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