}

	r, err := f.Open()
	if err != nil {
		t.Errorf("%v", err)
		return
	}

	// For very large files, just check that the size is correct.
	// The content is expected to be all zeros.
	// Don't bother uncompressing: too big.
	if ft.Content == nil && ft.File == "" && ft.Size > 0 {
		if size != ft.Size {
			t.Errorf("%v: uncompressed size %#x, want %#x", ft.Name, size, ft.Size)
		}
		r.Close()
		return
	}

to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()
	Unlock()
}
</pre>

<p>
If <code>S1</code> and <code>S2</code> also implement
</p>

<pre>
func (p T) Lock() { … }
func (p T) Unlock() { … }
</pre>

<p>
they implement the <code>Locker</code> interface as well
as the <code>File</code> interface.

to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()
	Unlock()
}
</pre>

<p>
If <code>S1</code> and <code>S2</code> also implement
</p>

<pre>
func (p T) Lock() { … }
func (p T) Unlock() { … }
</pre>

<p>
they implement the <code>Locker</code> interface as well
as the <code>File</code> interface.