Oracle: How to convert CLOB to BLOB

FUNCTION clob_to_blob(p_clob IN CLOB) RETURN BLOB IS
v_blob BLOB;
v_offset NUMBER DEFAULT 1;
v_amount NUMBER DEFAULT 4096;
v_offsetwrite NUMBER DEFAULT 1;
v_amountwrite NUMBER;
v_buffer VARCHAR2(4096 CHAR);
BEGIN
dbms_lob.createtemporary(v_blob, TRUE);

Begin
LOOP
dbms_lob.READ(p_clob, v_amount, v_offset, v_buffer);

v_amountwrite := utl_raw.length(utl_raw.cast_to_raw(v_buffer));
dbms_lob.WRITE(v_blob, v_amountwrite, v_offsetwrite, utl_raw.cast_to_raw(v_buffer));

v_offsetwrite := v_offsetwrite + v_amountwrite;

v_offset := v_offset + v_amount;
v_amount := 4096;
END LOOP;
EXCEPTION
WHEN no_data_found THEN
NULL;
End;
RETURN v_blob;
END clob_to_blob;