I haven't used POI very much. Rather new to the POI/HSSF game, but been around Java for a while. Kais seems to mention memory issues with writing large files. Are there any gotcha's that I should be aware of? Anything specific to avoid? I may have need to go into the 20-40 mb range. I know, it's insane to stuff that much rot in a sheet - but it honestly may need to be done in this case. Again, I'm just investigating, and need to know what to be aware of, before jumping into it with both feet. Any light you can shed on it would be much appreciated...
Thanks in advance, Jeff --- Kais Dukes <[EMAIL PROTECTED]> wrote: > Dear Michael > > I can offer my answers to these questions, with the > disclaimer that these > are based on my own observations. > > From my use of POIFS: > > (1) POIFS seems to have no trouble with large files, > in terms of XBATs. > Memory is another question. > (2) You are right that XBAT is not the usual name, > in Microsoft speak, and > reading standard docs on OLE2, it is the DIF. > (3) I have noticed these issues. In the > implementations I have written for > OLE2 structured storage, it appears that the > Microsoft implementation will > correctly read your OLE2 files regardless of how you > distribute BAT or XBAT > blocks (as long as there correctly pointed to). > (4) The POIFS implementation doesn't seem to hard > code sector sizes, these > have been abstacted (e.g. contants). It may be the > case that switching these > would result in the code still working, although I > have not tested. > (5) Related to the issue of sector sizes, the next > version of Windows > (Longhorn) will have much better support sector > sizes other than 512 bytes, > so I would hope a future POIFS system to deal with > this correctly. > > -----Original Message----- > From: Michael Zalewski > [mailto:[EMAIL PROTECTED] > Sent: 26 February 2004 14:43 > To: POI Users List > Subject: RE: Problem generating a large file when > following the > POIFSstandard > > > I don't mean to add fuel to the fire. But I have > some questions: > > 1. Brandon pointed out that a C++ implementation > based on POIFS has trouble > writing files larger than 6.8 MB, where XBATs must > be created. Do we know > that POIFS creates these large files correctly? Has > anyone used HSSF to make > a XLS larger than 7 MB? How much heap space was > required? > > 2. For that matter, where does the term XBAT come > from? I thought it was > called DIF (Double Indirect FAT). > > 3. There are some other differences that I notice in > the way POIFS handles > things versus COMPOBJ.DLL. The most notable is that > HSSF does not put > something called the 'Storage Class ID' into the > root entry or the OLE Doc > file header. But Excel doesn't seem to care. POIFS > has no support for > 'CompObj' stream, which is required for embedding > (and is used for Word and > Project even when the files are not embedded - but > again the application > doesn't seem to care if the stream is present or not > when the document is > read from a file). POIFS cannot create a document > stream of 0 length (it's a > known bug). And finally, POIFS puts the directory > structure in block 0 > whereas Office always puts the document stream into > block 0. None of these > differences should account for Brandon's problems (I > don't think). > > 4. Does POIFS support any block size other than 512 > bytes? Not sure, but I > think Microsoft Map uses a larger sector size. Since > POIFSConstants.BIG_BLOCK_SIZE is statically defined > (instead of interpreting > the value at offset 30 from the beginning of the > file. This value is (I > guess) ignored by POIFS, but should be interpreted > as the base 2 logarithm > of the large sector size (so it should be 9 for 512 > bytes used by Microsoft > Office, and I think 10 for 1024 bytes on some files > produced by Microsoft > Map). > > If Brandon's C++ derivative supports the variant > block sizes, perhaps he > could try using a 1024 block size. Doing this should > allow you to go to over > 12 MB without the need for XBATs (or DIFs). I would > really like to know if > that works - but I seriously wonder if he would > report back anyway. > > Note: I am not at all certain about Microsoft Map. > Just had reports of > someone using POIFS to read that file, and > everything was 'one block off'. > When (if) I ever follow up on it, I will report > results back to this list > (unless I get viciously shouted down). > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: > [EMAIL PROTECTED] > For additional commands, e-mail: > [EMAIL PROTECTED] > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: > [EMAIL PROTECTED] > For additional commands, e-mail: > [EMAIL PROTECTED] > > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
