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HPACK Compression library for Go
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README.md
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huffman_tables.go
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integers.go
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README.md

HPACK library

Build Status godoc

This library implements RFC7541, HPACK: Header Compression for HTTP/2, which includes:

  • Primitive Type Representations
    • Variable integer sizes (with prefix lengths)
    • String literals (incl. Huffman decoding)
  • Static & Dynamic indexes
  • Dynamic Table evictions
  • Header block parsing

You can read about HPACK and this implementation here.

Usage

Most users of this library will be implementing HTTP/2.

decoder := hpack.NewDecoder(negotiatedDynamicTableSizeMax)
headerBlock := recvHeaderBlockAndContinuations()
headers, err := decoder.Decode(headerBlock)

The Decode function expects a complete header block. HTTP/2 specifies that a header block can be split across multiple frames, in a HEADER or PUSH_PROMISE frame plus optional CONTINUATION frames.

Users should concatenate the header block fragments together and only call Decode when a frame with the END_HEADERS flag is received.

Development

Generating Huffman lookup tables

The lookup tables are code generated from the Huffman codes in the HPACK specification. This ensures the lookup tables are available at runtime with no initialization required.

Run the following command to generate the lookup tables used for Huffman decoding:

go run cmd/generate_huffman_tables/main.go | gofmt > huffman_tables.go

License

Copyright 2016 Chris Moos

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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