Professional Node.js: Building Javascript Based Scalable Software

Chapter 4

Using Buffers to Manipulate, Encode, and Decode Binary Data

WHAT’S IN THIS CHAPTER?

• Understanding why you need buffers in Node
• Creating a buffer from a string
• Converting a buffer to a string
• Manipulating the bytes in a buffer
• Slicing and copying a buffer

JavaScript is good at handling strings, but because it was initially designed to manipulate HTML documents, it is not very good at handling binary data. JavaScript doesn’t have a byte type — it just has numbers — or structured types, or even byte arrays: It just has strings.

Because Node is based on JavaScript, Node can handle text protocols like HTTP, but you can also use it to talk to databases, manipulate images, and handle file uploads. As you can imagine, doing this using only strings is very difficult. In the early days, Node handled binary data by encoding each byte inside a text character, but that proved to be wasteful, slow, unreliable, and hard to manipulate.

To make these types of binary-handling tasks easier, Node includes a binary buffer implementation, which is exposed as a JavaScript API under the Buffer pseudo-class. A buffer length is specified in bytes, and you can randomly set and get bytes from a buffer.

NOTE Another thing that is special about this buffer class is that the memory where the data sits is allocated outside of the JavaScript VM memory heap. This means that these objects will not be moved around by the garbage-collection algorithm: It will sit in this permanent memory address without ...