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parser: implement DecodeLayerContainer
Changes: * add DecodingLayerContainer to contain/search DecodingLayer values: * add DecodingLayerFunc type as a decoder closure; * add DecodingLayerMap, DecodingLayerSparse, DecodingLayerArray as implementations of DecodingLayerContainer; * add code generation for the reference LayersDecoder method implementation. * refactor DecodingLayerParser: * use DecodingLayerMap by default; * add SetDecodingLayerContainer method to initialize parser. Signed-off-by: Yerden Zhumabekov <[email protected]>
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3 files changed

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‎gen.go‎

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// Copyright 2019 The GoPacket Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree.
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// +build ignore
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// This file generates LayersDecoder function for DecodingLayerContainer
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// go run gen.go | gofmt > layers_decoder.go
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package main
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import (
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"fmt"
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"os"
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"time"
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)
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const headerFmt = `// Copyright 2019 The GoPacket Authors. All rights reserved.
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package gopacket
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// Created by gen.go, don't edit manually
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// Generated at %s
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// LayersDecoder returns DecodingLayerFunc for specified
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// DecodingLayerContainer, LayerType value to start decoding with and
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// some DecodeFeedback.
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func LayersDecoder(dl DecodingLayerContainer, first LayerType, df DecodeFeedback) DecodingLayerFunc {
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firstDec, ok := dl.Decoder(first)
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if !ok {
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return func([]byte, *[]LayerType) (LayerType, error) {
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return first, nil
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}
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}
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`
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var funcBody = `return func(data []byte, decoded *[]LayerType) (LayerType, error) {
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*decoded = (*decoded)[:0] // Truncated decoded layers.
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typ := first
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decoder := firstDec
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for {
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if err := decoder.DecodeFromBytes(data, df); err != nil {
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return LayerTypeZero, err
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}
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*decoded = append(*decoded, typ)
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typ = decoder.NextLayerType()
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if data = decoder.LayerPayload(); len(data) == 0 {
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break
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}
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if decoder, ok = dlc.Decoder(typ); !ok {
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return typ, nil
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}
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}
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return LayerTypeZero, nil
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}`
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func main() {
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fmt.Fprintf(os.Stderr, "Writing results to stdout\n")
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types := []string{
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"DecodingLayerSparse",
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"DecodingLayerArray",
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"DecodingLayerMap",
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}
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fmt.Printf(headerFmt, time.Now())
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for _, t := range types {
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fmt.Printf("if dlc, ok := dl.(%s); ok {", t)
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fmt.Println(funcBody)
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fmt.Println("}")
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}
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fmt.Println("dlc := dl")
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fmt.Println(funcBody)
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fmt.Println("}")
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}

‎layers_decoder.go‎

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// Copyright 2019 The GoPacket Authors. All rights reserved.
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package gopacket
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// Created by gen.go, don't edit manually
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// Generated at 2019-06-18 11:37:31.308731293 +0600 +06 m=+0.000842599
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// LayersDecoder returns DecodingLayerFunc for specified
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// DecodingLayerContainer, LayerType value to start decoding with and
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// some DecodeFeedback.
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func LayersDecoder(dl DecodingLayerContainer, first LayerType, df DecodeFeedback) DecodingLayerFunc {
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firstDec, ok := dl.Decoder(first)
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if !ok {
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return func([]byte, *[]LayerType) (LayerType, error) {
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return first, nil
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}
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}
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if dlc, ok := dl.(DecodingLayerSparse); ok {
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return func(data []byte, decoded *[]LayerType) (LayerType, error) {
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*decoded = (*decoded)[:0] // Truncated decoded layers.
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typ := first
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decoder := firstDec
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for {
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if err := decoder.DecodeFromBytes(data, df); err != nil {
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return LayerTypeZero, err
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}
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*decoded = append(*decoded, typ)
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typ = decoder.NextLayerType()
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if data = decoder.LayerPayload(); len(data) == 0 {
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break
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}
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if decoder, ok = dlc.Decoder(typ); !ok {
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return typ, nil
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}
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}
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return LayerTypeZero, nil
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}
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}
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if dlc, ok := dl.(DecodingLayerArray); ok {
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return func(data []byte, decoded *[]LayerType) (LayerType, error) {
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*decoded = (*decoded)[:0] // Truncated decoded layers.
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typ := first
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decoder := firstDec
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for {
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if err := decoder.DecodeFromBytes(data, df); err != nil {
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return LayerTypeZero, err
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}
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*decoded = append(*decoded, typ)
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typ = decoder.NextLayerType()
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if data = decoder.LayerPayload(); len(data) == 0 {
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break
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}
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if decoder, ok = dlc.Decoder(typ); !ok {
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return typ, nil
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}
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}
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return LayerTypeZero, nil
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}
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}
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if dlc, ok := dl.(DecodingLayerMap); ok {
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return func(data []byte, decoded *[]LayerType) (LayerType, error) {
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*decoded = (*decoded)[:0] // Truncated decoded layers.
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typ := first
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decoder := firstDec
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for {
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if err := decoder.DecodeFromBytes(data, df); err != nil {
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return LayerTypeZero, err
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}
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*decoded = append(*decoded, typ)
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typ = decoder.NextLayerType()
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if data = decoder.LayerPayload(); len(data) == 0 {
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break
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}
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if decoder, ok = dlc.Decoder(typ); !ok {
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return typ, nil
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}
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}
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return LayerTypeZero, nil
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}
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}
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dlc := dl
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return func(data []byte, decoded *[]LayerType) (LayerType, error) {
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*decoded = (*decoded)[:0] // Truncated decoded layers.
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typ := first
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decoder := firstDec
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for {
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if err := decoder.DecodeFromBytes(data, df); err != nil {
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return LayerTypeZero, err
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}
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*decoded = append(*decoded, typ)
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typ = decoder.NextLayerType()
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if data = decoder.LayerPayload(); len(data) == 0 {
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break
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}
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if decoder, ok = dlc.Decoder(typ); !ok {
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return typ, nil
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}
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}
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return LayerTypeZero, nil
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}
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}

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