header_from_twkb_state()

static void header_from_twkb_state ( twkb_parse_state *  s )

static

Definition at line 490 of file lwin_twkb.c.

References byte_from_twkb_state(), twkb_parse_state::factor, twkb_parse_state::factor_m, twkb_parse_state::factor_z, twkb_parse_state::has_bbox, twkb_parse_state::has_idlist, twkb_parse_state::has_m, twkb_parse_state::has_size, twkb_parse_state::has_z, twkb_parse_state::is_empty, LWDEBUG, twkb_parse_state::lwtype, lwtype_from_twkb_type(), twkb_parse_state::ndims, precision, twkb_parse_state::size, twkb_parse_state_uvarint(), ovdump::type, and unzigzag8().

Referenced by lwgeom_from_twkb_state().

{
        LWDEBUG(2,"Entering magicbyte_from_twkb_state");

        uint8_t extended_dims;

        /* Read the first two bytes */
        uint8_t type_precision = byte_from_twkb_state(s);
        uint8_t metadata = byte_from_twkb_state(s);

        /* Strip type and precision out of first byte */
        uint8_t type = type_precision & 0x0F;
        int8_t precision = unzigzag8((type_precision & 0xF0) >> 4);

        /* Convert TWKB type to internal type */
        s->lwtype = lwtype_from_twkb_type(type);

        /* Convert the precision into factor */
        s->factor = pow(10, (double)precision);

        /* Strip metadata flags out of second byte */
        s->has_bbox   =  metadata & 0x01;
        s->has_size   = (metadata & 0x02) >> 1;
        s->has_idlist = (metadata & 0x04) >> 2;
        extended_dims = (metadata & 0x08) >> 3;
        s->is_empty   = (metadata & 0x10) >> 4;

        /* Flag for higher dims means read a third byte */
        if ( extended_dims )
        {
                int8_t precision_z, precision_m;

                extended_dims = byte_from_twkb_state(s);

                /* Strip Z/M presence and precision from ext byte */
                s->has_z    = (extended_dims & 0x01);
                s->has_m    = (extended_dims & 0x02) >> 1;
                precision_z = (extended_dims & 0x1C) >> 2;
                precision_m = (extended_dims & 0xE0) >> 5;

                /* Convert the precision into factor */
                s->factor_z = pow(10, (double)precision_z);
                s->factor_m = pow(10, (double)precision_m);
        }
        else
        {
                s->has_z = 0;
                s->has_m = 0;
                s->factor_z = 0;
                s->factor_m = 0;
        }

        /* Read the size, if there is one */
        if ( s->has_size )
        {
                s->size = twkb_parse_state_uvarint(s);
        }

        /* Calculate the number of dimensions */
        s->ndims = 2 + s->has_z + s->has_m;

        return;
}

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