FFI::Platypus::Memory(3)

NAME
FFI::Platypus::Memory - Memory functions for FFI

VERSION
version 2.10

SYNOPSIS
 use FFI::Platypus::Memory;

 # allocate 64 bytes of memory using the
 # libc malloc function.
 my $pointer = malloc 64;

 # use that memory wisely
 ...

 # free the memory when you are done.
 free $pointer;

DESCRIPTION
This module provides an interface to common memory functions provided by the standard C library. They may be useful when constructing interfaces to C libraries with FFI. It works mostly with the "opaque" type and it is worth reviewing the section on opaque pointers in FFI::Platypus::Type.

Allocating memory and forgetting to free it is a common source of memory leaks in C and when using this module. Very recent Perls have a "defer" keyword that lets you automatically call functions like "free" when a block ends. This can be especially handy when you have multiple code paths or possible exceptions to keep track of.

 use feature 'defer';
 use FFI::Platypus::Memory qw( malloc free );

 sub run {
   my $ptr = malloc 66;
   defer { free $ptr };

   my $data = do_something($ptr);

   # do not need to remember to place free $ptr here, as it will
   # run through defer.

   return $data;
 }

If you are not lucky enough to have the "defer" feature in your version of Perl you may be able to use Feature::Compat::Defer, which will use the feature if available, and provides its own mostly compatible version if not.

FUNCTIONS

  calloc
 my $pointer = calloc $count, $size;

The "calloc" function contiguously allocates enough space for $count objects that are $size bytes of memory each.

  free
 free $pointer;

The "free" function frees the memory allocated by "malloc", "calloc", "realloc" or "strdup". It is important to only free memory that you yourself have allocated. A good way to crash your program is to try and free a pointer that some C library has returned to you.

  malloc
 my $pointer = malloc $size;

The "malloc" function allocates $size bytes of memory.

  memcpy
 memcpy $dst_pointer, $src_pointer, $size;

The "memcpy" function copies $size bytes from $src_pointer to $dst_pointer. It also returns $dst_pointer.

  memset
 memset $buffer, $value, $length;

The "memset" function writes $length bytes of $value to the address specified by $buffer.

  realloc
 my $new_pointer = realloc $old_pointer, $size;

The "realloc" function reallocates enough memory to fit $size bytes. It copies the existing data and frees $old_pointer.

If you pass "undef" in as $old_pointer, then it behaves exactly like "malloc":

 my $pointer = realloc undef, 64; # same as malloc 64

  strcpy
 strcpy $opaque, $string;

Copies the string to the memory location pointed to by $opaque.

  strdup
 my $pointer = strdup $string;

The "strdup" function allocates enough memory to contain $string and then copies it to that newly allocated memory. This version of "strdup" returns an opaque pointer type, not a string type. This may seem a little strange, but returning a string type would not be very useful in Perl.

  strndup
 my $pointer = strndup $string, $max;

The same as "strdup" above, except at most $max characters will be copied in the new string.

SEE ALSO

FFI::Platypus
    Main Platypus documentation.

AUTHOR
Author: Graham Ollis <plicease@cpan.org>

Contributors:

Bakkiaraj Murugesan (bakkiaraj)

Dylan Cali (calid)

pipcet

Zaki Mughal (zmughal)

Fitz Elliott (felliott)

Vickenty Fesunov (vyf)

Gregor Herrmann (gregoa)

Shlomi Fish (shlomif)

Damyan Ivanov

Ilya Pavlov (Ilya33)

Petr Písař (ppisar)

Mohammad S Anwar (MANWAR)

Håkon Hægland (hakonhagland, HAKONH)

Meredith (merrilymeredith, MHOWARD)

Diab Jerius (DJERIUS)

Eric Brine (IKEGAMI)

szTheory

José Joaquín Atria (JJATRIA)

Pete Houston (openstrike, HOUSTON)

Lukas Mai (MAUKE)

COPYRIGHT AND LICENSE
This software is copyright (c) 2015-2022 by Graham Ollis.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.