/*      $NetBSD: mtctxres.c,v 1.4 2007/03/30 20:40:52 ghen Exp $        */

#include <port_before.h>
#ifdef DO_PTHREADS
#include <pthread.h>
#endif
#include <errno.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <resolv_mt.h>
#include <port_after.h>

#ifdef DO_PTHREADS
static pthread_key_t    key;
static int              mt_key_initialized = 0;

static int              __res_init_ctx(void);
static void             __res_destroy_ctx(void *);

#if defined(sun) && !defined(__GNUC__)
#pragma init    (_mtctxres_init)
#endif
#endif

static mtctxres_t       sharedctx;

#ifdef DO_PTHREADS
/*
 * Initialize the TSD key. By doing this at library load time, we're
 * implicitly running without interference from other threads, so there's
 * no need for locking.
 */
static void
_mtctxres_init(void) {
        int pthread_keycreate_ret;

        pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
        if (pthread_keycreate_ret == 0)
                mt_key_initialized = 1;
}
#endif

/*
 * To support binaries that used the private MT-safe interface in
 * Solaris 8, we still need to provide the __res_enable_mt()
 * and __res_disable_mt() entry points. They're do-nothing routines.
 */
int
__res_enable_mt(void) {
        return (-1);
}

int
__res_disable_mt(void) {
        return (0);
}

#ifdef DO_PTHREADS
static int
__res_init_ctx(void) {

        mtctxres_t      *mt;
        int             ret;


        if (pthread_getspecific(key) != 0) {
                /* Already exists */
                return (0);
        }

        if ((mt = malloc(sizeof (mtctxres_t))) == 0) {
                errno = ENOMEM;
                return (-1);
        }

        memset(mt, 0, sizeof (mtctxres_t));

        if ((ret = pthread_setspecific(key, mt)) != 0) {
                free(mt);
                errno = ret;
                return (-1);
        }

        return (0);
}

static void
__res_destroy_ctx(void *value) {

        mtctxres_t      *mt = (mtctxres_t *)value;

        if (mt != 0)
                free(mt);
}
#endif

mtctxres_t *
___mtctxres(void) {
#ifdef DO_PTHREADS
        mtctxres_t      *mt;

        /*
         * This if clause should only be executed if we are linking
         * statically.  When linked dynamically _mtctxres_init() should
         * be called at binding time due the #pragma above.
         */
        if (!mt_key_initialized) {
                static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
                if (pthread_mutex_lock(&keylock) == 0) {
                        _mtctxres_init();
                        (void) pthread_mutex_unlock(&keylock);
                }
        }

        /*
         * If we have already been called in this thread return the existing
         * context.  Otherwise recreat a new context and return it.  If
         * that fails return a global context.
         */
        if (mt_key_initialized) {
                if (((mt = pthread_getspecific(key)) != 0) ||
                    (__res_init_ctx() == 0 &&
                     (mt = pthread_getspecific(key)) != 0)) {
                        return (mt);
                }
        }
#endif
        return (&sharedctx);
}