syscall for node.js

Execute POSIX/Linux syscall command from Node.js.

Usage, see syscall reference:

``js
var syscall = require('jskernel-sys').syscall;

// Print Hello world in console using kernel's syscall command.
var buf = new Buffer('Hello world\n');
syscall(1, 1, buf, buf.length);

// Where, on x86_64 Linux:
// 1 - sys_write system call
// 1 - STDOUT file descriptor
// buf - pointer to data in memory
// buf.length - size of the memory block to print
`

See jskernel-posix for POSIX command implementation.

Reference

$3

`ts
type TArg = number|string|Buffer;
function syscall(command: number, ...args: TArg[]): number;
function syscall64(command: number, ...args: TArg[]): [number, number];
`

syscall accepts up to 6 command arguments args, which are treated as
follows depending on their type:

- number is put directly in the appropriate CPU register as is.
- string gets converted to C's char * string and that pointer is put in CPU register.
- Buffer pointer to the raw data in-memory is put in CPU register.

syscall return a number which is the result returned by the kernel,
numbers below -1 usually represent an error.

$3

Returns a Buffer object of size size that is mapped to memory location
specified in addr argument.

`ts
function malloc(addr: number, size: number): Buffer;
`

$3

Return memory address of Buffer's data contents.

`ts
function addr(buffer: Buffer): number;
function addr64(buffer: Buffer): [number, number];
`

addr64 returns a tuple which represents 64-bit number, where first element contains the lower
32 bits and second element has the high 32 bits.

$3

Execute assembly code, buffer contains raw op-codes to run.

`ts
function asm(buffer: Buffer);
`

$3

Returns errno variable.

`ts
function errno(): number;
``

Installation

npm i jskernel-sys

Compiles on Ubuntu 14.04 x86_64 running under Docker with Node.js 4.4.3, has not
been tested on other machines.

Building addon:

node-gyp configure
node-gyp rebuild