Native bindings for creating Buffers atop shared memory in node.js
npm install shmmapNative bindings for mmap complemented with POSIX shm for creating (and safely destroying) actual shared memory segments for sharing large data between node.js processes beneath things like Buffer / Uint8Array.
``bash`
$ npm install --save shmmap
js
const cp = require('child_process');
const shmmap = require('shmmap');// create a 4 MiB buffer
let nl_test = 4 1024 1024;
let [s_key, at_test] = shmmap.create(nl_test);
// write some data to it
let nl_half = nl_test>>1;
for(let i_write=0; i_write at_test[i_write] = i_write % 255;;
}
// spawn another process
let u_proc = cp.fork(__dirname+'/child.js', [s_key, at_test.byteLength, nl_half]);
// wait for process to exit
u_proc.on('exit', () => {
// count the sum
let c_sum = 0;
for(let i_read=0; i_read c_sum += at_test[i_read];
}
// output sum to console
console.log('parent sum: '+c_sum);
// sanity check that zero-th position has special value set
console.log('parent 0: '+at_test[0]);
});
`In child.js:
`js
const shmmap = require('shmmap');// open shared memory segment
let at_shared = shmmap.read_write(process.argv[2], +process.argv[3]);
// count sum
let c_sum = 0;
let nl_half = +process.argv[4];
for(let i_read=0; i_read c_sum += at_shared[i_read];
}
// write a value to zero-th position
at_shared[0] = 100;
// output sum to console
console.log('child sum: '+c_sum);
`#### Results
`
child sum: 2097152
parent sum: 2097251
parent 0: 100
`As we can see, the 'child' successfully mutates the zero-th value in the buffer that is shared between the two processes.
API
shmmap.create(byteLength: uint) -- creates a Buffer with the given byteLength atop a new shared memory segment.
- returns an Array of [key: path, data: buffer] -- where key is the string you would pass over IPC to another process to open the shared memory segment somewhere else.
shmmap.read(key: path, byteLength: uint) -- creates a Buffer with the given byteLength atop an existing shared memory segment, in read-only mode.
- returns the Buffer
shmmap.read_write(key: path, byteLength: uint) -- creates a Buffer with the given byteLength atop an existing shared memory segment, in read-write mode.
- returns the Buffer
shmmap.release(key: path) -- releases the current process' hold on the shared memory segment at key.
- returns undefined`