-- https://stackoverflow.com/questions/19539408/error-when-decoding-base-64-to-blob
CREATE OR REPLACE FUNCTION base64_decode(p_content CLOB) RETURN BLOB
	IS
		C_CHUNK_SIZE CONSTANT INTEGER := 4000; -- should be a multiple of 4
		C_NON_BASE64_SYM_PATTERN CONSTANT VARCHAR2(20) := '[^A-Za-z0-9+/]';
		l_chunk_buf VARCHAR2(4000);
		l_chunk_b64_buf RAW(3000);
		l_chunk_offset INTEGER := 1;
		l_chunk_size INTEGER;
		l_res BLOB;

		FUNCTION get_next_full_base64_chunk(l_data CLOB, p_cur_pos IN OUT INTEGER, p_desired_size INTEGER, p_cur_size IN OUT INTEGER) RETURN VARCHAR2 IS
			l_res VARCHAR2(4000);
			l_tail_desired_size INTEGER;
		BEGIN
			l_res := dbms_lob.substr(l_data, p_desired_size, p_cur_pos);
			p_cur_pos := p_cur_pos + p_desired_size;
			IF l_res IS NULL THEN
				RETURN NULL;
			END IF;

			l_res := regexp_replace(l_res, C_NON_BASE64_SYM_PATTERN, '');
			p_cur_size := p_cur_size + length(l_res);

			l_tail_desired_size := 4 - mod(p_cur_size, 4);
			IF l_tail_desired_size = 4 THEN
				RETURN l_res;
			ELSE
				RETURN l_res || get_next_full_base64_chunk(l_data, p_cur_pos, l_tail_desired_size, p_cur_size);
			END IF;
		END;

	BEGIN
		dbms_lob.createtemporary(l_res, false);

		WHILE true
		LOOP
			l_chunk_size := 0;
			l_chunk_buf := get_next_full_base64_chunk(p_content, l_chunk_offset, C_CHUNK_SIZE, l_chunk_size);
			EXIT WHEN l_chunk_buf IS NULL;
			l_chunk_b64_buf := utl_encode.base64_decode(utl_raw.cast_to_raw(l_chunk_buf));
			dbms_lob.writeappend(l_res, utl_raw.length(l_chunk_b64_buf), l_chunk_b64_buf);
		END LOOP;

		RETURN l_res;
	END;
/
DECLARE
	l_clob CLOB;
BEGIN