Bundling Code With *FFI::Platypus

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  <small>
    <a href="https://alienfile.org/">alienfile.org</a>/<a href="https://alienfile.org/ffi-stat">ffi-stat</a>
  </small>
  /
  <a href="https://twitter.com/plicease">@plicease</a>
  /
  <a href="https://tprc2022.sched.com/event/ylap/lightning-talks-day-1">The Perl Conference (lightning talk)</a>
  /
  22 June 2022
</div>

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# Bundling Code With *FFI::Platypus*
## How **FFI::C::Stat** was born

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<div class="nx-header-title">🌻 Bundling Code With Platypus</div>

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# It all began

* Archive::Libarchive::FFI
 * Comprehensive Perl bindings for libarchive
 * Using FFI::Raw

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# Cheating

```C
const struct stat* archive_entry_stat(struct archive_entry *);
```

--
count: false
```
sub archive_entry_stat {
  my($entry) = @_;
  no strict 'refs';
  map { &{"archive_entry_$_"}($entry) } qw ( dev ino mode nlink uid gid rdev
                                             atime mtime ctime );
}
```

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# Why?

```C
struct stat {
    dev_t     st_dev;         /* ID of device containing file */
    ino_t     st_ino;         /* Inode number */
    mode_t    st_mode;        /* File type and mode */
    nlink_t   st_nlink;       /* Number of hard links */
    uid_t     st_uid;         /* User ID of owner */
    gid_t     st_gid;         /* Group ID of owner */
    dev_t     st_rdev;        /* Device ID (if special file) */
    off_t     st_size;        /* Total size, in bytes */
    blksize_t st_blksize;     /* Block size for filesystem I/O */
    blkcnt_t  st_blocks;      /* Number of 512B blocks allocated */

/* Since Linux 2.6, the kernel supports nanosecond
       precision for the following timestamp fields.
       For the details before Linux 2.6, see NOTES. */

struct timespec st_atim;  /* Time of last access */
    struct timespec st_mtim;  /* Time of last modification */
    struct timespec st_ctim;  /* Time of last status change */

#define st_atime st_atim.tv_sec      /* Backward compatibility */
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
};
```

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# FFI::Platypus + Bundled code install/runtime

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# FFI::C::Stat implementation

```C
dev_t stat__dev(struct stat *self) {
  return self->st_dev;
}

dev_t stat__rdev(struct stat *self) {
  return self->st_rdev;
}
```

--
count: false
```
$ffi->attach( dev  => ['stat'] => 'dev_t' );
$ffi->attach( rdev => ['stat'] => 'dev_t' );
```

--
count: false
```
$ffi->attach( stat => ['archive_entry'] => opaque => sub {
  my($xsub, $self) = @_;
  my $ptr = $xsub->($self);
  defined $ptr ? FFI::C::Stat->clone($ptr) : undef;
});
```

---

# Why?

* now properly complete libarchive bindings
--
count: false
* useful for APIs that return `stat` structures
--
count: false
* bundling code can solve some corner cases

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# Bug!

* [https://github.com/PerlFFI/FFI-C-Stat/issues/5]

---

# Questions

* <img src="img/www.svg"     class="nx-icon"> <a href="https://alienfile.org/ffi-stat">alienfile.org/ffi-stat</a>
* <img src="img/irc.svg"     class="nx-icon"> [\#native](https://kiwiirc.com/nextclient/#irc://irc.perl.org/#native?nick=mc-guest-?) on [irc.perl.org](http://irc.perl.org)
* <img src="img/github.svg"  class="nx-icon"> [github.com/PerlAlien](https://github.com/PerlAlien)
* <img src="img/github.svg"  class="nx-icon"> [github.com/PerlFFI](https://github.com/PerlFFI)
* <img src="img/twitter.svg" class="nx-icon"> [@plicease](https://twitter.com/plicease)