npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

shm-typed-array

v0.1.1

Published

IPC shared memory for NodeJs. Use as Buffer or TypedArray.

Downloads

426

Readme

IPC shared memory for Node.js
Use as Buffer or TypedArray
Supports System V and POSIX shared memory
npm travis

Install

$ npm install shm-typed-array

Windows is not supported.

System V vs POSIX

Versions 0.0.* support only System V memory segments.
Starting from version 0.1.0 POSIX memory objects are also supported.

System V is the classic way to use shared memory, stores IPC objects internally in the kernel.
POSIX is newer, but not fully supported in MacOS, uses the file system interface.

To create POSIX memory objects, use string parameter key in API.
Eg. shm.create(100, 'Buffer', '/test') will create virtual file /dev/shm/test in tmpfs for Linix.

To create System V memory segment, use numeric parameter key in API.
Eg. shm.create(100, 'Buffer', 1234) or shm.create(100) to autogenerate key.

API

shm.create (count, typeKey, key?, perm?)

Create shared memory segment/object.
count - number of elements (not bytes),
typeKey - type of elements ('Buffer' by default, see list below),
key - integer/null to create System V memory segment, or string to create POSIX memory object,
perm - permissions flag (default is 660).
Returns shared memory Buffer or descendant of TypedArray object, class depends on param typeKey.
Or returns null if shm already exists with provided key.
For System V: returned object has property key - integer key of created System V shared memory segment, to use in shm.get(key).
For POSIX: shared memory objects are not automatically destroyed. You should call shm.destroy(key) manually on process cleanup or if you don't need the object anymore.

shm.get (key, typeKey)

Get created shared memory segment/object by key.
Returns null if shm not exists with provided key.

shm.detach (key, forceDestroy?)

Detach shared memory segment/object.
For System V: If there are no other attaches for a segment, it will be destroyed automatically (even if forceDestroy is not true).
For POSIX: Unlike System V segments, POSIX object will not be destroyed automatically. You need to destroy it manually by providing true to forceDestroy argument or using shm.destroy(key).

shm.destroy (key)

Destroy shared memory segment/object.
Same as shm.detach(key, true)

shm.detachAll ()

Detach all created shared memory segments and objects.
Will be automatically called on process exit, see Cleanup.

shm.getTotalSize()

Get total size of all used (mapped) shared memory in bytes.

shm.getTotalCreatedSize()

Get total size of all created shared memory in bytes.

shm.LengthMax

Max length of shared memory segment (count of elements, not bytes)
2^31 for 64bit, 2^30 for 32bit

Types:

shm.BufferType = {
	'Buffer': shm.SHMBT_BUFFER,
	'Int8Array': shm.SHMBT_INT8,
	'Uint8Array': shm.SHMBT_UINT8,
	'Uint8ClampedArray': shm.SHMBT_UINT8CLAMPED,
	'Int16Array': shm.SHMBT_INT16,
	'Uint16Array': shm.SHMBT_UINT16,
	'Int32Array': shm.SHMBT_INT32,
	'Uint32Array': shm.SHMBT_UINT32,
	'Float32Array': shm.SHMBT_FLOAT32,
	'Float64Array': shm.SHMBT_FLOAT64,
};

Cleanup

This library does cleanup of created SHM segments/objects only on normal exit of process, see exit event.
If you want to do cleanup on terminate signals like SIGINT, SIGTERM, please use node-cleanup / node-death and add code to exit handlers:

shm.detachAll();

Also note that POSIX shared memory objects are not automatically destroyed. You should call shm.destroy('/your_name') manually if you don't need it anymore.

Usage

See example.js

Usage of memory segments:

const cluster = require('cluster');
const shm = require('shm-typed-array');

var buf, arr;
if (cluster.isMaster) {
	buf = shm.create(4096); //4KB
	arr = shm.create(1000000*100, 'Float32Array'); //100M floats
	buf[0] = 1;
	arr[0] = 10.0;
	console.log('[Master] Typeof buf:', buf.constructor.name,
		'Typeof arr:', arr.constructor.name);
	
	var worker = cluster.fork();
	worker.on('online', function() {
		this.send({ msg: 'shm', bufKey: buf.key, arrKey: arr.key });
		var i = 0;
		setInterval(function() {
			buf[0] += 1;
			arr[0] /= 2;
			console.log(i + ' [Master] Set buf[0]=', buf[0],
				' arr[0]=', arr ? arr[0] : null);
			i++;
			if (i == 5) {
				groupSuicide();
			}
		}, 500);
	});
} else {
	process.on('message', function(data) {
		var msg = data.msg;
		if (msg == 'shm') {
			buf = shm.get(data.bufKey);
			arr = shm.get(data.arrKey, 'Float32Array');
			console.log('[Worker] Typeof buf:', buf.constructor.name,
				'Typeof arr:', arr.constructor.name);
			var i = 0;
			setInterval(function() {
				console.log(i + ' [Worker] Get buf[0]=', buf[0],
					' arr[0]=', arr ? arr[0] : null);
				i++;
				if (i == 2) {
					shm.detach(data.arrKey);
					arr = null; //otherwise process will drop
				}
			}, 500);
		} else if (msg == 'exit') {
			process.exit();
		}
	});
}

function groupSuicide() {
	if (cluster.isMaster) {
		for (var id in cluster.workers) {
		    cluster.workers[id].send({ msg: 'exit'});
		    cluster.workers[id].destroy();
		}
		process.exit();
	}
}

Output:

[Master] Typeof buf: Buffer Typeof arr: Float32Array
[Worker] Typeof buf: Buffer Typeof arr: Float32Array
0 [Master] Set buf[0]= 2  arr[0]= 5
0 [Worker] Get buf[0]= 2  arr[0]= 5
1 [Master] Set buf[0]= 3  arr[0]= 2.5
1 [Worker] Get buf[0]= 3  arr[0]= 2.5
2 [Master] Set buf[0]= 4  arr[0]= 1.25
2 [Worker] Get buf[0]= 4  arr[0]= null
3 [Master] Set buf[0]= 5  arr[0]= 0.625
3 [Worker] Get buf[0]= 5  arr[0]= null
4 [Master] Set buf[0]= 6  arr[0]= 0.3125
shm segments destroyed: 2