Package list golang-github-dnstap-golang-dnstap / 5bbfd07 FrameStreamOutput.go
5bbfd07

Tree @5bbfd07 (Download .tar.gz)

FrameStreamOutput.go @5bbfd07raw · history · blame

/*
 * Copyright (c) 2014 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"
	"log"
	"os"

	"github.com/farsightsec/golang-framestream"
)

// FrameStreamOutput implements a dnstap Output to an io.Writer.
type FrameStreamOutput struct {
	outputChannel chan []byte
	wait          chan bool
	enc           *framestream.Encoder
}

// NewFrameStreamOutput creates a FrameStreamOutput writing dnstap data to
// the given io.Writer.
func NewFrameStreamOutput(w io.Writer) (o *FrameStreamOutput, err error) {
	o = new(FrameStreamOutput)
	o.outputChannel = make(chan []byte, outputChannelSize)
	o.enc, err = framestream.NewEncoder(w, &framestream.EncoderOptions{ContentType: FSContentType})
	if err != nil {
		return
	}
	o.wait = make(chan bool)
	return
}

// NewFrameStreamOutputFromFilename creates a file with the namee 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)
}

// 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()
// logs a fatal error exits the program.
//
// RunOutputLoop satisfies the dnstap Output interface.
func (o *FrameStreamOutput) RunOutputLoop() {
	for frame := range o.outputChannel {
		if _, err := o.enc.Write(frame); err != nil {
			log.Fatalf("framestream.Encoder.Write() failed: %s\n", err)
			break
		}
	}
	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.enc.Flush()
	o.enc.Close()
}