/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include "nscd_db.h"
#include "nscd_log.h"

/*
 * Access control structure for a piece of nscd data. This structure
 * is always tagged before the nscd data. nscd_alloc, which should
 * be used to allocate memory that requires access control or usage
 * count control, will initialize this access control structure at the
 * start of the memory returned to the caller.
 */
struct nscd_access_s {
        void            *data;                  /* addr of real data */
        void            (*free_func)(nscd_acc_data_t *data); /* destructor */
        mutex_t         mutex;                  /* protect this structure */
        mutex_t         *data_mutex;
        rwlock_t        *data_rwlock;
        cond_t          *data_cond;
        int             nUse;                   /* usage count */
        int             type;
        int             delete;                 /* no longer available */
        nscd_seq_num_t  seq_num;                /* sequence number */
};

/* size should be in multiple of 8 */
static int sizeof_access = roundup(sizeof (nscd_access_t));

#define ABORT_DUE_TO_NO_VALID_NSCD_ACCESS_DATA 0
#define ASSERT_ACCESS_DATA \
        if (access->data != data) \
                assert(ABORT_DUE_TO_NO_VALID_NSCD_ACCESS_DATA)

#define SET_ACCESS_PTR \
                access = (nscd_access_t *) \
                        ((void *)((char *)data - sizeof_access))

static void _nscd_free(nscd_acc_data_t  *data);

/*
 * FUNCTION: _nscd_release
 *
 * Decrements the usage count maintained in the access data
 * tagged before 'data'. Delete the nscd data item if the delete
 * flag is set and the usage count reaches 0.
 */
void
_nscd_release(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        char            *me = "_nscd_release";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
                (me, "data = %p, access->data = %p, "
                "seq = %lld, nUse = %d\n",
                data, access->data, access->seq_num, access->nUse);
        ASSERT_ACCESS_DATA;

        (void) mutex_lock(&access->mutex);
        access->nUse--;
        if (access->nUse < 0) {
#define ACCESS_NUSE_LESS_THAN_ZERO 0
                assert(ACCESS_NUSE_LESS_THAN_ZERO);
        }
        if (access->nUse <= 0 &&
                access->delete == 1) {

                _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
                (me, "deleting data %p\n", access->data);
                (access->free_func)(access->data);

                /*
                 * if we get here, no other thread could be
                 * holding the access->mutex lock, It is safe
                 * to free the memory containing the mutex
                 * structure. No mutex_unlock is necessary.
                 */
                _nscd_free(data);
        } else
                (void) mutex_unlock(&access->mutex);
}


/*
 * FUNCTION: _nscd_destroy
 *
 * Marks the nscd data item as to-be-deleted and then releases
 * (If the usage count happens to be zero, then _nscd_release()
 * will destroy the data.)
 *
 * Note that _nscd_destroy should only be called if the
 * caller has created the nscd data with _nscd_alloc
 * (with the exception of _nscd_set). That nscd data
 * item should be private to the caller.
 */
static void
_nscd_destroy(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        char            *me = "_nscd_destroy";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        (void) mutex_lock(&access->mutex);
        access->delete = 1;
        (void) mutex_unlock(&access->mutex);

        _nscd_release(data);
}

/*
 * FUNCTION: _nscd_get
 *
 * Increment the usage count by one if 'data' can
 * be found in the internal address database.
 */
nscd_acc_data_t *
_nscd_get(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        void            *ret = data;
        rwlock_t        *addr_rwlock;
        char            *me = "_nscd_get";

        if (data == NULL)
                return (NULL);

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p, seq#= %lld, nUse = %d\n",
                data, access->data, access->seq_num, access->nUse);
        ASSERT_ACCESS_DATA;

        /*
         * see if this addr is still valid,
         * if so, _nscd_is_int_addr will
         * do a read lock on the returned
         * multiple readers/single writer lock
         * to prevent the access data from being
         * deleted while it is being accessed.
         */
        if ((addr_rwlock = _nscd_is_int_addr(data,
                        access->seq_num)) == NULL) {
                _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
                (me, "internal address %p not found\n", data);
                assert(addr_rwlock != NULL);
                return (NULL);
        }

        (void) mutex_lock(&access->mutex);
        if (access->delete == 1)
                ret = NULL;
        else
                access->nUse++;
        (void) mutex_unlock(&access->mutex);

        /*
         * done with the multiple readers/single writer lock
         */
        (void) rw_unlock(addr_rwlock);

        return (ret);
}

/*
 * FUNCTION: _nscd_set
 *
 * _nscd_set sets the address of a nscd data item
 * to 'new' and delete the old nscd data (old).
 * The pointer 'new' is returned.
 */
nscd_acc_data_t *
_nscd_set(
        nscd_acc_data_t *old,
        nscd_acc_data_t *new)
{
        nscd_acc_data_t *old_data, *new_data;
        char            *me = "_nscd_set";

        if (new == old)
                return (old);

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "new = %p, old = %p\n", new, old);

        old_data = _nscd_get(old);
        new_data = _nscd_get(new);

        if (old_data != new_data) {

                _nscd_destroy(old_data);
                _nscd_release(new_data);
                return (new_data);
        }

        /* if old_data == new_data, both must be NULL */
        return (NULL);
}

/*
 * FUNCTION: _nscd_rdlock
 *
 * Lock (rw_rdlock) a nscd data item for reading. The caller
 * needs to call _nscd_rw_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_rdlock(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        void            *ret;
        char            *me = "_nscd_rdlock";

        ret = _nscd_get(data);

        if (ret == NULL)
                return (NULL);

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_rwlock != NULL);

        (void) rw_rdlock(access->data_rwlock);

        return (ret);
}

/*
 * FUNCTION: _nscd_wrlock
 *
 * Lock (rw_wrlock) a nscd data item for writing. The caller
 * needs to call _nscd_rw_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_wrlock(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        void            *ret;
        char            *me = "_nscd_wrlock";

        ret = _nscd_get(data);

        if (ret == NULL)
                return (NULL);

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_rwlock != NULL);

        (void) rw_wrlock(access->data_rwlock);

        return (ret);
}

/*
 * FUNCTION: _nscd_rw_unlock
 *
 * Unlock (rw_unlock) a locked nscd data item.
 */
void
_nscd_rw_unlock(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        char            *me = "_nscd_rw_unlock";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n",
                data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_rwlock != NULL);

        (void) rw_unlock(access->data_rwlock);
        _nscd_release(data);
}

/*
 * FUNCTION: _nscd_rw_unlock_no_release
 *
 * Unlock (rw_unlock) a locked nscd data item but without release
 * it, i.e., without decrement the usage count to indicate that
 * the data item is still being referenced.
 */
void
_nscd_rw_unlock_no_release(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;

        if (data == NULL)
                return;

        SET_ACCESS_PTR;
        ASSERT_ACCESS_DATA;

        assert(access->data_rwlock != NULL);

        (void) rw_unlock(access->data_rwlock);
}

/*
 * FUNCTION: _nscd_mutex_lock
 *
 * Lock (mutex_lock) a nscd data item. The caller needs
 * to call _nscd_mutex_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_mutex_lock(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        void            *ret;
        char            *me = "_nscd_mutex_lock";

        ret = _nscd_get(data);

        if (ret == NULL)
                return (NULL);

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_mutex != NULL);

        (void) mutex_lock(access->data_mutex);

        return (ret);
}


/*
 * FUNCTION: _nscd_mutex_unlock
 *
 * Unlock a locked nscd data item (that were locked by _nscd_mutex_lock)..
 */
void
_nscd_mutex_unlock(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        char            *me = "_nscd_mutex_unlock";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_mutex != NULL);

        (void) mutex_unlock(access->data_mutex);
        _nscd_release(data);
}

/*
 * FUNCTION: _nscd_cond_wait
 *
 * Perform a condition wait with the cond_t and mutex_t associated
 * with data.
 */
void
_nscd_cond_wait(
        nscd_acc_data_t *data, cond_t *cond)
{
        nscd_access_t   *access;
        char            *me = "_nscd_cond_wait";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_cond != NULL && access->data_mutex != NULL);

        if (cond == NULL)
                (void) cond_wait(access->data_cond, access->data_mutex);
        else
                (void) cond_wait(cond, access->data_mutex);
}

/*
 * FUNCTION: _nscd_cond_signal
 *
 * Perform a condition signal with the cond_t associated with 'data'.
 */
void
_nscd_cond_signal(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;
        char            *me = "_nscd_cond_signal";

        if (data == NULL)
                return;

        SET_ACCESS_PTR;

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p\n", data, access->data);
        ASSERT_ACCESS_DATA;

        assert(access->data_cond != NULL);

        (void) cond_signal(access->data_cond);
}

/*
 * FUNCTION: _nscd_alloc
 *
 * Allocate a piece of nscd memory. 'data_free'
 * is the function to invoke to free the data
 * stored in this memory, i.e., the desctrctor.
 * 'option' indicate whether a mutex or a
 * readers/writer (or both, or none) should also
 * be allocated.
 */
nscd_acc_data_t *
_nscd_alloc(
        int             type,
        size_t          size,
        void            (*data_free)(nscd_acc_data_t *data),
        int             option)
{
        nscd_access_t   *access;
        nscd_acc_data_t *ptr;
        nscd_seq_num_t  seq_num;
        rwlock_t        *rwlock = NULL;
        mutex_t         *mutex = NULL;
        cond_t          *cond = NULL;

        if ((ptr = (nscd_acc_data_t *)calloc(1,
                        size + sizeof_access)) == NULL)
                return (NULL);
        if (option & NSCD_ALLOC_MUTEX) {
                if ((mutex = (mutex_t *)calloc(1, sizeof (mutex_t))) ==
                                NULL) {
                        free(ptr);
                        return (NULL);
                } else
                        (void) mutex_init(mutex, USYNC_THREAD, NULL);
        }
        if (option & NSCD_ALLOC_RWLOCK) {
                if ((rwlock = (rwlock_t *)calloc(1, sizeof (rwlock_t))) ==
                                NULL) {
                        free(ptr);
                        free(mutex);
                        return (NULL);
                } else
                        (void) rwlock_init(rwlock, USYNC_THREAD, NULL);
        }
        if (option & NSCD_ALLOC_COND) {
                if ((cond = (cond_t *)calloc(1, sizeof (cond_t))) ==
                                NULL) {
                        free(ptr);
                        free(mutex);
                        free(rwlock);
                        return (NULL);
                } else
                        (void) cond_init(cond, USYNC_THREAD, NULL);
        }

        /* get current sequence number */
        seq_num = _nscd_get_seq_num();

        access = (nscd_access_t *)ptr;
        access->data = (char *)ptr + sizeof_access;
        access->data_mutex = mutex;
        access->data_rwlock = rwlock;
        access->data_cond = cond;
        access->nUse = 0;
        access->delete = 0;
        access->type = type;
        access->free_func = data_free;
        access->seq_num = seq_num;

        /* add the address to the internal address database */
        if (_nscd_add_int_addr(access->data, type,
                        seq_num) != NSCD_SUCCESS) {
                free(ptr);
                return (NULL);
        }

        return (access->data);
}

/*
 * FUNCTION: _nscd_free
 *
 * Free a piece of nscd memory.
 */
static void
_nscd_free(
        nscd_acc_data_t *data)
{
        nscd_access_t   *access;

        if (data == NULL)
                return;

        SET_ACCESS_PTR;
        ASSERT_ACCESS_DATA;

        /* remove the address from the internal address database */
        _nscd_del_int_addr(access->data, access->seq_num);

        if (access->data_mutex)
                free(access->data_mutex);
        if (access->data_rwlock)
                free(access->data_rwlock);
        if (access->data_cond)
                free(access->data_cond);

        (void) memset(access, 0, sizeof (*access));

        free(access);
}