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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2014-2015 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package grubenv
import (
"bytes"
"fmt"
"os"
"github.com/snapcore/snapd/strutil"
)
// FIXME: support for escaping (embedded \n in grubenv) missing
type Env struct {
env map[string]string
ordering []string
path string
}
func NewEnv(path string) *Env {
return &Env{
env: make(map[string]string),
path: path,
}
}
func (g *Env) Get(name string) string {
return g.env[name]
}
func (g *Env) Set(key, value string) {
if !strutil.ListContains(g.ordering, key) {
g.ordering = append(g.ordering, key)
}
g.env[key] = value
}
func (g *Env) Load() error {
buf, err := os.ReadFile(g.path)
if err != nil {
return err
}
if len(buf) != 1024 {
return fmt.Errorf("grubenv %q must be exactly 1024 byte, got %d", g.path, len(buf))
}
if !bytes.HasPrefix(buf, []byte("# GRUB Environment Block\n")) {
return fmt.Errorf("cannot find grubenv header in %q", g.path)
}
rawEnv := bytes.Split(buf, []byte("\n"))
for _, env := range rawEnv[1:] {
l := bytes.SplitN(env, []byte("="), 2)
// be liberal in what you accept
if len(l) < 2 {
continue
}
k := string(l[0])
v := string(l[1])
g.env[k] = v
g.ordering = append(g.ordering, k)
}
return nil
}
func (g *Env) Save() error {
w := bytes.NewBuffer(nil)
w.Grow(1024)
fmt.Fprintf(w, "# GRUB Environment Block\n")
for _, k := range g.ordering {
if _, err := fmt.Fprintf(w, "%s=%s\n", k, g.env[k]); err != nil {
return err
}
}
if w.Len() > 1024 {
return fmt.Errorf("cannot write grubenv %q: bigger than 1024 bytes (%d)", g.path, w.Len())
}
content := w.Bytes()[:w.Cap()]
for i := w.Len(); i < len(content); i++ {
content[i] = '#'
}
// write in place to avoid the file moving on disk
// (thats what grubenv is also doing)
f, err := os.Create(g.path)
if err != nil {
return err
}
if _, err := f.Write(content); err != nil {
return err
}
if err := f.Sync(); err != nil {
return err
}
return f.Close()
}
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