@markusjx/shared_memory

Installation

npm install @markusjx/shared_memory

Requires Node.js 12 or later

Note on any global properties

The global property only have an effect on Windows machines, when running on any other machine, the passed value will be ignored. When passing true as an argument, the shared memory block will be accessible globally. In that case, the program must be run with administrator rights. On linux, any program creating a shared memory block must be executed with root rights.

Read more here.

Usage

Import the module

const shared_memory = require('@markusjx/shared_memory');

Class shared_memory

shared_memory.generateId

Generate an id for a shared memory block.

Arguments:

• global?: boolean - Whether the memory block can be read globally. Defaults to false.

Returns

string - The generated id

shared_memory.generateIdAsync

Generate an id for a shared memory block. Async call.

Arguments

• global?: boolean - Whether the memory block can be read globally. Defaults to false.

Returns

Promise<string> - The generated id

new shared_memory

Create a new shared memory block.

Arguments

• name: string - The name (id) of the memory block
• sizeInBytes: number - The size of the memory block in bytes
• global?: boolean - Whether the memory block can be read globally. Defaults to false.
• host?: boolean - Whether to create the memory block. Defaults to true.

Throws

Error - If a memory block with the given id already exists (if host is set to true), or the block couldn't be attached.

shared_memory.set data

Copy a string to the shared memory block.

Arguments

• data: string - The data to copy

Throws

Error - If the string is too big for the buffer

shared_memory.get data

Get a string from the memory block. Reads std::max(strlen(buffer), sizeof(buffer)) bytes from the buffer. The string length therefore is determined by either a delimiting \0 or the length of the buffer.

Returns

string - The read data

shared_memory.set buffer

Copy data from a node Buffer to the memory block.

Arguments

• data: Buffer - The data to copy

Throws

Error - If the Buffer is larger than the shared memory block

shared_memory.get buffer

Read data from the memory block into a node Buffer. Always reads sizeof(buffer) into the result Buffer.

Returns

Buffer - The read data

shared_memory.write

Write some data to the buffer. Writes either a string or a node Buffer.

Arguments

• data: string | Buffer - The data to copy

Returns

void

Throws

Error - If the shared memory block is too small for the data to write

shared_memory.read

Read a string from the memory. Reads std::max(strlen(buffer), sizeof(buffer)) bytes from the buffer. The string length therefore is determined by either a delimiting \0 or the length of the buffer.

Returns

string - the read data

shared_memory.readBuffer

Read data from the memory block into a node Buffer. Always reads sizeof(buffer) into the result Buffer.

Returns

Buffer - The read data

Example

Host code:

const shared_memory = require('@markusjx/shared_memory');

// Generate a memory id
const id = shared_memory.generateId();

// Create a new shared memory block
// with a size of 1024 bytes
const memory = new shared_memory(id, 1024, false, true);

// Write data to the memory
memory.data = "Some data";

// Signal the client that the data is ready
// Wait until the client has read all the data

// Write some new data in form of a buffer
memory.buffer = Buffer.from("Some data");

// Signal the client that the data is ready

Client code:

import shared_memory from "./index";

// Attach the created memory
const memory = new shared_memory(id, 1024, false, false);

// Wait until the data is ready

// Read the data 
const read = memory.data;

// Signal the host that the data has been read
// Wait until the next data is ready

// Read the data into a buffer.
// This will contain all of the data in the memory block.
const buf = memory.buffer;