bug in file.write() ?

[John Machin]

On 31 Jul 2003 15:43:34 -0700, pu at vo.lu (Patrick Useldinger) wrote:

>Hi,
>
>I think I found a bug in the write method of file objects. It seems as
>if before writing each block, a check was done in order to verifiy
>that there is enough space left for the *whole* file, not for the
>*remaining* data to be written.

This is very unlikely --- it is difficult to determine reliably the
available space on a disk or tape volume; if one were really
interested, one would do it once before trying to write the file, not
before writing each block. No, the expected implementation, which you
can check against reality by inspecting the source (fileobject.c), is
just to attempt to write, and throw an informative-as-possible
exception if the write fails.

Despite the appearance that you have about 6KB margin of safety,  you
will probably find that you don't have any --- the quoted size of the
source file doesn't include the unused space in the last cluster or
block or whatever. It's a while since I've had to concern myself with
this sort of detail, but it's a good bet that the "chunk" size on your
disk is 8Kb or more and you're out of luck.

>
>It happens both under 2.3 and 2.2.3.
>Any ideas? 

[snip]

>  File "C:\Python23\lib\shutil.py", line 39, in copyfile
>    copyfileobj(fsrc, fdst)
>  File "C:\Python23\lib\shutil.py", line 24, in copyfileobj
>    fdst.write(buf)
>IOError: [Errno 28] No space left on device
>
>I:\My Programs\dfc>dir f:
> Volume in drive F is Backup 01
> Volume Serial Number is E2CB-1650
>
> Directory of F:\
>
>18/05/2002  15:39       <DIR>          .
>18/05/2002  15:39       <DIR>          ..
>01/08/2003  00:25          299.630.592 dfcArchive cheetah
>20030731-234648 F.zip
>               1 File(s)    299.630.592 bytes
>               2 Dir(s)     299.636.736 bytes free
>
[snip]