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package database
import (
"database/sql"
"encoding/json"
"errors"
)
// Atomically check the lock status of a state and lock it if unlocked. Returns
// true if the function locked the state, otherwise returns false and the lock
// parameter is updated to the value of the existing lock
func (db *DB) SetLockOrGetExistingLock(path string, lock any) (bool, error) {
ret := false
return ret, db.WithTransaction(func(tx *sql.Tx) error {
var lockData []byte
if err := tx.QueryRowContext(db.ctx, `SELECT lock FROM states WHERE path = ?;`, path).Scan(&lockData); err != nil {
if errors.Is(err, sql.ErrNoRows) {
if lockData, err = json.Marshal(lock); err != nil {
return err
}
_, err = tx.ExecContext(db.ctx, `INSERT INTO states(path, lock) VALUES (?, json(?))`, path, lockData)
ret = true
return err
} else {
return err
}
}
if lockData != nil {
return json.Unmarshal(lockData, lock)
}
var err error
if lockData, err = json.Marshal(lock); err != nil {
return err
}
_, err = tx.ExecContext(db.ctx, `UPDATE states SET lock = json(?) WHERE path = ?;`, lockData, path)
ret = true
return err
})
}
func (db *DB) Unlock(path, 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 path = ? and lock = json(?);`, path, data)
if err != nil {
return false, err
}
n, err := result.RowsAffected()
return n == 1, err
}
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