Introduction to hpack.js

hpack.js is a powerful JavaScript library that implements the HPACK compression algorithm for HTTP/2.
It is designed to compress and decompress HTTP/2 headers efficiently.

Key APIs and Examples

1. Encoder

The Encoder class is used to compress HTTP/2 headers.

  
    const { Encoder } = require('hpack.js')
    const encoder = new Encoder()

    const headers = [
      [':method', 'GET'],
      [':path', '/index.html']
    ]
    
    const compressed = encoder.encode(headers)
    console.log(compressed)
  

2. Decoder

The Decoder class is used to decompress HTTP/2 headers.

  
    const { Decoder } = require('hpack.js')
    const decoder = new Decoder()
    
    const compressedHeaders = new Uint8Array([....]) // Use your compressed header array
    const headers = decoder.decode(compressedHeaders)
    console.log(headers)
  

3. Update Dynamic Table Size

You can update the dynamic table size to control the context for compression and decompression.

  
    const { Encoder, Decoder } = require('hpack.js')

    const encoder = new Encoder()
    encoder.setTableSize(4096)

    const decoder = new Decoder()
    decoder.setTableSize(4096)
  

4. Handling Huffman Encoding

HPACK supports Huffman encoding for better compressibility.

  
    const { Encoder, Decoder } = require('hpack.js')

    const encoder = new Encoder()
    const headers = [[ ':method', 'GET' ], [ ':path', '/huffman' ]]
    const compressed = encoder.encode(headers, true) // true to enable Huffman encoding
    
    const decoder = new Decoder()
    const decodedHeaders = decoder.decode(compressed)
    console.log(decodedHeaders)
  

Application Example with hpack.js

Here is an example of a simple application that uses hpack.js to compress and decompress HTTP/2 headers.

  
    const { Encoder, Decoder } = require('hpack.js')
    
    // Create encoder and decoder instances
    const encoder = new Encoder()
    const decoder = new Decoder()
    
    // Example HTTP/2 headers to compress
    const headers = [
      [':status', '200'],
      ['content-type', 'text/html'],
      ['content-length', '1234']
    ]
    
    // Compress headers
    const compressedHeaders = encoder.encode(headers)
    console.log('Compressed Headers:', compressedHeaders)
    
    // Decompress headers
    const decompressedHeaders = decoder.decode(compressedHeaders)
    console.log('Decompressed Headers:', decompressedHeaders)
  

Conclusion

hpack.js is a vital tool for anyone working with HTTP/2. Its capabilities to compress and decompress HTTP/2 headers efficiently can greatly improve performance and reduce latency. Give it a try in your projects and see the benefits it brings!

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