util: Add a simple log wrapper for io.Writer

This lets logger interfaces that use io.Writer get met by our logging
interface.

util/log.go

@@ -0,0 +1,32 @@
+// Mgmt
+// Copyright (C) 2013-2021+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package util
+
+// LogWriter is a simple interface that wraps our logf interface.
+// TODO: Logf should end in (n int, err error) like fmt.Printf does!
+type LogWriter struct {
+	Prefix string
+	Logf   func(format string, v ...interface{})
+}
+
+// Write satisfies the io.Writer interface.
+func (obj *LogWriter) Write(p []byte) (n int, err error) {
+	// TODO: logf should pass through (n int, err error)
+	obj.Logf(obj.Prefix + string(p))
+	return len(p), nil // TODO: hack for now
+}