CAM Lookup Table for Single-Pass Deflate Header Decoding

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Solution Overview

Problem

Current Deflate decompression methods are inefficient, particularly when processing small buffers, as they require multiple passes through the header data to reconstruct Huffman codes, leading to significant processing time and cycles, especially in applications like tiered memory systems where speed is crucial.

Innovation Solution

A hardware decompression accelerator utilizing a content-addressable memory (CAM) for header parsing and an arithmetic logic unit (ALU) for Huffman symbol decoding, which eliminates the need for a second pass through the header data by using a CAM-based approach to generate a lookup table during the first pass, allowing for faster processing and reduced cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional multi-pass header processing is used to reconstruct Huffman codes, then decompression accuracy is maintained, but processing time and cycles increase significantly

Engineering Contradiction:

Improvedecompression accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary actions by generating the complete lookup table during the first pass through the header data, including all code-length mappings and symbol associations. This preliminary construction of the decoding infrastructure eliminates the need for subsequent passes, as the lookup table is fully prepared and ready for immediate use during the actual decompression process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the decompression process into distinct phases: a first pass dedicated to header parsing and lookup table generation, and a second pass for actual data decompression using the pre-built table. This segmentation allows each phase to be optimized independently, with the header processing phase completing all necessary setup work before the decompression phase begins.

Inventive Principle:

Principle #1Segmentation

2Reliability

If multiple passes through header data are performed to build Huffman code tables, then complete code reconstruction is achieved, but processing cycles increase

Engineering Contradiction:

Improvecode reconstruction completenessVSAvoidprocessing cycles

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuity of useful action by ensuring that the first pass through the header data accomplishes both header parsing and complete lookup table generation in an unbroken sequence. The hardware decoder continuously processes header information and populates the lookup table without interruption or need to restart, maintaining productive action throughout the entire header processing period.

Inventive Principle:

Principle #20Continuity of useful action

3Device complexity

If sequential header processing is used, then processing logic is simple, but decompression speed decreases

Engineering Contradiction:

Improveprocessing logic complexityVSAvoiddecompression speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The patent replaces the mechanical sequential processing system with a hardware-based parallel processing system. The hardware decoder uses content-addressable memory and parallel comparison logic to simultaneously evaluate multiple code-length mappings against the input data, substituting the step-by-step mechanical approach with concurrent hardware operations that achieve both speed and simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a hardware lookup table as an intermediary structure between the header data and the decompression output. This intermediary table pre-computes and stores all necessary code-length mappings, allowing the decoder to quickly translate compressed data into uncompressed form without complex real-time calculations, thus bridging the gap between simple logic and high speed.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12021551B2Method and apparatus for efficient deflate decompression using content-addressable data structures

Publication Date: 2024.06.25 INTEL CORP

AI summary

Apparatus and method for efficient compression block decoding using content-addressable structure for header processing. For example, one embodiment of an apparatus comprises: a header parser to extract a sequence of tokens and corresponding length values from a header of a compression block, the tokens and corresponding length values associated with a type of compression used to compress a payload of the compression block; and a content-addressable data structure builder to construct a content-addressable data structure based on the tokens and length values, the content-addressable data structure builder to write an entry in the content-addressable data structure comprising a length value and a count value, the count value indicating a number of times the length value was previously written to an entry in the content-addressable data structure.