[Gdal-dev] Bug in OGDI Driver when accessing tiles (FAILURE: 1: End of selection)

[Reiner Beck]

(2nd try - the first one went to gdal-dev at remotesensing.org - sorry if 
you receive this twice)

Hello List,

there seems to be a bug in the OGDI driver when accessing tiles which 
are directly "under" the previously fetched tile.

Here's what I do:
- The driver is a RPF dataset and the sub-dataset used is a Matrix layer.
  This is a layer with a colortable, not the RGB Image layer.
- The error does only occur for single band access.
- I read the image data tile by tile using the 
GDALRasterBand::RasterIO() method.
- For example, the Image Size is 6144x3072, Tile Size is 256x256, No of 
Tiles is 24x12.
- For internal reasons, the tiles are fetched somewhat randomly.
- The error occurs only in case a tile is read, followed by a read to a 
tile which is directly
  under the previously read tile.

Example:
First tile to read is [3, 7]:

This results in calls to:
  poBand->RasterIO(GF_Read, 768, 1792, 256, 256, poinerToMyBuffer, 256, 
256, 1, 1, 256);

and GDAL internal to
  OGDIRasterBand::EstablishAccess(768, 1792, 256, 256, 256, 256);

Let's assume this works.


Next tile to read is [3, 8]:

This results in calls to:
  poBand->RasterIO(GF_Read, 768, 2048, 256, 256, poinerToMyBuffer, 256, 
256, 1, 1, 256)
and GDAL internal to
  OGDIRasterBand::EstablishAccess(768, 2048, 256, 256, 256, 256);

In this case, the method EstablishAccess() will not call 
cln_SelectRegion() and the read will fail with an error 1 "End of 
selection". This happens in the OGDI RPF driver, function 
dyn_getNextObjectRaster(). However, I think the error is in the GDAL part.


Workaround:
In case the if statement in EstablishAccess() is commented out (not the 
body of the statement), it works:
/*
/if( poODS->nCurrentIndex == -1 / / || ABS(sWin.west - 
poODS->sCurrentBounds.west) > 0.0001 / / || ABS(sWin.east - 
poODS->sCurrentBounds.east) > 0.0001 / / || ABS(sWin.north - 
(poODS->sCurrentBounds.north - poODS->nCurrentIndex * 
poODS->sCurrentBounds.ns_res)) > dfNSTolerance / / || 
ABS(sWin.ew_res/poODS->sCurrentBounds.ew_res - 1.0) > 0.0001/ / || 
ABS(sWin.ns_res - poODS->sCurrentBounds.ns_res) > dfNSTolerance )/ /
*/
Not sure if this is the best solution though ...


Version:
gdal 1.2.6 and ogdi 3.1.4. However, the affected code seems to be 
identical to the most recent versions (checked against gdal 1.3.1 and 
ogdi 3.1.5).

Cheers
Reiner