On 21.04.2013 17:13, Michaël Michaud wrote: > Hi >> well - the SRID code is the only thing that seems to be added between JTS >> 1.7 and 1.8. >> >> some more observations: >> >> what Larry's DBQuery actually does is stripping MBR header and end marker >> from the spatiallite blob and handing it over to JTS. as Michael correctly >> discovered is the endianess byte used differently in there, so what actually >> would need to be done is the WKB would have to be postprocessed before >> giving it to JTS. but before we try that: >> >> i had a look at >> >> https://sourceforge.net/apps/mediawiki/jump-pilot/index.php?title=OpenJUMP_with_SpatialLite#Using_SpatiaLite_with_Spatialite_Reader_Plugin >> sources and it seems to bring with a full blown BLOB parser. >> >> Jukka, Michael: could you check if this plugin suffers from the same >> problem? i would guess not. if not, we could reuse the parser, single it out >> as a jar etc. > I recently patched Spatialite Plugin after Jukka'request, but it suffers > from the same problem (parser just read the first few bytes then use JTS > WKBReader). > > I had a look in JTS WKBParser (which is short and easy to read). > > The key part is in readGeometry(), lines > int byteOrder = byteOrderWKB == WKBConstants.wkbNDR ? > ByteOrderValues.LITTLE_ENDIAN : ByteOrderValues.BIG_ENDIAN; > dis.setOrder(byteOrder); > > Unfortunately, this method is private. > We could suggest to Martin to change it to > > switch(byteOrderWKB) { > case WKBConstants.wkbNDR: > dis.setOrder(ByteOrderValues.LITTLE_ENDIAN); > break; > case WKBConstants.wkbXDR:dis.setOrder(ByteOrderValues.BIG_ENDIAN); > break; > case 0x69 : // keep previous byte order, this is a spatialite > geometry > break; > default : > throw Exception("This case is neither a pure wkb neither a > spatialite wkb"); > } > > Seems that it could tolerate spatialite geometry and be as strict as it > is now for wkb. > > What do you think ? >
oh. i see, the reader switches to big endian because of the 0x69 value.. can't be good ;) wrt. to the patch. it works around the standard. having a switch case is good, to find corrupt datasets. adding spatialite specifics is a mixup of standards. maybe a class that extends JTS's WKBParser implementing the specifics (cutting header,end, 0x69) would be a cleaner solutions. but as you say: up to Martin. we can always extend WKBParser ourselfs if he doesn't like it upstream. ..ede ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
