mirror of
https://github.com/restic/restic.git
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318 lines
7.6 KiB
Go
318 lines
7.6 KiB
Go
package pack
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"sync"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/errors"
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"github.com/restic/restic/internal/restic"
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"github.com/restic/restic/internal/crypto"
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)
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// Packer is used to create a new Pack.
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type Packer struct {
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blobs []restic.Blob
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bytes uint
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k *crypto.Key
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wr io.Writer
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m sync.Mutex
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}
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// NewPacker returns a new Packer that can be used to pack blobs together.
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func NewPacker(k *crypto.Key, wr io.Writer) *Packer {
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return &Packer{k: k, wr: wr}
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}
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// Add saves the data read from rd as a new blob to the packer. Returned is the
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// number of bytes written to the pack.
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func (p *Packer) Add(t restic.BlobType, id restic.ID, data []byte) (int, error) {
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p.m.Lock()
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defer p.m.Unlock()
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c := restic.Blob{Type: t, ID: id}
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n, err := p.wr.Write(data)
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c.Length = uint(n)
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c.Offset = p.bytes
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p.bytes += uint(n)
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p.blobs = append(p.blobs, c)
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return n, errors.Wrap(err, "Write")
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}
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var entrySize = uint(binary.Size(restic.BlobType(0)) + binary.Size(uint32(0)) + len(restic.ID{}))
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// headerEntry is used with encoding/binary to read and write header entries
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type headerEntry struct {
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Type uint8
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Length uint32
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ID restic.ID
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}
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// Finalize writes the header for all added blobs and finalizes the pack.
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// Returned are the number of bytes written, including the header.
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func (p *Packer) Finalize() (uint, error) {
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p.m.Lock()
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defer p.m.Unlock()
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bytesWritten := p.bytes
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hdrBuf := bytes.NewBuffer(nil)
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bytesHeader, err := p.writeHeader(hdrBuf)
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if err != nil {
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return 0, err
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}
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encryptedHeader := make([]byte, 0, hdrBuf.Len()+p.k.Overhead()+p.k.NonceSize())
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nonce := crypto.NewRandomNonce()
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encryptedHeader = append(encryptedHeader, nonce...)
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encryptedHeader = p.k.Seal(encryptedHeader, nonce, hdrBuf.Bytes(), nil)
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// append the header
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n, err := p.wr.Write(encryptedHeader)
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if err != nil {
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return 0, errors.Wrap(err, "Write")
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}
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hdrBytes := restic.CiphertextLength(int(bytesHeader))
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if n != hdrBytes {
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return 0, errors.New("wrong number of bytes written")
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}
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bytesWritten += uint(hdrBytes)
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// write length
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err = binary.Write(p.wr, binary.LittleEndian, uint32(restic.CiphertextLength(len(p.blobs)*int(entrySize))))
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if err != nil {
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return 0, errors.Wrap(err, "binary.Write")
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}
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bytesWritten += uint(binary.Size(uint32(0)))
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p.bytes = uint(bytesWritten)
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return bytesWritten, nil
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}
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// writeHeader constructs and writes the header to wr.
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func (p *Packer) writeHeader(wr io.Writer) (bytesWritten uint, err error) {
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for _, b := range p.blobs {
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entry := headerEntry{
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Length: uint32(b.Length),
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ID: b.ID,
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}
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switch b.Type {
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case restic.DataBlob:
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entry.Type = 0
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case restic.TreeBlob:
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entry.Type = 1
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default:
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return 0, errors.Errorf("invalid blob type %v", b.Type)
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}
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err := binary.Write(wr, binary.LittleEndian, entry)
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if err != nil {
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return bytesWritten, errors.Wrap(err, "binary.Write")
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}
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bytesWritten += entrySize
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}
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return
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}
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// Size returns the number of bytes written so far.
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func (p *Packer) Size() uint {
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p.m.Lock()
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defer p.m.Unlock()
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return p.bytes
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}
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// Count returns the number of blobs in this packer.
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func (p *Packer) Count() int {
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p.m.Lock()
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defer p.m.Unlock()
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return len(p.blobs)
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}
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// Blobs returns the slice of blobs that have been written.
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func (p *Packer) Blobs() []restic.Blob {
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p.m.Lock()
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defer p.m.Unlock()
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return p.blobs
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}
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// Writer return the underlying writer.
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func (p *Packer) Writer() io.Writer {
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return p.wr
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}
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func (p *Packer) String() string {
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return fmt.Sprintf("<Packer %d blobs, %d bytes>", len(p.blobs), p.bytes)
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}
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var (
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// size of the header-length field at the end of the file
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headerLengthSize = binary.Size(uint32(0))
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// we require at least one entry in the header, and one blob for a pack file
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minFileSize = entrySize + crypto.Extension + uint(headerLengthSize)
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)
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const (
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maxHeaderSize = 16 * 1024 * 1024
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// number of header enries to download as part of header-length request
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eagerEntries = 15
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)
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// readRecords reads up to max records from the underlying ReaderAt, returning
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// the raw header, the total number of records in the header, and any error.
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// If the header contains fewer than max entries, the header is truncated to
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// the appropriate size.
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func readRecords(rd io.ReaderAt, size int64, max int) ([]byte, int, error) {
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var bufsize int
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bufsize += max * int(entrySize)
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bufsize += crypto.Extension
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bufsize += headerLengthSize
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if bufsize > int(size) {
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bufsize = int(size)
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}
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b := make([]byte, bufsize)
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off := size - int64(bufsize)
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if _, err := rd.ReadAt(b, off); err != nil {
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return nil, 0, err
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}
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hlen := binary.LittleEndian.Uint32(b[len(b)-headerLengthSize:])
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b = b[:len(b)-headerLengthSize]
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debug.Log("header length: %v", hlen)
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var err error
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switch {
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case hlen == 0:
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err = InvalidFileError{Message: "header length is zero"}
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case hlen < crypto.Extension:
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err = InvalidFileError{Message: "header length is too small"}
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case (hlen-crypto.Extension)%uint32(entrySize) != 0:
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err = InvalidFileError{Message: "header length is invalid"}
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case int64(hlen) > size-int64(headerLengthSize):
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err = InvalidFileError{Message: "header is larger than file"}
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case int64(hlen) > maxHeaderSize:
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err = InvalidFileError{Message: "header is larger than maxHeaderSize"}
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}
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if err != nil {
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return nil, 0, errors.Wrap(err, "readHeader")
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}
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total := (int(hlen) - crypto.Extension) / int(entrySize)
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if total < max {
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// truncate to the beginning of the pack header
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b = b[len(b)-int(hlen):]
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}
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return b, total, nil
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}
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// readHeader reads the header at the end of rd. size is the length of the
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// whole data accessible in rd.
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func readHeader(rd io.ReaderAt, size int64) ([]byte, error) {
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debug.Log("size: %v", size)
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if size < int64(minFileSize) {
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err := InvalidFileError{Message: "file is too small"}
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return nil, errors.Wrap(err, "readHeader")
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}
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// assuming extra request is significantly slower than extra bytes download,
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// eagerly download eagerEntries header entries as part of header-length request.
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// only make second request if actual number of entries is greater than eagerEntries
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b, c, err := readRecords(rd, size, eagerEntries)
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if err != nil {
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return nil, err
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}
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if c <= eagerEntries {
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// eager read sufficed, return what we got
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return b, nil
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}
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b, _, err = readRecords(rd, size, c)
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if err != nil {
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return nil, err
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}
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return b, nil
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}
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// InvalidFileError is return when a file is found that is not a pack file.
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type InvalidFileError struct {
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Message string
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}
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func (e InvalidFileError) Error() string {
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return e.Message
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}
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// List returns the list of entries found in a pack file.
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func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, err error) {
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buf, err := readHeader(rd, size)
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if err != nil {
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return nil, err
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}
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if len(buf) < k.NonceSize()+k.Overhead() {
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return nil, errors.New("invalid header, too small")
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}
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nonce, buf := buf[:k.NonceSize()], buf[k.NonceSize():]
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buf, err = k.Open(buf[:0], nonce, buf, nil)
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if err != nil {
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return nil, err
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}
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hdrRd := bytes.NewReader(buf)
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entries = make([]restic.Blob, 0, uint(len(buf))/entrySize)
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pos := uint(0)
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for {
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e := headerEntry{}
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err = binary.Read(hdrRd, binary.LittleEndian, &e)
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if errors.Cause(err) == io.EOF {
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break
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}
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if err != nil {
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return nil, errors.Wrap(err, "binary.Read")
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}
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entry := restic.Blob{
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Length: uint(e.Length),
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ID: e.ID,
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Offset: pos,
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}
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switch e.Type {
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case 0:
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entry.Type = restic.DataBlob
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case 1:
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entry.Type = restic.TreeBlob
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default:
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return nil, errors.Errorf("invalid type %d", e.Type)
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}
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entries = append(entries, entry)
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pos += uint(e.Length)
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}
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return entries, nil
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}
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