This function must be called at most once and before calling
PL_initialise().
The memory area designated by data and size must
contain the resource data and be in the format as produced by
qsave_program/2.
The memory area is accessed by PL_initialise()
as well as calls to open_resource/3.237This
implies that the data must remain accessible during the lifetime of the
process if open_resource/3
is used. Future versions may provide a function to detach the resource
database and cause open_resource/3
to raise an exception.
For example, we can include the bootstrap data into an embedded
executable using the steps below. The advantage of this approach is that
it is fully supported by any OS and you obtain a single file executable.
- Create a saved state using qsave_program/2
or
% swipl -o state -c file.pl ...
- Create a C source file from the state using e.g., the Unix utility xxd(1):
% xxd -i state > state.h
- Embed Prolog as in the example below. Instead of calling the
toplevel you probably want to call your application code.
#include <SWI-Prolog.h>
#include "state.h"
int
main(int argc, char **argv)
{ if ( !PL_set_resource_db_mem(state, state_len) ||
!PL_initialise(argc, argv) )
PL_halt(1);
return PL_toplevel();
}
Alternative to xxd, it is possible to use inline assembler,
e.g. the gcc incbin instruction. Code for
gcc was provided by Roberto Bagnara on the SWI-Prolog
mailinglist. Given the state in a file state, create the
following assembler program:
.globl _state
.globl _state_end
_state:
.incbin "state"
_state_end:
Now include this as follows:
#include <SWI-Prolog.h>
#if __linux
#define STATE _state
#define STATE_END _state_end
#else
#define STATE state
#define STATE_END state_end
#endif
extern unsigned char STATE[];
extern unsigned char STATE_END[];
int
main(int argc, char **argv)
{ if ( !PL_set_resource_db_mem(STATE, STATE_END - STATE) ||
!PL_initialise(argc, argv) )
PL_halt(1);
return PL_toplevel();
}
As Jose Morales pointed at
https://github.com/graphitemaster/incbin,
which contains a portability layer on top of the above idea.
