FrameStreamOutput.go

/*
 * Copyright (c) 2014,2019 by Farsight Security, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package dnstap

import (
	"io"
	"os"
)

// FrameStreamOutput implements a dnstap Output to an io.Writer.
type FrameStreamOutput struct {
	outputChannel chan []byte
	wait          chan bool
	w             Writer
	log           Logger
}

// NewFrameStreamOutput creates a FrameStreamOutput writing dnstap data to
// the given io.Writer.
func NewFrameStreamOutput(w io.Writer) (o *FrameStreamOutput, err error) {
	ow, err := NewWriter(w, nil)
	if err != nil {
		return nil, err
	}
	return &FrameStreamOutput{
		outputChannel: make(chan []byte, outputChannelSize),
		wait:          make(chan bool),
		w:             ow,
		log:           nullLogger{},
	}, nil
}

// NewFrameStreamOutputFromFilename creates a file with the name fname,
// truncates it if it exists, and returns a FrameStreamOutput writing to
// the newly created or truncated file.
func NewFrameStreamOutputFromFilename(fname string) (o *FrameStreamOutput, err error) {
	if fname == "" || fname == "-" {
		return NewFrameStreamOutput(os.Stdout)
	}
	w, err := os.Create(fname)
	if err != nil {
		return
	}
	return NewFrameStreamOutput(w)
}

// SetLogger sets an alternate logger for the FrameStreamOutput. The default
// is no logging.
func (o *FrameStreamOutput) SetLogger(logger Logger) {
	o.log = logger
}

// GetOutputChannel returns the channel on which the FrameStreamOutput accepts
// data.
//
// GetOutputData satisfies the dnstap Output interface.
func (o *FrameStreamOutput) GetOutputChannel() chan []byte {
	return o.outputChannel
}

// RunOutputLoop processes data received on the channel returned by
// GetOutputChannel, returning after the CLose method is called.
// If there is an error writing to the Output's writer, RunOutputLoop()
// returns, logging an error if a logger is configured with SetLogger()
//
// RunOutputLoop satisfies the dnstap Output interface.
func (o *FrameStreamOutput) RunOutputLoop() {
	for frame := range o.outputChannel {
		if _, err := o.w.WriteFrame(frame); err != nil {
			o.log.Printf("FrameStreamOutput: Write error: %v, returning", err)
			close(o.wait)
			return
		}
	}
	close(o.wait)
}

// Close closes the channel returned from GetOutputChannel, and flushes
// all pending output.
//
// Close satisifies the dnstap Output interface.
func (o *FrameStreamOutput) Close() {
	close(o.outputChannel)
	<-o.wait
	o.w.Close()
}