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pbf

Node 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.

Performance

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

Examples

Using Compiled Code

Install pbf and compile a JavaScript module from a .proto file:

$ npm install -g pbf
$ pbf example.proto > example.js

Then read and write objects using the module like this:

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:

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

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

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

Install using NPM with npm install pbf, then import as a module:

import Pbf from 'pbf';

Or use as a module directly in the browser with jsDelivr:

<script type="module">
    import Pbf from 'https://cdn.jsdelivr.net/npm/pbf/+esm';
</script>

Alternatively, there's a browser bundle with a Pbf global variable:

<script src="https://cdn.jsdelivr.net/npm/pbf"></script>

API

Create a Pbf object, optionally given a Buffer or Uint8Array as input data:

// 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:

pbf.length; // length of the underlying buffer
pbf.pos; // current offset for reading or writing

Reading

Read a sequence of fields:

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:

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:

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:

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()
  • readFixed32()
  • readFixed64()
  • readSFixed32()
  • readSFixed64()
  • readBoolean()
  • readFloat()
  • readDouble()
  • readString()
  • readBytes()
  • skip(value)

Packed reading methods:

  • readPackedVarint(arr, isSigned) (appends read items to arr)
  • readPackedSVarint(arr)
  • readPackedFixed32(arr)
  • readPackedFixed64(arr)
  • readPackedSFixed32(arr)
  • readPackedSFixed64(arr)
  • readPackedBoolean(arr)
  • readPackedFloat(arr)
  • readPackedDouble(arr)

Writing

Write values:

pbf.writeVarint(123);
pbf.writeString("Hello world");

Write an embedded message:

pbf.writeMessage(1, writeObj, obj);

function writeObj(obj, pbf) {
    pbf.writeStringField(obj.name);
    pbf.writeVarintField(obj.version);
}

Field writing methods:

  • writeVarintField(tag, val)
  • writeSVarintField(tag, val)
  • writeFixed32Field(tag, val)
  • writeFixed64Field(tag, val)
  • writeSFixed32Field(tag, val)
  • writeSFixed64Field(tag, val)
  • writeBooleanField(tag, val)
  • writeFloatField(tag, val)
  • writeDoubleField(tag, val)
  • writeStringField(tag, val)
  • writeBytesField(tag, buffer)

Packed field writing methods:

  • writePackedVarint(tag, val)
  • writePackedSVarint(tag, val)
  • writePackedSFixed32(tag, val)
  • writePackedSFixed64(tag, val)
  • writePackedBoolean(tag, val)
  • writePackedFloat(tag, val)
  • writePackedDouble(tag, val)

Scalar writing methods:

  • writeVarint(val)
  • writeSVarint(val)
  • writeSFixed32(val)
  • writeSFixed64(val)
  • writeBoolean(val)
  • writeFloat(val)
  • writeDouble(val)
  • writeString(val)
  • writeBytes(buffer)

Message writing methods:

  • writeMessage(tag, fn[, obj])
  • writeRawMessage(fn[, obj])

Misc methods:

  • realloc(minBytes) - pad the underlying buffer size to accommodate the given number of bytes; note that the size increases exponentially, so it won't necessarily equal the size of data written
  • finish() - 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.

Proto Schema to JavaScript

If installed globally, pbf provides a binary that compiles proto files into JavaScript modules. Usage:

$ pbf <proto_path> [--no-write] [--no-read] [--legacy]

The --no-write and --no-read switches remove corresponding code in the output. The --legacy switch makes it generate a CommonJS module instead of ESM.

Pbf will generate read<Identifier> and write<Identifier> 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.