libapa...:Bucket(3pm)

📦
version 2.0.13 · 12 versions
, in ubuntu stonking

👑 libapa...:Bucket(3pm)

okay so this one comes from the User Contributed Perl Documentation corner of the world, and it's literally about buckets. no cap. it's giving plumbing but make it cute 🫶

✨ NAME ✨

APR::Bucket — Perl API for manipulating APR Buckets 💖

🎀 Synopsis 🎀

bestie, here's the whole vibe in one go. copy it, stare at it, love it:

use APR::Bucket ();
my $ba = $c->bucket_alloc;

$b1 = APR::Bucket->new($ba, "aaa");
$b2 = APR::Bucket::eos_create($ba);
$b3 = APR::Bucket::flush_create($ba);

$b2->is_eos;
$b3->is_flush;

$len = $b1->length;
$len = $b1->read($data);
$type = $b1->type;

$b1->insert_after($b2);
$b1->insert_before($b3);
$b1->remove;
$b1->destroy;

$b2->delete; # remove+destroy

$b4 = APR::Bucket->new($ba, "to be setaside");
$b4->setaside($pool);

🌸 Description 🌸

so APR::Bucket lets you create, manipulate and delete APR buckets. that's the whole main character job description 💅

now, the insert methods? yeah, those are gonna confuse you at first, and that's okay, we've all been there 😭 here's the cheat code: read the function right to left. that's it. that's the tip. read it backwards and suddenly it makes sense, iykyk.

and honestly, this next code sample is the visualizer you need — just watch the bucket brigade snap together line by line:

my $bb = APR::Brigade->new($r->pool, $ba);
my $d1 = APR::Bucket->new($ba, "d1");
my $d2 = APR::Bucket->new($ba, "d2");
my $f1 = APR::Bucket::flush_create($ba);
my $f2 = APR::Bucket::flush_create($ba);
my $e1 = APR::Bucket::eos_create($ba);
                                 # head->tail
$bb->insert_head(  $d1); # head->d1->tail
$d1->insert_after( $d2); # head->d1->d2->tail
$d2->insert_before($f1); # head->d1->f1->d2->tail
$d2->insert_after( $f2); # head->d1->f1->d2->f2->tail
$bb->insert_tail(  $e1); # head->d1->f1->d2->f2->e1->tail

see how each comment is just the chain getting one link longer? iconic 🌈 that's the entire energy of this module, explained in five lines of comments.

and bestie… we're literally just getting started, the rest is coming 👀✨

✨ API ✨

So APR::Bucket hands you all of these functions and/or methods, bestie. Buckle up, there's a lot of them but they're all lowkey iconic:

🗑️ delete

Tell the bucket to yeet itself out of the bucket brigade it belongs to, and then destroy itself. It's giving self-care.

$bucket->delete();
  • obj: $bucket ( an APR::Bucket object )
  • ret: no return value
  • since: 2.0.00

If the bucket isn't attached to any bucket brigade at all, this operation just destroys the bucket. No brigade, no problem.

delete is a convenience wrapper, and internally it's literally just doing:

$b->remove;
$b->destroy;

Examples:

Say $bb already exists and is filled with buckets — we're gonna replace the existing data buckets with new buckets that have upcased data:

for (my $b = $bb->first; $b; $b = $bb->next($b)) {
   if ($b->read(my $data)) {
        my $nb = APR::Bucket->new($bb->bucket_alloc, uc $data);
        $b->insert_before($nb);
        $b->delete;
        $b = $nb;
    }
}

💀 destroy

Free the resources used by a bucket. If multiple buckets are referring to the same resource, it gets freed when the last one goes away. Sharing is caring, apparently.

$bucket->destroy();
  • obj: $bucket ( an APR::Bucket object )
  • ret: no return value
  • since: 2.0.00
A bucket needs to be destroyed if it was removed from a bucket brigade, or you're gonna have a memory leak. Not the vibe. 🙈

And if a bucket is linked to a bucket brigade, it needs to be removed from it before it can be destroyed.

Usually, instead of calling:

$b->remove;
$b->destroy;

it's way better to just call delete, which does exactly that. Periodt.

🏁 eos_create

Create an EndOfStream bucket.

$b = APR::Bucket::eos_create($ba);
  • arg1: $ba ( an APR::BucketAlloc object )
    • The freelist from which this bucket should be allocated
  • ret: $b ( an APR::Bucket object )
    • The new bucket
  • since: 2.0.00

This bucket type is basically the "that's all folks" of bucket types — it indicates that there is no more data coming from down the filter stack. All filters should flush any buffered data at this point. ✨

Example:

use APR::Bucket ();
use Apache2::Connection ();
my $ba = $c->bucket_alloc;
my $eos_b = APR::Bucket::eos_create($ba);

🚽 flush_create

Create a flush bucket.

$b = APR::Bucket::flush_create($ba);
  • arg1: $ba ( an APR::BucketAlloc object )
    • The freelist from which this bucket should be allocated
  • ret: $b ( an APR::Bucket object )
    • The new bucket
  • since: 2.0.00

This bucket type is telling filters "hey bestie, flush your data." There's no guarantee that they will flush it, but honestly this is the best we can do. 🫶

➡️ insert_after

Insert a list of buckets after a specified bucket.

$after_bucket->insert_after($add_bucket);
  • obj: $after_bucket ( an APR::Bucket object )
    • The bucket to insert after
  • arg1: $add_bucket ( an APR::Bucket object )
    • The buckets to insert. It says buckets, since $add_bucket may have more buckets attached after itself.
  • ret: no return value
  • since: 2.0.00

⬅️ insert_before

Insert a list of buckets before a specified bucket.

$before_bucket->insert_before($add_bucket);
  • obj: $before_bucket ( an APR::Bucket object )
    • The bucket to insert before
  • arg1: $add_bucket ( an APR::Bucket object )
    • The buckets to insert. It says buckets, since $add_bucket may have more buckets attached after itself.
  • ret: no return value
  • since: 2.0.00

🔚 is_eos

Determine if a bucket is an EOS bucket.

$ret = $bucket->is_eos();
  • obj: $bucket ( an APR::Bucket object )
  • ret: $ret ( boolean )
  • since: 2.0.00

💦 is_flush

Determine if a bucket is a FLUSH bucket.

$ret = $bucket->is_flush();
  • obj: $bucket ( an APR::Bucket object )
  • ret: $ret ( boolean )
  • since: 2.0.00

📏 length

Get the length of the data in the bucket.

$len = $b->length;
  • obj: $b ( an APR::Bucket object )
  • ret: $len ( integer )
    • If the length is unknown, $len value will be -1.
  • since: 2.0.00

🌱 new

Create a new bucket and initialize it with data:

$nb = APR::Bucket->new($ba, $data);
$nb =          $b->new($ba, $data);
$nb = APR::Bucket->new($ba, $data, $offset);
$nb = APR::Bucket->new($ba, $data, $offset, $len);
  • obj: $b ( APR::Bucket object or class )
  • arg1: $ba ( an APR::BucketAlloc object )
  • arg2: $data ( string )
    • The data to initialize with.
Important: in order to avoid unnecessary data copying the variable is stored in the bucket object. That means that if you modify $data after passing it to new() you will modify the data in the bucket as well. To avoid that pass to new() a copy which you won't modify. No cap, this one will get you. 😭
  • opt arg3: $offset ( number )
    • Optional offset inside $data. Default: 0.
  • opt arg4: $len ( number )
    • Optional partial length to read.
    • If $offset is specified, then:
length $buffer - $offset;

will be used. Otherwise the default is to use:

length $buffer;
  • ret: $nb ( an APR::Bucket object )
    • a newly created bucket object
  • since: 2.0.00

Examples:

  1. Create a new bucket using a whole string:
use APR::Bucket ();
my $data = "my data";
my $b = APR::Bucket->new($ba, $data);

now the bucket contains the string 'my data'.

  1. Create a new bucket using a sub-string:
use APR::Bucket ();
my $data   = "my data";
my $offset = 3;
my $b = APR::Bucket->new($ba, $data, $offset);

now the bucket contains the string 'data'.

  1. Create a new bucket not using the whole length and starting from an offset:
use APR::Bucket ();
my $data   = "my data";
my $offset = 3;
my $len    = 3;
my $b = APR::Bucket->new($ba, $data, $offset, $len);

now the bucket contains the string 'dat'.

📖 read

Read the data from the bucket.

$len = $b->read($buffer);
$len = $b->read($buffer, $block);
  • obj: $b ( an APR::Bucket object )
    • The bucket to read from
  • arg1: $buffer ( SCALAR )
    • The buffer to fill. All previous data will be lost. Gone. Poof. 💨
  • opt arg2: $block ( an APR::Const :read_type constant )
    • optional reading mode constant.
    • By default the read is blocking, via APR::Const::BLOCK_READ constant.
  • ret: $len ( number )
    • How many bytes were actually read
    • $buffer gets populated with the string that is read. It will contain an empty string if there was nothing to read.
  • since: 2.0.00
  • excpt: APR::Error
It's important to know that certain bucket types (e.g. file bucket), may perform a split and insert extra buckets following the current one. Therefore never call $b->remove, before calling $b->read, or you may lose data. Like, actually. Don't do it. 💀

Examples:

Blocking read:

my $len = $b->read(my $buffer);

Non-blocking read:

use APR::Const -compile 'NONBLOCK_READ';
my $len = $b->read(my $buffer, APR::Const::NONBLOCK_READ);

✂️ remove

Tell the bucket to remove itself from the bucket brigade it belongs to.

$bucket->remove();
  • obj: $bucket ( an APR::Bucket object )
  • ret: no return value
  • since: 2.0.00

If the bucket isn't attached to any bucket brigade, this operation just doesn't do anything. It's giving "no thoughts, head empty." 🦋

When the bucket is removed, it's not destroyed. Usually you do this to move the bucket to another bucket brigade, or to copy the data way before destroying the bucket. If the bucket wasn't moved to another bucket brigade, it must be destroyed.

Examples:

Assuming $bb1 already exists and is filled with buckets, move every odd bucket number to $bb2 and every even to $bb3:

my $bb2 = APR::Brigade->new($c->pool, $c->bucket_alloc);
my $bb3 = APR::Brigade->new($c->pool, $c->bucket_alloc);
my $count = 0;
while (my $bucket = $bb->first) {
    $count++;
    $bucket->remove;
    $count % 2
        ? $bb2->insert_tail($bucket)
        : $bb3->insert_tail($bucket);
}

🛡️ setaside

Ensure the bucket's data lasts at least as long as the given pool:

my $status = $b->setaside($pool);
  • obj: $b ( an APR::Bucket object )
  • arg1: $pool ( an APR::Pool object )
  • ret: ( an APR::Const status constant )
    • On success, APR::Const::SUCCESS is returned. Otherwise a failure code is returned.
  • excpt: APR::Error
    • when your code deals only with mod_perl buckets, you don't have to ask for the return value. If this method is called in the VOID context, i.e.:
$b->setaside($pool);

mod_perl will do the error checking on your behalf, and if the return code is not APR::Const::SUCCESS, an APR::Error exception will be thrown.

  • However if your code doesn't know which bucket types it may need to setaside, you may want to check the return code and deal with any errors. For example one of the possible error codes is APR::Const::ENOTIMPL. As of this writing the pipe and socket buckets can't setaside(), in which case you may want to look at the ap_save_brigade() implementation.
  • since: 2.0.00

Usually setaside is called by certain output filters, in order to buffer socket writes of smaller buckets into a single write. This method works on all bucket types (not only the mod_perl bucket type), but as explained in the exceptions section, not all bucket types implement this method.

When a mod_perl bucket is setaside, its data is detached from the original perl scalar and copied into a pool bucket. That allows downstream filters to deal with the data originally owned by a Perl interpreter, making it possible for that interpreter to go away and do other things, or be destroyed. Main character energy for the interpreter, honestly. 👑

🔍 type

Get the type of the data in the bucket.

$type = $b->type;
  • obj: $b ( an APR::Bucket object )
  • ret: $type ( an APR::BucketType object )
  • since: 2.0.00

You need to invoke APR::BucketType methods to access the data.

Example:

Create a flush bucket and read its type's name:

use APR::Bucket ();
use APR::BucketType ();
my $b = APR::Bucket::flush_create($ba);
my $type = $b->type;
my $type_name =  $type->name; # FLUSH

The type name will be 'FLUSH' in this example. 🌸

🚧 Unsupported API 🚧

Okay bestie, real talk. APR::Socket also ships an auto-generated Perl interface for a few other methods, and ngl these ones have not been tested at this moment, so their API is a subject to change. 😬 They'll get finalized later, whenever a need arises. So like... they're giving "we'll circle back" energy.

If you want to rely on any of the following methods, pls pls pls contact the the mod_perl development mailing list so we can help each other take the steps necessary to shift the method to an officially supported API. 🫶 Team effort, periodt.

💾 data 💾

$data = $b->data;

Gives a C pointer to the address of the data in the bucket. And honestly? I can't see what use can be done of it in Perl. 🤷 It's a pointer, it's out here existing, that's the whole update.

  • obj: $b ( APR::Bucket object )
  • ret: $data ( C pointer )
  • since: subject to change

🎀 start 🎀

$start = $b->start;

It gives the offset to when a new bucket is created with a non-zero offset value:

my $b = APR::Bucket->new($ba, $data, $offset, $len);

So if the offset was 3. $start will be 3 too. Math is mathing, slay. ✨

I fail to see what it can be useful for to the end user (it's mainly used internally). Like, it's lowkey just vibing in the internals doing its little thing.

  • obj: $b ( APR::Bucket object )
  • ret: $start ( offset number )
  • since: subject to change
Heads up: everything in this section is unsupported and subject to change, so don't build your whole personality around it. 💀

👀 SEE ALSO 👀

mod_perl 2.0 documentation. Go read it, it's the main character. 📖

mod_perl 2.0 and its core modules are copyrighted under The Apache Software License, Version 2.0.

👑 Authors 👑

The mod_perl development team and numerous contributors. Iconic behavior, no cap. 💖

and that's a wrap on this page, bestie!! 🎉 brought to you by perl v5.42.3, dated 2026-08-20, filed under libapa...:Bucket(3pm) — go forth and bucket responsibly 🌸🦋💅

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