github.com/fawick/restic@v0.1.1-0.20171126184616-c02923fbfc79/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  	rd, err := be.Load(ctx, h, len(p), offset)
    29  	if err != nil {
    30  		return 0, err
    31  	}
    32  
    33  	n, err = io.ReadFull(rd, p)
    34  	e := rd.Close()
    35  	if err == nil {
    36  		err = e
    37  	}
    38  
    39  	debug.Log("ReadAt(%v) ReadFull returned %v bytes", h, n)
    40  
    41  	return n, errors.Wrapf(err, "ReadFull(%v)", h)
    42  }