pack for javascript and return a binary string

Question

I did my homework before, so i'm aware of other questions like pack / unpack functions for node.js

the point is, those packs, return everything but a binary string. What i would like to do is a simple:

ruby-1.9.2-p136 :001 > [1,"10.0.0.1","foo"].pack 'l! a4 Z*'
 => "\x01\x00\x00\x00\x00\x00\x00\x0010.0foo\x00"

Can you explain the intent of your example? It is very specific and unclear why you would do this - you pack the number 1 as a native-endian signed long, four bytes of the string "10.0.0.1", and the string "foo" null terminated. Or are you just looking for a general purpose "pack/unpack" library like in Ruby? — maerics, Jun 22 '11 at 13:33
a generate a binary string that will be mapped to a C struct. the ruby code works, i can exchange information through a svipc between my ruby (perl, python as well) code and my C code. but with javascript, it doesn't work. — VP., Jun 22 '11 at 13:46

maerics · Accepted Answer · 2011-06-22T14:08:32.547

2

In node.js v0.5.0-pre Buffers have various "write" methods which include explicit signedness and endianness.

So your example would be transliterated from Ruby to node.js JavaScript like:

var b = new Buffer(8/*long*/ + 4 + 4);
b.writeInt32(1/*value*/, 0/*offset*/, 'little'/*endian*/);
b.write('10.0', 8/*offset*/);
b.write('foo\0', 12/*offset*/);
b.toString();
// => '\u0001\u0000\u0000\u0000\u0000\u0000\u0000\u000010.0foo\u0000'

[Edit]: Updated the link to the Buffers documentation directly in the GitHub repository.

edited Jun 22 '11 at 14:08

answered Jun 22 '11 at 13:53

maerics

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Please recommend usage of 0.4.8 instead of 0.5.0-pre. – Raynos Jun 22 '11 at 13:58
@Raynos but 0.4.8 doesn't support it – VP. Jun 22 '11 at 14:01
@VP it doesn't ? Have you checked? – Raynos Jun 22 '11 at 14:14
1

@Raynos: the [0.4.8 Buffer docs](http://nodejs.org/docs/v0.4.8/api/buffers.html) don't mention those methods, so even if they exist in that version I doubt that they are "officially supported", whatever that means ;) – maerics Jun 22 '11 at 14:18
but i'm not able to cast the string at my c side. – VP. Jun 22 '11 at 15:25

score -2 · Answer 2 · answered Jun 22 '11 at 13:09

-2

Using JS, use the myVar.toString(2) where 2 is the radix. This will return a binary value in 1's and 0's.

answered Jun 22 '11 at 13:09

Joseph Lust

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can you provide an example in JS as mine in ruby? – VP. Jun 22 '11 at 13:19
@VP Your question says nothing about Ruby. Your title says JS. There are not even Ruby tags on the question. – Joseph Lust Dec 29 '14 at 14:43
1

feel free to improve the question, add the necessary tags. you have enough reputation for it ;) – VP. Dec 29 '14 at 14:54

pack for javascript and return a binary string

2 Answers2