a low-level, lightweight protocol buffers implementation in JavaScript
npm install pbf
!Bundle size
A low-level, fast, ultra-lightweight (3KB gzipped) JavaScript library for decoding and encoding protocol buffers, a compact binary format for structured data serialization. Works both in Node and the browser. Supports lazy decoding and detailed customization of the reading/writing code.
This library is extremely fast — much faster than native JSON.parse/JSON.stringify
and the protocol-buffers module.
Here's a result from running a real-world benchmark on Node v6.5
(decoding and encoding a sample of 439 vector tiles, 22.6 MB total):
- pbf decode: 387ms, or 57 MB/s
- pbf encode: 396ms, or 56 MB/s
- protocol-buffers decode: 837ms, or 26 MB/s
- protocol-buffers encode: 4197ms, or 5 MB/s
- JSON.parse: 1540ms, or 125 MB/s (parsing an equivalent 77.5 MB JSON file)
- JSON.stringify: 607ms, or 49 MB/s
#### Using Compiled Code
Install pbf and compile a JavaScript module from a .proto file:
``bash`
$ npm install -g pbf
$ pbf example.proto > example.js
Then read and write objects using the module like this:
`js
import Pbf from 'pbf';
import {readExample, writeExample} from './example.js';
// read
var obj = readExample(new Pbf(buffer));
// write
const pbf = new Pbf();
writeExample(obj, pbf);
const buffer = pbf.finish();
`
Alternatively, you can compile a protobuf schema file directly in the code:
`js
import {compile} from 'pbf/compile';
import schema from 'protocol-buffers-schema';
const proto = schema.parse(fs.readFileSync('example.proto'));
const {readExample, writeExample} = compile(proto);
`
#### Custom Reading
`js
var data = new Pbf(buffer).readFields(readData, {});
function readData(tag, data, pbf) {
if (tag === 1) data.name = pbf.readString();
else if (tag === 2) data.version = pbf.readVarint();
else if (tag === 3) data.layer = pbf.readMessage(readLayer, {});
}
function readLayer(tag, layer, pbf) {
if (tag === 1) layer.name = pbf.readString();
else if (tag === 3) layer.size = pbf.readVarint();
}
`
#### Custom Writing
`js
var pbf = new Pbf();
writeData(data, pbf);
var buffer = pbf.finish();
function writeData(data, pbf) {
pbf.writeStringField(1, data.name);
pbf.writeVarintField(2, data.version);
pbf.writeMessage(3, writeLayer, data.layer);
}
function writeLayer(layer, pbf) {
pbf.writeStringField(1, layer.name);
pbf.writeVarintField(2, layer.size);
}
`
Install using NPM with npm install pbf, then import as a module:
`js`
import Pbf from 'pbf';
Or use as a module directly in the browser with jsDelivr:
`html`
Alternatively, there's a browser bundle with a Pbf global variable:
`html`
Create a Pbf object, optionally given a Buffer or Uint8Array as input data:
`js
// parse a pbf file from disk in Node
const pbf = new Pbf(fs.readFileSync('data.pbf'));
// parse a pbf file in a browser after an ajax request with responseType="arraybuffer"
const pbf = new Pbf(new Uint8Array(xhr.response));
`
Pbf object properties:
`js`
pbf.length; // length of the underlying buffer
pbf.pos; // current offset for reading or writing
#### Reading
Read a sequence of fields:
`js`
pbf.readFields((tag) => {
if (tag === 1) pbf.readVarint();
else if (tag === 2) pbf.readString();
else ...
});
It optionally accepts an object that will be passed to the reading function for easier construction of decoded data,
and also passes the Pbf object as a third argument:
`js
const result = pbf.readFields(readField, {})
function readField(tag, result, pbf) {
if (tag === 1) result.id = pbf.readVarint();
}
`
To read an embedded message, use pbf.readMessage(fn[, obj]) (in the same way as read).
Read values:
`js`
const value = pbf.readVarint();
const str = pbf.readString();
const numbers = pbf.readPackedVarint();
For lazy or partial decoding, simply save the position instead of reading a value,
then later set it back to the saved value and read:
`js`
const fooPos = -1;
pbf.readFields((tag) => {
if (tag === 1) fooPos = pbf.pos;
});
...
pbf.pos = fooPos;
pbf.readMessage(readFoo);
Scalar reading methods:
* readVarint(isSigned) (pass true if you expect negative varints)readSVarint()
*
*
*
*
*
*
*
*
*
*
*
Packed reading methods:
* readPackedVarint(arr, isSigned) (appends read items to arr)readPackedSVarint(arr)
*
*
*
*
*
*
*
*
#### Writing
Write values:
`js`
pbf.writeVarint(123);
pbf.writeString("Hello world");
Write an embedded message:
`js
pbf.writeMessage(1, writeObj, obj);
function writeObj(obj, pbf) {
pbf.writeStringField(obj.name);
pbf.writeVarintField(obj.version);
}
`
Field writing methods:
* writeVarintField(tag, val)
*
*
*
*
*
*
*
*
*
*
Packed field writing methods:
* writePackedVarint(tag, val)
*
*
*
*
*
*
Scalar writing methods:
* writeVarint(val)
*
*
*
*
*
*
*
*
Message writing methods:
* writeMessage(tag, fn[, obj])
*
Misc methods:
* realloc(minBytes) - pad the underlying buffer size to accommodate the given number of bytes;finish()
note that the size increases exponentially, so it won't necessarily equal the size of data written
* - make the current buffer ready for reading and return the data as a buffer slice
For an example of a real-world usage of the library, see vector-tile-js.
If installed globally, pbf provides a binary that compiles proto files into JavaScript modules. Usage:
`bash`
$ pbf
The --no-write and --no-read switches remove corresponding code in the output.--legacy
The switch makes it generate a CommonJS module instead of ESM.
Pbf will generate read and write functions for every message in the schema. For nested messages, their names will be concatenated — e.g. Message inside Test will produce readTestMessage and writeTestMessage functions.
* read(pbf) - decodes an object from the given Pbf instance.write(obj, pbf)
* - encodes an object into the given Pbf` instance (usually empty).
The resulting code is clean and simple, so it's meant to be customized.