Type:	Package
Title:	Shared Memory Atomic Operations
Version:	1.2.0
Date:	2025-03-28
Description:	Implements named semaphores from the 'boost' 'C++' library https://www.boost.org/ for interprocess communication. Multiple 'R' sessions on the same host can block (with optional timeout) on a semaphore until it becomes positive, then atomically decrement it and unblock. Any session can increment the semaphore.
URL:	https://cmmr.github.io/semaphore/, https://github.com/cmmr/semaphore
BugReports:	https://github.com/cmmr/semaphore/issues
License:	MIT + file LICENSE
Encoding:	UTF-8
RoxygenNote:	7.3.2
Config/testthat/edition:	3
LinkingTo:	Rcpp, BH
Imports:	Rcpp
Suggests:	testthat
NeedsCompilation:	yes
Packaged:	2025-03-28 19:19:40 UTC; Daniel
Author:	Daniel P. Smith [aut, cre], Alkek Center for Metagenomics and Microbiome Research [cph, fnd]
Maintainer:	Daniel P. Smith <dansmith01@gmail.com>
Repository:	CRAN
Date/Publication:	2025-03-29 00:30:02 UTC

Shared Memory Atomic Operations

Description

A semaphore is an integer that the operating system keeps track of. Any process that knows the semaphore's identifier can increment or decrement its value, though it cannot be decremented below zero.

When the semaphore is zero, calling decrement_semaphore(wait = FALSE) will return FALSE whereas decrement_semaphore(wait = TRUE) will block until the semaphore is incremented by another process. If multiple processes are blocked, a single call to increment_semaphore() will only unblock one of the blocked processes.

It is possible to wait for a specific amount of time, for example, decrement_semaphore(wait = 10) will wait for 10 seconds. If the semaphore is incremented within those 10 seconds, the function will immediately return TRUE. Otherwise it will return FALSE at the 10 second mark.

Usage

create_semaphore(id = NULL, value = 0, cleanup = TRUE)

increment_semaphore(id)

decrement_semaphore(id, wait = TRUE)

remove_semaphore(id)

Arguments

Value

• create_semaphore() - The created semaphore's identifier (string), invisibly unless id=NULL.

• increment_semaphore() - TRUE on success or FALSE on error, invisibly.

• decrement_semaphore() - TRUE if the decrement was successful or FALSE otherwise, invisibly when wait=Inf.

• remove_semaphore() - TRUE on success or FALSE on error.

Examples

    library(semaphore) 
    
    s <- create_semaphore()
    print(s)
    
    increment_semaphore(s)
    decrement_semaphore(s, wait = FALSE)
    decrement_semaphore(s, wait = FALSE)
    
    remove_semaphore(s)