Standard library

nox.sharedmem

Named shared-memory segments for communicating between separate operating-system processes (two noxc run invocations, a server and a helper). Within one program, use channels or nox.atomic instead.

Text

import nox.sharedmem
from nox.sharedmem import SharedBuffer, SharedMemError

Capability: shared_memory (macOS and Linux; unavailable in freestanding profiles).

Functions and methods#

Member	Description
`open(name, size)`	opens the segment called `name` (creating it with `size` bytes if it does not exist) and maps it; names look like `"/myapp-state"`; raises `SharedMemError` on failure
`unlink(name)`	permanently removes the segment's name (segments live until unlinked)
`SharedBuffer.lock()`, `unlock()`	a spin lock stored in the segment: take it around any read-modify-write; pair it with `defer buf.unlock()`
`SharedBuffer.read_int(offset)`, `write_int(offset, value)`	a 64-bit integer at a byte offset
`SharedBuffer.read_str(offset, length)`, `write_str(offset, value)`	`length` bytes as text / write the bytes of a string
`SharedBuffer.close()`	unmaps it in this process only; other processes keep their mapping

The segment is plain bytes: you decide the layout. Keep offsets inside size and, when two processes interpret the layout, agree on it. lock protects the segment as a whole; it is not re-entrant.

Nox

import nox.sharedmem
from nox.sharedmem import SharedBuffer

nox.sharedmem.unlink("/noxdocdemo")
b: SharedBuffer = nox.sharedmem.open("/noxdocdemo", 4096)
b.lock()
b.write_int(0, 12345)
b.write_str(16, "hello")
b.unlock()

c: SharedBuffer = nox.sharedmem.open("/noxdocdemo", 4096)
c.lock()
print(c.read_int(0), c.read_str(16, 5))
c.unlock()
c.close()
b.close()
nox.sharedmem.unlink("/noxdocdemo")

Output

12345 hello

Notes#

Always unlink a segment you created when it is no longer needed, otherwise it persists after the program exits.
The segment's name is global to the machine: use a distinctive prefix and treat the segment as untrusted input from other local processes.

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