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Embed context into ReaderAt

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The io.Reader interface does not support contexts, such that it is
necessary to embed the context into the backendReaderAt struct. This has
the problem that a reader might suddenly stop working when it's
contained context is canceled. However, this is now problem here as the
reader instances never escape the calling function.
This commit is contained in:
Michael Eischer 2020-10-06 15:59:00 +02:00
parent d6cfe857b7
commit e638b46a13
4 changed files with 13 additions and 10 deletions
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2
cmd/restic/cmd_debug.go
View file

@ -87,7 +87,7 @@ func printPacks(ctx context.Context, repo *repository.Repository, wr io.Writer)
return repo.List(ctx, restic.PackFile, func(id restic.ID, size int64) error { return repo.List(ctx, restic.PackFile, func(id restic.ID, size int64) error {
h := restic.Handle{Type: restic.PackFile, Name: id.String()} h := restic.Handle{Type: restic.PackFile, Name: id.String()}
blobs, err := pack.List(repo.Key(), restic.ReaderAt(repo.Backend(), h), size) blobs, err := pack.List(repo.Key(), restic.ReaderAt(ctx, repo.Backend(), h), size)
if err != nil { if err != nil {
Warnf("error for pack %v: %v\n", id.Str(), err) Warnf("error for pack %v: %v\n", id.Str(), err)
return nil return nil

4
internal/pack/pack_test.go
View file

@ -128,7 +128,7 @@ func TestUnpackReadSeeker(t *testing.T) {
handle := restic.Handle{Type: restic.PackFile, Name: id.String()} handle := restic.Handle{Type: restic.PackFile, Name: id.String()}
rtest.OK(t, b.Save(context.TODO(), handle, restic.NewByteReader(packData))) rtest.OK(t, b.Save(context.TODO(), handle, restic.NewByteReader(packData)))
verifyBlobs(t, bufs, k, restic.ReaderAt(b, handle), packSize) verifyBlobs(t, bufs, k, restic.ReaderAt(context.TODO(), b, handle), packSize)
} }
func TestShortPack(t *testing.T) { func TestShortPack(t *testing.T) {
@ -141,5 +141,5 @@ func TestShortPack(t *testing.T) {
handle := restic.Handle{Type: restic.PackFile, Name: id.String()} handle := restic.Handle{Type: restic.PackFile, Name: id.String()}
rtest.OK(t, b.Save(context.TODO(), handle, restic.NewByteReader(packData))) rtest.OK(t, b.Save(context.TODO(), handle, restic.NewByteReader(packData)))
verifyBlobs(t, bufs, k, restic.ReaderAt(b, handle), packSize) verifyBlobs(t, bufs, k, restic.ReaderAt(context.TODO(), b, handle), packSize)
} }

2
internal/repository/repository.go
View file

@ -679,7 +679,7 @@ func (r *Repository) List(ctx context.Context, t restic.FileType, fn func(restic
func (r *Repository) ListPack(ctx context.Context, id restic.ID, size int64) ([]restic.Blob, int64, error) { func (r *Repository) ListPack(ctx context.Context, id restic.ID, size int64) ([]restic.Blob, int64, error) {
h := restic.Handle{Type: restic.PackFile, Name: id.String()} h := restic.Handle{Type: restic.PackFile, Name: id.String()}
blobs, err := pack.List(r.Key(), restic.ReaderAt(r.Backend(), h), size) blobs, err := pack.List(r.Key(), restic.ReaderAt(ctx, r.Backend(), h), size)
if err != nil { if err != nil {
return nil, 0, err return nil, 0, err
} }

15
internal/restic/readerat.go
View file

@ -9,17 +9,20 @@ import (
) )
type backendReaderAt struct { type backendReaderAt struct {
be Backend ctx context.Context
h Handle be Backend
h Handle
} }
func (brd backendReaderAt) ReadAt(p []byte, offset int64) (n int, err error) { func (brd backendReaderAt) ReadAt(p []byte, offset int64) (n int, err error) {
return ReadAt(context.TODO(), brd.be, brd.h, offset, p) return ReadAt(brd.ctx, brd.be, brd.h, offset, p)
} }
// ReaderAt returns an io.ReaderAt for a file in the backend. // ReaderAt returns an io.ReaderAt for a file in the backend. The returned reader
func ReaderAt(be Backend, h Handle) io.ReaderAt { // should not escape the caller function to avoid unexpected interactions with the
return backendReaderAt{be: be, h: h} // embedded context
func ReaderAt(ctx context.Context, be Backend, h Handle) io.ReaderAt {
return backendReaderAt{ctx: ctx, be: be, h: h}
} }
// ReadAt reads from the backend handle h at the given position. // ReadAt reads from the backend handle h at the given position.