using mmap on large (> 2 Gig) files

sturlamolden sturlamolden at yahoo.no
Tue Oct 24 02:51:43 CEST 2006


myeates at jpl.nasa.gov wrote:
> Hi
> Anyone ever done this? It looks like Python2.4 won't take a length arg
> > 2 Gig since its not seen as an int.

Looking at Python's source (mmapmodule.c), it seems that "mmap.mmap"
always sets the offset argument in Windows MapViewOfFile and UNIX to 0.
This means that it is always mapping from the beginning of the file.
Thus, Python's mmap module is useless for large files. This is really
bad coding. The one that wrote mmapmodule.c didn't consider the
posibility that a 64 bit file system like NTFS can harbour files to
large to fit in a 32 address space. Thus,
mmapmodule.c needs to be fixed before it can be used for large files.




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