From 6d779d8606daf97f44dc13a89a78d1389d03f96b Mon Sep 17 00:00:00 2001
From: Phuntsok Drak-pa <phundrak@phundrak.fr>
Date: Sat, 9 Jun 2018 03:18:28 +0200
Subject: [PATCH] Changed file writing method to dynamic bit-packing

---
 src/bitpack.cc |  2 +-
 src/bitpack.hh |  3 +++
 src/io.cc      | 22 ++++++----------------
 3 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/src/bitpack.cc b/src/bitpack.cc
index e8934f6..cad6111 100644
--- a/src/bitpack.cc
+++ b/src/bitpack.cc
@@ -40,7 +40,7 @@ vuchar pack_n(const vuint16::const_iterator t_input_begin,
   vuchar ret{};
 
   // max value with current number of bits + 1
-  const int max_value = ipow(2, t_n);
+  const int max_value = ipow(2, t_n) - 1;
 
   uchar current_char = 0;
   int step = t_n / 8;
diff --git a/src/bitpack.hh b/src/bitpack.hh
index f47bf7d..c061bc7 100644
--- a/src/bitpack.hh
+++ b/src/bitpack.hh
@@ -19,4 +19,7 @@ std::vector<unsigned char>
 pack_16(const std::vector<std::uint16_t>::const_iterator,
         const std::vector<std::uint16_t>::const_iterator);
 
+/// \brief Bat-packs the input dynamically
+std::vector<unsigned char> pack(const std::vector<std::uint16_t>);
+
 #endif /* LZW_SRC_BITPACK_H_ */
diff --git a/src/io.cc b/src/io.cc
index dce2531..0b3ec0e 100644
--- a/src/io.cc
+++ b/src/io.cc
@@ -4,7 +4,9 @@
  */
 
 #include "io.hh"
+#include "bitpack.hh"
 #include <array>
+#include <algorithm>
 
 #ifdef Debug
 constexpr bool debug_mode = true;
@@ -71,21 +73,9 @@ void write_file(FILE *const t_out, const vvuint16 &t_text) {
  *  \param t_chunk Chunk to be written to \p t_out
  */
 void write_chunk(FILE *const t_out, const vuint16 &t_chunk) {
-  const auto chunk_size = static_cast<uint16_t>(t_chunk.size());
+  const auto output = pack(t_chunk);
+  const auto chunk_size = static_cast<uint16_t>(output.size());
   fwrite(&chunk_size, sizeof(chunk_size), 1, t_out);
-  std::array<unsigned char, 3> data = {0, 0, 0};
-  for (size_t i = 0; i < t_chunk.size(); ++i) {
-    if (i % 2 == 0) {
-      data[0] = static_cast<unsigned char>(t_chunk[i] >> 4);
-      data[1] = static_cast<unsigned char>(t_chunk[i] << 4);
-    } else {
-      data[1] |= static_cast<unsigned char>(t_chunk[i] >> 8) & 0xC;
-      data[2] = static_cast<unsigned char>(t_chunk[i]);
-      fwrite(data.data(), sizeof(data[0]), 3, t_out);
-      data.fill(0);
-    }
-  }
-  if (t_chunk.size() % 2 != 0) {
-    fwrite(data.data(), sizeof(data[0]), 3, t_out);
-  }
+  fwrite((const char *)(output.data()), sizeof(output[0]), output.size(),
+         t_out);
 }