mirror of
https://github.com/la5nta/pat
synced 2026-08-07 22:32:06 -04:00
62 lines
1 KiB
Go
62 lines
1 KiB
Go
package forms
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import (
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"encoding/json"
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"io"
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"os"
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)
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type Sequence struct {
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f *os.File
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err error
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}
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func OpenSequence(path string) Sequence {
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f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0o644)
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return Sequence{f, err}
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}
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func (s Sequence) Close() error {
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if s.err != nil {
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return s.err
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}
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return s.f.Close()
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}
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func (s Sequence) Load() (int64, error) {
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if s.err != nil {
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return 0, s.err
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}
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if _, err := s.f.Seek(0, io.SeekStart); err != nil {
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return 0, err
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}
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var seq int64
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if err := json.NewDecoder(s.f).Decode(&seq); err != nil {
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if err != io.EOF {
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return 0, err
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}
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}
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return seq, nil
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}
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func (s Sequence) Set(seq int64) (int64, error) {
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if s.err != nil {
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return 0, s.err
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}
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if err := s.f.Truncate(0); err != nil {
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return 0, err
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}
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if _, err := s.f.Seek(0, io.SeekStart); err != nil {
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return 0, err
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}
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defer s.f.Sync()
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return seq, json.NewEncoder(s.f).Encode(&seq)
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}
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func (s Sequence) Incr(increment int64) (int64, error) {
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seq, err := s.Load()
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if err != nil {
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return 0, err
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}
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return s.Set(seq + increment)
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}
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