shared-structs

shared-structs

Share a struct backed by the same underlying buffer between C and JavaScript

npm install shared-struct

Useful for doing bulk updates of data in native modules with no context switching cost.

Usage

const sharedStructs = require('shared-structs')

const structs = sharedStructs(`
  struct aStruct {
    int32_t i;
    char buf[1024];
    char someChar;
    int someInt;
  }
`)

const struct = structs.aStruct()

struct.i = 42
struct.buf[0] = 42

// pass this to c, and it will be able to parse it
console.log(struct.rawBuffer)

Also supports nested structs and most other things you'd normally use in c!

See example/example.js for more.

API

structs = sharedStructs(src, [options])

Parses the structs specified in the global scope of src and returns JavaScript implementations of each.

Each property is exposed as a normal JavaScript property you can get/set.

All changes are reflected in .rawBuffer which you can pass to a c program and parse with the same struct.

Options include:

{
  defines: {
    CUSTOM_DEFINE_HERE: 42 // add a custom define is defined elsewhere
  },
  sizes: {
    foo: 1024 // set the size of struct foo if defined elsewhere
  },
  alignment: {
    foo: 8 // set the alignment of struct foo if defined elsewhere
  }
}

Writing strings

There is a small helper included in require('shared-structs/strings') that allows you to encode/decode c style strings into char buffers

const strings = require('shared-structs/strings')

// encode
strings.encode('hello world', struct.buf)

// decode
console.log(strings.decode(struct.buf))

License

MIT