Memory-mapped raster backend

[fb71]

Efficiently handle rasters that exceed heap and main memory size.

Current implementation ueses default DataBuffer backend for WriteableRaster as backend for GridCoverage. DataBuffer uses a plan primitive[] array for data storage. That is, a raster can have max. 2G = 46K x 46K raster elements and allocates 2GB x 8 = 16GB size on heap.

Goals

• process raster more independently of actual memory and heap size
• allow to process rasters > 2GB on 32bit systems
• maybe use memory-mapped files as persistent storage, avoid write/encode after processing

TODO

• eviction: limit mapped files on 32bit systems
• memory sensitive on 32bit systems (soft references and check for allocation error)
• check whole-file version for 64bit systems
• stride/tile version
• check memory-mapped files as persistent storage
• check double/float/int data type for modules