Add in-memory file

ipblocklist/files/mem.go

@@ -0,0 +1,37 @@
+package files
+
+import (
+	"context"
+	"io"
+	"net"
+	"strings"
+)
+
+type memFile struct {
+	data string
+}
+
+func (m memFile) Open(ctx context.Context) (io.ReadCloser, error) {
+	return io.NopCloser(strings.NewReader(m.data)), nil
+}
+
+func (m memFile) String() string {
+	return "mem"
+}
+
+func NewMem(networks []*net.IPNet) (File) {
+	builder := strings.Builder{}
+
+	if len(networks) > 0 {
+		builder.WriteString(networks[0].String())
+	}
+
+	for i := 1; i < len(networks); i++ {
+		builder.WriteString("\n")
+		builder.WriteString(networks[i].String())
+	}
+
+	return memFile{
+		data:  builder.String(),
+	}
+}