github.com/mckael/restic@v0.8.3/internal/restic/readerat.go (about)

     1  package restic
     2  
     3  import (
     4  	"context"
     5  	"io"
     6  
     7  	"github.com/restic/restic/internal/debug"
     8  	"github.com/restic/restic/internal/errors"
     9  )
    10  
    11  type backendReaderAt struct {
    12  	be Backend
    13  	h  Handle
    14  }
    15  
    16  func (brd backendReaderAt) ReadAt(p []byte, offset int64) (n int, err error) {
    17  	return ReadAt(context.TODO(), brd.be, brd.h, offset, p)
    18  }
    19  
    20  // ReaderAt returns an io.ReaderAt for a file in the backend.
    21  func ReaderAt(be Backend, h Handle) io.ReaderAt {
    22  	return backendReaderAt{be: be, h: h}
    23  }
    24  
    25  // ReadAt reads from the backend handle h at the given position.
    26  func ReadAt(ctx context.Context, be Backend, h Handle, offset int64, p []byte) (n int, err error) {
    27  	debug.Log("ReadAt(%v) at %v, len %v", h, offset, len(p))
    28  
    29  	err = be.Load(ctx, h, len(p), offset, func(rd io.Reader) (ierr error) {
    30  		n, ierr = io.ReadFull(rd, p)
    31  
    32  		return ierr
    33  	})
    34  	if err != nil {
    35  		return 0, err
    36  	}
    37  
    38  	debug.Log("ReadAt(%v) ReadFull returned %v bytes", h, n)
    39  
    40  	return n, errors.Wrapf(err, "ReadFull(%v)", h)
    41  }