Adding upstream version 3.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

sz.go

@@ -0,0 +1,51 @@
+package archiver
+
+import (
+	"fmt"
+	"io"
+	"path/filepath"
+
+	"github.com/golang/snappy"
+)
+
+// Snappy facilitates Snappy compression.
+type Snappy struct{}
+
+// Compress reads in, compresses it, and writes it to out.
+func (s *Snappy) Compress(in io.Reader, out io.Writer) error {
+	w := snappy.NewBufferedWriter(out)
+	defer w.Close()
+	_, err := io.Copy(w, in)
+	return err
+}
+
+// Decompress reads in, decompresses it, and writes it to out.
+func (s *Snappy) Decompress(in io.Reader, out io.Writer) error {
+	r := snappy.NewReader(in)
+	_, err := io.Copy(out, r)
+	return err
+}
+
+// CheckExt ensures the file extension matches the format.
+func (s *Snappy) CheckExt(filename string) error {
+	if filepath.Ext(filename) != ".sz" {
+		return fmt.Errorf("filename must have a .sz extension")
+	}
+	return nil
+}
+
+func (s *Snappy) String() string { return "sz" }
+
+// NewSnappy returns a new, default instance ready to be customized and used.
+func NewSnappy() *Snappy {
+	return new(Snappy)
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Compressor(new(Snappy))
+	_ = Decompressor(new(Snappy))
+)
+
+// DefaultSnappy is a default instance that is conveniently ready to use.
+var DefaultSnappy = NewSnappy()