TextOutput.go

/*
 * 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 "bufio"
import "io"
import "log"
import "os"

import "github.com/golang/protobuf/proto"

type TextFormatFunc func(*Dnstap) ([]byte, bool)

type TextOutput struct {
    format          TextFormatFunc
    outputChannel   chan []byte
    wait            chan bool
    writer          *bufio.Writer
}

func NewTextOutput(writer io.Writer, format TextFormatFunc) (o *TextOutput) {
    o = new(TextOutput)
    o.format = format
    o.outputChannel = make(chan []byte, outputChannelSize)
    o.writer = bufio.NewWriter(writer)
    o.wait = make(chan bool)
    return
}

func NewTextOutputFromFilename(fname string, format TextFormatFunc) (o *TextOutput, err error) {
    if fname == "" || fname == "-" {
        return NewTextOutput(os.Stdout, format), nil
    }
    writer, err := os.Create(fname)
    if err != nil {
        return
    }
    return NewTextOutput(writer, format), nil
}

func (o *TextOutput) GetOutputChannel() (chan []byte) {
    return o.outputChannel
}

func (o *TextOutput) RunOutputLoop() {
    dt := &Dnstap{}
    for frame := range o.outputChannel {
        if err := proto.Unmarshal(frame, dt); err != nil {
            log.Fatalf("dnstap.TextOutput: proto.Unmarshal() failed: %s\n", err)
            break
        }
        buf, ok := o.format(dt)
        if !ok {
            log.Fatalf("dnstap.TextOutput: text format function failed\n")
            break
        }
        if _, err := o.writer.Write(buf); err != nil {
            log.Fatalf("dnstap.TextOutput: write failed: %s\n", err)
            break
        }
        o.writer.Flush()
    }
    close(o.wait)
}

func (o *TextOutput) Close() {
    close(o.outputChannel)
    <-o.wait
    o.writer.Flush()
}