Shared Brotli Compressed Data Format
draft-vandevenne-shared-brotli-format-06
Network Working Group J. Alakuijala
Internet-Draft T. Duong
Intended Status: Informational E. Kliuchnikov
Expires: Feb 04, 2021 R. Obryk
Z. Szabadka
L. Vandevenne
Google, Inc
Aug 2020
Shared Brotli Compressed Data Format
draft-vandevenne-shared-brotli-format-06
Abstract
This specification defines a data format for shared brotli
compression, which adds support for shared dictionaries, large
window, patching and a container format to brotli [RFC7932].
Shared dictionaries and large window support allow significant
compression gains compared to regular brotli, and patching allows
smaller patches of binary files.
Status of this Memo
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This Internet-Draft will expire on Feb 04, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Intended audience . . . . . . . . . . . . . . . . . . . . 3
1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Compliance . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5. Definitions of terms and conventions used . . . . . . . . 4
1.5.1. Packing into bytes . . . . . . . . . . . . . . . . . 4
2. Shared Brotli Overview . . . . . . . . . . . . . . . . . . . . 5
3. Shared Dictionaries . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Custom Static Dictionaries . . . . . . . . . . . . . . . . 6
3.1.1. Transform Operations . . . . . . . . . . . . . . . . 7
3.2. LZ77 Dictionaries . . . . . . . . . . . . . . . . . . . . 9
4. Varint Encoding . . . . . . . . . . . . . . . . . . . . . . . 10
5. Shared Dictionary Stream . . . . . . . . . . . . . . . . . . . 10
6. Large Window Brotli Compressed Data Stream . . . . . . . . . . 13
7. Patching Format Compressed Data Stream . . . . . . . . . . . . 13
8. Shared Brotli Compressed Data Stream . . . . . . . . . . . . . 13
9. Shared Brotli Framing Format Stream . . . . . . . . . . . . . 14
9.1. Main Format . . . . . . . . . . . . . . . . . . . . . . . 14
9.2. Chunk Format . . . . . . . . . . . . . . . . . . . . . . 14
9.3. Metadata Format . . . . . . . . . . . . . . . . . . . . . 17
9.4. Chunk Specifications . . . . . . . . . . . . . . . . . . 18
9.4.1. Padding Chunk (Type 0) . . . . . . . . . . . . . . . 18
9.4.2. Metadata Chunk (Type 1) . . . . . . . . . . . . . . 18
9.4.3. Data Chunk (Type 2) . . . . . . . . . . . . . . . . 19
9.4.4. First Partial Data Chunk (Type 3) . . . . . . . . . 19
9.4.5. Middle Partial Data Chunk (Type 4) . . . . . . . . . 19
9.4.6. Last Partial Data Chunk (Type 5) . . . . . . . . . . 20
9.4.7. Footer Metadata Chunk (Type 6) . . . . . . . . . . . 20
9.4.8. Global Metadata Chunk (Type 7) . . . . . . . . . . . 20
9.4.9. Repeat Metadata Chunk (Type 8) . . . . . . . . . . . 21
9.4.10. Central Directory Chunk (Type 9) . . . . . . . . . 22
9.4.11. Final Footer Chunk (Type 10) . . . . . . . . . . . 22
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