Generating a dynamic library
In a previous post I showed how to generate a dynamic library from jpl toolkit, for linux systems (libcspice.so) and for Windows (libcspice.dll).
Before we proceed to the compilation of the library in the Termux environment, let's talk of the programs that we have just compiled from sources launching the script importCSpice.csh.
Open Termux in your phone and activate ssh:
sshd (and press Enter, from now on I take it for granted)
In your PC open your terminal emulator (cmd on Windows, gnome-terminal or whatever in Linux) and type:
ssh u0_a119@192.168.1.120 -p 8022 (use your own coordinates, this is an example, see previous post)
when you are in, type:
~ $ ls -l total 107956 drwx------ 9 u0_a119 u0_a119 4096 Apr 8 2017 cspice -rw------- 1 u0_a119 u0_a119 110530560 Apr 10 2017 cspice.tar -rw------- 1 u0_a119 u0_a119 84 Apr 10 2017 importCSpice.csh drwx------ 2 u0_a119 u0_a119 4096 Dec 6 19:26 storage ~ $
the directory cspice has been created during the compilation process
it contains several subdirs:
~ $ ls cspice data doc etc exe include lib makeall.csh src ~ $
let's look inside cspice/exe
$ ls cspice/exe brief ckbrief.exe dskexp inspekt.exe msopck spacit.exe states tictoc.exe version brief.exe commnt dskexp.exe mkdsk msopck.exe spkdiff states.exe tobin version.exe chronos commnt.exe frmdiff mkdsk.exe simple spkdiff.exe subpt tobin.exe chronos.exe dskbrief frmdiff.exe mkspk simple.exe spkmerge subpt.exe toxfr ckbrief dskbrief.exe inspekt mkspk.exe spacit spkmerge.exe tictoc toxfr.exe ~ $
all of these files are executables, but built for different systems. The ones without extension are used in aarch64 architecture, those ending with .exe are for Windows.
You can personally check the nature of these executables, but first you must install the package file:
pkg install file
now change to subdirectory cspice/exe:
cd cspice/exe
and type file brief
~/cspice/exe $ file brief brief: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /system/bin/linker64, not stripped ~/cspice/exe $
this executable is one of our interest. We'll make a good use of it later. If you type file brief.exe instead:
~/cspice/exe $ file brief.exe brief.exe: PE32+ executable (console) x86-64, for MS Windows ~/cspice/exe $
this exe file won't run in your phone, it's generated for cgywin, which is a posix compatible programming environment for Windows systems.
Just for curiosity, launch brief:
~/cspice/exe $ ./brief
WARNING: linker: /data/data/com.termux/files/home/cspice/exe/brief: unsupported flags DT_FLAGS_1=0x8000001
BRIEF -- Version 4.0.0, September 8, 2010 -- Toolkit Version N0066
BRIEF is a command-line utility program that displays a summary for
one or more binary SPK or binary PCK files. The program usage is:
% brief [-options] file [file ...]
The most useful options are shown below. For the complete set of
options, run BRIEF with the -h option. The order of options is not
significant. The case of option keys is significant: they must be
lowercase as shown below.
-c display centers of motion/relative-to frames
-t display summary in a tabular format
-a treat all files as a single file
-utc display times in UTC calendar date format (needs LSK)
-utcdoy display times in UTC day-of-year format (needs LSK)
-etsec display times as ET seconds past J2000
An LSK file must be provided on the command line to display times in
UTC formats. FK file(s) must be provided on the command line to
display names of any frames that are not built into the Toolkit.
~/cspice/exe $
Let's proceed to the creation of a dynamic library.
Change directory to cspice/src/cspice
~/cspice/src $ cd ~ $ cd cspice/src/cspice ~/.../src/cspice $ ls F77_aloc.c daftb.c et2lst_c.c lnknxt.c rav2xf_c.c spkr15.c vnorm_c.c zzeknres.c SpiceCK.h dafus_c.c et2utc.c lnkprv.c rawio.h spkr17.c vnormg.c zzeknrml.c SpiceCel.h dafwcr.c et2utc_c.c lnksiz.c raxisa.c spkr18.c vnormg_c.c zzekordc.c... a lot of files ...
dafrfr_c.c errint_c.c lnkfsl.c r_sqrt.c spkr08.c vlcomg_c.c zzeklled.c dafrrr.c errprt.c lnkhl.c r_tan.c spkr09.c vminug.c zzekllei.c dafrs_c.c errprt_c.c lnkila.c r_tanh.c spkr10.c vminug_c.c zzeklltc.c dafrwa.c esrchc.c lnkilb.c radrec.c spkr12.c vminus.c zzeklltd.c dafrwd.c esrchc_c.c lnkini.c radrec_c.c spkr13.c vminus_c.c zzekllti.c daft2b.c et2lst.c lnknfn.c rav2xf.c spkr14.c vnorm.c zzekmloc.c ~/.../src/cspice $
It's a huge amount of C sources, we need to compile them in a standard .so dynamic library.
within the same directory type:
gcc -Wall -O2 -fPIC -shared -o libcspice.so *.c -lm -ldl
You deserve a brief explanation of the options I have given to the compiler:
gcc is the compiler, here used as assembler, compiler and linker altogether, any further consideration is beyond our scope.
-Wall stands for the maximum warning alert level, during compilation you'll see a ton of warnings.
-O2 is the optimization level, set to a good level compatible with robustness.
-fPIC -shared is the combination of two instructions aimed at generating a shared library with Position Independent Code (PIC)
-o libcspice.so is the name I have choosen for the compiled library, "lib" and ".so" are the structural parts.
*.c are all the C sources that are present in this directory
-lm -ldl are linked libraries, math and dynamic loader
After some time and a big amount of warnings, hopefully no errors found, you'll see a new file in your directory, libcspice.so. Move it to your home directory, to have it handy
mv libcspice.so ~/
Ok, it's enough for now, see you in the next post
