I ve seen a BLR display tool (in Jason Wharton s IB admin tool), but it would only display BLR names, not transliterate back to SQL/proc language. I think what you re looking for doesn t exist.

You can get BLR documentation here, though.

There is nice BLR (binary) to BLR (text) decoder in Firebird itself. You can enable it with set blob all (or set blobdisplay all). You can call it from ISQL:

SQL> set term !;
SQL> create procedure p1
CON> as
CON>   declare n integer = 1;
CON> begin
CON>   n = n * 2;
CON> end!
SQL> set term ;!
SQL> 
SQL> set blob all;
SQL> commit;
SQL> 
SQL> select rdb$procedure_blr from rdb$procedures where rdb$procedure_name =  P1 ;

RDB$PROCEDURE_BLR 
================= 
             1a:3 
==============================================================================
RDB$PROCEDURE_BLR:  
            blr_version5,
            blr_begin,
               blr_message, 1, 1,0,
                  blr_short, 0,
               blr_begin,
                  blr_declare, 0,0, blr_long, 0,
                  blr_assignment,
                     blr_literal, blr_long, 0, 1,0,0,0,
                     blr_variable, 0,0,
                  blr_stall,
                  blr_label, 0,
                     blr_begin,
                        blr_begin,
                           blr_assignment,
                              blr_multiply,
                                 blr_variable, 0,0,
                                 blr_literal, blr_long, 0, 2,0,0,0,
                              blr_variable, 0,0,
                           blr_end,
                        blr_end,
                  blr_end,
               blr_send, 1,
                  blr_begin,
                     blr_assignment,
                        blr_literal, blr_short, 0, 0,0,
                        blr_parameter, 1, 0,0,
                     blr_end,
               blr_end,
            blr_eoc

==============================================================================

If you still have the database there is a chance the procedure source is still there somewhere but marked as deleted. You may try to open the database file on a hex editor and search for the procedure name.