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).
Designed to be a building block for writing customized decoders and encoders.
If you need an all-purpose protobuf JS library that does most of the work for you,
take a look at protocol-buffers too.
Examples
Using Compiled Code
Install pbf
and compile a JavaScript module from a .proto
file:
$ npm install -g pbf
$ pbf test.proto > test.js
Then read and write objects using the module like this:
var obj = Test.read(new Pbf(buffer));
var buffer = Test.write(obj, new Pbf());
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
Node and Browserify:
npm install pbf
Making a browser build:
npm install
npm run build-dev
npm run build-min
API
Create a Pbf
object, optionally given a Buffer
or Uint8Array
as input data:
var pbf = new Pbf(fs.readFileSync('data.pbf'));
var pbf = new Pbf(new Uint8Array(xhr.response));
Pbf
object properties:
pbf.length;
pbf.pos;
Reading
Read a sequence of fields:
pbf.readFields(function (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:
var result = pbf.readFields(callback, {})
function callback(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:
var value = pbf.readVarint();
var str = pbf.readString();
var 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:
var fooPos = -1;
pbf.readFields(function (tag) {
if (tag === 1) fooPos = pbf.pos;
});
...
pbf.pos = fooPos;
pbf.readMessage(readFoo);
Scalar reading methods:
readVarint()
readSVarint()
readVarint64()
(readVarint
version that handles negative int64
values)readFixed32()
readFixed64()
readSFixed32()
readSFixed64()
readBoolean()
readFloat()
readDouble()
readString()
readBytes()
skip(value)
Packed reading methods:
readPackedVarint()
readPackedSVarint()
readPackedFixed32()
readPackedFixed64()
readPackedSFixed32()
readPackedSFixed64()
readPackedBoolean()
readPackedFloat()
readPackedDouble()
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 slicedestroy()
- dispose the buffer
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] [--browser]
The --no-write
and --no-read
switches remove corresponding code in the output.
The --browser
switch makes the module work in browsers instead of Node.
The resulting module exports each message by name with the following methods:
read(pbf)
- decodes an object from the given Pbf
instancewrite(obj, pbf)
- encodes an object into the given Pbf
instance (usually empty)
The resulting code is pretty short and easy to understand, so you can customize it easily.
Changelog
1.3.3 (Jul 31, 2015)
- Added
writeRawMessage
method for writing a message without a tag, useful for creating pbfs with multiple top-level messages.
1.3.2 (Mar 5, 2015)
- Added
readVarint64
method for proper decoding of negative int64
-encoded values.
1.3.1 (Feb 20, 2015)
- Fixed pbf proto compile tool generating broken writing code.
1.3.0 (Feb 5, 2015)
- Added
pbf
binary that compiles .proto
files into Pbf
-based JavaScript modules.
1.2.0 (Jan 5, 2015)
Breaking API changes
- Changed
writeMessage
signature to (tag, fn, obj)
(see example in the docs)
for a huge encoding performance improvement. - Replaced
readPacked
and writePacked
methods that accept type as a string
with readPackedVarint
, etc. for each type (better performance and simpler API).
Improvements
- 5x faster encoding in Node (vector tile benchmark).
- 40x faster encoding and 3x faster decoding in the browser (vector tile benchmark).
1.1.4 (Jan 2, 2015)
- Significantly improved
readPacked
and writePacked
performance (the tile reading benchmark is now 70% faster).
1.1.3 (Dec 26, 2014)
Brings tons of improvements and fixes over the previous version (0.0.2
).
Basically makes the library complete.
Improvements
- Improved performance of both reading and writing.
- Made the browser build 3 times smaller.
- Added convenience
readFields
and readMessage
methods for a much easier reading API. - Added reading methods:
readFloat
, readBoolean
, readSFixed32
, readSFixed64
. - Added writing methods:
writeUInt64
, writeSFixed32
, writeSFixed64
. - Improved
readDouble
and readString
to use native Buffer methods under Node. - Improved
readString
and writeString
to use HTML5 TextEncoder
and TextDecoder
where available. - Made
Pbf
buffer
argument optional. - Added extensive docs and examples in the readme.
- Added an extensive test suite that brings test coverage up to 100%.
Breaking API changes
- Renamed
readBuffer
/writeBuffer
to readBytes
/writeBytes
. - Renamed
readUInt32
/writeUInt32
to readFixed32
/writeFixed32
, etc. - Renamed
writeTaggedVarint
to writeVarintField
, etc. - Changed
writePacked
signature from (type, tag, items)
to (tag, type, items)
.
Bugfixes
- Fixed
readVarint
to handle varints bigger than 6 bytes. - Fixed
readSVarint
to handle number bigger than 2^30
. - Fixed
writeVarint
failing on some integers. - Fixed
writeVarint
not throwing an error on numbers that are too big. - Fixed
readUInt64
always failing. - Fixed writing to an empty buffer always failing.