add huffman tree structure and serialisation

2 files changed, 78 insertions, 0 deletions

diff --git a/tests/thuffmantree.nim b/tests/thuffmantree.nim
new file mode 100644
index 0000000..ec40bdb
--- /dev/null
+++ b/tests/thuffmantree.nim
@@ -0,0 +1,74 @@
+# 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 unittest, streams
+import bitreader, bitwriter, huffmantree
+
+suite "huffmantree":
+  let tree = huffmanBranch(
+    huffmanLeaf(1'u),
+    huffmanBranch(
+      huffmanLeaf(2'u),
+      huffmanLeaf(3'u)))
+
+  test "equality":
+    check huffmanLeaf(12'u) == huffmanLeaf(12'u)
+    check huffmanLeaf(12'u) != huffmanLeaf(21'u)
+    check huffmanLeaf(12'u) != huffmanBranch(huffmanLeaf(12'u), huffmanLeaf(12'u))
+    check huffmanBranch(huffmanLeaf(12'u), huffmanLeaf(21'u)) == huffmanBranch(huffmanLeaf(12'u), huffmanLeaf(21'u))
+    check huffmanBranch(huffmanLeaf(12'u), huffmanLeaf(21'u)) != huffmanBranch(huffmanLeaf(12'u), huffmanLeaf(1'u))
+    check tree == tree
+
+  test "maxValue":
+    check tree.maxValue() == 3
+
+  test "deserialise":
+    let stream = newStringStream()
+    defer: stream.close()
+    let bitWriter = stream.bitWriter()
+    bitWriter.writeBits(valueLengthFieldBitLength, 2'u8)
+    bitWriter.writeBool(false)   # root
+    bitWriter.writeBool(true)    # 1 leaf
+    bitWriter.writeBits(2, 1'u)
+    bitWriter.writeBool(false)   # right branch
+    bitWriter.writeBool(true)    # 2 leaf
+    bitWriter.writeBits(2, 2'u)
+    bitWriter.writeBool(true)    # 3 leaf
+    bitWriter.writeBits(2, 3'u)
+    bitWriter.flush()
+
+    stream.setPosition(0)
+    let bitReader = stream.bitReader()
+    check huffmantree.deserialise(bitReader, uint) == tree
+
+  test "serialise":
+    let stream = newStringStream()
+    defer: stream.close()
+    let bitWriter = stream.bitWriter()
+    tree.serialise(bitWriter)
+    bitWriter.flush()
+
+    stream.setPosition(0)
+    let bitReader = stream.bitReader()
+    check bitReader.readBits(valueLengthFieldBitLength, uint8) == 2
+    check bitReader.readBool() == false  # root
+    check bitReader.readBool() == true   # 1 leaf
+    check bitReader.readBits(2, uint8) == 1
+    check bitReader.readBool() == false  # right branch
+    check bitReader.readBool() == true   # 2 leaf
+    check bitReader.readBits(2, uint8) == 2
+    check bitReader.readBool() == true   # 3 leaf
+    check bitReader.readBits(2, uint8) == 3
diff --git a/tests/tintegers.nim b/tests/tintegers.nim
index 956e4aa..851e926 100644
--- a/tests/tintegers.nim
+++ b/tests/tintegers.nim
@@ -27,6 +27,10 @@ suite "integers":
     check truncateToUint8(0x00FA'u16) == 0xFA'u8
     check truncateToUint8(0xFFFA'u16) == 0xFA'u8
 
+  test "bitLength":
+    check bitLength(0b1_1111) == 5
+    check bitLength(0b1000_0000) == 8
+
   test "leastSignificantBits":
     check leastSignificantBits(0xFF'u8, 3) == 0b0000_0111'u8
     check leastSignificantBits(0b0001_0101'u8, 3) == 0b0000_0101'u8