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159 lines
5.4 KiB
Go
159 lines
5.4 KiB
Go
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package driver
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import (
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"fmt"
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"io"
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"os"
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)
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var ErrNotSupported = fmt.Errorf("not supported")
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// Driver provides all of the system-level functions in a common interface.
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// The context should call these with full paths and should never use the `os`
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// package or any other package to access resources on the filesystem. This
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// mechanism let's us carefully control access to the context and maintain
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// path and resource integrity. It also gives us an interface to reason about
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// direct resource access.
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//
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// Implementations don't need to do much other than meet the interface. For
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// example, it is not required to wrap os.FileInfo to return correct paths for
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// the call to Name().
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type Driver interface {
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// Note that Open() returns a File interface instead of *os.File. This
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// is because os.File is a struct, so if Open was to return *os.File,
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// the only way to fulfill the interface would be to call os.Open()
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Open(path string) (File, error)
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OpenFile(path string, flag int, perm os.FileMode) (File, error)
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Stat(path string) (os.FileInfo, error)
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Lstat(path string) (os.FileInfo, error)
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Readlink(p string) (string, error)
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Mkdir(path string, mode os.FileMode) error
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Remove(path string) error
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Link(oldname, newname string) error
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Lchmod(path string, mode os.FileMode) error
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Lchown(path string, uid, gid int64) error
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Symlink(oldname, newname string) error
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MkdirAll(path string, perm os.FileMode) error
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RemoveAll(path string) error
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// TODO(aaronl): These methods might move outside the main Driver
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// interface in the future as more platforms are added.
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Mknod(path string, mode os.FileMode, major int, minor int) error
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Mkfifo(path string, mode os.FileMode) error
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}
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// File is the interface for interacting with files returned by continuity's Open
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// This is needed since os.File is a struct, instead of an interface, so it can't
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// be used.
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type File interface {
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io.ReadWriteCloser
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io.Seeker
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Readdir(n int) ([]os.FileInfo, error)
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}
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func NewSystemDriver() (Driver, error) {
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// TODO(stevvooe): Consider having this take a "hint" path argument, which
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// would be the context root. The hint could be used to resolve required
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// filesystem support when assembling the driver to use.
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return &driver{}, nil
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}
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// XAttrDriver should be implemented on operation systems and filesystems that
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// have xattr support for regular files and directories.
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type XAttrDriver interface {
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// Getxattr returns all of the extended attributes for the file at path.
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// Typically, this takes a syscall call to Listxattr and Getxattr.
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Getxattr(path string) (map[string][]byte, error)
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// Setxattr sets all of the extended attributes on file at path, following
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// any symbolic links, if necessary. All attributes on the target are
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// replaced by the values from attr. If the operation fails to set any
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// attribute, those already applied will not be rolled back.
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Setxattr(path string, attr map[string][]byte) error
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}
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// LXAttrDriver should be implemented by drivers on operating systems and
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// filesystems that support setting and getting extended attributes on
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// symbolic links. If this is not implemented, extended attributes will be
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// ignored on symbolic links.
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type LXAttrDriver interface {
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// LGetxattr returns all of the extended attributes for the file at path
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// and does not follow symlinks. Typically, this takes a syscall call to
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// Llistxattr and Lgetxattr.
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LGetxattr(path string) (map[string][]byte, error)
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// LSetxattr sets all of the extended attributes on file at path, without
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// following symbolic links. All attributes on the target are replaced by
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// the values from attr. If the operation fails to set any attribute,
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// those already applied will not be rolled back.
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LSetxattr(path string, attr map[string][]byte) error
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}
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type DeviceInfoDriver interface {
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DeviceInfo(fi os.FileInfo) (maj uint64, min uint64, err error)
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}
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// driver is a simple default implementation that sends calls out to the "os"
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// package. Extend the "driver" type in system-specific files to add support,
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// such as xattrs, which can add support at compile time.
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type driver struct{}
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var _ File = &os.File{}
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// LocalDriver is the exported Driver struct for convenience.
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var LocalDriver Driver = &driver{}
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func (d *driver) Open(p string) (File, error) {
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return os.Open(p)
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}
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func (d *driver) OpenFile(path string, flag int, perm os.FileMode) (File, error) {
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return os.OpenFile(path, flag, perm)
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}
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func (d *driver) Stat(p string) (os.FileInfo, error) {
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return os.Stat(p)
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}
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func (d *driver) Lstat(p string) (os.FileInfo, error) {
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return os.Lstat(p)
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}
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func (d *driver) Mkdir(p string, mode os.FileMode) error {
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return os.Mkdir(p, mode)
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}
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// Remove is used to unlink files and remove directories.
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// This is following the golang os package api which
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// combines the operations into a higher level Remove
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// function. If explicit unlinking or directory removal
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// to mirror system call is required, they should be
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// split up at that time.
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func (d *driver) Remove(path string) error {
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return os.Remove(path)
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}
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func (d *driver) Link(oldname, newname string) error {
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return os.Link(oldname, newname)
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}
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func (d *driver) Lchown(name string, uid, gid int64) error {
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// TODO: error out if uid excesses int bit width?
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return os.Lchown(name, int(uid), int(gid))
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}
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func (d *driver) Symlink(oldname, newname string) error {
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return os.Symlink(oldname, newname)
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}
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func (d *driver) MkdirAll(path string, perm os.FileMode) error {
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return os.MkdirAll(path, perm)
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}
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func (d *driver) RemoveAll(path string) error {
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return os.RemoveAll(path)
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}
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