Revise and optimize icons handling

[N-R-K]

This pretty much reworks the entire icon system. Some notable changes:

• The extensions are put into a statically generated hash-table instead
  of a sorted array. We use Robin-Hood insertion to reduce the max probe
  length. Currently we need to probe only 2 slots for O_EMOJI and only
  3 for O_NERD/O_ICONS.
• I've opted not to use a perfect-hash since the perfect hashes
  generated by gperf used some
  huge lookup table. The hash function also wasn't as minimal as I'd
  like.
• Colors are now using X-Macros. This should speed up startup since we
  don't have to search icons_ext linearly to find unique colors.
• The hash-table generator outputs a more space optimized struct icon_pair using a char array instead of char pointer. This brings
  down the binary size from 145KiB when using O_NERD down to
  137KiB.
• Some unnecessary duplication and indirection has been reduced by using
  the ICON_STR() macro.

[jarun]

Simply awesome!!! 👍

[jarun]

@N-R-K Can you please update the ToDo list?

[jarun]

If I try to bypass make (to use musl-gcc) I get the following error:

musl-gcc -march=native -O3 -DNORL -DNOLC -DNOMOUSE -DNOBATCH -DTOURBIN_QSORT -DNOSSN -DNOUG -DNOX11 -DEMOJI -std=c11 -Wall -Wextra -Wshadow -I../netbsd-curses/libcurses -I../musl-fts -o nnn src/nnn.c -Wl,-Bsymbolic-functions -lpthread -L/opt/nnn-libs -lcurses -lterminfo -lfts -static
src/nnn.c:128:10: fatal error: icons-generated.h: No such file or directory
  128 | #include "icons-generated.h"
      |          ^~~~~~~~~~~~~~~~~~~
compilation terminated.

What should I use instead of -DEMOJI?

[jarun]

The following works:

make O_EMOJI=1
musl-gcc -march=native -O3 -DNORL -DNOLC -DNOMOUSE -DNOBATCH -DTOURBIN_QSORT -DNOSSN -DNOUG -DNOX11 -DEMOJI -std=c11 -Wall -Wextra -Wshadow -I../netbsd-curses/libcurses -I../musl-fts -o nnn src/nnn.c -Wl,-Bsymbolic-functions -lpthread -L/opt/nnn-libs -lcurses -lterminfo -lfts

[N-R-K]

If I try to bypass make (to use musl-gcc) I get the following error:

musl-gcc -march=native -O3 -DNORL -DNOLC -DNOMOUSE -DNOBATCH -DTOURBIN_QSORT -DNOSSN -DNOUG -DNOX11 -DEMOJI -std=c11 -Wall -Wextra -Wshadow -I../netbsd-curses/libcurses -I../musl-fts -o nnn src/nnn.c -Wl,-Bsymbolic-functions -lpthread -L/opt/nnn-libs -lcurses -lterminfo -lfts -static
src/nnn.c:128:10: fatal error: icons-generated.h: No such file or directory
  128 | #include "icons-generated.h"
      |          ^~~~~~~~~~~~~~~~~~~
compilation terminated.

What should I use instead of -DEMOJI?

First the "generator" needs to be built:

$ gcc -DICONS_GENERATE -DEMOJI -o src/icons-hash-gen src/icons-hash.c

Then the hash-table needs to be generated with the generator:

$ ./src/icons-hash-gen > src/icons-generated.h

Now you should be able to run the compile command manually as long as both the generator and nnn is build with the same icon set (-DEMOJI).

The makefile already takes care of this. So just doing make O_EMOJI=1 src/icons-generated.h to generate the hash-table and then manually compiling nnn with -DEMOJI would also work.

[jarun]

Settled with:

CC=musl-gcc make O_EMOJI=1 src/icons-generated.h
musl-gcc -march=native -O3 -DNORL -DNOLC -DNOMOUSE -DNOBATCH -DTOURBIN_QSORT -DNOSSN -DNOUG -DNOX11 -DEMOJI -std=c11 -Wall -Wextra -Wshadow -I../netbsd-curses/libcurses -I../musl-fts -o nnn src/nnn.c -Wl,-Bsymbolic-functions -lpthread -L/opt/nnn-libs -lcurses -lterminfo -lfts -static

Thank you!

[N-R-K]

Updated the performance section on the wiki :)

Also note that I still see some room for improvements. For example a lot of the extensions use the same icon. So instead of wasting 4 bytes (for O_NERD and O_ICONS) or 9 bytes (for O_EMOJI) per slot, we can store the unique icons in a separate array and store a single byte index into that array.

There's also the possibility of using a minimal-perfect-hash, which can reduce memory usage by shrinking the table size but might make the hash-function/lookup slower. I still have lot more to learn and research on this topic.

I'll see if I can make some time next weekend to implement and benchmark some of these ideas. If they turn out to be overall improvement, then I'll open the PR.

[jarun]

Thank you! Keep it up!

[jarun]

With the above options and musl-gcc, dynamically linked binary size:

-rwxrwxr-x 1 vaio vaio 116632 Jul 22 23:33 nnn*

Static:

-rwxrwxr-x 1 vaio vaio 399504 Jul 22 23:04 /usr/local/bin/nnn*

Great improvement!