pbf v4.0.1
pbf
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)
(passtrue
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 toarr
)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 writtenfinish()
- 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 givenPbf
instance.write(obj, pbf)
- encodes an object into the givenPbf
instance (usually empty).
The resulting code is clean and simple, so it's meant to be customized.
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