root/src/misc/objects.c

/*****************************************************************************
 * objects.c: vlc_object_t handling
 *****************************************************************************
 * Copyright (C) 2004-2008 the VideoLAN team
 *
 * Authors: Samuel Hocevar <sam@zoy.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/**
 * \file
 * This file contains the functions to handle the vlc_object_t type
 *
 * Unless otherwise stated, functions in this file are not cancellation point.
 * All functions in this file are safe w.r.t. deferred cancellation.
 */


/*****************************************************************************
 * Preamble
 *****************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <vlc_common.h>

#include "../libvlc.h"
#include <vlc_vout.h>
#include <vlc_aout.h>
#include "audio_output/aout_internal.h"

#include <vlc_access.h>
#include <vlc_demux.h>
#include <vlc_stream.h>

#include <vlc_sout.h>
#include "stream_output/stream_output.h"

#include "vlc_interface.h"
#include "vlc_codec.h"
#include "vlc_filter.h"

#include "variables.h"
#ifndef WIN32
# include <unistd.h>
#else
# include <io.h>
# include <fcntl.h>
# include <errno.h> /* ENOSYS */
#endif
#include <assert.h>

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int  DumpCommand( vlc_object_t *, char const *,
                         vlc_value_t, vlc_value_t, void * );

static vlc_object_t * FindObject    ( vlc_object_t *, int, int );
static vlc_object_t * FindObjectName( vlc_object_t *, const char *, int );
static void           PrintObject   ( vlc_object_t *, const char * );
static void           DumpStructure ( vlc_object_t *, int, char * );

static vlc_list_t   * NewList       ( int );
static void           ListReplace   ( vlc_list_t *, vlc_object_t *, int );
/*static void           ListAppend    ( vlc_list_t *, vlc_object_t * );*/
static int            CountChildren ( vlc_object_t *, int );
static void           ListChildren  ( vlc_list_t *, vlc_object_t *, int );

static void vlc_object_destroy( vlc_object_t *p_this );
static void vlc_object_detach_unlocked (vlc_object_t *p_this);
static void vlc_object_dump( vlc_object_t *p_this );

/*****************************************************************************
 * Local structure lock
 *****************************************************************************/
static vlc_mutex_t structure_lock;
static unsigned    object_counter = 0;

static void close_nocancel (int fd)
{
    int canc = vlc_savecancel ();
    close (fd);
    vlc_restorecancel (canc);
}

void *__vlc_custom_create( vlc_object_t *p_this, size_t i_size,
                           int i_type, const char *psz_type )
{
    vlc_object_t *p_new;
    vlc_object_internals_t *p_priv;

    /* NOTE:
     * VLC objects are laid out as follow:
     * - first the LibVLC-private per-object data,
     * - then VLC_COMMON members from vlc_object_t,
     * - finally, the type-specific data (if any).
     *
     * This function initializes the LibVLC and common data,
     * and zeroes the rest.
     */
    p_priv = calloc( 1, sizeof( *p_priv ) + i_size );
    if( p_priv == NULL )
        return NULL;

    assert (i_size >= sizeof (vlc_object_t));
    p_new = (vlc_object_t *)(p_priv + 1);

    p_new->i_object_type = i_type;
    p_new->psz_object_type = psz_type;
    p_new->psz_object_name = NULL;

    p_new->b_die = false;
    p_new->b_error = false;
    p_new->b_dead = false;
    p_new->b_force = false;

    p_new->psz_header = NULL;

    if (p_this)
        p_new->i_flags = p_this->i_flags
            & (OBJECT_FLAGS_NODBG|OBJECT_FLAGS_QUIET|OBJECT_FLAGS_NOINTERACT);

    p_priv->p_vars = calloc( sizeof( variable_t ), 16 );

    if( !p_priv->p_vars )
    {
        free( p_priv );
        return NULL;
    }

    if( p_this == NULL )
    {
        if( i_type == VLC_OBJECT_LIBVLC )
            p_new->p_libvlc = (libvlc_int_t*)p_new;
        else
        {
            p_new->p_libvlc = NULL;
            vlc_mutex_init( &structure_lock );
        }

        p_this = p_priv->next = p_priv->prev = p_new;
    }
    else
        p_new->p_libvlc = p_this->p_libvlc;

    vlc_spin_init( &p_priv->ref_spin );
    p_priv->i_refcount = 1;
    p_priv->pf_destructor = NULL;
    p_priv->b_thread = false;
    p_new->p_parent = NULL;
    p_priv->pp_children = NULL;
    p_priv->i_children = 0;

    p_new->p_private = NULL;

    /* Initialize mutexes and condvars */
    vlc_mutex_init( &p_priv->lock );
    vlc_cond_init( &p_priv->wait );
    vlc_mutex_init( &p_priv->var_lock );
    vlc_spin_init( &p_priv->spin );
    p_priv->pipes[0] = p_priv->pipes[1] = -1;

    p_priv->next = p_this;
    vlc_mutex_lock( &structure_lock );
    p_priv->prev = vlc_internals (p_this)->prev;
    vlc_internals (p_this)->prev = p_new;
    vlc_internals (p_priv->prev)->next = p_new;
    p_new->i_object_id = object_counter++; /* fetch THEN increment */
    vlc_mutex_unlock( &structure_lock );

    if( i_type == VLC_OBJECT_LIBVLC )
    {
        int canc = vlc_savecancel ();
        var_Create( p_new, "list", VLC_VAR_STRING | VLC_VAR_ISCOMMAND );
        var_AddCallback( p_new, "list", DumpCommand, NULL );
        var_Create( p_new, "tree", VLC_VAR_STRING | VLC_VAR_ISCOMMAND );
        var_AddCallback( p_new, "tree", DumpCommand, NULL );
        var_Create( p_new, "vars", VLC_VAR_STRING | VLC_VAR_ISCOMMAND );
        var_AddCallback( p_new, "vars", DumpCommand, NULL );
        vlc_restorecancel (canc);
    }

    return p_new;
}


/**
 * Allocates and initializes a vlc object.
 *
 * @param i_type known object type (all of them are negative integer values),
 *               or object byte size (always positive).
 *
 * @return the new object, or NULL on error.
 */
void * __vlc_object_create( vlc_object_t *p_this, int i_type )
{
    const char   * psz_type;
    size_t         i_size;

    switch( i_type )
    {
        case VLC_OBJECT_INTF:
            i_size = sizeof(intf_thread_t);
            psz_type = "interface";
            break;
        case VLC_OBJECT_DECODER:
            i_size = sizeof(decoder_t);
            psz_type = "decoder";
            break;
        case VLC_OBJECT_PACKETIZER:
            i_size = sizeof(decoder_t);
            psz_type = "packetizer";
            break;
        case VLC_OBJECT_ENCODER:
            i_size = sizeof(encoder_t);
            psz_type = "encoder";
            break;
        case VLC_OBJECT_AOUT:
            i_size = sizeof(aout_instance_t);
            psz_type = "audio output";
            break;
        case VLC_OBJECT_OPENGL:
            i_size = sizeof( vout_thread_t );
            psz_type = "opengl";
            break;
        case VLC_OBJECT_ANNOUNCE:
            i_size = sizeof( announce_handler_t );
            psz_type = "announce";
            break;
        default:
            assert( i_type > 0 ); /* unknown type?! */
            i_size = i_type;
            i_type = VLC_OBJECT_GENERIC;
            psz_type = "generic";
            break;
    }

    return vlc_custom_create( p_this, i_size, i_type, psz_type );
}


/**
 ****************************************************************************
 * Set the destructor of a vlc object
 *
 * This function sets the destructor of the vlc object. It will be called
 * when the object is destroyed when the its refcount reaches 0.
 * (It is called by the internal function vlc_object_destroy())
 *****************************************************************************/
void __vlc_object_set_destructor( vlc_object_t *p_this,
                                  vlc_destructor_t pf_destructor )
{
    vlc_object_internals_t *p_priv = vlc_internals(p_this );
    p_priv->pf_destructor = pf_destructor;
}

/**
 ****************************************************************************
 * Destroy a vlc object (Internal)
 *
 * This function destroys an object that has been previously allocated with
 * vlc_object_create. The object's refcount must be zero and it must not be
 * attached to other objects in any way.
 *
 * This function must be called with cancellation disabled (currently).
 *****************************************************************************/
static void vlc_object_destroy( vlc_object_t *p_this )
{
    vlc_object_internals_t *p_priv = vlc_internals( p_this );

    /* Objects are always detached beforehand */
    assert( !p_this->p_parent );

    /* Send a kill to the object's thread if applicable */
    vlc_object_kill( p_this );

    /* Call the custom "subclass" destructor */
    if( p_priv->pf_destructor )
        p_priv->pf_destructor( p_this );

    /* Any thread must have been cleaned up at this point. */
    assert( !p_priv->b_thread );

    /* Destroy the associated variables, starting from the end so that
     * no memmove calls have to be done. */
    while( p_priv->i_vars )
    {
        var_Destroy( p_this, p_priv->p_vars[p_priv->i_vars - 1].psz_name );
    }

    free( p_priv->p_vars );
    vlc_mutex_destroy( &p_priv->var_lock );

    free( p_this->psz_header );

    if( p_this->p_libvlc == NULL )
        /* We are the global object ... no need to lock. */
        vlc_mutex_destroy( &structure_lock );

    FREENULL( p_this->psz_object_name );

#if defined(WIN32) || defined(UNDER_CE)
    /* if object has an associated thread, close it now */
    if( p_priv->thread_id )
       CloseHandle(p_priv->thread_id);
#endif

    vlc_spin_destroy( &p_priv->ref_spin );
    vlc_mutex_destroy( &p_priv->lock );
    vlc_cond_destroy( &p_priv->wait );
    vlc_spin_destroy( &p_priv->spin );
    if( p_priv->pipes[1] != -1 )
        close( p_priv->pipes[1] );
    if( p_priv->pipes[0] != -1 )
        close( p_priv->pipes[0] );

    free( p_priv );
}


/** Inter-object signaling */

void __vlc_object_lock( vlc_object_t *obj )
{
    vlc_mutex_lock( &(vlc_internals(obj)->lock) );
}

void __vlc_object_unlock( vlc_object_t *obj )
{
    vlc_assert_locked( &(vlc_internals(obj)->lock) );
    vlc_mutex_unlock( &(vlc_internals(obj)->lock) );
}

#ifdef WIN32
# include <winsock2.h>
# include <ws2tcpip.h>

/**
 * select()-able pipes emulated using Winsock
 */
static int pipe (int fd[2])
{
    SOCKADDR_IN addr;
    int addrlen = sizeof (addr);

    SOCKET l = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP), a,
           c = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if ((l == INVALID_SOCKET) || (c == INVALID_SOCKET))
        goto error;

    memset (&addr, 0, sizeof (addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
    if (bind (l, (PSOCKADDR)&addr, sizeof (addr))
     || getsockname (l, (PSOCKADDR)&addr, &addrlen)
     || listen (l, 1)
     || connect (c, (PSOCKADDR)&addr, addrlen))
        goto error;

    a = accept (l, NULL, NULL);
    if (a == INVALID_SOCKET)
        goto error;

    closesocket (l);
    //shutdown (a, 0);
    //shutdown (c, 1);
    fd[0] = c;
    fd[1] = a;
    return 0;

error:
    if (l != INVALID_SOCKET)
        closesocket (l);
    if (c != INVALID_SOCKET)
        closesocket (c);
    return -1;
}

#undef  read
#define read( a, b, c )  recv (a, b, c, 0)
#undef  write
#define write( a, b, c ) send (a, b, c, 0)
#undef  close
#define close( a )       closesocket (a)
#endif /* WIN32 */

/**
 * Returns the readable end of a pipe that becomes readable once termination
 * of the object is requested (vlc_object_kill()).
 * This can be used to wake-up out of a select() or poll() event loop, such
 * typically when doing network I/O.
 *
 * Note that the pipe will remain the same for the lifetime of the object.
 * DO NOT read the pipe nor close it yourself. Ever.
 *
 * @param obj object that would be "killed"
 * @return a readable pipe descriptor, or -1 on error.
 */
int __vlc_object_waitpipe( vlc_object_t *obj )
{
    int pfd[2] = { -1, -1 };
    vlc_object_internals_t *internals = vlc_internals( obj );
    bool killed = false;

    vlc_spin_lock (&internals->spin);
    if (internals->pipes[0] == -1)
    {
        /* This can only ever happen if someone killed us without locking: */
        assert (internals->pipes[1] == -1);
        vlc_spin_unlock (&internals->spin);

        if (pipe (pfd))
            return -1;

        vlc_spin_lock (&internals->spin);
        if (internals->pipes[0] == -1)
        {
            internals->pipes[0] = pfd[0];
            internals->pipes[1] = pfd[1];
            pfd[0] = pfd[1] = -1;
        }
        killed = obj->b_die;
    }
    vlc_spin_unlock (&internals->spin);

    if (killed)
    {
        /* Race condition: vlc_object_kill() already invoked! */
        int fd;

        vlc_spin_lock (&internals->spin);
        fd = internals->pipes[1];
        internals->pipes[1] = -1;
        vlc_spin_unlock (&internals->spin);

        msg_Dbg (obj, "waitpipe: object already dying");
        if (fd != -1)
            close (fd);
    }

    /* Race condition: two threads call pipe() - unlikely */
    if (pfd[0] != -1)
        close (pfd[0]);
    if (pfd[1] != -1)
        close (pfd[1]);

    return internals->pipes[0];
}


/**
 * Waits for the object to be signaled (using vlc_object_signal()).
 * It is assumed that the caller has locked the object. This function will
 * unlock the object, and lock it again before returning.
 * If the object was signaled before the caller locked the object, it is
 * undefined whether the signal will be lost or will wake the process.
 *
 * This function is a cancellation point. In case of cancellation, the object
 * will be in locked state.
 *
 * @return true if the object is dying and should terminate.
 */
void __vlc_object_wait( vlc_object_t *obj )
{
    vlc_object_internals_t *priv = vlc_internals( obj );
    vlc_assert_locked( &priv->lock);
    vlc_cond_wait( &priv->wait, &priv->lock );
}


/**
 * Waits for the object to be signaled (using vlc_object_signal()), or for
 * a timer to expire. It is asserted that the caller holds the object lock.
 *
 * This function is a cancellation point. In case of cancellation, the object
 * will be in locked state.
 *
 * @return 0 if the object was signaled before the timer expiration, or
 * ETIMEDOUT if the timer expired without any signal.
 */
int __vlc_object_timedwait( vlc_object_t *obj, mtime_t deadline )
{
    vlc_object_internals_t *priv = vlc_internals( obj );
    vlc_assert_locked( &priv->lock);
    return vlc_cond_timedwait( &priv->wait, &priv->lock, deadline );
}


/**
 * Signals an object for which the lock is held.
 * At least one thread currently sleeping in vlc_object_wait() or
 * vlc_object_timedwait() will wake up, assuming that there is at least one
 * such thread in the first place. Otherwise, it is undefined whether the
 * signal will be lost or will wake up one or more thread later.
 */
void __vlc_object_signal_unlocked( vlc_object_t *obj )
{
    vlc_assert_locked (&(vlc_internals(obj)->lock));
    vlc_cond_signal( &(vlc_internals(obj)->wait) );
}


/**
 * Requests termination of an object.
 * If the object is LibVLC, also request to terminate all its children.
 */
void __vlc_object_kill( vlc_object_t *p_this )
{
    vlc_object_internals_t *priv = vlc_internals( p_this );
    int fd;

    vlc_thread_cancel( p_this );
    vlc_object_lock( p_this );
    p_this->b_die = true;

    vlc_spin_lock (&priv->spin);
    fd = priv->pipes[1];
    priv->pipes[1] = -1;
    vlc_spin_unlock (&priv->spin);

    if( fd != -1 )
    {
        msg_Dbg (p_this, "waitpipe: object killed");
        close_nocancel (fd);
    }

    vlc_cond_broadcast (&priv->wait);
    /* This also serves as a memory barrier toward vlc_object_alive(): */
    vlc_object_unlock( p_this );
}


/**
 * Find an object given its ID.
 *
 * This function looks for the object whose i_object_id field is i_id.
 * This function is slow, and often used to hide bugs. Do not use it.
 * If you need to retain reference to an object, yield the object pointer with
 * vlc_object_yield(), use the pointer as your reference, and call
 * vlc_object_release() when you're done.
 */
void * vlc_object_get( libvlc_int_t *p_anchor, int i_id )
{
    vlc_object_t *obj = NULL;
#ifndef NDEBUG
    int canc = vlc_savecancel ();
    fprintf (stderr, "Use of deprecated vlc_object_get(%d) ", i_id);
    vlc_backtrace ();
    vlc_restorecancel (canc);
#endif
    vlc_mutex_lock( &structure_lock );

    for( obj = vlc_internals (p_anchor)->next;
         obj != VLC_OBJECT (p_anchor);
         obj = vlc_internals (obj)->next )
    {
        if( obj->i_object_id == i_id )
        {
            vlc_object_yield( obj );
            goto out;
        }
    }
    obj = NULL;
#ifndef NDEBUG
    fprintf (stderr, "Object %d does not exist\n", i_id);
#endif
out:
    vlc_mutex_unlock( &structure_lock );
    return obj;
}

/**
 ****************************************************************************
 * find a typed object and increment its refcount
 *****************************************************************************
 * This function recursively looks for a given object type. i_mode can be one
 * of FIND_PARENT, FIND_CHILD or FIND_ANYWHERE.
 *****************************************************************************/
void * __vlc_object_find( vlc_object_t *p_this, int i_type, int i_mode )
{
    vlc_object_t *p_found;

    /* If we are of the requested type ourselves, don't look further */
    if( !(i_mode & FIND_STRICT) && p_this->i_object_type == i_type )
    {
        vlc_object_yield( p_this );
        return p_this;
    }

    /* Otherwise, recursively look for the object */
    if ((i_mode & 0x000f) == FIND_ANYWHERE)
    {
#ifndef NDEBUG
        if (i_type == VLC_OBJECT_PLAYLIST)
            msg_Err (p_this, "using vlc_object_find(VLC_OBJECT_PLAYLIST) "
                     "instead of pl_Yield()");
#endif
        return vlc_object_find (p_this->p_libvlc, i_type,
                                (i_mode & ~0x000f)|FIND_CHILD);
    }

    vlc_mutex_lock( &structure_lock );
    p_found = FindObject( p_this, i_type, i_mode );
    vlc_mutex_unlock( &structure_lock );
    return p_found;
}

#undef vlc_object_find_name
/**
 * Finds a named object and increment its reference count.
 * Beware that objects found in this manner can be "owned" by another thread,
 * be of _any_ type, and be attached to any module (if any). With such an
 * object reference, you can set or get object variables, emit log messages,
 * and read write-once object parameters (i_object_id, psz_object_type, etc).
 * You CANNOT cast the object to a more specific object type, and you
 * definitely cannot invoke object type-specific callbacks with this.
 *
 * @param p_this object to search from
 * @param psz_name name of the object to search for
 * @param i_mode search direction: FIND_PARENT, FIND_CHILD or FIND_ANYWHERE.
 *
 * @return a matching object (must be released by the caller),
 * or NULL on error.
 */
vlc_object_t *vlc_object_find_name( vlc_object_t *p_this,
                                    const char *psz_name, int i_mode )
{
    vlc_object_t *p_found;

    /* If have the requested name ourselves, don't look further */
    if( !(i_mode & FIND_STRICT)
        && p_this->psz_object_name
        && !strcmp( p_this->psz_object_name, psz_name ) )
    {
        vlc_object_yield( p_this );
        return p_this;
    }

    vlc_mutex_lock( &structure_lock );

    /* Otherwise, recursively look for the object */
    if( (i_mode & 0x000f) == FIND_ANYWHERE )
    {
        vlc_object_t *p_root = p_this;

        /* Find the root */
        while( p_root->p_parent != NULL &&
               p_root != VLC_OBJECT( p_this->p_libvlc ) )
        {
            p_root = p_root->p_parent;
        }

        p_found = FindObjectName( p_root, psz_name,
                                 (i_mode & ~0x000f)|FIND_CHILD );
        if( p_found == NULL && p_root != VLC_OBJECT( p_this->p_libvlc ) )
        {
            p_found = FindObjectName( VLC_OBJECT( p_this->p_libvlc ),
                                      psz_name, (i_mode & ~0x000f)|FIND_CHILD );
        }
    }
    else
    {
        p_found = FindObjectName( p_this, psz_name, i_mode );
    }

    vlc_mutex_unlock( &structure_lock );

    return p_found;
}

/**
 * Increment an object reference counter.
 */
void __vlc_object_yield( vlc_object_t *p_this )
{
    vlc_object_internals_t *internals = vlc_internals( p_this );

    vlc_spin_lock( &internals->ref_spin );
    /* Avoid obvious freed object uses */
    assert( internals->i_refcount > 0 );
    /* Increment the counter */
    internals->i_refcount++;
    vlc_spin_unlock( &internals->ref_spin );
}

/*****************************************************************************
 * Decrement an object refcount
 * And destroy the object if its refcount reach zero.
 *****************************************************************************/
void __vlc_object_release( vlc_object_t *p_this )
{
    vlc_object_internals_t *internals = vlc_internals( p_this );
    bool b_should_destroy;

    vlc_spin_lock( &internals->ref_spin );
    assert( internals->i_refcount > 0 );

    if( internals->i_refcount > 1 )
    {
        /* Fast path */
        /* There are still other references to the object */
        internals->i_refcount--;
        vlc_spin_unlock( &internals->ref_spin );
        return;
    }
    vlc_spin_unlock( &internals->ref_spin );

    /* Slow path */
    /* Remember that we cannot hold the spin while waiting on the mutex */
    vlc_mutex_lock( &structure_lock );
    /* Take the spin again. Note that another thread may have yielded the
     * object in the (very short) mean time. */
    vlc_spin_lock( &internals->ref_spin );
    b_should_destroy = --internals->i_refcount == 0;
    vlc_spin_unlock( &internals->ref_spin );

    if( b_should_destroy )
    {
#ifndef NDEBUG
        if( VLC_OBJECT(p_this->p_libvlc) == p_this )
        {
            /* Test for leaks */
            vlc_object_t *leaked = internals->next;
            while( leaked != p_this )
            {
                /* We are leaking this object */
                fprintf( stderr,
                         "ERROR: leaking object (id:%i, type:%s, name:%s)\n",
                         leaked->i_object_id, leaked->psz_object_type,
                         leaked->psz_object_name );
                /* Dump object to ease debugging */
                vlc_object_dump( leaked );
                fflush(stderr);
                leaked = vlc_internals (leaked)->next;
            }

            if( internals->next != p_this )
                /* Dump libvlc object to ease debugging */
                vlc_object_dump( p_this );
        }
#endif
        /* Remove the object from object list
         * so that it cannot be encountered by vlc_object_get() */
        vlc_internals (internals->next)->prev = internals->prev;
        vlc_internals (internals->prev)->next = internals->next;

        /* Detach from parent to protect against FIND_CHILDREN */
        vlc_object_detach_unlocked (p_this);
        /* Detach from children to protect against FIND_PARENT */
        for (int i = 0; i < internals->i_children; i++)
            internals->pp_children[i]->p_parent = NULL;
    }

    vlc_mutex_unlock( &structure_lock );

    if( b_should_destroy )
    {
        int canc;

        free( internals->pp_children );
        internals->pp_children = NULL;
        internals->i_children = 0;
        canc = vlc_savecancel ();
        vlc_object_destroy( p_this );
        vlc_restorecancel (canc);
    }
}

/**
 ****************************************************************************
 * attach object to a parent object
 *****************************************************************************
 * This function sets p_this as a child of p_parent, and p_parent as a parent
 * of p_this. This link can be undone using vlc_object_detach.
 *****************************************************************************/
void __vlc_object_attach( vlc_object_t *p_this, vlc_object_t *p_parent )
{
    if( !p_this ) return;

    vlc_mutex_lock( &structure_lock );

    /* Attach the parent to its child */
    assert (!p_this->p_parent);
    p_this->p_parent = p_parent;

    /* Attach the child to its parent */
    vlc_object_internals_t *priv = vlc_internals( p_parent );
    INSERT_ELEM( priv->pp_children, priv->i_children, priv->i_children,
                 p_this );

    vlc_mutex_unlock( &structure_lock );
}


static void vlc_object_detach_unlocked (vlc_object_t *p_this)
{
    vlc_assert_locked (&structure_lock);

    if (p_this->p_parent == NULL)
        return;

    vlc_object_internals_t *priv = vlc_internals( p_this->p_parent );

    int i_index, i;

    /* Remove p_this's parent */
    p_this->p_parent = NULL;

    /* Remove all of p_parent's children which are p_this */
    for( i_index = priv->i_children ; i_index-- ; )
    {
        if( priv->pp_children[i_index] == p_this )
        {
            priv->i_children--;
            for( i = i_index ; i < priv->i_children ; i++ )
                priv->pp_children[i] = priv->pp_children[i+1];
        }
    }

    if( priv->i_children )
    {
        priv->pp_children = (vlc_object_t **)realloc( priv->pp_children,
                               priv->i_children * sizeof(vlc_object_t *) );
    }
    else
    {
        /* Special case - don't realloc() to zero to avoid leaking */
        free( priv->pp_children );
        priv->pp_children = NULL;
    }
}


/**
 ****************************************************************************
 * detach object from its parent
 *****************************************************************************
 * This function removes all links between an object and its parent.
 *****************************************************************************/
void __vlc_object_detach( vlc_object_t *p_this )
{
    if( !p_this ) return;

    vlc_mutex_lock( &structure_lock );
    if( !p_this->p_parent )
        msg_Err( p_this, "object is not attached" );
    else
        vlc_object_detach_unlocked( p_this );
    vlc_mutex_unlock( &structure_lock );
}


/**
 ****************************************************************************
 * find a list typed objects and increment their refcount
 *****************************************************************************
 * This function recursively looks for a given object type. i_mode can be one
 * of FIND_PARENT, FIND_CHILD or FIND_ANYWHERE.
 *****************************************************************************/
vlc_list_t * __vlc_list_find( vlc_object_t *p_this, int i_type, int i_mode )
{
    vlc_list_t *p_list;
    int i_count = 0;

    /* Look for the objects */
    switch( i_mode & 0x000f )
    {
    case FIND_ANYWHERE:
        /* Modules should probably not be object, and the module should perhaps
         * not be shared across LibVLC instances. In the mean time, this ugly
         * hack is brought to you by Courmisch. */
        if (i_type == VLC_OBJECT_MODULE)
            return vlc_list_find ((vlc_object_t *)p_module_bank,
                                  i_type, FIND_CHILD);
        return vlc_list_find (p_this->p_libvlc, i_type, FIND_CHILD);

    case FIND_CHILD:
        vlc_mutex_lock( &structure_lock );
        i_count = CountChildren( p_this, i_type );
        p_list = NewList( i_count );

        /* Check allocation was successful */
        if( p_list->i_count != i_count )
        {
            vlc_mutex_unlock( &structure_lock );
            msg_Err( p_this, "list allocation failed!" );
            p_list->i_count = 0;
            break;
        }

        p_list->i_count = 0;
        ListChildren( p_list, p_this, i_type );
        vlc_mutex_unlock( &structure_lock );
        break;

    default:
        msg_Err( p_this, "unimplemented!" );
        p_list = NewList( 0 );
        break;
    }

    return p_list;
}

/**
 * Gets the list of children of an objects, and increment their reference
 * count.
 * @return a list (possibly empty) or NULL in case of error.
 */
vlc_list_t *__vlc_list_children( vlc_object_t *obj )
{
    vlc_list_t *l;
    vlc_object_internals_t *priv = vlc_internals( obj );

    vlc_mutex_lock( &structure_lock );
    l = NewList( priv->i_children );
    for (int i = 0; i < l->i_count; i++)
    {
        vlc_object_yield( priv->pp_children[i] );
        l->p_values[i].p_object = priv->pp_children[i];
    }
    vlc_mutex_unlock( &structure_lock );
    return l;
}

/*****************************************************************************
 * DumpCommand: print the current vlc structure
 *****************************************************************************
 * This function prints either an ASCII tree showing the connections between
 * vlc objects, and additional information such as their refcount, thread ID,
 * etc. (command "tree"), or the same data as a simple list (command "list").
 *****************************************************************************/
static int DumpCommand( vlc_object_t *p_this, char const *psz_cmd,
                        vlc_value_t oldval, vlc_value_t newval, void *p_data )
{
    libvlc_int_t *p_libvlc = p_this->p_libvlc;

    (void)oldval; (void)p_data;
    if( *psz_cmd == 'l'</