| 238 | | Upon creation of the quadtree the user specifies a maximum number of points to be held in cache. |
| 239 | | |
| 240 | | |
| 241 | | |
| | 241 | Upon creation of the quadtree the user specifies a maximum number of points to be held in memory. Whenever a new bucket is created inside {{{PointBucket::cache()}}} the {{{CacheMinder::updateCache(int requestSize, PointBucket* pointBucket, bool force)}}} method is called with {{{requestSize}}} parameter equal to the number of points that will be held in that bucket. This number is then added to {{{CacheMinder::cacheUsed}}} variable and compared to {{{CacheMinder::totalCache}}} equal to maximum number of points that can be held in memory. If the sum of the to is smaller then maxim cache size the {{{cachUsed}}} variable is updated and a pointer to the bucket is added to the queue ({{{std::deque}}}) of cached buckets. If total amount of cache requested is greater then allowed maximum the buckets are taken from the front of the queue and uncached until there's enough space for the new bucket. (A note here: the {{{force}}} variable in {{{updateCache()}}} method is actually obsolete as it's always set to true). \\ \\ |
| | 242 | When a bucket needs to be uncached, because there is no more room for new buckets in memory, {{{PointBucket::uncache()}}} method is called which serializes the bucket by compressing it and writes it to a file. Two lso compression is used for this together with two static variables to reduce the memory overhead. The serialization code looks like this: |
| | 243 | {{{ |
| | 244 | #!div style="font-size: 100%" |
| | 245 | {{{#!c++ |
| | 246 | // static shared working memory |
| | 247 | unsigned char *PointBucket::workingMemory = (unsigned char*) malloc(LZO1B_MEM_COMPRESS); |
| | 248 | unsigned char *PointBucket::compressedData = (unsigned char*) malloc(ceil(sizeof(LidarPoint) * capacity_ * 1.08)); |
| | 249 | |
| | 250 | // then inside PointBucket::uncache() |
| | 251 | lzo_init(); |
| | 252 | lzo1b_2_compress((const unsigned char*) points_[k], sizeof (LidarPoint) * numberOfPoints_[k], |
| | 253 | compressedData, &compressedDataSize_[k], workingMemory); |
| | 254 | |
| | 255 | fwrite(compressedData, 1, compressedDataSize_[k], file); |
| | 256 | fclose(file); |
| | 257 | }}} |
| | 258 | }}} |
| | 259 | Once the data has been written, the bucket is deleted from memory and {{{CacheMinder::update_cache()}}} method gets called with negative {{{requestSize}}} to update the amount of used cache. \\ \\ |
| | 260 | If a {{{setPoint()}}} or {{{getPoint()}}} method is called on an uncached bucked it is simply re-created from the file an {{{CacheMinder::updateCache()}}} is called to reflect these changes. |