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/*! \page vlibOgr GRASS-OGR data provider
by GRASS Development Team (https://grass.osgeo.org)
\tableofcontents
\section vLibPseudoTopo Pseudo-topology
Reduced topology: each boundary is attached to one area only,
i.e. smoothing, simplification, removing small areas etc. will not
work properly for adjacent areas or areas within areas.
Full topology is only available for native GRASS vectors or can only
be built after all polygons are converted to areas and cleaned as done
by <tt>v.in.ogr</tt>.
\section vlibFrmtFileFormat Frmt file format specification
Frmt is a plain text file which contains basic information about
external format of linked vector map. Each line contains key, value
pairs separated by comma.
OGR specific format is described by:
- FORMAT - ogr
- DSN - OGR datasource name
- LAYER - OGR layer name
Example:
\verbatim
FORMAT: ogr
DSN: /path/to/shapefiles
LAYER: cities
\endverbatim
OGR layer can be linked via <tt>v.external</tt> command. When linking
OGR layer pseudo-topology ('topo') is built including spatial index
file ('sidx') and category index file ('cidx'). Additionally also
feature index file (see \ref vlibFidxFileFormat) is created.
\section vlibFidxFileFormat Fidx file format specification
Note: <tt>finfo</tt> is an instance of \ref Format_info structure.
<table border="1" style="border-collapse: collapse" cellpadding="5">
<tr><td><b>Name</b></td><td><b>Type</b></td><td><b>Number</b></td><td><b>Description</b></td></tr>
<tr><td>Version_Major </td><td>C</td><td>1</td><td>file version (major)</td></tr>
<tr><td>Version_Minor </td><td>C</td><td>1</td><td>file version (minor)</td></tr>
<tr><td>Back_Major</td><td>C</td><td>1</td><td>supported from GRASS version (major)</td></tr>
<tr><td>Back_Minor</td><td>C</td><td>1</td><td>supported from GRASS version (minor)</td></tr>
<tr><td>byte_order</td><td>C</td><td>1</td><td>little or big endian
flag; files are written in machine native order but
files in both little and big endian order may be
readl; zero for little endian</td></tr>
<tr><td>length</td><td>L</td><td>1</td><td>header size</td></tr>
<tr><td>fInfo.ogr.offset_num</td><td>I</td><td>1</td><td>number of records</td></tr>
<tr><td>fInfo.ogr.offset</td><td>I</td><td>offset_num</td><td>offsets</td></tr>
</table>
*/
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