Сжатие по Хаффману

Исходный код реализации алгоритма сжатия по Хаффману (Visual C++) - скачать.

Алгоритм Хаффмана - теория.

Исходный код реализации алгоритма сжатия по Хаффману

// Huffman.cpp 

#include <stdio.h>
#include <stdlib.h>


short           father[512];
unsigned short  code[256], heap_length;
unsigned long   compress_charcount, file_size, heap[257];
unsigned char   code_length[256];
long            frequency_count[512]; // встречаемость символов
short           decomp_tree[512]; // дерево декодирования

FILE            *ifile, *ofile; // входной и выходной файлы

//=========================================================
/* ФУНКЦИИ ДЛЯ КОМПРЕССИИ */

//---------------------------------------------------------
// реорганизация структкры heap
void reheap (unsigned short heap_entry)
{
 register unsigned short  index;
 register unsigned short  flag = 1;

 unsigned long   heap_value;

 heap_value = heap[heap_entry];

 while ((heap_entry <= (heap_length >> 1)) && (flag))
 {
  index = heap_entry << 1;

  if (index < heap_length)
   if (frequency_count[heap[index]] >=
     frequency_count[heap[index+1]])
    index++;

  if (frequency_count[heap_value]
   < frequency_count[heap[index]])
   flag--;
  else
  {
   heap[heap_entry] = heap[index];
   heap_entry       = index;
  }
 }

 heap[heap_entry] = heap_value;
}
//---------------------------------------------------------
// Сжатие данных
void compress_image ()
{
 register unsigned int    thebyte = 0;
 register short           loop1;
 register unsigned short  current_code;
 register unsigned long   loop;

 unsigned short  current_length, dvalue;
 unsigned long   curbyte = 0;
 short           curbit = 7;


 for (loop = 0L; loop < file_size; loop++)
 {
  dvalue         = (unsigned short) getc (ifile);
  current_code   = code[dvalue];
  current_length = (unsigned short) code_length[dvalue];

  for (loop1 = current_length-1; loop1 >= 0; --loop1)
  {
   if ((current_code >> loop1) & 1)
    thebyte |= (char) (1 << curbit);

   if (--curbit < 0)
   {
    putc (thebyte, ofile);
    thebyte = 0;
    curbyte++;
    curbit = 7;
   }
  }
 }
 putc (thebyte, ofile);
 compress_charcount = ++curbyte;
}
//---------------------------------------------------------
// Генерация таблицы кодирования
unsigned short  generate_code_table ()
{
 register unsigned short  loop;
 register unsigned short  current_length;
 register unsigned short  current_bit;

 unsigned short  bitcode;
 short           parent;

 for (loop = 0; loop < 256; loop++)
  if (frequency_count[loop])
  {
   current_length = bitcode = 0;
   current_bit = 1;
   parent = father[loop];

   while (parent)
   {
    if (parent < 0)
    {
     bitcode += current_bit;
     parent = -parent;
    }
    parent = father[parent];
    current_bit <<= 1;
    current_length++;
   }

   code[loop] = bitcode;

   if (current_length > 16)
    return (0);
   else
    code_length[loop] = (unsigned char) current_length;
  }
  else
   code[loop] = code_length[loop] = 0;

 return (1);
}
//---------------------------------------------------------
// Построение дерева кодирования
void build_code_tree ()
{
 register unsigned short  findex;
 register unsigned long   heap_value;


 while (heap_length != 1)
 {
  heap_value = heap[1];
  heap[1]    = heap[heap_length--];

  reheap (1);
  findex = heap_length + 255;

  frequency_count[findex] = frequency_count[heap[1]] +
                                frequency_count[heap_value];
  father[heap_value] =  findex;
  father[heap[1]]    = -findex;
  heap[1]            =  findex;

  reheap (1);
 }

 father[256] = 0;
}
//---------------------------------------------------------
// построение heap'а по частотам встречаемости при инициализации
void build_initial_heap ()
{
 register unsigned short  loop;
 heap_length = 0;

 for (loop = 0; loop < 256; loop++)
  if (frequency_count[loop])
   heap[++heap_length] = (unsigned long) loop;

 for (loop = heap_length; loop > 0; loop--)
  reheap (loop);
}
//---------------------------------------------------------
// подсчет количества встречаемости каждого символа
void get_frequency_count ()
{
 register unsigned long  loop;

 for (loop = 0; loop < file_size; loop++)
  frequency_count[getc (ifile)]++;
}
//=========================================================
/* ФУНКЦИИ ДЛЯ КОМПРЕССИИ */

//---------------------------------------------------------
// Построение дерева декомпрессии
void  build_decomp_tree ()
{
 register unsigned short  loop1;
 register unsigned short  current_index;

 unsigned short  loop;
 unsigned short  current_node = 1;

 decomp_tree[1] = 1;

 for (loop = 0; loop < 256; loop++)
 {
  if (code_length[loop])
  {
   current_index = 1;
   for (loop1 = code_length[loop] - 1; loop1 > 0; loop1--)
   {
    current_index = (decomp_tree[current_index] << 1) +
     ((code[loop] >> loop1) & 1);
    if (!(decomp_tree[current_index]))
     decomp_tree[current_index] = ++current_node;
   }
   decomp_tree[(decomp_tree[current_index] << 1) +
   (code[loop] & 1)] = -loop;
  }
 }
}
//---------------------------------------------------------
// декомпрессия данных
void  decompress_image ()
{
 register unsigned short  cindex = 1;
 register char            curchar;
 register short           bitshift;

 unsigned long  charcount = 0L;


 while (charcount < file_size)
 {
  curchar = (char) getc (ifile);

  for (bitshift = 7; bitshift >= 0; --bitshift)
  {
   cindex = (cindex << 1) + ((curchar >> bitshift) & 1);

   if (decomp_tree[cindex] <= 0)
   {
    putc ((int) (-decomp_tree[cindex]), ofile);

    if ((++charcount) == file_size)
     bitshift = 0;
    else
     cindex = 1;
   }
   else
    cindex = decomp_tree[cindex];
  }
 }
}
//=========================================================
// компрессия файла
void Encode()
{
 fseek (ifile, 0L, 2);
 file_size = (unsigned long) ftell (ifile);
 fseek (ifile, 0L, 0);
 get_frequency_count ();
 build_initial_heap ();
 build_code_tree ();
 if (!generate_code_table ())
  printf ("ERROR!  Code value out of range. Cannot compress.\n");
 else
 {
  fwrite (&file_size, sizeof (file_size), 1, ofile);
  fwrite (code, 2, 256, ofile);
  fwrite (code_length, 1, 256, ofile);
  fseek (ifile, 0L, 0);
  compress_image ();
 };
}
//=========================================================
// декомпрессия файла
void Decode()
{
 fread (&file_size, sizeof (file_size), 1, ifile);
 fread (code, 2, 256, ifile);
 fread (code_length, 1, 256, ifile);
 build_decomp_tree ();
 decompress_image();
 fclose (ofile);
        
}
//=========================================================
// главная функция
int _tmain(int argc, _TCHAR* argv[])
{
 // проверка аргументов
 if (argc < 4 || argc > 4)
 {
  printf("Usage: Huffman e(encode)|d(decode) infile outfile\n");
  return -1;
 }
      
 // открытие входного файла
 if ((ifile = fopen (argv[2], "rb")) == NULL)
 {
  printf("Error input file.\n");
  return -1;
 };

 // открытие выходного файла
 if ((ofile = fopen (argv[3], "wb")) == NULL)
 {
  printf("Error output file.\n");
  fclose (ifile);
  return -1;
 };

 if (tolower(argv [1] [0]) == 'e')
  Encode (); // коппрессия
 else if (tolower(argv [1] [0]) == 'd')
  Decode (); // декомпрессия
  
 fclose (ofile);
 fclose (ifile);

 return 0;

}