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```{index} single: FFI::Platypus::Memory
```

# FFI::Platypus::Memory

Memory functions for FFI

## VERSION

version 2.12

## SYNOPSIS

```perl
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](Type.md).

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.

```perl
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](https://metacpan.org/pod/Feature::Compat::Defer), which will use
the feature if available, and provides its own mostly compatible version
if not.

## FUNCTIONS

### calloc

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

The `calloc` function contiguously allocates enough space for _$count_
objects that are _$size_ bytes of memory each.

### free

```perl
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

```perl
my $pointer = malloc $size;
```

The `malloc` function allocates _$size_ bytes of memory.

### memcpy

```perl
memcpy $dst_pointer, $src_pointer, $size;
```

The `memcpy` function copies _$size_ bytes from _$src\_pointer_ to
_$dst\_pointer_.  It also returns _$dst\_pointer_.

### memset

```perl
memset $buffer, $value, $length;
```

The `memset` function writes _$length_ bytes of _$value_ to the address
specified by _$buffer_.

### realloc

```perl
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`:

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

### strcpy

```perl
strcpy $opaque, $string;
```

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

### strdup

```perl
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

```perl
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](../Platypus.md)

    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.