Converting from a BASE64 BLOB

Question

I have a BLOB column which contains BASE64 encoded jpegs.
I want to decode these from BASE64 such that I can get the original JPEG.
I've written a function to do this (based on an example found here but modified slightly since my source is a BLOB not a CLOB: http://blogs.dayneo.co.za/2012/07/base64-decode-using-plsql.html)
     FUNCTION base64_decode(p_file IN BLOB)
     RETURN BLOB IS
      l_BASE64_LN_LENGTH constant pls_integer := 30000;
      l_result           blob := empty_blob();
      l_pos              number := 1;
      l_amount           number;
      l_buffer           raw(32767);
      l_rbuf             raw(32767);
      l_length           pls_integer;
     begin
      DBMS_LOB.createTemporary(l_result, true, dbms_lob.CALL);
      l_length  := DBMS_LOB.getLength(p_file);
      while l_pos <= l_length loop
       l_amount := l_BASE64_LN_LENGTH;
       dbms_lob.read(p_file, l_amount, l_pos, l_rbuf);
       l_buffer := utl_encode.base64_decode(l_rbuf);
       dbms_lob.writeappend(l_result,
                            utl_raw.length(l_buffer),
                            l_buffer);
       l_pos    := l_pos + l_BASE64_LN_LENGTH;
      end loop;
      return l_result;
     END base64_decode;This works absolutely fine where the input BLOB (p_file) is less than 30000 bytes i.e. I can save the generated BLOB and open it in a graphics application.
However, if the input BLOB (p_file) is larger than 30000 bytes, when I save the resultant BLOB (i.e. l_result) and try to open it with a graphics application such as Windows Picture Viewer I get the message "Drawing failed".
Any thoughts, comments or suggestions would be very much appreciated.
Thanks,
Andy

Answer 1

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This works absolutely fine where the input BLOB (p_file) is less than 30000 bytes i.e. I can save the generated BLOB and open it in a graphics application.
However, if the input BLOB (p_file) is larger than 30000 bytes, when I save the resultant BLOB (i.e. l_result) and try to open it with a graphics application such as Windows Picture Viewer I get the message "Drawing failed".
>
You can't just append and try to decode an arbitrary number of bytes in your loop. You are like having this problem
>
Conversion needs to be done in properly aligned chunks. And I use base64 conversions for MIME purposes.
>
See the solution by Oracle ACE Billy Verreynne Posted: May 29, 2012 9:28 AM at
Re: BASE64 (PDF) CLOB to BLOB