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https://github.com/ukrbublik/shm-typed-array
IPC shared memory for NodeJs. Use as Buffer or TypedArray.
https://github.com/ukrbublik/shm-typed-array
buffer ipc nodejs shared-memory sharedarraybuffer shm typescript
Last synced: 7 days ago
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IPC shared memory for NodeJs. Use as Buffer or TypedArray.
- Host: GitHub
- URL: https://github.com/ukrbublik/shm-typed-array
- Owner: ukrbublik
- License: mit
- Created: 2016-11-09T00:37:36.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2024-05-15T07:19:01.000Z (6 months ago)
- Last Synced: 2024-11-06T05:00:28.811Z (14 days ago)
- Topics: buffer, ipc, nodejs, shared-memory, sharedarraybuffer, shm, typescript
- Language: C++
- Homepage:
- Size: 104 KB
- Stars: 71
- Watchers: 4
- Forks: 9
- Open Issues: 6
-
Metadata Files:
- Readme: readme.md
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
README
IPC shared memory for Node.js
Use as `Buffer` or `TypedArray`
Supports System V and POSIX shared memory
[](https://www.npmjs.com/package/shm-typed-array) [](https://travis-ci.com/github/ukrbublik/shm-typed-array)
# Install
``` bash
$ npm install shm-typed-array
```
Windows is not supported.
# System V vs POSIX
Versions 0.0.* support only [System V memory segments](https://man7.org/linux/man-pages/man7/sysvipc.7.html).
Starting from version 0.1.0 [POSIX memory objects](https://man7.org/linux/man-pages/man7/shm_overview.7.html) 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](#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](#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](#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:
```js
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](https://nodejs.org/api/process.html#process_event_exit).
If you want to do cleanup on terminate signals like `SIGINT`, `SIGTERM`, please use [node-cleanup](https://github.com/jtlapp/node-cleanup) / [node-death](https://github.com/jprichardson/node-death) and add code to exit handlers:
```js
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](https://github.com/ukrbublik/shm-typed-array/blob/master/test/example.js)
Usage of memory segments:
``` js
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
```