Set cache subfolders number according to media number
Created by: paolobenve
now we are using a two-character name for cache subfolders. With many media, subfolders get too populated.
The number of characters to use for subfolders could depend on media number, so that every subfolder get the reduction and thumbnails for no more than, say, 32 media. Since every media produces 12/13 images in cache, this would correspond to about 400 images in every folder.
The formula:
ncharacters = int(log16(nmedia/2))
n < 32 ---> ncharacters = 0, 0 subfolders
32 <= n < 512 ---> ncharacters = 1, 16 subfolders
512 <= n < 8192 ---> ncharacters = 2, 256 subfolders
8192 <= n < 131072 ---> ncharacters = 3, 256 subfolders, 16 subsubfolders
131072 <= n < 2097152 ---> ncharacters = 4, 256 subfolders, 256 subsubfolders
...
Edited by Paolo Benvenuto