package backend import ( "context" "io" "github.com/restic/restic/internal/debug" "github.com/restic/restic/internal/errors" ) type backendReaderAt struct { ctx context.Context be Backend h Handle } func (brd backendReaderAt) ReadAt(p []byte, offset int64) (n int, err error) { return ReadAt(brd.ctx, brd.be, brd.h, offset, p) } // ReaderAt returns an io.ReaderAt for a file in the backend. The returned reader // should not escape the caller function to avoid unexpected interactions with the // 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. func ReadAt(ctx context.Context, be Backend, h Handle, offset int64, p []byte) (n int, err error) { debug.Log("ReadAt(%v) at %v, len %v", h, offset, len(p)) err = be.Load(ctx, h, len(p), offset, func(rd io.Reader) (ierr error) { n, ierr = io.ReadFull(rd, p) return ierr }) if err != nil { return 0, errors.Wrapf(err, "ReadFull(%v)", h) } debug.Log("ReadAt(%v) ReadFull returned %v bytes", h, n) return n, nil }