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99f7fd74e3
As mentioned in issue [#1560](https://github.com/restic/restic/pull/1560#issuecomment-364689346) this changes the signature for `backend.Save()`. It now takes a parameter of interface type `RewindReader`, so that the backend implementations or our `RetryBackend` middleware can reset the reader to the beginning and then retry an upload operation. The `RewindReader` interface also provides a `Length()` method, which is used in the backend to get the size of the data to be saved. This removes several ugly hacks we had to do to pull the size back out of the `io.Reader` passed to `Save()` before. In the `s3` and `rest` backend this is actively used.
91 lines
1.9 KiB
Go
91 lines
1.9 KiB
Go
package restic
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import (
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"bytes"
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"io"
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"github.com/restic/restic/internal/errors"
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)
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// RewindReader allows resetting the Reader to the beginning of the data.
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type RewindReader interface {
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io.Reader
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// Rewind rewinds the reader so the same data can be read again from the
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// start.
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Rewind() error
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// Length returns the number of bytes that can be read from the Reader
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// after calling Rewind.
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Length() int
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}
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// ByteReader implements a RewindReader for a byte slice.
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type ByteReader struct {
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*bytes.Reader
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Len int
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}
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// Rewind restarts the reader from the beginning of the data.
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func (b *ByteReader) Rewind() error {
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_, err := b.Reader.Seek(0, io.SeekStart)
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return err
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}
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// Length returns the number of bytes read from the reader after Rewind is
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// called.
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func (b *ByteReader) Length() int {
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return b.Len
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}
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// statically ensure that *ByteReader implements RewindReader.
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var _ RewindReader = &ByteReader{}
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// NewByteReader prepares a ByteReader that can then be used to read buf.
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func NewByteReader(buf []byte) *ByteReader {
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return &ByteReader{
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Reader: bytes.NewReader(buf),
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Len: len(buf),
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}
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}
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// statically ensure that *FileReader implements RewindReader.
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var _ RewindReader = &FileReader{}
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// FileReader implements a RewindReader for an open file.
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type FileReader struct {
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io.ReadSeeker
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Len int
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}
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// Rewind seeks to the beginning of the file.
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func (f *FileReader) Rewind() error {
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_, err := f.ReadSeeker.Seek(0, io.SeekStart)
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return errors.Wrap(err, "Seek")
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}
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// Length returns the length of the file.
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func (f *FileReader) Length() int {
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return f.Len
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}
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// NewFileReader wraps f in a *FileReader.
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func NewFileReader(f io.ReadSeeker) (*FileReader, error) {
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pos, err := f.Seek(0, io.SeekEnd)
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if err != nil {
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return nil, errors.Wrap(err, "Seek")
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}
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fr := &FileReader{
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ReadSeeker: f,
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Len: int(pos),
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}
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err = fr.Rewind()
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if err != nil {
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return nil, err
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}
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return fr, nil
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}
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