[R-sig-Geo] readGDAL does not close connections

[Paul Hiemstra]

Dear r-sig-geo list,

I'm struggeling with readGDAL (rgdal package) not closing its file 
connections (I suspect). I am trying to construct a timeseries of 
rainfall using the following loop (conceptual code):

pt = SpatialPoint()
rainfall = numeric(length = length(listofiles))
for(i in 1:length(listofiles)) {
    grid = readGDAL(listofiles[i])
    rainfall[i] = grd$value[overlay(grid, pt)]
}

There are more than 35000 grids (HDF5) that I loop over (2007 - 15 
minutes interval). After reading about 1000 grids my program fails:

HDF5:"radar/2007/01/11/RAD_NL21_PCP_NA_200701111515.h5"://image1/image_data 
has GDAL driver HDF5Image
and has 256 rows and 256 columns
Error in gzfile(file, "r") : unable to open connection
In addition: Warning message:
In gzfile(file, "r") :
  cannot open compressed file '/home/hiemstra/lib/R/rgdal/DESCRIPTION'

I suspect that readGDAL opens connections to the files, but does not 
close them and the program fails because too many files have been 
openened simultaneously. I do not get messages like "Closing GDAL 
dataset handle 0x8ff7900...  destroyed ... done." when I run the script. 
Does anybody on the r-sig-geo list have similar experiences?

kind regards,
Paul

ps Additional information on my session
 > sessionInfo()
R version 2.6.1 (2007-11-26)
i486-pc-linux-gnu

locale:
LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_US.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] rgdal_0.5-24   maptools_0.7-7 foreign_0.8-23 automap_0.4-3  
classInt_0.1-9
[6] e1071_1.5-17   class_7.2-41   gstat_0.9-43   sp_0.9-23

loaded via a namespace (and not attached):
[1] grid_2.6.1      lattice_0.17-6  rcompgen_0.1-17

I run Debian Lenny

-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone: 	+31302535773
Fax:	+31302531145
http://intamap.geo.uu.nl/~paul