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# gzip-like LZSS compressor
# Copyright (C) 2018 Pacien TRAN-GIRARD
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
import lists, tables, sugar
import ../bitio/integers, ../huffman/huffmantree
import listpolyfill, lzssnode
const maxChainByteLength = 32_000 * wordBitLength
type LzssChain* =
SinglyLinkedList[LzssNode]
proc lzssChain*(): LzssChain =
initSinglyLinkedList[LzssNode]()
proc decode*(lzssChain: LzssChain): seq[uint8] =
result = newSeqOfCap[uint8](maxChainByteLength)
for node in lzssChain.items:
case node.kind:
of character:
result.add(node.character)
of reference:
let absolutePos = result.len - node.relativePos
result.add(result.toOpenArray(absolutePos, absolutePos + node.length - 1))
proc stats*(lzssChain: LzssChain): tuple[characters: CountTableRef[uint8], lengths, positions: CountTableRef[int]] =
result = (newCountTable[uint8](), newCountTable[int](), newCountTable[int]())
for node in lzssChain.items:
case node.kind:
of character:
result.characters.inc(node.character)
of reference:
result.lengths.inc(node.length)
result.positions.inc(node.relativePos)
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