[GRASS-dev] [GRASS GIS] #1685: r.in.ascii -s for SURFER does not work in grass7

[GRASS GIS]

#1685: r.in.ascii -s for SURFER does not work in grass7
-----------------------------------------------+----------------------------
 Reporter:  helena                             |       Owner:  grass-dev@…              
     Type:  defect                             |      Status:  new                      
 Priority:  minor                              |   Milestone:  7.0.0                    
Component:  Raster                             |     Version:  svn-trunk                
 Keywords:  raster import, Surfer, r.in.ascii  |    Platform:  All                      
      Cpu:  OSX/Intel                          |  
-----------------------------------------------+----------------------------
Changes (by hamish):

  * keywords:  raster import, Surfer => raster import, Surfer, r.in.ascii
  * platform:  MacOSX => All


Comment:

 the error message in g7 lib/gis/seek.c is now just "Unable to seek"; it's
 not a fundamental limitation just a regular bug AFAICT.

 I found a binary Surfer6 grid file sitting on an old drive, and could
 convert it to an ascii grid:
 {{{
   gdal_translate -of GSAG helens2.grd helens2a.grd
   r.in.ascii -s in=helens2a.grd out=helens2
 }}}

 and I can reproduce your error. It happens in r.in.ascii/main.c on this
 G_fseek(), while processing the last row of the map.

 {{{
     for (row = 0; row < nrows; row += 1) {
         fread(rast, Rast_cell_size(data_type), ncols, ft);
         Rast_put_row(cf, rast, data_type);
         G_fseek(ft, sz, SEEK_CUR);
     }
     fclose(ft);
     unlink(temp);

     Rast_close(cf);
 }}}


 G_ftell(ft) reports the position as 1308 but G_fseek() wants to move
 sz=-2616 bytes (negative as surfer ascii grids are stored bottom to top),
 and runs past the end (i.e. start) of the file. note 1308*2 = 2616. I
 presume the array is off by 1 row and the first line of data is either
 repeated or empty.

 here is row, nrows, sz, and on the newline G_ftell() position for the last
 few rows:
 {{{
 460 466  -2616
 7848
 461 466  -2616
 6540
 462 466  -2616
 5232
 463 466  -2616
 3924
 464 466  -2616
 2616
 465 466  -2616
 1308
 ERROR: Unable to seek
 }}}


 The import works fine in grass 6.x.


 Hamish

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1685#comment:1>
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