setxattr(path string, attr map[string][]byte) error
+}
+
+// LXAttrDriver should be implemented by drivers on operating systems and
+// filesystems that support setting and getting extended attributes on
+// symbolic links. If this is not implemented, extended attributes will be
+// ignored on symbolic links.
+type LXAttrDriver interface {
+	// LGetxattr returns all of the extended attributes for the file at path
+	// and does not follow symlinks. Typically, this takes a syscall call to
+	// Llistxattr and Lgetxattr.
+	LGetxattr(path string) (map[string][]byte, error)
+
+	// LSetxattr sets all of the extended attributes on file at path, without
+	// following symbolic links. All attributes on the target are replaced by
+	// the values from attr. If the operation fails to set any attribute,
+	// those already applied will not be rolled back.
+	LSetxattr(path string, attr map[string][]byte) error
+}
+
+type DeviceInfoDriver interface {
+	DeviceInfo(fi os.FileInfo) (maj uint64, min uint64, err error)
+}
+
+// driver is a simple default implementation that sends calls out to the "os"
+// package. Extend the "driver" type in system-specific files to add support,
+// such as xattrs, which can add support at compile time.
+type driver struct{}
+
+var _ Driver = &driver{}
+
+func (d *driver) Open(p string) (*os.File, error) {
+	return os.Open(p)
+}
+
+func (d *driver) Stat(p string) (os.FileInfo, error) {
+	return os.Stat(p)
+}
+
+func (d *driver) Lstat(p string) (os.FileInfo, error) {
+	return os.Lstat(p)
+}
+
+func (d *driver) Readlink(p string) (string, error) {
+	return os.Readlink(p)
+}
+
+func (d *driver) Mkdir(p string, mode os.FileMode) error {
+	return os.Mkdir(p, mode)
+}
+
+// Remove is used to unlink files and remove directories.
+// This is following the golang os package api which
+// combines the operations into a higher level Remove
+// function. If explicit unlinking or directory removal
+// to mirror system call is required, they should be
+// split up at that time.
+func (d *driver) Remove(path string) error {
+	return os.Remove(path)
+}
+
+func (d *driver) Link(oldname, newname string) error {
+	return os.Link(oldname, newname)
+}
+
+func (d *driver) Lchown(name, uidStr, gidStr string) error {
+	uid, err := strconv.Atoi(uidStr)
+	if err != nil {
+		return err
+	}
+	gid, err := strconv.Atoi(gidStr)
+	if err != nil {
+		return err
+	}
+	return os.Lchown(name, uid, gid)
+}
+
+func (d *driver) Symlink(oldname, newname string) error {
+	return os.Symlink(oldname, newname)
+}
+
+func (d *driver) Mknod(path string, mode os.FileMode, major, minor int) error {
+	return mknod(path, mode, major, minor)
+}
+
+func (d *driver) Mkfifo(path string, mode os.FileMode) error {
+	if mode&os.ModeNamedPipe == 0 {
+		return errors.New("mode passed to Mkfifo does not have the named pipe bit set")
+	}
+	// mknod with a mode that has ModeNamedPipe set creates a fifo, not a
+	// device.
+	return mknod(path, mode, 0, 0)
+}