variables.c

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                 entry );

    vlc_mutex_unlock( &p_this->var_lock );

    return VLC_SUCCESS;
}

/**
 * Remove a callback from a variable
 *
 * pf_callback and p_data have to be given again, because different objects
 * might have registered the same callback function.
 */
int __var_DelCallback( vlc_object_t *p_this, const char *psz_name,
                       vlc_callback_t pf_callback, void *p_data )
{
    int i_entry, i_var;
    variable_t *p_var;

    vlc_mutex_lock( &p_this->var_lock );

    i_var = GetUnused( p_this, psz_name );
    if( i_var < 0 )
    {
        vlc_mutex_unlock( &p_this->var_lock );
        return i_var;
    }

    p_var = &p_this->p_vars[i_var];

    for( i_entry = p_var->i_entries ; i_entry-- ; )
    {
        if( p_var->p_entries[i_entry].pf_callback == pf_callback
            && p_var->p_entries[i_entry].p_data == p_data )
        {
            break;
        }
    }

    if( i_entry < 0 )
    {
        vlc_mutex_unlock( &p_this->var_lock );
        return VLC_EGENERIC;
    }

    REMOVE_ELEM( p_var->p_entries, p_var->i_entries, i_entry );

    vlc_mutex_unlock( &p_this->var_lock );

    return VLC_SUCCESS;
}

/* Following functions are local */

/*****************************************************************************
 * GetUnused: find an unused variable from its name
 *****************************************************************************
 * We do i_tries tries before giving up, just in case the variable is being
 * modified and called from a callback.
 *****************************************************************************/
static int GetUnused( vlc_object_t *p_this, const char *psz_name )
{
    int i_var, i_tries = 0;

    while( VLC_TRUE )
    {
        i_var = Lookup( p_this->p_vars, p_this->i_vars, psz_name );
        if( i_var < 0 )
        {
            return VLC_ENOVAR;
        }

        if( ! p_this->p_vars[i_var].b_incallback )
        {
            return i_var;
        }

        if( i_tries++ > 100 )
        {
            msg_Err( p_this, "caught in a callback deadlock?" );
            return VLC_ETIMEOUT;
        }

        vlc_mutex_unlock( &p_this->var_lock );
        msleep( THREAD_SLEEP );
        vlc_mutex_lock( &p_this->var_lock );
    }
}

/*****************************************************************************
 * HashString: our cool hash function
 *****************************************************************************
 * This function is not intended to be crypto-secure, we only want it to be
 * fast and not suck too much. This one is pretty fast and did 0 collisions
 * in wenglish's dictionary.
 *****************************************************************************/
static uint32_t HashString( const char *psz_string )
{
    uint32_t i_hash = 0;

    while( *psz_string )
    {
        i_hash += *psz_string++;
        i_hash += i_hash << 10;
        i_hash ^= i_hash >> 8;
    }

    return i_hash;
}

/*****************************************************************************
 * Insert: find an empty slot to insert a new variable
 *****************************************************************************
 * We use a recursive inner function indexed on the hash. This function does
 * nothing in the rare cases where a collision may occur, see Lookup()
 * to see how we handle them.
 * XXX: does this really need to be written recursively?
 *****************************************************************************/
static int Insert( variable_t *p_vars, int i_count, const char *psz_name )
{
    if( i_count == 0 )
    {
        return 0;
    }

    return InsertInner( p_vars, i_count, HashString( psz_name ) );
}

static int InsertInner( variable_t *p_vars, int i_count, uint32_t i_hash )
{
    int i_middle;

    if( i_hash <= p_vars[0].i_hash )
    {
        return 0;
    }

    if( i_hash >= p_vars[i_count - 1].i_hash )
    {
        return i_count;
    }

    i_middle = i_count / 2;

    /* We know that 0 < i_middle */
    if( i_hash < p_vars[i_middle].i_hash )
    {
        return InsertInner( p_vars, i_middle, i_hash );
    }

    /* We know that i_middle + 1 < i_count */
    if( i_hash > p_vars[i_middle + 1].i_hash )
    {
        return i_middle + 1 + InsertInner( p_vars + i_middle + 1,
                                           i_count - i_middle - 1,
                                           i_hash );
    }

    return i_middle + 1;
}

/*****************************************************************************
 * Lookup: find an existing variable given its name
 *****************************************************************************
 * We use a recursive inner function indexed on the hash. Care is taken of
 * possible hash collisions.
 * XXX: does this really need to be written recursively?
 *****************************************************************************/
static int Lookup( variable_t *p_vars, int i_count, const char *psz_name )
{
    uint32_t i_hash;
    int i, i_pos;

    if( i_count == 0 )
    {
        return -1;
    }

    i_hash = HashString( psz_name );

    i_pos = LookupInner( p_vars, i_count, i_hash );

    /* Hash not found */
    if( i_hash != p_vars[i_pos].i_hash )
    {
        return -1;
    }

    /* Hash found, entry found */
    if( !strcmp( psz_name, p_vars[i_pos].psz_name ) )
    {
        return i_pos;
    }

    /* Hash collision! This should be very rare, but we cannot guarantee
     * it will never happen. Just do an exhaustive search amongst all
     * entries with the same hash. */
    for( i = i_pos - 1 ; i > 0 && i_hash == p_vars[i].i_hash ; i-- )
    {
        if( !strcmp( psz_name, p_vars[i].psz_name ) )
        {
            return i;
        }
    }

    for( i = i_pos + 1 ; i < i_count && i_hash == p_vars[i].i_hash ; i++ )
    {
        if( !strcmp( psz_name, p_vars[i].psz_name ) )
        {
            return i;
        }
    }

    /* Hash found, but entry not found */
    return -1;
}

static int LookupInner( variable_t *p_vars, int i_count, uint32_t i_hash )
{
    int i_middle;

    if( i_hash <= p_vars[0].i_hash )
    {
        return 0;
    }

    if( i_hash >= p_vars[i_count-1].i_hash )
    {
        return i_count - 1;
    }

    i_middle = i_count / 2;

    /* We know that 0 < i_middle */
    if( i_hash < p_vars[i_middle].i_hash )
    {
        return LookupInner( p_vars, i_middle, i_hash );
    }

    /* We know that i_middle + 1 < i_count */
    if( i_hash > p_vars[i_middle].i_hash )
    {
        return i_middle + LookupInner( p_vars + i_middle,
                                       i_count - i_middle,
                                       i_hash );
    }

    return i_middle;
}

/*****************************************************************************
 * CheckValue: check that a value is valid wrt. a variable
 *****************************************************************************
 * This function checks p_val's value against p_var's limitations such as
 * minimal and maximal value, step, in-list position, and modifies p_val if
 * necessary.
 *****************************************************************************/
static void CheckValue ( variable_t *p_var, vlc_value_t *p_val )
{
    /* Check that our variable is in the list */
    if( p_var->i_type & VLC_VAR_HASCHOICE && p_var->choices.i_count )
    {
        int i;

        /* FIXME: the list is sorted, dude. Use something cleverer. */
        for( i = p_var->choices.i_count ; i-- ; )
        {
            if( p_var->pf_cmp( *p_val, p_var->choices.p_values[i] ) == 0 )
            {
                break;
            }
        }

        /* If not found, change it to anything vaguely valid */
        if( i < 0 )
        {
            /* Free the old variable, get the new one, dup it */
            p_var->pf_free( p_val );
            *p_val = p_var->choices.p_values[p_var->i_default >= 0
                                          ? p_var->i_default : 0 ];
            p_var->pf_dup( p_val );
        }
    }

    /* Check that our variable is within the bounds */
    switch( p_var->i_type & VLC_VAR_TYPE )
    {
        case VLC_VAR_INTEGER:
            if( p_var->i_type & VLC_VAR_HASSTEP && p_var->step.i_int
                 && (p_val->i_int % p_var->step.i_int) )
            {
                p_val->i_int = (p_val->i_int + (p_var->step.i_int / 2))
                               / p_var->step.i_int * p_var->step.i_int;
            }
            if( p_var->i_type & VLC_VAR_HASMIN
                 && p_val->i_int < p_var->min.i_int )
            {
                p_val->i_int = p_var->min.i_int;
            }
            if( p_var->i_type & VLC_VAR_HASMAX
                 && p_val->i_int > p_var->max.i_int )
            {
                p_val->i_int = p_var->max.i_int;
            }
            break;
        case VLC_VAR_FLOAT:
            if( p_var->i_type & VLC_VAR_HASSTEP && p_var->step.f_float )
            {
                float f_round = p_var->step.f_float * (float)(int)( 0.5 +
                                        p_val->f_float / p_var->step.f_float );
                if( p_val->f_float != f_round )
                {
                    p_val->f_float = f_round;
                }
            }
            if( p_var->i_type & VLC_VAR_HASMIN
                 && p_val->f_float < p_var->min.f_float )
            {
                p_val->f_float = p_var->min.f_float;
            }
            if( p_var->i_type & VLC_VAR_HASMAX
                 && p_val->f_float > p_var->max.f_float )
            {
                p_val->f_float = p_var->max.f_float;
            }
            break;
        case VLC_VAR_TIME:
            /* FIXME: TODO */
            break;
    }
}

/*****************************************************************************
 * InheritValue: try to inherit the value of this variable from the same one
 *               in our closest parent.
 *****************************************************************************/
static int InheritValue( vlc_object_t *p_this, const char *psz_name,
                         vlc_value_t *p_val, int i_type )
{
    int i_var;
    variable_t *p_var;

    /* No need to take the structure lock,
     * we are only looking for our parents */

    if( !p_this->p_parent )
    {
        switch( i_type & VLC_VAR_TYPE )
        {
        case VLC_VAR_FILE:
        case VLC_VAR_DIRECTORY:
        case VLC_VAR_STRING:
        case VLC_VAR_MODULE:
            p_val->psz_string = config_GetPsz( p_this, psz_name );
            if( !p_val->psz_string ) p_val->psz_string = strdup("");
            break;
        case VLC_VAR_FLOAT:
            p_val->f_float = config_GetFloat( p_this, psz_name );
            break;
        case VLC_VAR_INTEGER:
        case VLC_VAR_HOTKEY:
            p_val->i_int = config_GetInt( p_this, psz_name );
            break;
        case VLC_VAR_BOOL:
            p_val->b_bool = config_GetInt( p_this, psz_name );
            break;
        case VLC_VAR_LIST:
        {
            char *psz_orig, *psz_var;
            vlc_list_t *p_list = malloc(sizeof(vlc_list_t));
            p_val->p_list = p_list;
            p_list->i_count = 0;

            psz_var = psz_orig = config_GetPsz( p_this, psz_name );
            while( psz_var && *psz_var )
            {
                char *psz_item = psz_var;
                vlc_value_t val;
                while( *psz_var && *psz_var != ',' ) psz_var++;
                if( *psz_var == ',' )
                {
                    *psz_var = '\0';
                    psz_var++;
                }
                val.i_int = strtol( psz_item, NULL, 0 );
                INSERT_ELEM( p_list->p_values, p_list->i_count,
                             p_list->i_count, val );
                /* p_list->i_count is incremented twice by INSERT_ELEM */
                p_list->i_count--;
                INSERT_ELEM( p_list->pi_types, p_list->i_count,
                             p_list->i_count, VLC_VAR_INTEGER );
            }
            if( psz_orig ) free( psz_orig );
            break;
        }
        default:
            return VLC_ENOOBJ;
            break;
        }

        return VLC_SUCCESS;
    }

    /* Look for the variable */
    vlc_mutex_lock( &p_this->p_parent->var_lock );

    i_var = Lookup( p_this->p_parent->p_vars, p_this->p_parent->i_vars,
                    psz_name );

    if( i_var >= 0 )
    {
        /* We found it! */
        p_var = &p_this->p_parent->p_vars[i_var];

        /* Really get the variable */
        *p_val = p_var->val;

        /* Duplicate value if needed */
        p_var->pf_dup( p_val );

        vlc_mutex_unlock( &p_this->p_parent->var_lock );
        return VLC_SUCCESS;
    }

    vlc_mutex_unlock( &p_this->p_parent->var_lock );

    /* We're still not there */

    return InheritValue( p_this->p_parent, psz_name, p_val, i_type );
}