Struct HuffmanTable

pub struct HuffmanTable {
    pub(crate) maxcode: [i32; 18],
    pub(crate) offset: [i32; 18],
    pub(crate) lookup: [i32; 512],
    pub(crate) ac_lookup: Option<[i16; 512]>,
    pub(crate) values: [u8; 256],
}

A struct which contains necessary tables for decoding a JPEG huffman encoded bitstream

Fields

maxcode: [i32; 18]

largest code of length k

offset: [i32; 18]

offset for codes of length k Answers the question, where do code-lengths of length k end Element 0 is unused

lookup: [i32; 512]

lookup table for fast decoding

top bits above HUFF_LOOKAHEAD contain the code length.

Lower (8) bits contain the symbol in order of increasing code length.

ac_lookup: Option<[i16; 512]>

A table which can be used to decode small AC coefficients and do an equivalent of receive_extend

values: [u8; 256]

Directly represent contents of a JPEG DHT marker

# number of symbols with codes of length k bits Symbols in order of increasing code length

Implementations

impl HuffmanTable

pub fn new( codes: &[u8; 17], values: [u8; 256], is_dc: bool, is_progressive: bool, ) -> Result<HuffmanTable, DecodeErrors>

pub fn new_unfilled( codes: &[u8; 17], values: &[u8], is_dc: bool, is_progressive: bool, ) -> Result<HuffmanTable, DecodeErrors>

Create a new huffman tables with values that aren’t fixed used by fill_mjpeg_tables

fn make_derived_table( &mut self, is_dc: bool, _is_progressive: bool, bits: &[u8; 17], ) -> Result<(), DecodeErrors>

Compute derived values for a Huffman table

This routine performs some validation checks on the table