Escaping special characters in RAW/BLOB

Question

Hi!
I have a BLOB column that needs to be exported into a CSV Textfile. Sounds a bit scary but works fine when you escape the critical bytes.
I need to do the following replacement:
5C -> 5C 5C ( = \ )
22 -> 5C 22 ( = " )
00 -> 5C 30 ( = ?? )
0A -> 5C 0A ( = LF )
0D -> 5C 0D ( = CR )
If I use the replace function on my raw string, I can replace the bytes representing characters or numbers without a problem. " and \ also works fine but the nonprintable ones don't work - I guess implicit type conversion to varchar is the cause.
Anyway, I want to replace this stuff, but I couldn't find any native binary replace function. How can this be done? Do I have to write my own function? I fear byte by byte manipulation in PL/SQL on large data will not be very performing...
Thanks, Mac

Answer 1

so here's my function, feel free so use
function get_raw_escaped (
pv_data_source raw
return raw
is
lv_data_escaped raw(32767) := null;
lv_length          number;
lv_offset          number;
lv_chunk_bin     raw(100);
lv_chunk_hex     varchar2(100);
begin
     lv_length := utl_raw.length(pv_data_source);
     if lv_length = 0 then return null; end if;
     for lv_offset in 1..lv_length loop
          lv_chunk_bin := utl_raw.substr (pv_data_source, lv_offset, 1);
          lv_chunk_hex := rawtohex(lv_chunk_bin);
          CASE lv_chunk_hex
               WHEN '00' THEN lv_chunk_hex := '5C30';
               WHEN '0A' THEN lv_chunk_hex := '5C0A';
               WHEN '0D' THEN lv_chunk_hex := '5C0D';
               WHEN '22' THEN lv_chunk_hex := '5C22';
               WHEN '5C' THEN lv_chunk_hex := '5C5C';
          ELSE null;
          END CASE;
          lv_chunk_bin := hextoraw(lv_chunk_hex);
          lv_data_escaped := utl_raw.concat(lv_data_escaped, lv_chunk_bin);
     end loop;
     return lv_data_escaped;
end;