Large file support

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#75 Large file support

Milestone: Next_Release_(example)

Status: open

Owner: Stas Sergeev

Labels: 4Gb file support (1)

Priority: 5

Updated: 2014-02-23

Created: 2014-02-21

Creator: store

Private: No

Hi,
I was wondering if it is possible to add read/write support for files over 2GB
While I can access files from the native Linux file system the drive size is reported only as 2Gb some of the databases I use are over 3GB and cannot be access from dosemu.

any advice or help would be greatly appreciated.

Discussion

Stas Sergeev - 2014-02-21

Removed partition size limit: commit e99574ef81dc5
Enjoy.

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- store - 2014-02-21
  
  Hi,
  thank you very much.
  no i can list files bigger than 2GB but I still cannot copy or write to files bigger than 2Gb.
  
  any help is again greatly appriciated
  
  Last edit: store 2014-02-21
  
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Stas Sergeev - 2014-02-21

status: open --> closed

assigned_to: Stas Sergeev
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Stas Sergeev - 2014-02-21

status: closed --> open
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Stas Sergeev - 2014-02-21

What error do you get?

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- store - 2014-02-21
  
  when i run in freedos if i type dir i can see the full 3GB of the file but when i for example try to copy that file only 2GB of the file is copied and the copy stops
  
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Stas Sergeev - 2014-02-21

It may be a freedos limitation.
dosemu should do 4Gb I suppose.
Could you try win95's DOS-7?

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Stas Sergeev - 2014-02-21

Hmm, here:
http://en.wikipedia.org/wiki/Large_file_support
it is said that DOS-7 enforces the 2Gb
limit for compatibility too...
Puzzled.
They say it has some new API for 4Gb files.
I wonder what could it be.
Maybe if you use an 'xcopy' command from
DOS-7 (and DOS-7 itself too), it will allow
you to use 4Gb?

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Bart Oldeman - 2014-02-21

Hi Stas,

first of all your patch has some problems: the spc value is a byte value and can now overflow for large partitions. It should really not be higher than 64; even 128 is too high because DOS programs multiply spcbps=128512=65536 using 16 bit MUL and that overflows.

To properly report higher values than 2G for partitions DOSEMU would need to hook int21/ax=7303.

As for the file size - yes DOS has many issues with files > 2G; indeed the DOS program is supposed to open the file using a newer API: int21/AH=6c with BH bit 4 set. Many DOS C programs assume that negative file offsets are not valid. There could indeed also be FreeDOS problems here too.

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Stas Sergeev - 2014-02-21

OK, I put a 64 limit instead of 32.
But I'd like to hear if maybe it works
fine with DOS-7+xcopy.

store: please do NOT update from git
this time (as I returned the limit)
and do the DOS-7 test if possible.

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- store - 2014-02-21
  
  Hi guys,
  Thank you for everything.
  Stas I'll try it tomorrow morning and get back to you.
  
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- store - 2014-02-21
  
  Hi guys,
  Thanks for the help.
  Stas I'll try it tomorrow and let you know.
  
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- store - 2014-02-22
  
  Hi,
  I tried DOS-7+xcopy, it's able to read to read the 3GB file but only writes a 2GB file. once the file reached 2GB xcopy attempts to overwrite the 2.GB file.
  
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- store - 2014-02-22
  
  Hello again,
  I have now run another test a VMware installed with freedos 1.1 using copy command can copy a 3GB file.
  dosemu running freedos 1.1 will copy only 2GB of the same 3Gb file.
  I hope that helps.
  
  Last edit: store 2014-02-22
  
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Bart Oldeman - 2014-02-23

Could you try the newest git devel checkout
86a4eae7d20
this fixes both free space reporting and issues with read/write > 2G. Please confirm.

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- store - 2014-02-23
  
  Thank you very much guys.
  
  its now working perfectly in both freedos and dos-7
  
  amazing support.
  thank you again.
  
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