Calculate the amount of disk space the block & undo files currently use
Declared in <node/blockstorage.h>
[[requires_capability(0x7f2e1b099648), requires_capability(0x7f2e26d1ada8), requires_capability(0x7f2e375e0e88), requires_capability(0x7f2e33368248), requires_capability(0x7f2e3542f238), requires_capability(0x7f2e28a73d98)]]
uint64_t
CalculateCurrentUsage();
The total size in bytes of the block and undo files on disk.