Unpack multibyte binary values from buffers
npm install @shinymayhem/binarybinary
======
Unpack multibyte binary values from buffers and streams.
You can specify the endianness and signedness of the fields to be unpacked too.
This module is a cleaner and more complete version of
bufferlist's binary module that
runs on pre-allocated buffers instead of a linked list.
Installation
============
To install with npm:
``
npm install @shinymayhem/binary
examples
========
stream.js
---------
` js
var binary = require('binary');
var ws = binary()
.word32lu('x')
.word16bs('y')
.word16bu('z')
.tap(function (vars) {
console.dir(vars);
})
;
process.stdin.pipe(ws);
process.stdin.resume();
`
output:
`
$ node examples/stream.js
abcdefgh
{ x: 1684234849, y: 25958, z: 26472 }
^D
parse.js
--------
` js
var buf = new Buffer([ 97, 98, 99, 100, 101, 102, 0 ]);
var binary = require('binary');
var vars = binary.parse(buf)
.word16ls('ab')
.word32bu('cf')
.word8('x')
.vars
;
console.dir(vars);
`
output:
`
{ ab: 25185, cf: 1667523942, x: 0 }
methods
=======
var binary = require('binary')
var b = binary()
----------------
Return a new writable stream b that has the chainable methods documented below
for buffering binary input.
binary.parse(buf)
-----------------
Parse a static buffer in one pass. Returns a chainable interface with the
methods below plus a vars field to get at the variable stash as the last item
in a chain.
In parse mode, methods will set their keys to null if the buffer isn't bigbuffer()
enough except and scan() which read up up to the end of the buffer
and stop.
b.word{8,16,32,64}{l,b}{e,u,s}(key)
-----------------------------------
Parse bytes in the buffer or stream given:
* number of bits
* endianness ( l : little, b : big ),
* signedness ( u and e : unsigned, s : signed )
These functions won't start parsing until all previous parser functions have run
and the data is available.
The result of the parse goes into the variable stash at key.key
If has dots (.s), it refers to a nested address. If parent containerdst.addr
values don't exist they will be created automatically, so for instance you can
assign into and dst.port and the dst key in the variable stash{ addr : x, port : y }
will be afterwards.
` js
var vars = binary.parse(new Buffer([5, 0, 80, 11, 184]))
.word8lu('count')
.word16lu('ports.src')
.word16bu('ports.dst')
.vars;
console.log(vars)
//{ count: 5, ports: { src: 80, dst: 3000 } }
`
b.buffer(key, size)
-------------------
Take size bytes directly off the buffer stream, putting the resulting bufferkey
slice in the variable stash at . If size is a string, use the value atvars[size]. The key follows the same dotted address rules as the word
functions.
` js
var vars = binary.parse(new Buffer([4, 1, 0, 1, 0]))
.word8lu('dataLength')
.buffer('data', 'dataLength')
.vars;
console.log(vars.data)
//
`
b.scan(key, buffer)
-------------------
Search for buffer in the stream and store all the intervening data in thekey
stash at at , excluding the search buffer. If buffer passed as a string,
it will be converted into a Buffer internally.
For example, to read in a line you can just do:
` js`
var b = binary()
.scan('line', new Buffer('\r\n'))
.tap(function (vars) {
console.log(vars.line)
})
;
stream.pipe(b);
b.tap(cb)
---------
The callback cb is provided with the variable stash from all the previous
actions once they've all finished.
You can nest additional actions onto this inside the callback.` js
binary.parse(new Buffer([4, 1, 0, 1, 0]))
.word8lu('dataLength')
.tap(function (vars) {
var getInt;
if (vars.dataLength <= 4 && vars.dataLength !== 3) {
getInt = "word" + (8 * vars.dataLength) + "lu";
thisgetInt;
} else {
this.skip(vars.dataLength);
}
})
.vars;
console.log(vars);
//{ dataLength: 4, data: 65537 }
`
b.into(key, cb)
---------------
Like .tap(), except all nested actions will assign into a key in the vars
stash.
` js
var vars = binary.parse(new Buffer([45, 13, 8]))
.word8lu('avg')
.into('stdDev', function (inner) {
// e.g. q8.8 formatted std dev
this.word8lu('integer')
.word8lu('decimal');
console.log("inner", inner)
})
.vars;
console.log("outer", vars);
//inner { integer: 13, decimal: 8 }
//outer { avg: 45, stdDev: { integer: 13, decimal: 8 } }
`
b.loop(cb)
----------
Loop, each time calling cb(end, vars) for function end and the variablethis
stash with set to a new chain for nested parsing. The loop terminatesend
once is called.
` js
var entries = [];
var vars = binary.parse(new Buffer([3, 1, 97, 3, 99, 97, 116, 4, 119, 105, 110, 115]))
.word8lu('wordCount')
.loop(function (end, inner) {
this.word8lu('length')
.string('word', inner.length)
.vars;
entries.push(this.vars.word.toString('ascii'));
if (entries.length >= inner.wordCount) {
end();
}
console.log("inner", inner);
})
.vars;
console.log("outer", vars);
console.log("entries", entries);
//inner { wordCount: 3, length: 1, word: 'a' }
//inner { wordCount: 3, length: 3, word: 'cat' }
//inner { wordCount: 3, length: 4, word: 'wins' }
//outer { wordCount: 3, length: 4, word: 'wins' }
//entries [ 'a', 'cat', 'wins' ]
`
b.string(key, size)
---------
Read size bytes as a utf8 string, or read until end of buffer if size notkey
specified. Puts the resulting string in the variable stash at .size
If is a string, use the value at vars[size]. The key follows the same
dotted address rules as the word functions.
` js
var vars = binary.parse(new Buffer([97, 32, 99, 97, 116, 32, 119, 105, 110, 115]))
.string('res')
.vars;
console.log(vars);
// { res: 'a cat wins' }
`
b.cstring(key, size)
---------
Same as string(), but read as a null-terminated utf8 string (slices off the
null character and anything after it, or last character if no null found)
` js
var vars = binary.parse(new Buffer([97, 32, 99, 97, 116, 32, 119, 105, 110, 115, 0]))
.cstring('res')
.vars;
console.log(vars);
// { res: 'a cat wins' }
`
b.skip(size)
---------
Skip is a string, use the value at vars[size]. The
key follows the same dotted address rules as the word functions.
` js
var vars = binary.parse(new Buffer([5, 13, 80]))
.word8lu('count')
.skip(1)
.word8lu('port')
.vars;
console.log(vars);
//{ count: 5, port: 80 }
`
b.tell()
---------
Return the current offset in the buffer
` js
var pos = binary.parse(new Buffer([5, 0, 80, 11, 184]))
.word8lu('count')
.tell();
console.log(pos);
// 1
`
b.flush()
---------
Clear the variable stash entirely.
` js
var pos = binary.parse(new Buffer([5, 0, 80, 11, 184]))
.word8lu('preFlush')
.word8lu('preFlush2')
.flush()
.word8lu('postFlush')
.word8lu('postFlush2')
.tap(function (inner) {
console.log("inner", inner);
})
.vars;
console.log("outer:", vars);
//inner { postFlush: 80, postFlush2: 11 }
//outer: { preFlush: 5 } //not sure why
``
notes
=====
The word64 functions will only return approximations since javascript uses ieee
floating point for all number types. Mind the loss of precision.
license
=======
MIT