295 lines
7.6 KiB
Go
295 lines
7.6 KiB
Go
package brotli
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import "io"
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/* Copyright 2015 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Brotli state for partial streaming decoding. */
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const (
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stateUninited = iota
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stateLargeWindowBits
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stateInitialize
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stateMetablockBegin
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stateMetablockHeader
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stateMetablockHeader2
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stateContextModes
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stateCommandBegin
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stateCommandInner
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stateCommandPostDecodeLiterals
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stateCommandPostWrapCopy
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stateUncompressed
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stateMetadata
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stateCommandInnerWrite
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stateMetablockDone
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stateCommandPostWrite1
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stateCommandPostWrite2
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stateHuffmanCode0
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stateHuffmanCode1
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stateHuffmanCode2
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stateHuffmanCode3
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stateContextMap1
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stateContextMap2
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stateTreeGroup
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stateDone
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)
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const (
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stateMetablockHeaderNone = iota
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stateMetablockHeaderEmpty
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stateMetablockHeaderNibbles
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stateMetablockHeaderSize
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stateMetablockHeaderUncompressed
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stateMetablockHeaderReserved
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stateMetablockHeaderBytes
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stateMetablockHeaderMetadata
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)
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const (
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stateUncompressedNone = iota
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stateUncompressedWrite
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)
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const (
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stateTreeGroupNone = iota
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stateTreeGroupLoop
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)
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const (
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stateContextMapNone = iota
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stateContextMapReadPrefix
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stateContextMapHuffman
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stateContextMapDecode
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stateContextMapTransform
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)
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const (
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stateHuffmanNone = iota
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stateHuffmanSimpleSize
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stateHuffmanSimpleRead
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stateHuffmanSimpleBuild
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stateHuffmanComplex
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stateHuffmanLengthSymbols
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)
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const (
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stateDecodeUint8None = iota
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stateDecodeUint8Short
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stateDecodeUint8Long
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)
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const (
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stateReadBlockLengthNone = iota
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stateReadBlockLengthSuffix
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)
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type Reader struct {
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src io.Reader
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buf []byte // scratch space for reading from src
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in []byte // current chunk to decode; usually aliases buf
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state int
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loop_counter int
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br bitReader
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buffer struct {
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u64 uint64
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u8 [8]byte
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}
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buffer_length uint32
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pos int
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max_backward_distance int
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max_distance int
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ringbuffer_size int
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ringbuffer_mask int
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dist_rb_idx int
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dist_rb [4]int
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error_code int
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sub_loop_counter uint32
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ringbuffer []byte
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ringbuffer_end []byte
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htree_command []huffmanCode
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context_lookup []byte
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context_map_slice []byte
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dist_context_map_slice []byte
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literal_hgroup huffmanTreeGroup
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insert_copy_hgroup huffmanTreeGroup
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distance_hgroup huffmanTreeGroup
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block_type_trees []huffmanCode
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block_len_trees []huffmanCode
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trivial_literal_context int
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distance_context int
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meta_block_remaining_len int
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block_length_index uint32
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block_length [3]uint32
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num_block_types [3]uint32
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block_type_rb [6]uint32
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distance_postfix_bits uint32
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num_direct_distance_codes uint32
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distance_postfix_mask int
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num_dist_htrees uint32
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dist_context_map []byte
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literal_htree []huffmanCode
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dist_htree_index byte
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repeat_code_len uint32
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prev_code_len uint32
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copy_length int
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distance_code int
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rb_roundtrips uint
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partial_pos_out uint
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symbol uint32
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repeat uint32
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space uint32
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table [32]huffmanCode
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symbol_lists symbolList
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symbols_lists_array [huffmanMaxCodeLength + 1 + numCommandSymbols]uint16
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next_symbol [32]int
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code_length_code_lengths [codeLengthCodes]byte
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code_length_histo [16]uint16
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htree_index int
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next []huffmanCode
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context_index uint32
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max_run_length_prefix uint32
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code uint32
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context_map_table [huffmanMaxSize272]huffmanCode
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substate_metablock_header int
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substate_tree_group int
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substate_context_map int
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substate_uncompressed int
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substate_huffman int
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substate_decode_uint8 int
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substate_read_block_length int
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is_last_metablock uint
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is_uncompressed uint
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is_metadata uint
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should_wrap_ringbuffer uint
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canny_ringbuffer_allocation uint
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large_window bool
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size_nibbles uint
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window_bits uint32
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new_ringbuffer_size int
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num_literal_htrees uint32
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context_map []byte
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context_modes []byte
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dictionary *dictionary
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transforms *transforms
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trivial_literal_contexts [8]uint32
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}
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func decoderStateInit(s *Reader) bool {
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s.error_code = 0 /* BROTLI_DECODER_NO_ERROR */
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initBitReader(&s.br)
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s.state = stateUninited
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s.large_window = false
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s.substate_metablock_header = stateMetablockHeaderNone
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s.substate_tree_group = stateTreeGroupNone
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s.substate_context_map = stateContextMapNone
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s.substate_uncompressed = stateUncompressedNone
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s.substate_huffman = stateHuffmanNone
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s.substate_decode_uint8 = stateDecodeUint8None
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s.substate_read_block_length = stateReadBlockLengthNone
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s.buffer_length = 0
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s.loop_counter = 0
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s.pos = 0
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s.rb_roundtrips = 0
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s.partial_pos_out = 0
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s.block_type_trees = nil
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s.block_len_trees = nil
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s.ringbuffer_size = 0
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s.new_ringbuffer_size = 0
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s.ringbuffer_mask = 0
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s.context_map = nil
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s.context_modes = nil
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s.dist_context_map = nil
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s.context_map_slice = nil
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s.dist_context_map_slice = nil
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s.sub_loop_counter = 0
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s.literal_hgroup.codes = nil
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s.literal_hgroup.htrees = nil
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s.insert_copy_hgroup.codes = nil
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s.insert_copy_hgroup.htrees = nil
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s.distance_hgroup.codes = nil
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s.distance_hgroup.htrees = nil
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s.is_last_metablock = 0
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s.is_uncompressed = 0
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s.is_metadata = 0
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s.should_wrap_ringbuffer = 0
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s.canny_ringbuffer_allocation = 1
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s.window_bits = 0
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s.max_distance = 0
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s.dist_rb[0] = 16
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s.dist_rb[1] = 15
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s.dist_rb[2] = 11
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s.dist_rb[3] = 4
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s.dist_rb_idx = 0
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s.block_type_trees = nil
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s.block_len_trees = nil
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s.symbol_lists.storage = s.symbols_lists_array[:]
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s.symbol_lists.offset = huffmanMaxCodeLength + 1
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s.dictionary = getDictionary()
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s.transforms = getTransforms()
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return true
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}
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func decoderStateMetablockBegin(s *Reader) {
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s.meta_block_remaining_len = 0
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s.block_length[0] = 1 << 24
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s.block_length[1] = 1 << 24
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s.block_length[2] = 1 << 24
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s.num_block_types[0] = 1
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s.num_block_types[1] = 1
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s.num_block_types[2] = 1
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s.block_type_rb[0] = 1
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s.block_type_rb[1] = 0
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s.block_type_rb[2] = 1
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s.block_type_rb[3] = 0
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s.block_type_rb[4] = 1
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s.block_type_rb[5] = 0
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s.context_map = nil
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s.context_modes = nil
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s.dist_context_map = nil
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s.context_map_slice = nil
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s.literal_htree = nil
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s.dist_context_map_slice = nil
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s.dist_htree_index = 0
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s.context_lookup = nil
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s.literal_hgroup.codes = nil
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s.literal_hgroup.htrees = nil
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s.insert_copy_hgroup.codes = nil
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s.insert_copy_hgroup.htrees = nil
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s.distance_hgroup.codes = nil
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s.distance_hgroup.htrees = nil
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}
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func decoderStateCleanupAfterMetablock(s *Reader) {
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s.context_modes = nil
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s.context_map = nil
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s.dist_context_map = nil
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s.literal_hgroup.htrees = nil
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s.insert_copy_hgroup.htrees = nil
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s.distance_hgroup.htrees = nil
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}
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func decoderHuffmanTreeGroupInit(s *Reader, group *huffmanTreeGroup, alphabet_size uint32, max_symbol uint32, ntrees uint32) bool {
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var max_table_size uint = uint(kMaxHuffmanTableSize[(alphabet_size+31)>>5])
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group.alphabet_size = uint16(alphabet_size)
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group.max_symbol = uint16(max_symbol)
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group.num_htrees = uint16(ntrees)
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group.htrees = make([][]huffmanCode, ntrees)
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group.codes = make([]huffmanCode, (uint(ntrees) * max_table_size))
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return !(group.codes == nil)
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}
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