Geometry to wkt curve polygon

In Oracle Spatial the conversion of arc's to WKT seems not supported as it is not part of the simple feature specification. On this page you will find:

• a spatial function to stroke the arc's
• a custom function to output polygons with arc's

SQL arc stroking with Oracle Spatial:

select SDO_UTIL.TO_WKTGEOMETRY( SDO_GEOM.SDO_ARC_DENSIFY(geom, 0.0005, 'arc_tolerance=0.01'))
  from (select MDSYS.SDO_GEOMETRY(2003, 90112, NULL, 
           MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,3,1,2,1,3,2,2,7,2,1)
           , MDSYS.SDO_ORDINATE_ARRAY(161312.26, 383399.949, 161312.42, 383399.78
           , 161315.461, 383401.401, 161317.344, 383404.288, 161317.296, 383404.342
           , 161312.26, 383399.949)) as geom from dual)
  ;

Result:

POLYGON ((161312.26 383399.949, 161312.42 383399.78, 161313.087535512 383399.978123147
  , 161313.731792268 383400.242300498, 161314.346252635 383400.569859498
  , 161314.924700414 383400.957486391, 161315.461283728 383401.401259743
  , 161315.950574223 383401.896690114, 161316.387621984 383402.438765474
  , 161316.76800561 383403.022001908, 161317.087876943 383403.640499096
  , 161317.344 383404.288, 161317.296 383404.342, 161312.26 383399.949))

SQL curve WKT with custom function:

select GEOMETRY_TO_CURVEPOLYGON_WKT(geom)
  from (select MDSYS.SDO_GEOMETRY(2003, 90112, NULL, 
           MDSYS.SDO_ELEM_INFO_ARRAY(1,1005,3,1,2,1,3,2,2,7,2,1)
           , MDSYS.SDO_ORDINATE_ARRAY(161312.26, 383399.949, 161312.42, 383399.78
           , 161315.461, 383401.401, 161317.344, 383404.288, 161317.296, 383404.342
           , 161312.26, 383399.949)) as geom from dual)
  ;

Result:

CURVEPOLYGON(COMPOUNDCURVE((161312.26 383399.949,161312.42 383399.78)
  ,CIRCULARSTRING(161312.42 383399.78,161315.461 383401.401,161317.344 383404.288)
  ,(161317.344 383404.288,161317.296 383404.342,161312.26 383399.949)))

PL/SQL curve polygon function:

create or replace FUNCTION GEOMETRY_TO_CURVEPOLYGON_WKT( geom IN mdsys.Sdo_geometry ) RETURN CLOB is
    -- FUNCTION geometry --> curvepolygon wkt
    -- (c) 2012-01 Synaxion Urbidata
    -- exception voor foutieve of niet-ondersteunde geometrie, ondersteund zijn:
    -- - (curve)polygon, optioneel met 1 of meer gaten
    elem_info_i PLS_INTEGER;
    start_index PLS_INTEGER;
    until_index PLS_INTEGER;
    geometry_type VARCHAR2(12) := 'POLYGON';
    element_type PLS_INTEGER;
    element_interpretation PLS_INTEGER;
    subelements_num PLS_INTEGER;
    subelements_type PLS_INTEGER;
    ring CLOB;
    exterior CLOB;
    interiors CLOB;
    
    function num_to_char(n number) return varchar2 is
    begin
      if trunc(n)=n then
        return trim(to_char(n,'9999999999.0'));
      else
        return to_char(n);
      end if;
    end;
    
    function read_elem_info(i PLS_INTEGER) return PLS_INTEGER is
    begin
      IF i+2 > geom.sdo_elem_info.COUNT THEN
        raise_application_error(-20002, 'The elemtinfo count ('||to_char(geom.sdo_elem_info.COUNT)||') is not a multitude of 3');
      END IF;
      start_index:=geom.sdo_elem_info( i );
      element_type := geom.sdo_elem_info( i+1 );
      element_interpretation:=geom.sdo_elem_info( i+2 );
      -- next start index: 'until_index'
      IF i+3 <= geom.sdo_elem_info.COUNT THEN
        until_index:=geom.sdo_elem_info(i+3);
      ELSE
        until_index:=geom.Sdo_ordinates.COUNT+1;
      END IF;
      RETURN i+3;
    end;
    
    function read_ring(start_index PLS_INTEGER, until_index PLS_INTEGER) return clob is
    begin
      declare
        j PLS_INTEGER;
        r clob;
      begin
        r:=null;
        -- check index, create ring
        IF start_index<=geom.Sdo_ordinates.COUNT
        and start_index > 0
        and until_index+1-2<=geom.Sdo_ordinates.COUNT
        and until_index-2>0
        and start_index<until_index-1
        THEN
          j:=start_index;
          WHILE j < until_index LOOP
            IF not r is NULL THEN
              r := r||',';
            END IF;
            r := r || num_to_char( geom.sdo_ordinates(j+0) ) || ' ' || num_to_char( geom.sdo_ordinates(j+1) );
            j:=j+2;
          END LOOP;
        ELSE
          raise_application_error(-20003, 'GEOMETRY_TO_CURVEPOLYGON_WKT: the offset does not point to any coordinates');
        END IF;
        return r;
      end;      
    end;
BEGIN
    IF geom is NULL THEN
      RETURN NULL;    
    ELSIF NOT geom.sdo_elem_info IS NULL THEN
      IF geom.sdo_gtype = 2003 THEN          
        exterior:=NULL;
        interiors:=NULL;
        elem_info_i:=1;
        WHILE elem_info_i <= geom.sdo_elem_info.COUNT LOOP

          elem_info_i:=read_elem_info(elem_info_i);
          
          -- curve polygons
          IF element_type in (1005,2005) THEN 
            geometry_type:='CURVEPOLYGON';
            subelements_num:=element_interpretation;
            subelements_type:=element_type;
            ring:=NULL;
            WHILE subelements_num>0 LOOP
              subelements_num:=subelements_num-1;
              elem_info_i:=read_elem_info(elem_info_i);
              IF NOT ring is NULL THEN
                ring:=ring||',';
              END IF;

              -- if not last segment then add first point of next segment
              IF subelements_num>0 AND until_index<geom.sdo_ordinates.COUNT+1 THEN
                until_index:=until_index+2;
              END IF;
              
              IF element_interpretation=1 THEN
                ring:=ring||'('||read_ring(start_index,until_index)||')';
              ELSIF element_interpretation=2 THEN
                 ring:=ring||'CIRCULARSTRING('||read_ring(start_index,until_index)||')';
              ELSE
                raise_application_error(-20003, 'GEOMETRY_TO_CURVEPOLYGON_WKT: the interpretation of subelement ('||to_char(element_interpretation)||') should be 1 (straight) or 2 (curve)');
              END IF;                
            END LOOP;
            IF subelements_type=1005 AND exterior is NULL THEN
              exterior:='COMPOUNDCURVE('||ring||')';
            ELSIF subelements_type=2005 THEN
              interiors:=interiors || ',' || 'COMPOUNDCURVE('||ring||')';
            ELSE
              raise_application_error(-20004, 'GEOMETRY_TO_CURVEPOLYGON_WKT: unsupported coumpound geometry');
            END IF;
          ELSIF element_type=1003 AND exterior is NULL THEN
            exterior:='(' || read_ring(start_index,until_index) || ')';
          ELSIF element_type=2003 THEN
            interiors:=interiors || ',' || '(' || read_ring(start_index,until_index) || ')';
          ELSE
            raise_application_error(-20005, 'GEOMETRY_TO_CURVEPOLYGON_WKT: unsupported geometry');
          END IF;
          
        END LOOP;
        RETURN geometry_type || '(' || exterior || interiors || ')';
      ELSE
        raise_application_error(-20006, 'GEOMETRY_TO_CURVEPOLYGON_WKT: unsupported geometry');
      END IF; -- geom.sdo_gtype = 2003
    ELSE
      raise_application_error(-20006, 'GEOMETRY_TO_CURVEPOLYGON_WKT: unsupported geometry');
    END IF; -- NOT geom.sdo_elem_info IS NULL    
    
    EXCEPTION WHEN OTHERS THEN
      --RETURN NULL;
      RETURN DBMS_UTILITY.FORMAT_ERROR_BACKTRACE || SQLERRM;
END;
/