Добавлена четвертая задача пятой главы

Занимательное программирование/5/4_sound/main.cpp

@@ -0,0 +1,157 @@
+#include <iostream>
+#include <fstream>
+#include <cstring>
+#include <array>
+#include <list>
+#include <vector>
+#include <cstdint>
+#include <sstream>
+#include "huffman.hpp"
+
+int show_usage()
+{
+    std::cerr << "Usage: sound (compress|decompress) input_file output_file." << std::endl;
+    return 1;
+}
+
+std::array<char, 44> read_header(std::ifstream& input_file)
+{
+    std::array<char, 44> wav_header;
+
+    input_file.read(wav_header.data(), wav_header.size());
+
+    return wav_header;
+}
+
+std::list<char> read_first_context(std::istreambuf_iterator<char>& input_iterator)
+{
+    std::list<char> result;
+
+    result.push_back(*input_iterator);
+    ++input_iterator;
+    result.push_back(*input_iterator);
+    ++input_iterator;
+
+    return result;
+}
+
+int fc(const std::list<char>& context)
+{
+    auto c1 = context.front();
+    auto c2 = context.back();
+
+    return c1 + (c1 - c2);
+}
+
+int archive(const char *input_name, const char *output_name)
+{
+    std::ifstream input_file{ input_name, std::ios::binary | std::ios::in };
+    input_file.exceptions(std::ios::badbit | std::ios::failbit);
+
+    std::array<char, 44> wav_header = read_header(input_file);
+
+    if (input_file.gcount() != 44)
+    {
+        // Not enough bytes available to read the header.
+        return 2;
+    }
+    std::istreambuf_iterator<char> wav_iterator(input_file), input_end;
+    std::list<char> context = read_first_context(wav_iterator);
+
+    std::ofstream output_file{ output_name, std::ios::binary | std::ios::trunc | std::ios::in };
+    output_file.exceptions(std::ios::badbit | std::ios::failbit);
+
+    output_file.write(wav_header.data(), wav_header.size());
+    output_file.write(&context.front(), 1);
+    output_file.write(&context.back(), 1);
+
+    std::vector<std::uint8_t> encoding;
+
+    while (wav_iterator != input_end)
+    {
+        int guess = fc(context);
+        int error = *wav_iterator - guess;
+
+        // Update the context.
+        context.pop_back();
+        context.push_back(*wav_iterator);
+
+        encoding.push_back(error >> 8);
+        encoding.push_back(error);
+
+        ++wav_iterator;
+    }
+    compress(encoding, output_file);
+    return 0;
+}
+
+int unarchive(const char *input_name, const char *output_name)
+{
+    std::ifstream input_file{ input_name, std::ios::binary | std::ios::in };
+    input_file.exceptions(std::ios::badbit | std::ios::failbit);
+
+    std::array<char, 44> wav_header = read_header(input_file);
+
+    if (input_file.gcount() != 44)
+    {
+        // Not enough bytes available to read the header.
+        return 2;
+    }
+    std::istreambuf_iterator<char> wav_iterator(input_file), input_end;
+    std::list<char> context = read_first_context(wav_iterator);
+    std::stringstream encoding_stream;
+    std::vector<std::uint8_t> encoded_wav{ wav_iterator, input_end };
+
+    decompress(encoded_wav, encoding_stream);
+
+    std::ofstream output_file{ output_name, std::ios::binary | std::ios::trunc | std::ios::in };
+    output_file.exceptions(std::ios::badbit | std::ios::failbit);
+
+    output_file.write(wav_header.data(), wav_header.size());
+    output_file.write(&context.front(), 1);
+    output_file.write(&context.back(), 1);
+
+    std::string encoding = encoding_stream.str();
+    auto current_encoding = std::cbegin(encoding);
+
+    while (current_encoding != std::cend(encoding))
+    {
+        std::uint8_t first_byte = *current_encoding;
+        ++current_encoding;
+        std::uint8_t second_byte = *current_encoding;
+        ++current_encoding;
+        int error = (first_byte << 8) | second_byte;
+
+        int guess = fc(context);
+        char element = error + guess;
+
+        // Update the context.
+        context.pop_back();
+        context.push_back(element);
+
+        output_file.write(&element, 1);
+    }
+
+    return 0;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 4)
+    {
+        return show_usage();
+    }
+    if (std::strcmp(argv[1], "compress") == 0)
+    {
+        return archive(argv[2], argv[3]);
+    }
+    else if (std::strcmp(argv[1], "decompress") == 0)
+    {
+        return unarchive(argv[2], argv[3]);
+    }
+    else
+    {
+        return show_usage();
+    }
+    return 0;
+}