FFI::Platypus::Record(3pm)

1FFI::Platypus::Record(3U)ser Contributed Perl DocumentatiFoFnI::Platypus::Record(3)
2
3
4

NAME

6       FFI::Platypus::Record - FFI support for structured records data
7

VERSION

9       version 1.43
10

SYNOPSIS

12       C:
13
14        struct my_person {
15          int         age;
16          const char  title[3];
17          const char *name
18        };
19
20        void process_person(struct my_person *person)
21        {
22          /* ... */
23        }
24
25       Perl:
26
27        package MyPerson;
28
29        use FFI::Platypus::Record;
30
31        record_layout_1(
32          'int'       => 'age',
33          'string(3)' => 'title',
34          'string rw' => 'name',
35        );
36
37        package main;
38
39        use FFI::Platypus 1.00;
40
41        my $ffi = FFI::Platypus->new( api => 1 );
42        $ffi->lib("myperson.so");
43        $ffi->type("record(MyPerson)" => 'MyPerson');
44
45        my $person = MyPerson->new(
46          age   => 40,
47          title => "Mr.",
48          name  => "John Smith",
49        );
50
51        $ffi->attach( process_person => [ 'MyPerson*' ] => 'void' );
52
53        process_person($person);
54
55        $person->age($person->age + 1); # another year older
56
57        process_person($person);
58

DESCRIPTION

60       [version 0.21]
61
62       This module provides a mechanism for building classes that can be used
63       to mange structured data records (known as C as "structs" and in some
64       languages as "records").  A structured record is a series of bytes that
65       have structure understood by the C or other foreign language library
66       that you are interfacing with.  It is designed for use with FFI and
67       FFI::Platypus, though it may have other applications.
68
69       Before you get to deep into using this class you should also consider
70       the FFI::C, which provides some overlapping functionality.  Briefly, it
71       comes down to this:
72
73       FFI::Platypus::Record
74           Supports:
75
76           C pointers to "struct" types
77           Passing C "struct"s by-value.
78
79           Does not support:
80
81           C "union" types.
82           C arrays of "struct" and "union" types.
83       FFI::C
84           Supports:
85
86           C "struct" and"union" types
87           C arrays of "struct" and "union" types.
88
89           Does not support:
90
91           Passing C "struct"s by-value.
92
93           String members are as of this writing a TODO for FFI::C, but should
94           be coming soon!
95

FUNCTIONS

97   record_layout_1
98        record_layout_1($ffi, $type => $name, ... );
99        record_layout_1(\@ffi_args, $type => $name, ... );
100        record_layout_1($type => $name, ... );
101
102       Define the layout of the record.  You may optionally provide an
103       instance of FFI::Platypus as the first argument in order to use its
104       type aliases.  Alternatively you may provide constructor arguments that
105       will be passed to the internal platypus instance.  Thus this is the
106       same:
107
108        my $ffi = FFI::Platypus->new( lang => 'Rust', api => 1 );
109        record_layout_1( $ffi, ... );
110        # same as:
111        record_layout_1( [ lang => 'Rust' ], ... );
112
113       and this is the same:
114
115        my $ffi = FFI::Platypus->new( api => 1 );
116        record_layout_1( $ffi, ... );
117        # same as:
118        record_layout_1( ... );
119
120       Then you provide members as type/name pairs.
121
122       For each member you declare, "record_layout_1" will create an accessor
123       which can be used to read and write its value. For example imagine a
124       class "Foo":
125
126        package Foo;
127
128        use FFI::Platypus::Record;
129
130        record_layout_1(
131          int          => 'bar',  #  int bar;
132          'string(10)' => 'baz',  #  char baz[10];
133        );
134
135       You can get and set its fields with like named "bar" and "baz"
136       accessors:
137
138        my $foo = Foo->new;
139
140        $foo->bar(22);
141        my $value = $foo->bar;
142
143        $foo->baz("grimlock\0\0"); # should be 10 characters long
144        my $string_value = $foo->baz; # includes the trailing \0\0
145
146       You can also pass initial values in to the constructor, either passing
147       as a list of key value pairs or by passing a hash reference:
148
149        $foo = Foo->new(
150          bar => 22,
151          baz => "grimlock\0\0",
152        );
153
154        # same as:
155
156        $foo = Foo->new( {
157          bar => 22,
158          baz => "grimlock\0\0",
159        } );
160
161       If there are members of a record that you need to account for in terms
162       of size and alignment, but do not want to have an accessor for, you can
163       use ":" as a place holder for its name:
164
165        record_layout_1(
166          'int'        => ':',
167          'string(10)' => 'baz',
168        );
169
170       strings
171
172       So far I've shown fixed length strings.  These are declared with the
173       word "string" followed by the length of the string in parentheticals.
174       Fixed length strings are included inside the record itself and do not
175       need to be allocated or deallocated separately from the record.
176       Variable length strings must be allocated on the heap, and thus require
177       a sense of "ownership", that is whomever allocates variable length
178       strings should be responsible for also free'ing them.  To handle this,
179       you can add a "ro" or "rw" trait to a string field.  The default is
180       "ro", means that you can get, but not set its value:
181
182        package Foo;
183
184        record_layout_1(
185          'string ro' => 'bar',  # same type as 'string' and 'string_ro'
186        );
187
188        package main;
189
190        my $foo = Foo->new;
191
192        my $string = $foo->bar;  # GOOD
193        $foo->bar("starscream"); # BAD
194
195       If you specify a field is "rw", then you can set its value:
196
197        package Foo;
198
199        record_layout_1(
200          'string rw' => 'bar',  # same type as 'string_rw'
201        );
202
203        package main;
204
205        my $foo = Foo->new;
206
207        my $string = $foo->bar;  # GOOD
208        $foo->bar("starscream"); # GOOD
209
210       Any string value that is pointed to by the record will be free'd when
211       it falls out of scope, so you must be very careful that any "string rw"
212       fields are not set or modified by C code.  You should also take care
213       not to copy any record that has a "rw" string in it because its values
214       will be free'd twice!
215
216        use Clone qw( clone );
217
218        my $foo2 = clone $foo;  # BAD  bar will be free'd twice
219
220       arrays
221
222       Arrays of integer, floating points and opaque pointers are supported.
223
224        package Foo;
225
226        record_layout_1(
227          'int[10]' => 'bar',
228        );
229
230        my $foo = Foo->new;
231
232        $foo->bar([1,2,3,4,5,6,7,8,9,10]); # sets the values for the array
233        my $list = $foo->bar;  # returns a list reference
234
235        $foo->bar(5, -6); # sets the 5th element in the array to -6
236        my $item = $foo->bar(5); gets the 5th element in the array
237
238   record_layout
239        record_layout($ffi, $type => $name, ... );
240        record_layout(\@ffi_args, $type => $name, ... );
241        record_layout($type => $name, ... );
242
243       This function works like "record_layout" except that "api => 0" is used
244       instead of "api => 1".  All new code should use "record_layout_1"
245       instead.
246

CAVEATS

248       These useful features (and probably more) are missing, and unlikely to
249       be added.
250
251       Unions
252       Nested records
253
254       If you need these features, consider using FFI::C instead.
255

AUTHOR

277       Author: Graham Ollis <plicease@cpan.org>
278
279       Contributors:
280
281       Bakkiaraj Murugesan (bakkiaraj)
282
283       Dylan Cali (calid)
284
285       pipcet
286
287       Zaki Mughal (zmughal)
288
289       Fitz Elliott (felliott)
290
291       Vickenty Fesunov (vyf)
292
293       Gregor Herrmann (gregoa)
294
295       Shlomi Fish (shlomif)
296
297       Damyan Ivanov
298
299       Ilya Pavlov (Ilya33)
300
301       Petr Pisar (ppisar)
302
303       Mohammad S Anwar (MANWAR)
304
305       Håkon Hægland (hakonhagland, HAKONH)
306
307       Meredith (merrilymeredith, MHOWARD)
308
309       Diab Jerius (DJERIUS)
310
311       Eric Brine (IKEGAMI)
312
313       szTheory
314

COPYRIGHT AND LICENSE

316       This software is copyright (c) 2015,2016,2017,2018,2019,2020 by Graham
317       Ollis.
318
319       This is free software; you can redistribute it and/or modify it under
320       the same terms as the Perl 5 programming language system itself.
321
322
323
324perl v5.32.1                      2021-03-18          FFI::Platypus::Record(3)