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 compil‐
20       ing the code with the right flags, though it requires simple perl and C
21       wrapper routines to be written. You may prefer to use PP, which is much
22       more portable. See PDL::PP. You should definitely use the latter for a
23       'proper' PDL module, or if you run in to the limitations of this mod‐
24       ule.
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 struc‐
31       tures as arguments, there is now way of doing portable general argument
32       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 applica‐
44       tions.
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 reprensation of piddles in PDL
60       which is more complicated because of threading, dataflow, etc. It will
61       usually be found somewhere like /usr/local/lib/perl5/site_perl/PDL/pdl‐
62       simple.h
63
64       Thus to actually use this to call real functions one would need to
65       right a wrapper.  e.g. to call a 2D image processing routine:
66
67        void myimage_processer(double* image, int nx, int ny);
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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 check‐
76       ing.
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 cor‐
88       rect 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.
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FUNCTIONS

99       callext
100
101       Call a function in an external library using Perl dynamic loading
102
103         callext('file.so', 'foofunc', $x, $y); # pass piddles to foofunc()
104
105       The file must be compiled with dynamic loading options (see
106       "callext_cc"). See the module docs "PDL::Callext" for a description of
107       the API.
108
109       callext_cc
110
111       Compile external C code for dynamic loading
112
113       Usage:
114
115        % perl -MPDL::CallExt -e callext_cc file.c -o file.so
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117       This works portably because when Perl has built in knowledge of how to
118       do dynamic loading on the system on which it was installed.  See the
119       module docs "PDL::Callext" for a description of the API.
120

AUTHORS

122       Copyright (C) Karl Glazebrook 1997.  All rights reserved. There is no
123       warranty. You are allowed to redistribute this software / documentation
124       under certain conditions. For details, see the file COPYING in the PDL
125       distribution. If this file is separated from the PDL distribution, the
126       copyright notice should be included in the file.
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130perl v5.8.8                       2005-02-03                        CallExt(3)
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