mike
1a39f54858
- All ipadm-internal messages (usage, prompts, errors) are now English - Usage text is built programmatically from a (left, desc) row list with computed column width instead of hand-aligned spaces, so it can't drift out of alignment again when rows are added/changed - README's literal usage block updated to match; rest of the repo docs stay German
93 lines
2.2 KiB
Go
93 lines
2.2 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"os"
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"strings"
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"syscall"
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)
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// LineStore gives locked read-modify-write access to a flat text file with
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// one record per line. Lines starting with '#' and blank lines are ignored.
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// parse/format convert between a line and a record of type T.
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type LineStore[T any] struct {
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path string
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file *os.File
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header string
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parse func(line string) (T, error)
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format func(v T) string
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}
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func openLineStore[T any](path, header string, parse func(string) (T, error), format func(T) string) (*LineStore[T], error) {
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if err := os.MkdirAll(dirOf(path), 0755); err != nil {
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return nil, fmt.Errorf("cannot create directory for %s: %w", path, err)
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}
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f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
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if err != nil {
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return nil, fmt.Errorf("cannot open %s: %w", path, err)
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}
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if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX); err != nil {
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f.Close()
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return nil, fmt.Errorf("cannot lock %s: %w", path, err)
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}
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return &LineStore[T]{path: path, file: f, header: header, parse: parse, format: format}, nil
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}
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func (s *LineStore[T]) Close() error {
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syscall.Flock(int(s.file.Fd()), syscall.LOCK_UN)
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return s.file.Close()
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}
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func (s *LineStore[T]) Load() ([]T, error) {
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if _, err := s.file.Seek(0, 0); err != nil {
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return nil, err
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}
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var items []T
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sc := bufio.NewScanner(s.file)
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lineNo := 0
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for sc.Scan() {
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lineNo++
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line := strings.TrimRight(sc.Text(), "\r\n")
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if line == "" || strings.HasPrefix(line, "#") {
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continue
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}
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v, err := s.parse(line)
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if err != nil {
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return nil, fmt.Errorf("%s:%d: %w", s.path, lineNo, err)
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}
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items = append(items, v)
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}
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if err := sc.Err(); err != nil {
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return nil, err
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}
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return items, nil
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}
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func (s *LineStore[T]) Save(items []T) error {
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var b strings.Builder
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b.WriteString(s.header)
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for _, v := range items {
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b.WriteString(s.format(v))
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b.WriteString("\n")
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}
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if err := s.file.Truncate(0); err != nil {
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return err
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}
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if _, err := s.file.Seek(0, 0); err != nil {
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return err
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}
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if _, err := s.file.WriteString(b.String()); err != nil {
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return err
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}
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return s.file.Sync()
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}
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func dirOf(path string) string {
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i := strings.LastIndexByte(path, '/')
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if i <= 0 {
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return "."
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}
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return path[:i]
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}
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