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178 lines
3.9 KiB
Markdown
178 lines
3.9 KiB
Markdown
binary
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======
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Unpack multibyte binary values from buffers and streams.
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You can specify the endianness and signedness of the fields to be unpacked too.
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This module is a cleaner and more complete version of
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[bufferlist](https://github.com/substack/node-bufferlist)'s binary module that
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runs on pre-allocated buffers instead of a linked list.
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[](http://travis-ci.org/substack/node-binary)
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examples
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========
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stream.js
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---------
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``` js
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var binary = require('binary');
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var ws = binary()
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.word32lu('x')
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.word16bs('y')
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.word16bu('z')
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.tap(function (vars) {
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console.dir(vars);
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})
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;
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process.stdin.pipe(ws);
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process.stdin.resume();
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```
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output:
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```
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$ node examples/stream.js
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abcdefgh
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{ x: 1684234849, y: 25958, z: 26472 }
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^D
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```
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parse.js
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--------
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``` js
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var buf = new Buffer([ 97, 98, 99, 100, 101, 102, 0 ]);
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var binary = require('binary');
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var vars = binary.parse(buf)
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.word16ls('ab')
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.word32bu('cf')
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.word8('x')
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.vars
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;
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console.dir(vars);
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```
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output:
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```
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{ ab: 25185, cf: 1667523942, x: 0 }
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```
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methods
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=======
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`var binary = require('binary')`
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var b = binary()
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----------------
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Return a new writable stream `b` that has the chainable methods documented below
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for buffering binary input.
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binary.parse(buf)
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-----------------
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Parse a static buffer in one pass. Returns a chainable interface with the
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methods below plus a `vars` field to get at the variable stash as the last item
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in a chain.
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In parse mode, methods will set their keys to `null` if the buffer isn't big
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enough except `buffer()` and `scan()` which read up up to the end of the buffer
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and stop.
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b.word{8,16,32,64}{l,b}{e,u,s}(key)
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-----------------------------------
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Parse bytes in the buffer or stream given:
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* number of bits
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* endianness ( l : little, b : big ),
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* signedness ( u and e : unsigned, s : signed )
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These functions won't start parsing until all previous parser functions have run
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and the data is available.
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The result of the parse goes into the variable stash at `key`.
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If `key` has dots (`.`s), it refers to a nested address. If parent container
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values don't exist they will be created automatically, so for instance you can
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assign into `dst.addr` and `dst.port` and the `dst` key in the variable stash
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will be `{ addr : x, port : y }` afterwards.
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b.buffer(key, size)
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-------------------
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Take `size` bytes directly off the buffer stream, putting the resulting buffer
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slice in the variable stash at `key`. If `size` is a string, use the value at
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`vars[size]`. The key follows the same dotted address rules as the word
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functions.
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b.scan(key, buffer)
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-------------------
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Search for `buffer` in the stream and store all the intervening data in the
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stash at at `key`, excluding the search buffer. If `buffer` passed as a string,
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it will be converted into a Buffer internally.
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For example, to read in a line you can just do:
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``` js
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var b = binary()
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.scan('line', new Buffer('\r\n'))
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.tap(function (vars) {
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console.log(vars.line)
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})
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;
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stream.pipe(b);
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```
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b.tap(cb)
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---------
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The callback `cb` is provided with the variable stash from all the previous
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actions once they've all finished.
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You can nest additional actions onto `this` inside the callback.
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b.into(key, cb)
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---------------
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Like `.tap()`, except all nested actions will assign into a `key` in the `vars`
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stash.
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b.loop(cb)
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----------
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Loop, each time calling `cb(end, vars)` for function `end` and the variable
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stash with `this` set to a new chain for nested parsing. The loop terminates
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once `end` is called.
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b.flush()
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---------
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Clear the variable stash entirely.
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installation
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============
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To install with [npm](http://github.com/isaacs/npm):
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```
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npm install binary
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```
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notes
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=====
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The word64 functions will only return approximations since javascript uses ieee
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floating point for all number types. Mind the loss of precision.
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license
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=======
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MIT
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