Re: [cc65] C128 Bank Switching and cc65

Chiron,

Thanks for the ideas.  Fortunately, I had already done something similar
after consulting with Jim Brain a bit.  Here's how CBM-Command works with
directories.

When a drive is selected, it opens the directory and starts reading it into
a sliding window structure.  There are three variables involved: the length
of the sliding structure (right now set to 30), the current
slidingStructureStartIndex and the current index.  If the current directory
entry falls within the range of the slidingStructureStartIndex and the
sliding structure length, then it retains the information about that
directory entry, otherwise it simply counts the record and moves on until
the end of the directory is reached.

When the user is viewing the directory a fourth variable called
displayStartAt is used to determine what is the first record to show on the
screen.  displayStartAt is managed such that it is always within the bounds
of the sliding window.  CBM-Command can display 19 records at a time, so
this leaves a buffer around the top and bottom of the visible list so that
the user can scroll up and down a bit before having to retrieve data from
the disk drive, which can be very slow (worst case scenario is a 1541 with
lots of files and no fast load cart/rom).

So, at the end of the day, regardless of the size of the drive we are only
holding directory entries for up to 30 records.  There is an index structure
which has 9 bytes (pointer to a string for the name, unsigned int size,
unsigned char type, unsigned int index and pointer to the next node) of data
for each directory entry regardless of whether it is in the sliding window,
but this is unavoidable as far as I can tell.  I don't actually store the
cbm_dirent structs as the names are hard coded to 17 bytes and thus there's
a lot of waste in the typical directory.

If someone has a good idea on how to get rid of the linked list for the
index, I'm all ears.  I've already reduced the size for a node entry from
constant 27 to a minimum 9 bytes and just don't see a way to make it any
smaller.

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