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node-ioctl's Introduction

node-ioctl

node ioctl wrapper

Installation

Install with npm:

$ npm install ioctl

API

ioctl(fileDescriptor, request, data)

Parameters

  • fileDescriptor: Integer Target file descriptor, must be open.
  • request: Integer Device specific request code.
  • data: Integer|Buffer Request data.

Returns: Integer Usually zero is returned, some calls use the return value as a output parameter and may return a positive integer.

Throws: Throws on failed ioctl call.

Examples

Read bytes of the next pending datagram using FIONREAD. As it takes a pointer as a parameter, it's straightforward using a Buffer as a parameter.

var dgram = require('dgram');
var ioctl = require('ioctl');

var FIONREAD = 0x541B;

var s = dgram.createSocket('udp4');
s.bind(1234, function(err) {
    if (err) {
        throw err;
    }

    var s1 = dgram.createSocket('udp4');
    var message = new Buffer("Some bytes");
    s1.send(message, 0, message.length, 1234, "localhost", function(err, bytes) {
        var length = new Buffer(4);
        var ret = ioctl(s._handle.fd, FIONREAD, length);
        console.log('Pending bytes: ' + length.readInt32LE(0));
        s1.close();
        s.close();
    });
});

For other cases, involving complex structs, we can use the ref, ref-array and ref-struct modules.

var fs = require('fs');
var ioctl = require('ioctl');
var ref = require('ref');
var ArrayType = require('ref-array');
var StructType = require('ref-struct');

var TTY = '/dev/tty1';
var TCGETA = 0x5405;
var TIOCEXCL = 0x540C;

// #define NCC 8
// struct termio {
// unsigned short c_iflag; /* input mode flags */
// unsigned short c_oflag; /* output mode flags */
// unsigned short c_cflag; /* control mode flags */
// unsigned short c_lflag; /* local mode flags */
// unsigned char c_line; /* line discipline */
// unsigned char c_cc[NCC]; /* control characters */
// };

// define the "snd_hwdep_info" struct type
var termio = StructType({
    c_iflag : ref.types.ushort,
    c_oflag : ref.types.ushort,
    c_cflag : ref.types.ushort,
    c_lflag : ref.types.ushort,
    c_line : ref.types.uchar,
    c_cc : ArrayType(ref.types.uchar, 8)
});

fs.open(TTY, 'r+', function(err, fd) {
    if (err) {
        throw err;
    }

    var info = new termio();
    var ret = ioctl(fd, TCGETA, info.ref());
    console.log('TCGETA ret: ' + ret);
    console.log('c_iflag: ' + info.c_iflag);
    console.log('c_oflag: ' + info.c_oflag);
    console.log('c_cflag: ' + info.c_cflag);
    console.log('c_lflag: ' + info.c_lflag);
    console.log('c_line: ' + info.c_line);
    console.log('c_cc: ' + info.c_cc.buffer.toString());
    ret = ioctl(fd, TIOCEXCL);
    console.log('TIOCEXCL ret: ' + ret);
    fs.close(fd);
});

node-ioctl's People

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node-ioctl's Issues

Meaningful errors

Currently the ioctl return value is directly passed node land. This makes usage very hard to debug when a seemingly random negative integer is returned. This could be avoided by using strerror(errno) on errors.

Sign extension on 64-bit FreeBSD

I am using this node-ioctl module on a FreeBSD 64-bit operating system. When using an ioctl with a request value that has the top bit set (i.e. 0x8nnnnnnn), an 'ioctl sign-extension ioctl' warning is emitted from the kernel.

This is due to the request value passed from the node side being assigned to an int data type before being passed to the ioctl. On FreeBSD the request data type is an unsigned long , so sign extension occurs. I appreciate there is some complication here as the datatype of request is int in Linux and unsigned long in FreeBSD.

I would suggest changing the line:
int request = args[1]->Uint32Value();
to
unsigned int request = args[1]->Uint32Value();

though I'm not sure if this would cause compilation issues on Linux?

malloc(): memory corruption

Whenever I try to read the fb_fix_screeninfo, node.js crashes and says malloc(): memory corruption. My fb_fix_screeninfo structure looks like:

    StructType({
		id: ArrayType(ref.types.char,16),
		smem_start: ref.types.ulong,
		
		smem_len: ref.types.uint,
		type: ref.types.uint,
		type_aux: ref.types.uint,
		visual: ref.types.uint,
		xpanstep: ref.types.ushort,
		ypanstep: ref.types.ushort,
		line_length: ref.types.uint,
		mmio_start: ref.types.ulong,
		
		mmio_len: ref.types.uint,
		accel: ref.types.uint,
		capabilities: ref.types.ushort,
		reserved: ArrayType(ref.types.ushort,2)
	})

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