Function prepare [src]

Prepare the decoder to decode a compressed block. Loads the literals stream and Huffman tree from literals and reads the FSE tables from source. Errors returned: error.BitStreamHasNoStartBit if the (reversed) literal bitstream's first byte does not have any bits set error.TreelessLiteralsFirst literals is a treeless literals section and the decode state does not have a Huffman tree from a previous block error.RepeatModeFirst on the first call if one of the sequence FSE tables is set to repeat mode error.MalformedAccuracyLog if an FSE table has an invalid accuracy error.MalformedFseTable if there are errors decoding an FSE table error.EndOfStream if source ends before all FSE tables are read

Prototype

 pub fn prepare( self: *DecodeState, source: anytype, literals: LiteralsSection, sequences_header: SequencesSection.Header, ) !void

Parameters

self: *DecodeStateliterals: LiteralsSectionsequences_header: SequencesSection.Header

Source

  pub fn prepare(
    self: *DecodeState,
    source: anytype,
    literals: LiteralsSection,
    sequences_header: SequencesSection.Header,
) !void {
    self.literal_written_count = 0;
    self.literal_header = literals.header;
    self.literal_streams = literals.streams;

    if (literals.huffman_tree) |tree| {
        self.huffman_tree = tree;
    } else if (literals.header.block_type == .treeless and self.huffman_tree == null) {
        return error.TreelessLiteralsFirst;
    }

    switch (literals.header.block_type) {
        .raw, .rle => {},
        .compressed, .treeless => {
            self.literal_stream_index = 0;
            switch (literals.streams) {
                .one => |slice| try self.initLiteralStream(slice),
                .four => |streams| try self.initLiteralStream(streams[0]),
            }
        },
    }

    if (sequences_header.sequence_count > 0) {
        try self.updateFseTable(source, .literal, sequences_header.literal_lengths);
        try self.updateFseTable(source, .offset, sequences_header.offsets);
        try self.updateFseTable(source, .match, sequences_header.match_lengths);
        self.fse_tables_undefined = false;
    }
}  