A very bare-bones parser for Wireshark's config file

This is a peg parser using the pigeon PEG parser generator for golang:
https://pkg.go.dev/github.com/mna/pigeon. I also used this for parsing
tshark's stream reassembly output. This parser only really understands
the gui.column.format section at the moment e.g.

gui.column.format:
	"No.", "%m",
	"Time", "%t",
	"Source", "%s",
	"Destination", "%d",
	"Protocol", "%p",
	"Length", "%L",
	"Info", "%i"

I use this parser to provide an option to the user to import Wireshark's
column settings, if they're available.

shark/wiresharkcfg/cfg.go

@@ -0,0 +1,106 @@
+// Copyright 2019-2021 Graham Clark. All rights reserved.  Use of this source
+// code is governed by the MIT license that can be found in the LICENSE
+// file.
+
+package wiresharkcfg
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"strings"
+
+	homedir "github.com/mitchellh/go-homedir"
+	"github.com/shibukawa/configdir"
+)
+
+//======================================================================
+
+var NotFoundError = fmt.Errorf("Could not find wireshark preferences")
+var NotParsedError = fmt.Errorf("Could not parse wireshark preferences")
+
+type Config struct {
+	Strings map[string]string
+	Lists   map[string][]string
+}
+
+func NewDefault() (*Config, error) {
+	// See https://www.wireshark.org/docs/wsug_html_chunked/ChAppFilesConfigurationSection.html
+	// Wireshark had a ~/.wireshark directory before adopting XDG
+	tryXDG := true
+	cpath, err := homedir.Expand("~/.wireshark/preferences")
+	if err == nil {
+		_, err = os.Stat(cpath)
+		if err == nil {
+			tryXDG = false
+		}
+	}
+	if tryXDG {
+		stdConf := configdir.New("", "wireshark")
+		dirs := stdConf.QueryFolders(configdir.All)
+		cpath = path.Join(dirs[0].Path, "preferences")
+		_, err = os.Stat(cpath)
+		if os.IsNotExist(err) {
+			return nil, err
+		}
+	}
+
+	res := &Config{}
+	err = res.PopulateFrom(cpath)
+	return res, err
+}
+
+func (c *Config) PopulateFrom(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	parsed, err := ParseReader("", file)
+	if err != nil {
+		return err
+	}
+
+	*c = *(parsed.(*Config))
+	return nil
+}
+
+func (c *Config) GetList(key string) []string {
+	if c == nil {
+		return nil
+	}
+	if val, ok := c.Lists[key]; ok {
+		return val
+	}
+	return nil
+}
+
+func (c *Config) ColumnFormat() []string {
+	return c.GetList("gui.column.format")
+}
+
+func (c *Config) merge(other *Config) {
+	for k, v := range other.Strings {
+		c.Strings[k] = v
+	}
+	for k, v := range other.Lists {
+		c.Lists[k] = v
+	}
+}
+
+func (c *Config) String() string {
+	res := make([]string, 0, len(c.Strings)+len(c.Lists))
+	for k, v := range c.Strings {
+		res = append(res, fmt.Sprintf("%s: %s", k, v))
+	}
+	for k, v := range c.Lists {
+		v2 := strings.Join(v, ", ")
+		res = append(res, fmt.Sprintf("%s: %s", k, v2))
+	}
+	return strings.Join(res, "\n")
+}
+
+//======================================================================
+// Local Variables:
+// mode: Go
+// fill-column: 110
+// End: