# constants.h

Section: C Library Functions (3)

Updated: Wed May 13 2020

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## NAME

constants.h - Common constants used in decoder and encoder API.

## SYNOPSIS

### Macros

#define **BROTLI_LARGE_MAX_DISTANCE_BITS** 62U

*The theoretical maximum number of distance bits specified for large window brotli, for 64-bit encoders and decoders. *

#define **BROTLI_LARGE_MAX_WBITS** 30

*The maximum supported large brotli window bits by the encoder and decoder. *

#define **BROTLI_MAX_NPOSTFIX** 3

*Maximal number of 'postfix' bits. *

## Detailed Description

Common constants used in decoder and encoder API.

## Macro Definition Documentation

### #define BROTLI_LARGE_MAX_DISTANCE_BITS 62U

The theoretical maximum number of distance bits specified for large window brotli, for 64-bit encoders and decoders. Even when in practice 32-bit encoders and decoders only support up to 30 max distance bits, the value is set to 62 because it affects the large window brotli file format. Specifically, it affects the encoding of simple huffman tree for distances, see Specification RFC 7932 chapter 3.4.

### #define BROTLI_LARGE_MAX_WBITS 30

The maximum supported large brotli window bits by the encoder and decoder. Large window brotli allows up to 62 bits, however the current encoder and decoder, designed for 32-bit integers, only support up to 30 bits maximum.

### #define BROTLI_MAX_NPOSTFIX 3

Maximal number of 'postfix' bits. Number of 'postfix' bits is stored as 2 bits in meta-block header.

## Author

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