kovidgoyal/kitty · error

There are %d leftover bytes in the delta

Error message

There are %d leftover bytes in the delta

What it means

After applying a delta, FinishDelta found unconsumed delta bytes — the delta stream length doesn't align with the operation records, indicating truncation or corruption.

Source

Thrown at tools/rsync/api.go:183

// Apply a chunk of delta data
func (self *Patcher) UpdateDelta(data []byte) (err error) {
	self.unconsumed_delta_data = append(self.unconsumed_delta_data, data...)
	consumed, err := self.update_delta(self.unconsumed_delta_data)
	if err != nil {
		return err
	}
	self.unconsumed_delta_data = utils.ShiftLeft(self.unconsumed_delta_data, consumed)
	return
}

// Finish applying delta data
func (self *Patcher) FinishDelta() (err error) {
	if err = self.UpdateDelta([]byte{}); err != nil {
		return err
	}
	if len(self.unconsumed_delta_data) > 0 {
		return fmt.Errorf("There are %d leftover bytes in the delta", len(self.unconsumed_delta_data))
	}
	self.delta_input = nil
	self.delta_output = nil
	self.unconsumed_delta_data = nil
	if !self.rsync.checksum_done {
		return fmt.Errorf("The checksum was not received at the end of the delta data")
	}
	return
}

// Create a signature for the data source in src.
func (self *Patcher) CreateSignatureIterator(src io.Reader, output io.Writer) func() error {
	var it func() (BlockHash, error)
	finished := false
	var b [BlockHashSize]byte
	return func() error {
		if finished {
			return io.EOF

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Ensure all delta chunks were passed to UpdateDelta before FinishDelta
2. Verify the transport framing (lengths/pipes) delivers the complete byte stream
3. Re-request the delta from the sender

if err := patcher.FinishDelta(); err != nil { discard patched output; re-request delta and reapply }

When it happens

Trigger: Calling FinishDelta after UpdateDelta received a byte count that ends mid-operation; e.g. a network read cut short or extra bytes appended.

Common situations: Interrupted transfers, misframed pipes, or feeding the patcher partial chunks and finishing too early.

Related errors

• There were %d leftover bytes in the signature data
• Invalid weak_hash in signature header: %d
• rsync signature header has zero block size
• rsync signature header has too large block size %d > %d
• The checksum was not received at the end of the delta data

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/b141a4c24535377e. Report an issue: GitHub.