#ifndef UC_RESTART_COUNTER_H_
#define UC_RESTART_COUNTER_H_
/** @file
 * Simple support for keeping track of number of restarts.
 *
 * Certain protocols desire support for comminicating the number
 * of times an entity has restarted. 
 * The counter might also serve as a seed for sequence number generation
 * to minimize recycling a recently used sequence number.
 *
 * The number of times a process has been restarted is simply kept 
 * track of via a counter in a restart state ile in ascii representation.
 */

#ifdef __cplusplus
extern "C" {
#endif 

struct UCRestartCounter {
    unsigned int counter;
    int fd;
};

typedef enum {
    UC_RC_OK,
    /** accessing the file failed, inspect errno
     * for more info */
    UC_RC_ERR_FILE_ACCESS_ERROR,
    /* The file existed and is opened but
     * no valid number could be read from the file.
     * This is a transient error,
     * the now new counter is initialized to 0, and
     * written to the file */
    UC_RC_ERR_FILE_CONTENT_ERROR,
    /* UC_RC_FL_LOCK_FILE was specified but the file 
     * is already locked by some other process */
    UC_RC_ERR_FILE_LOCKED,
    /** unspecified error. Inspect errno. */
    UC_RC_ERR_UNSPECIFIED,
    /** Given  by uc_restart_counter_close if the 
     * file never was opened */
    UC_RC_ERR_NOT_OPENED,
} UCRCResult;

/** Lock the restart state file and keep it open.
 * e.g. to prevent several processes from being started
 * and  using the same restart state file.*/
#define UC_RC_FL_LOCK_FILE ( 1 << 0)

/** Read and update the current restart counter.
 * This is typically called once at program startup.
 * 
 * @param counter the counter to initialize
 * @param filename the filename to use to keep track of the state
 * @param flags one of UC_RC_FL_XX
 */
UCRCResult uc_restart_counter_init(struct UCRestartCounter *counter, 
                                   const char *filename,
                                   unsigned int flags);

/** Close the current restart counter file if it was opened with the 
 * UC_RC_FL_LOCK_FILE flag.
 *
 * @counter counter file to close. (uc_restart_counter can still be called 
 *          after * the file is closed)
 * @return UC_RC_OK or if the file was not kept open with UC_RC_ERR_FILE_LOCKED
 */        
UCRCResult uc_restart_counter_close(struct UCRestartCounter *counter);

/** Get the current restart counter.
 * In case uc_restart_counter_init failed, this will return 0.
 */
unsigned int uc_restart_counter_get(const struct UCRestartCounter *counter);


#ifdef __cplusplus
}
#endif 

#endif