1CallExt(3)            User Contributed Perl Documentation           CallExt(3)
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NAME

6       PDL::CallExt - call functions in external shared libraries
7

SYNOPSIS

9        use PDL::CallExt;
10        callext('file.so', 'foofunc', $x, $y); # pass piddles to foofunc()
11
12        % perl -MPDL::CallExt -e callext_cc file.c
13

DESCRIPTION

15       callext() loads in a shareable object (i.e. compiled code) using Perl's
16       dynamic loader, calls the named function and passes a list of piddle
17       arguments to it.
18
19       It provides a reasonably portable way of doing this, including
20       compiling the code with the right flags, though it requires simple perl
21       and C wrapper routines to be written. You may prefer to use PP, which
22       is much more portable. See PDL::PP. You should definitely use the
23       latter for a 'proper' PDL module, or if you run in to the limitations
24       of this module.
25

API

27       callext_cc() allows one to compile the shared objects using Perl's
28       knowledge of compiler flags.
29
30       The named function (e.g. 'foofunc') must take a list of piddle
31       structures as arguments, there is now way of doing portable general
32       argument construction hence this limitation.
33
34       In detail the code in the original file.c would look like this:
35
36        #include "pdlsimple.h" /* Declare simple piddle structs - note this .h file
37                                  contains NO perl/PDL dependencies so can be used
38                                  standalone */
39
40        int foofunc(int nargs, pdlsimple **args); /* foofunc prototype */
41
42       i.e. foofunc() takes an array of pointers to pdlsimple structs. The use
43       is similar to that of "main(int nargs, char **argv)" in UNIX C
44       applications.
45
46       pdlsimple.h defines a simple N-dimensional data structure which looks
47       like this:
48
49         struct pdlsimple {
50            int    datatype;  /* whether byte/int/float etc. */
51            void  *data;      /* Generic pointer to the data block */
52            int    nvals;     /* Number of data values */
53            PDL_Long *dims;   /* Array of data dimensions */
54            int    ndims;     /* Number of data dimensions */
55         };
56
57       (PDL_Long is always a 4 byte int and is defined in pdlsimple.h)
58
59       This is a simplification of the internal representation of piddles in
60       PDL which is more complicated because of threading, dataflow, etc. It
61       will usually be found somewhere like
62       /usr/local/lib/perl5/site_perl/PDL/pdlsimple.h
63
64       Thus to actually use this to call real functions one would need to
65       write a wrapper.  e.g. to call a 2D image processing routine:
66
67        void myimage_processer(double* image, int nx, int ny);
68
69        int foofunc(int nargs, pdlsimple **args) {
70           pdlsimple* image = pdlsimple[0];
71           myimage_processer( image->data, *(image->dims), *(image->dims+1) );
72           ...
73        }
74
75       Obviously a real wrapper would include more error and argument
76       checking.
77
78       This might be compiled (e.g. Linux):
79
80        cc -shared -o mycode.so mycode.c
81
82       In general Perl knows how to do this, so you should be able to get away
83       with:
84
85        perl -MPDL::CallExt -e callext_cc file.c
86
87       callext_cc() is a function defined in PDL::CallExt to generate the
88       correct compilation flags for shared objects.
89
90       If their are problems you will need to refer to you C compiler manual
91       to find out how to generate shared libraries.
92
93       See t/callext.t in the distribution for a working example.
94
95       It is up to the caller to ensure datatypes of piddles are correct - if
96       not peculiar results or SEGVs will result.
97

FUNCTIONS

99   callext
100       Call a function in an external library using Perl dynamic loading
101
102         callext('file.so', 'foofunc', $x, $y); # pass piddles to foofunc()
103
104       The file must be compiled with dynamic loading options (see
105       "callext_cc"). See the module docs "PDL::Callext" for a description of
106       the API.
107
108   callext_cc
109       Compile external C code for dynamic loading
110
111       Usage:
112
113        % perl -MPDL::CallExt -e callext_cc file.c -o file.so
114
115       This works portably because when Perl has built in knowledge of how to
116       do dynamic loading on the system on which it was installed.  See the
117       module docs "PDL::Callext" for a description of the API.
118

AUTHORS

120       Copyright (C) Karl Glazebrook 1997.  All rights reserved. There is no
121       warranty. You are allowed to redistribute this software / documentation
122       under certain conditions. For details, see the file COPYING in the PDL
123       distribution. If this file is separated from the PDL distribution, the
124       copyright notice should be included in the file.
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128perl v5.32.0                      2020-09-17                        CallExt(3)
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