/*
 * Copyright 2000, International Business Machines Corporation and others.
 * All Rights Reserved.
 * 
 * This software has been released under the terms of the IBM Public
 * License.  For details, see the LICENSE file in the top-level source
 * directory or online at http://www.openafs.org/dl/license10.html
 */

/*******************************************************************\
* 								    *
* 	Information Technology Center				    *
* 	Carnegie-Mellon University				    *
* 								    *
* 								    *
* 								    *
\*******************************************************************/

/*
	Include file for using Vice locking routines.
*/

#ifndef LOCK_H
#define LOCK_H

/* The following macros allow multi statement macros to be defined safely, i.e.
   - the multi statement macro can be the object of an if statement;
   - the call to the multi statement macro may be legally followed by a semi-colon.
   BEGINMAC and ENDMAC have been tested with both the portable C compiler and
   Hi-C.  Both compilers were from the Palo Alto 4.2BSD software releases, and
   both optimized out the constant loop code.  For an example of the use
   of BEGINMAC and ENDMAC, see the definition for ReleaseWriteLock, below.
   An alternative to this, using "if(1)" for BEGINMAC is not used because it
   may generate worse code with pcc, and may generate warning messages with hi-C.
*/

#define BEGINMAC do {
#define ENDMAC   } while (0)

#ifdef AFS_PTHREAD_ENV
#include <assert.h>
#include <pthread.h>
#define LOCK_LOCK(A) assert(pthread_mutex_lock(&(A)->mutex) == 0);
#define LOCK_UNLOCK(A) assert(pthread_mutex_unlock(&(A)->mutex) == 0);
#else /* AFS_PTHREAD_ENV */
#define LOCK_LOCK(A)
#define LOCK_UNLOCK(A)
#endif /* AFS_PTHREAD_ENV */

/* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
struct Lock {
    unsigned char	wait_states;	/* type of lockers waiting */
    unsigned char	excl_locked;	/* anyone have boosted, shared or write lock? */
    unsigned char	readers_reading;	/* # readers actually with read locks */
    unsigned char	num_waiting;	/* probably need this soon */
#ifdef AFS_PTHREAD_ENV
    pthread_mutex_t	mutex;		/* protects this structure */
    pthread_cond_t	read_cv;	/* wait for read locks */
    pthread_cond_t	write_cv;	/* wait for write/shared locks */
#endif /* AFS_PTHREAD_ENV */
};

extern void Afs_Lock_Obtain(struct Lock * lock, int how);
extern void Afs_Lock_ReleaseR(struct Lock *lock);
extern void Afs_Lock_ReleaseW(struct Lock * lock);
void Lock_Init(struct Lock *lock);
void Lock_Destroy(struct Lock *lock);

#define READ_LOCK	1
#define WRITE_LOCK	2
#define SHARED_LOCK	4
/* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
#define BOOSTED_LOCK 6

/* next defines wait_states for which we wait on excl_locked */
#define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)

#define ObtainReadLock(lock)\
	BEGINMAC \
	    LOCK_LOCK(lock) \
	    if (!((lock)->excl_locked & WRITE_LOCK) && !(lock)->wait_states)\
		(lock) -> readers_reading++;\
	    else\
		Afs_Lock_Obtain(lock, READ_LOCK); \
	    LOCK_UNLOCK(lock) \
	ENDMAC
    
#define ObtainReadLockNoBlock(lock, code)\
        BEGINMAC \
            LOCK_LOCK(lock) \
            if (!((lock)->excl_locked & WRITE_LOCK) && !(lock)->wait_states) {\
                (lock) -> readers_reading++;\
                code = 0;\
            }\
            else\
                code = -1; \
            LOCK_UNLOCK(lock) \
        ENDMAC

#define ObtainWriteLock(lock)\
	BEGINMAC \
	    LOCK_LOCK(lock) \
	    if (!(lock)->excl_locked && !(lock)->readers_reading)\
		(lock) -> excl_locked = WRITE_LOCK;\
	    else\
		Afs_Lock_Obtain(lock, WRITE_LOCK); \
	    LOCK_UNLOCK(lock) \
	ENDMAC
    
#define ObtainWriteLockNoBlock(lock, code)\
        BEGINMAC \
            LOCK_LOCK(lock) \
            if (!(lock)->excl_locked && !(lock)->readers_reading) {\
                (lock) -> excl_locked = WRITE_LOCK;\
                code = 0;\
            }\
            else\
                code = -1; \
            LOCK_UNLOCK(lock) \
        ENDMAC

#define ObtainSharedLock(lock)\
	BEGINMAC \
	    LOCK_LOCK(lock) \
	    if (!(lock)->excl_locked && !(lock)->wait_states)\
		(lock) -> excl_locked = SHARED_LOCK;\
	    else\
	        Afs_Lock_Obtain(lock, SHARED_LOCK); \
	    LOCK_UNLOCK(lock) \
	ENDMAC

#define ObtainSharedLockNoBlock(lock, code)\
        BEGINMAC \
            LOCK_LOCK(lock) \
            if (!(lock)->excl_locked && !(lock)->wait_states) {\
                (lock) -> excl_locked = SHARED_LOCK;\
                code = 0;\
            }\
            else\
                code = -1; \
            LOCK_UNLOCK(lock) \
        ENDMAC

#define BoostSharedLock(lock)\
	BEGINMAC \
	    LOCK_LOCK(lock) \
	    if (!(lock)->readers_reading)\
		(lock)->excl_locked = WRITE_LOCK;\
	    else\
		Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
	    LOCK_UNLOCK(lock) \
	ENDMAC

/* this must only be called with a WRITE or boosted SHARED lock! */
#define UnboostSharedLock(lock)\
	BEGINMAC\
	    LOCK_LOCK(lock) \
	    (lock)->excl_locked = SHARED_LOCK; \
	    if((lock)->wait_states) \
		Afs_Lock_ReleaseR(lock); \
	    LOCK_UNLOCK(lock) \
	ENDMAC

#ifdef notdef
/* this is what UnboostSharedLock looked like before the hi-C compiler */
/* this must only be called with a WRITE or boosted SHARED lock! */
#define UnboostSharedLock(lock)\
	((lock)->excl_locked = SHARED_LOCK,\
	((lock)->wait_states ?\
		Afs_Lock_ReleaseR(lock) : 0))
#endif /* notdef */

#define ReleaseReadLock(lock)\
	BEGINMAC\
	    LOCK_LOCK(lock) \
	    if (!--(lock)->readers_reading && (lock)->wait_states)\
		Afs_Lock_ReleaseW(lock) ; \
	    LOCK_UNLOCK(lock) \
	ENDMAC


#ifdef notdef
/* This is what the previous definition should be, but the hi-C compiler generates
  a warning for each invocation */
#define ReleaseReadLock(lock)\
	(!--(lock)->readers_reading && (lock)->wait_states ?\
		Afs_Lock_ReleaseW(lock)    :\
		0)
#endif /* notdef */

#define ReleaseWriteLock(lock)\
	BEGINMAC\
	    LOCK_LOCK(lock) \
	    (lock)->excl_locked &= ~WRITE_LOCK;\
	    if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
	    LOCK_UNLOCK(lock) \
	ENDMAC

#ifdef notdef
/* This is what the previous definition should be, but the hi-C compiler generates
   a warning for each invocation */
#define ReleaseWriteLock(lock)\
	((lock)->excl_locked &= ~WRITE_LOCK,\
	((lock)->wait_states ?\
		Afs_Lock_ReleaseR(lock) : 0))
#endif /* notdef */

/* can be used on shared or boosted (write) locks */
#define ReleaseSharedLock(lock)\
	BEGINMAC\
	    LOCK_LOCK(lock) \
	    (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
	    if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
	    LOCK_UNLOCK(lock) \
	ENDMAC

#ifdef notdef
/* This is what the previous definition should be, but the hi-C compiler generates
   a warning for each invocation */
/* can be used on shared or boosted (write) locks */
#define ReleaseSharedLock(lock)\
	((lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK),\
	((lock)->wait_states ?\
		Afs_Lock_ReleaseR(lock) : 0))
#endif /* notdef */

/* convert a write lock to a read lock */
#define ConvertWriteToReadLock(lock)\
	BEGINMAC\
	    LOCK_LOCK(lock) \
	    (lock)->excl_locked &= ~WRITE_LOCK;\
	    (lock)->readers_reading++;\
	    if ((lock)->wait_states & READ_LOCK) \
		Afs_Lock_WakeupR(lock) ; \
	    LOCK_UNLOCK(lock) \
	ENDMAC

/* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
#define LockWaiters(lock)\
	((int) ((lock)->num_waiting))

#define CheckLock(lock)\
	((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)

#define WriteLocked(lock)\
	((lock)->excl_locked & WRITE_LOCK)

#endif /* LOCK_H */
