selfupdate

Documentation

Index

• func Apply(update io.Reader, opts Options) error
• func CommitBinary(opts Options) error
• func PrepareAndCheckBinary(update io.Reader, opts Options) error
• func RollbackError(err error) error
• type Options
  • func (o *Options) CheckPermissions() error
• type Patcher
  • func NewBSDiffPatcher() Patcher

Functions

func Apply

func Apply(update io.Reader, opts Options) error

Apply performs an update of the current executable or opts.TargetFile, with the contents of the given io.Reader. When the update fails, it is unlikely that old executable is corrupted, but still, applications need to check the returned error with RollbackError() and notify the user of the bad news and ask them to recover manually.

func CommitBinary

func CommitBinary(opts Options) error

CommitBinary moves the new executable to the location of the current executable or opts.TargetPath if specified. It performs the following operations:

1. Renames /path/to/target to /path/to/.target.old
2. Renames /path/to/.target.new to /path/to/target
3. If the final rename is successful, deletes /path/to/.target.old, returns no error. On Windows, the removal of /path/to/target.old always fails, so instead Apply hides the old file instead.
4. If the final rename fails, attempts to roll back by renaming /path/to/.target.old back to /path/to/target.

If the roll back operation fails, the file system is left in an inconsistent state where there is no new executable file and the old executable file could not be be moved to its original location. In this case you should notify the user of the bad news and ask them to recover manually. Applications can determine whether the rollback failed by calling RollbackError, see the documentation on that function for additional detail.

func PrepareAndCheckBinary

func PrepareAndCheckBinary(update io.Reader, opts Options) error

PrepareAndCheckBinary reads the new binary content from io.Reader and performs the following actions:

1. If configured, applies the contents of the update io.Reader as a binary patch.
2. If configured, computes the checksum of the executable and verifies it matches.
3. If configured, verifies the signature with a public key.
4. Creates a new file, /path/to/.target.new with the TargetMode with the contents of the updated file

func RollbackError

func RollbackError(err error) error

RollbackError takes an error value returned by Apply and returns the error, if any, that occurred when attempting to roll back from a failed update. Applications should always call this function on any non-nil errors returned by Apply.

If no rollback was needed or if the rollback was successful, RollbackError returns nil, otherwise it returns the error encountered when trying to roll back.

Types

type Options

type Options struct {
	// TargetPath defines the path to the file to update.
	// The emptry string means 'the executable file of the running program'.
	TargetPath string

	// Create TargetPath replacement with this file mode. If zero, defaults to 0755.
	TargetMode os.FileMode

	// Checksum of the new binary to verify against. If nil, no checksum or signature verification is done.
	Checksum []byte

	// Use this hash function to generate the checksum. If not set, SHA256 is used.
	Hash crypto.Hash

	// If nil, treat the update as a complete replacement for the contents of the file at TargetPath.
	// If non-nil, treat the update contents as a patch and use this object to apply the patch.
	Patcher Patcher

	// Store the old executable file at this path after a successful update.
	// The empty string means the old executable file will be removed after the update.
	OldSavePath string
}

func (*Options) CheckPermissions

func (o *Options) CheckPermissions() error

CheckPermissions determines whether the process has the correct permissions to perform the requested update. If the update can proceed, it returns nil, otherwise it returns the error that would occur if an update were attempted.

type Patcher

type Patcher interface {
	Patch(old io.Reader, new io.Writer, patch io.Reader) error
}

Patcher defines an interface for applying binary patches to an old item to get an updated item.

func NewBSDiffPatcher

func NewBSDiffPatcher() Patcher

NewBSDiffPatcher returns a new Patcher that applies binary patches using the bsdiff algorithm. See http://www.daemonology.net/bsdiff/