51 lines
1.2 KiB
Go
51 lines
1.2 KiB
Go
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package database
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import (
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"encoding/json"
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)
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// Atomically check if there is an existing lock in place on the state. Returns
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// true if it can be set, otherwise returns false and lock is set to the value
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// of the existing lock
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func (db *DB) SetLockOrGetExistingLock(name string, lock any) (bool, error) {
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tx, err := db.Begin()
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if err != nil {
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return false, err
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}
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defer func() {
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if err != nil {
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_ = tx.Rollback()
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}
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}()
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var data []byte
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if err = tx.QueryRowContext(db.ctx, `SELECT lock FROM states WHERE name = ?;`, name).Scan(&data); err != nil {
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return false, err
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}
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if data != nil {
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err = json.Unmarshal(data, lock)
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return false, err
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}
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if data, err = json.Marshal(lock); err != nil {
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return false, err
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}
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_, err = tx.Exec(`UPDATE states SET lock = json(?) WHERE name = ?;`, data, name)
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if err != nil {
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return false, err
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}
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err = tx.Commit()
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return true, err
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}
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func (db *DB) Unlock(name, lock any) (bool, error) {
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data, err := json.Marshal(lock)
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if err != nil {
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return false, err
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}
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result, err := db.Exec(`UPDATE states SET lock = NULL WHERE name = ? and lock = json(?);`, name, data)
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if err != nil {
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return false, err
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}
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n, err := result.RowsAffected()
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return n == 1, err
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}
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