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restic/internal/backend/utils.go
2022-09-25 11:35:35 +02:00

116 lines
3.1 KiB
Go

package backend
import (
"bytes"
"context"
"fmt"
"io"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
)
// LoadAll reads all data stored in the backend for the handle into the given
// buffer, which is truncated. If the buffer is not large enough or nil, a new
// one is allocated.
func LoadAll(ctx context.Context, buf []byte, be restic.Backend, h restic.Handle) ([]byte, error) {
retriedInvalidData := false
err := be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
// make sure this is idempotent, in case an error occurs this function may be called multiple times!
wr := bytes.NewBuffer(buf[:0])
_, cerr := io.Copy(wr, rd)
if cerr != nil {
return cerr
}
buf = wr.Bytes()
// retry loading damaged data only once. If a file fails to download correctly
// the second time, then it is likely corrupted at the backend. Return the data
// to the caller in that case to let it decide what to do with the data.
if !retriedInvalidData && h.Type != restic.ConfigFile {
id, err := restic.ParseID(h.Name)
if err == nil && !restic.Hash(buf).Equal(id) {
debug.Log("retry loading broken blob %v", h)
retriedInvalidData = true
return errors.Errorf("loadAll(%v): invalid data returned", h)
}
}
return nil
})
if err != nil {
return nil, err
}
return buf, nil
}
// LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.
type LimitedReadCloser struct {
io.Closer
io.LimitedReader
}
// LimitReadCloser returns a new reader wraps r in an io.LimitedReader, but also
// exposes the Close() method.
func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
return &LimitedReadCloser{Closer: r, LimitedReader: io.LimitedReader{R: r, N: n}}
}
// DefaultLoad implements Backend.Load using lower-level openReader func
func DefaultLoad(ctx context.Context, h restic.Handle, length int, offset int64,
openReader func(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error),
fn func(rd io.Reader) error) error {
rd, err := openReader(ctx, h, length, offset)
if err != nil {
return err
}
err = fn(rd)
if err != nil {
_ = rd.Close() // ignore secondary errors closing the reader
return err
}
return rd.Close()
}
type memorizedLister struct {
fileInfos []restic.FileInfo
tpe restic.FileType
}
func (m *memorizedLister) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
if t != m.tpe {
return fmt.Errorf("filetype mismatch, expected %s got %s", m.tpe, t)
}
for _, fi := range m.fileInfos {
if ctx.Err() != nil {
break
}
err := fn(fi)
if err != nil {
return err
}
}
return ctx.Err()
}
func MemorizeList(ctx context.Context, be restic.Lister, t restic.FileType) (restic.Lister, error) {
if _, ok := be.(*memorizedLister); ok {
return be, nil
}
var fileInfos []restic.FileInfo
err := be.List(ctx, t, func(fi restic.FileInfo) error {
fileInfos = append(fileInfos, fi)
return nil
})
if err != nil {
return nil, err
}
return &memorizedLister{
fileInfos: fileInfos,
tpe: t,
}, nil
}