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/** @defgroup dnsdbzone Zone related functions
 *  @ingroup dnsdb
 *  @brief Functions used to manipulate a zone
 *
 *  Functions used to manipulate a zone
 *
 * @{
 */

#pragma once

#include <dnsdb/zdb_types.h>

#ifdef	__cplusplus
extern "C"
{
#endif

/**
 * Zone locking
 * 
 * Sets the owner of a zone.
 * 
 * The owner id has a format: the msb is reserved to say that the access is
 * exclusive to only one instance of the owner.
 * The remaining bits are the id.
 * 
 * Mostly used for the simple reader and various writers.
 * 
 * A new feature needs to be added: being able to pre-lock for an owner.
 * 
 * Explanation: I want to lock for the signing process.  But that process
 * is done in two or three phases.  The first phase is read-only (thus allowing
 * the server to work normally).  But I don't want sombody else, say, a dynamic
 * update, to lock the zone in the mean time. (Which would happen when the lock
 * is transferred from the reader to the signer (at the commit phase).
 * So I'll add a secondary owner, meant to tell "I lock as a reader BUT I also
 * reserve the right for myself later".  And later a transfer can be done to
 * the secondary as soon as the last reader unlocks.
 * 
 * zdb_zone_double_lock(zone, owner, secondary owner)
 * zdb_zone_try_double_lock(zone, owner, secondary owner)
 * zdb_zone_transfer_lock(zone, secondary owner)
 * 
 * The parameter would need to be repeated to detect inconsistencies (bugs)
 * 
 * This should have no effect on the normal locking mechanism, thus ensuring
 * no loss of speed.  The only goal is to avoid a race changing the owner.
 * 
 * Having only zdb_zone_transfer_lock(zone, old owner, new owner) cannot work
 * because nothing prevents two soon-to-be writers to lock and work in tandem.
 * 
 */

void zdb_zone_lock(zdb_zone *zone, u8 owner);

bool zdb_zone_trylock(zdb_zone *zone, u8 owner);

void zdb_zone_unlock(zdb_zone *zone, u8 owner);

bool zdb_zone_islocked(zdb_zone *zone);

/**
 * Returns TRUE iff the zone is locked by a writer (any other owner value than nobody and simple reader)
 * 
 * @param zone
 * @return 
 */

bool zdb_zone_iswritelocked(zdb_zone *zone);

/**
 * Reserves the secondary owner and to locks for the owner
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

void zdb_zone_double_lock(zdb_zone *zone, u8 owner, u8 secondary_owner);

/**
 * Tries to reserve the secondary owner and to lock for the owner
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

bool zdb_zone_try_double_lock(zdb_zone *zone, u8 owner, u8 secondary_owner);

/**
 * 
 * Unlocks one owner and sets the secondary owner to nobody
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

void zdb_zone_double_unlock(zdb_zone *zone, u8 owner, u8 secondary_owner);

/**
 * 
 * Puts the secondary lock in place of the lock when the locker count reaches 1
 * Followed by a zdb_zone_unlock
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

void zdb_zone_transfer_lock(zdb_zone *zone, u8 owner, u8 secondary_owner);

/**
 * 
 * Puts the secondary lock in place of the lock when the locker count reaches 1
 * Followed by a zdb_zone_unlock
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

bool zdb_zone_try_transfer_lock(zdb_zone *zone, u8 owner, u8 secondary_owner);

/**
 * 
 * Exchange the primary and secondary locks when the locker count reaches 1
 * Followed by a zdb_zone_unlock
 * 
 * @param zone
 * @param owner
 * @param secondary_owner
 */

void zdb_zone_exchange_locks(zdb_zone *zone, u8 owner, u8 secondary_owner);

#if DNSCORE_HAS_MUTEX_DEBUG_SUPPORT
void zdb_zone_lock_set_monitor();
#endif

/** @} */
