FFI::Platypus::Memory#

Memory functions for FFI

VERSION#

version 2.12

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#

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)