Rather than storing a pointer to another memory allocation in the
struct. This saves some memory and improves performance by significantly
decreasing the number of calls to [c|m]alloc() and free().
Here is the new multi-page listing functionality I promised in
5db9c2aea1.
It may look very easy, but getting this to work right wasn't,
unfortunately.
The displayed directory sizes are now fully correct, although in its
current state it's not all that intuitive because:
directory size != sum(size of all files and subdirectories)
This should probably be fixed later on by splitting the sizes into a
shared and non-shared part.
Also, the sizes displayed after a recalculation or deletion are
incorrect, I'll fix this later on.
The directory sizes are now incorrect as hard links will be counted
twice again (as if there wasn't any detection in the first place), but
this will get fixed by adding a shared size field.
This method of keeping track of hard links is a lot faster and allows
adding an interface which lists the found links.
When interrupinting the calculation process by pressing 'q' while
it's looping through a directory, or when a directory could be openend
but not chdir()'ed into, closedir() wasn't called.
Hard link detection is now done in a separate pass on the in-memory tree,
and duplicates can be 'removed' and 're-added' on the fly. When making any
changes in the tree, all hard links are re-added before the operation and
removed again afterwards.
While this guarantees that all hard link information is correct, it does
have a few drawbacks. I can currently think of two:
1. It's not the most efficient way to do it, and may be quite slow on
large trees. Will have to do some benchmarks later to see whether
it is anything to be concerned about.
2. The first encountered item is considered as 'counted' and all items
encountered after that are considered as 'duplicate'. Because the
order in which we traverse the tree doesn't always have to be the
same, the items that will be considered as 'duplicate' can vary with
each deletion or re-calculation. This might cause confusion for
people who aren't aware of how hard links work.
This actually makes the struct itself obsolete, as all information is now only
useful within calc.c itself and other files don't have to do anything with it.
