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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 tables
import ../bitio/integers, ../bitio/bitwriter
import huffmantree
type HuffmanEncoder*[T, U: SomeUnsignedInt] = object
codebook: TableRef[T, tuple[bitLength: int, value: U]]
proc buildCodebook*[T, U](tree: HuffmanTreeNode[T], codeType: typedesc[U]): TableRef[T, tuple[bitLength: int, value: U]] =
var codebook = newTable[T, tuple[bitLength: int, value: U]]()
proc addCode(node: HuffmanTreeNode[T], path: U, depth: int) =
case node.kind:
of branch:
addCode(node.left, path, depth + 1)
addCode(node.right, path or (1.U shl depth), depth + 1)
of leaf:
codebook[node.value] = (depth, path)
addCode(tree, 0.U, 0)
codebook
proc encoder*[T, U](tree: HuffmanTreeNode[T], codeType: typedesc[U]): HuffmanEncoder[T, U] =
HuffmanEncoder[T, U](codebook: buildCodebook(tree, codeType))
proc encode*[T, U](decoder: HuffmanEncoder[T, U], value: T): tuple[bitLength: int, value: U] =
decoder.codebook[value]
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