// walking the tree and copying it piecewise. If the directory tree
			// contains nested modules this could push a lot of unnecessary contents,
			// but for the golang.org/x repos it seems to be significantly (~2x)
			// faster than copying one file at a time (via filepath.WalkDir),
			// apparently due to high latency in 'adb' commands.
			if err := adb("push", modDir, deviceModDir); err != nil {

		// no action. Thus, we try an innocent seek to the current position
		// to see if Seek is really supported.
		pos1, err := sr.Seek(0, io.SeekCurrent)
		if pos1 >= 0 && err == nil {
			// Seek seems supported, so perform the real Seek.
			pos2, err := sr.Seek(n-1, io.SeekCurrent)
			if pos2 < 0 || err != nil {
				return err
			}
			seekSkipped = pos2 - pos1
		}
	}

				err = ErrChecksum
			}
		} else {
			// If there's not a data descriptor, we still compare
			// the CRC32 of what we've read against the file header
			// or TOC's CRC32, if it seems like it was set.
			if r.f.CRC32 != 0 && r.hash.Sum32() != r.f.CRC32 {
				err = ErrChecksum
			}
		}
	}
	r.err = err
	return
}

func (r *checksumReader) Close() error { return r.rc.Close() }