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|Pack ffi -- README.md|
This package deals with calling C functions from shared objects (DLLs) from Prolog without writing wrappers. There are several libraries that allows for creating an argument vector for a C function dynamically and call the function. One such library is libffi.
Giving such a library, calling C functions with arithmetic types
(integers, floats) is easy, but we still have to deal with structs,
unions, enums and the fact that most C libraries do not define the
target type directly but use some
typedef that binds the concrete type
depending on the platform. This package parses the C header file (`.h`)
or even a concrete C source file to extract the actual function return
and parameter types and all type definition that are involved in these
types. In addition it allows fetching constants defined using `#define`
Below is an example making the POSIX
statfs() function available.
:- use_module(library(ffi)). :- use_module(library(cerror)). :- c_import("#include <sys/vfs.h>", [ libc ], [ statfs(string, -struct(statfs), [int]) ]). statfs(File, FsStat) :- statfs(File, FsStat, Status), posix_status(Status, statfs, file, File).
The returned pointer may be handed to c_load/2 to extract fields. For example, to get the number of available blocks on the current file system we can make the call below. Note that we did not make any declarations about the structure or the involved integer types.
?- statfs(".", FsStat), c_load(FsStat[f_bavail], A). FsStat = <C struct statfs>(0x55a2c9d5bae0), A = 66197957.
Makefile.mingw. Please check
There is not yet public documentation. With all proper tools installed
(Prolog, LaTeX) and a Linux machine you should be able to type
doc directory to build the (incomplete) documentation.
Here is a PDF version, created at Feb 18, 2018
*as prefix operator will be changed to postfix. One may wish to write
*(Type)to avoid ambiguity.
examplesfor concrete code examples. Notably
examples/pythonprovides a rudimentary Python interface.