FileSystemCacheBin crashes if reader/writer for extension osgb cannot be loaded

[hwiesmann]

In the constructor _rw is assigned to the reader/writer of the extension osgb. Afterwards, there are no checks whether _rw contains a non null pointer value. Therefore, the program will crash when using _rw.

Hartwig

[gwaldron]

patched; please check and report bank. Thanks.

[hwiesmann]

Your fix is not working: in TerrainLayer::getCacheBin(const Profile* profile, const std::string& binId) metadata is read. If the read fails metadata is created and written (see below).

        // attempt to read the cache metadata:
        CacheBinMetadata meta( newBin->readMetadata() );

        if ( meta.isValid() ) // cache exists and is valid.
        {
            // verify that the cache if compatible with the tile source:
            if ( tileSource && getProfile() )
            {
                //todo: check the profile too
                if ( *meta._sourceDriver != tileSource->getOptions().getDriver() )
                {
                    OE_WARN << LC << "Cache has an incompatible driver or profile... disabling"
                        << std::endl;
                    setCachePolicy( CachePolicy::NO_CACHE );
                    return 0L;
                }
            }   

            else if ( isCacheOnly() && !_profile.valid() )
            {
                // in cacheonly mode, create a profile from the first cache bin accessed
                // (they SHOULD all be the same...)
                _profile = Profile::create( *meta._sourceProfile );
                _tileSize = *meta._sourceTileSize;
            }
        }

        else
        {
            // cache does not exist, so try to create it. A valid TileSource is necessary
            // for this.
            if ( tileSource && getProfile() )
            {
                // no existing metadata; create some.
                meta._cacheBinId      = binId;
                meta._sourceName      = this->getName();
                meta._sourceDriver    = tileSource->getOptions().getDriver();
                meta._sourceTileSize  = getTileSize();
                meta._sourceProfile   = getProfile()->toProfileOptions();
                meta._cacheProfile    = profile->toProfileOptions();
                meta._cacheCreateTime = DateTime().asTimeStamp();

                // store it in the cache bin.
                newBin->writeMetadata( meta.getConfig() );
            }
            else if ( isCacheOnly() )
            {
                OE_WARN << LC <<
                    "Failed to open a cache for layer "
                    "because cache_only policy is in effect and bin [" << binId << "] "
                    "could not be located."
                    << std::endl;
                return 0L;
            }
            else
            {
                OE_WARN << LC <<
                    "Failed to create cache bin [" << binId << "] "
                    "because there is no valid tile source."
                    << std::endl;
                return 0L;
            }
        }

Unfortunately, the failed read operation blocks any further operation. Therefore, also writing the metadata fails. This has the consequence that no new file system cache can be created.

Regards, Hartwig

[gwaldron]

I tried to patch this up differently; please give it a quick try. Didn't test it yet myself.

[hwiesmann]

Seems to work!