add huffman decoder

1 files changed, 34 insertions, 0 deletions

diff --git a/src/huffmandecoder.nim b/src/huffmandecoder.nim
new file mode 100644
index 0000000..4df712a
--- /dev/null
+++ b/src/huffmandecoder.nim
@@ -0,0 +1,34 @@
+# 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 huffmantree, bitreader
+
+type HuffmanDecoder*[T: SomeUnsignedInt] = object
+  tree: HuffmanTreeNode[T]
+
+proc decoder*[T](tree: HuffmanTreeNode[T]): HuffmanDecoder[T] =
+  HuffmanDecoder[T](tree: tree)
+
+proc decode*[T](decoder: HuffmanDecoder[T], bitReader: BitReader): T =
+  proc walk(node: HuffmanTreeNode[T]): T =
+    case node.kind:
+      of branch:
+        case bitReader.readBool():
+          of false: walk(node.left)
+          of true: walk(node.right)
+      of leaf:
+        node.value
+  walk(decoder.tree)