In article <45DC988E.7040800@obry.net>, Pascal Obry <pascal@obry.net> writes:
> Rob Norris a �crit :
>> Currently I'm using text_io which means I have to copy the whole thing
>> into memory, insert the line then over write the file with new
>> contents. direct_io is not an option (varing string lengths)
> 
> Use Text_IO ok, but why copy all in memory. Just write to a temp file,
> delete the original one and rename the temp file.
> 
>> What alternatives should I consider for making insertions faster?
>> (NB retrieval of a line needs to be fairly quick as well).
> 
> If you have a lot of modifications to do on the file, then you probably
> need to read all the file in memory to have good performances. In this
> case, read file in blocks using Stream_IO. Do the changes in memory and
> write it back in blocks using Stream_IO.

Or use an operating system feature that allows insertions.  GNAT Ada 95
on VMS is supposed to emulate DEC Ada features, so that should include
the Mixed_Indexed_IO package.  There will be more overhead in disk files
but for large files it is much better for inserting data in the middle.