1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
# 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, heapqueue
import huffmantree, lzssencoder
type WeighedHuffmanTreeNode[T] = ref object
weight: int
huffmanTreeNode: HuffmanTreeNode[T]
proc weighedHuffmanBranch[T](left, right: WeighedHuffmanTreeNode[T]): WeighedHuffmanTreeNode[T] =
WeighedHuffmanTreeNode[T](
weight: left.weight + right.weight,
huffmanTreeNode: huffmanBranch(left.huffmanTreeNode, right.huffmanTreeNode))
proc weighedHuffmanLeaf[T](value: T, weight: int): WeighedHuffmanTreeNode[T] =
WeighedHuffmanTreeNode[T](
weight: weight,
huffmanTreeNode: huffmanLeaf(value))
proc `<`*[T](left, right: WeighedHuffmanTreeNode[T]): bool =
left.weight < right.weight
proc symbolQueue[T](stats: CountTableRef[T]): HeapQueue[WeighedHuffmanTreeNode[T]] =
result = newHeapQueue[WeighedHuffmanTreeNode[T]]()
for item, count in stats.pairs: result.push(weighedHuffmanLeaf(item, count))
proc buildHuffmanTree*[T: SomeUnsignedInt](stats: CountTableRef[T]): HuffmanTreeNode[T] =
var symbolQueue = symbolQueue(stats)
while symbolQueue.len > 1: symbolQueue.push(weighedHuffmanBranch(symbolQueue.pop(), symbolQueue.pop()))
symbolQueue[0].huffmanTreeNode
|