@shinymayhem/binary
v0.4.1
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Unpack multibyte binary values from buffers
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binary
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
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
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 big
enough except buffer()
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
.
If key
has dots (.
s), it refers to a nested address. If parent container
values don't exist they will be created automatically, so for instance you can
assign into dst.addr
and dst.port
and the dst
key in the variable stash
will be { addr : x, port : y }
afterwards.
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 buffer
slice in the variable stash at key
. If size
is a string, use the value at
vars[size]
. The key follows the same dotted address rules as the word
functions.
var vars = binary.parse(new Buffer([4, 1, 0, 1, 0]))
.word8lu('dataLength')
.buffer('data', 'dataLength')
.vars;
console.log(vars.data)
//<Buffer 01 00 01 00>
b.scan(key, buffer)
Search for buffer
in the stream and store all the intervening data in the
stash at at key
, 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:
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.
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";
this[getInt]('data');
} 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.
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 variable
stash with this
set to a new chain for nested parsing. The loop terminates
once end
is called.
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 not
specified. Puts the resulting string in the variable stash at key
.
If size
is a string, use the value at vars[size]
. The key follows the same
dotted address rules as the word functions.
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)
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 bytes. If size
is a string, use the value at vars[size]
. The
key follows the same dotted address rules as the word functions.
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
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.
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