bson-json-transform

A Node.js Transform for streaming Bson into Json.
With this you can convert a large BSON to a JSON without exchausting your available RAM.

Included features: (can be turned on and off)

• Parse all BSON features as a stream.
• Option to skip first BSON "total size" header.
• Handling of Int64 despite JS' limitation

About Int64 and JavaScript

Due to the fact that in JavaScript any number is always a IEEE 754 64-bit floating point value, there's a side-effect of whole numbers being limited to 53 bits. When being larger than that - they are kind of rounded and loses precision of the lower bits. That is - the magnitude stays, but you lose the ones, the tens, and then the hunderds and so on - and they become zeros.

We handle parsing Int64 values from BSON by synthesizing the Int64 values and simulating the printing to string. There are different ways to handle it:

1. Always output as numeric values - but then if you read the JSON in a JavaScript environment, they will be rounded when larger than 53 bits.
2. Always output as string values, and thus not loosing the value, but loosing the type.
3. Output as numeric when it fits in 53bit boundaries, and as string when larger.

You can use the preserveInt64 option to choose how you would like to go about it.

Installation:

npm install --save bson-json-transform

The options you can pass are:

Name | Type | Default | Explanation ---- | ---- | ------- | ----------- hasHeader | Boolean | true | Does the stream begin with a BSON length header? arrayOfBsons | Boolean | false | Try to parse sequential BSONs until data runs out preserveInt64 | String|Boolean | 'auto' | Preserve Int64 when overflowing the JS 53bit limitation.- false - Do not try to preserve (large numbers may be truncated!)- 'number' - Always output as numbers. Be careful when you read those!- 'string' - Always output as a string.- 'auto' - Output as a string when over 53bits, and as a number when possible.

Usage example:

var fs = require('fs');
var BsonJsonTransform = require('bson-json-reader');

fs
	.createReadStream('my_data.bson')
	.pipe(BsonJsonTransform({ preserveInt64: 'string' }))
	.pipe(fs.createWriteStream('my_data.json'))
	.on('end', function (data) {
	    console.log('No more data!');
	});

Contributing

If you have anything to contribute, or functionality that you lack - you are more than welcome to participate in this! If anyone wishes to contribute unit tests - that also would be great :-)

Me

• Hi! I am Daniel Cohen Gindi. Or in short- Daniel.
• [email protected] is my email address.
• That's all you need to know.

Help

If you want to buy me a beer, you are very welcome to Thanks :-)

License

All the code here is under MIT license. Which means you could do virtually anything with the code. I will appreciate it very much if you keep an attribution where appropriate.

The MIT License (MIT)

Copyright (c) 2013 Daniel Cohen Gindi ([email protected])

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.