shm2_conf.h File Reference

Transport configuration for the shm2:// Iceoryx2 (next-generation) shared-memory transport. More...

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Detailed Description

Transport configuration for the shm2:// Iceoryx2 (next-generation) shared-memory transport.

Shm2Conf binds the shm2:// URL scheme to the Iceoryx2 shared-memory transport, the next-generation successor to the shm:// Iceoryx backend. Iceoryx2 keeps the zero-copy semantics of its predecessor but eliminates the standalone RouDi daemon: every participating process maps the shared-memory service directly. This simplifies deployment in containerised and read-only root-filesystem environments while preserving the same loan / release flow.

Shared-Memory Layout

Iceoryx2 service (file-backed POSIX SHM segment)
  +-----------------------------------------------+
  |  Per-publisher slot pool of fixed-size chunks |
  |  +------+ +------+ +------+ +------+ +------+ |
  |  | slot | | slot | | slot | | slot | | ...  | |
  |  +------+ +------+ +------+ +------+ +------+ |
  +--------^--------------------------^-----------+
           | loan()                   | release()
           |                          |
      Publisher process         Subscriber process

Loan / Release Flow

Publisher: slot = loan(size); fill(slot); publish(slot);
                                         \
                                          \--> per-subscriber notification queue
                                                    \
Subscriber: slot = take();                          \--> slot arrival
            consume(slot); release(slot);

Supported Node Types

Publisher	Subscriber	Server	Client	Getter	Setter
yes	yes	yes	yes	yes	yes

URL Format

shm2://<address>[?event=<name>&domain=<N>&depth=<N>&history=<N>&wait=<ms>][#<size>]

Component	Description
address	Iceoryx2 service/topic name (URL host concatenated with path)
event	Optional secondary event name (?event=)
domain	Domain ID (?domain=); defaults to 0
depth	Queue / loan capacity override; 0 uses the Iceoryx2 default
history	History count; URL default 0, or 1 for field nodes
wait	Blocking-wait timeout in ms; pub/sub only
size	Per-message memory size from URL fragment (see size syntax below)

Size Fragment Syntax

The URL fragment selects the per-message shared-memory chunk size. Supported suffixes are case-insensitive: B, K/KB, M/MB, G/GB. The value must fall in (0, kMaxMemSize].

shm2://my_topic#1M     // 1 MiB per message
shm2://my_topic#512K   // 512 KiB per message
shm2://my_topic        // default: 128 bytes per message

Backend-Specific Options

Option	Purpose	Default
size	Per-message chunk size	128 B
kMaxMemSize	Hard upper bound on size	32 MiB
depth	Slot pool capacity	backend default
history	Late-joining replay count	0 / 1

Note

Compiled only when VLINK_SUPPORT_SHM2 is defined.

address and event must each be at most 80 characters long.

wait mode is only valid for kPublisher / kSubscriber endpoints; using it with RPC or field nodes causes parse_protocol() to return false.

is_valid() additionally requires size in (0, kMaxMemSize] and domain, depth, history to be non-negative.