Descent3/czip/HuffmanBasic.cpp

/*
 * $Logfile: /DescentIII/Main/czip/HuffmanBasic.cpp $
 * $Revision: 2 $
 * $Date: 8/27/98 3:26p $
 * $Author: Jeff $
 *
 * Basic Huffman compression functions
 *
 * $Log: /DescentIII/Main/czip/HuffmanBasic.cpp $
 *
 * 2     8/27/98 3:26p Jeff
 * intial creation
 *
 * 1     8/27/98 3:26p Jeff
 *
 * $NoKeywords: $
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "CZip.h"

#define END_OF_STREAM 256

int CZip::hb_CompressFile(tVirtualFile *input, BITFILE *output) {
  ulong *counts;
  tH0Node *nodes;
  tH0Code *codes;
  int root_node;

  int original_pos = VFtell(output->file);

  counts = (ulong *)malloc(256 * sizeof(ulong));
  if (!counts)
    return -1;
  if ((nodes = (tH0Node *)malloc(514 * sizeof(tH0Node))) == NULL) {
    free(counts);
    return -1;
  }
  if ((codes = (tH0Code *)malloc(257 * sizeof(tH0Code))) == NULL) {
    free(counts);
    free(nodes);
    return -1;
  }

  memset(counts, 0, 256 * sizeof(ulong));
  memset(nodes, 0, 514 * sizeof(tH0Node));
  memset(codes, 0, 257 * sizeof(tH0Code));

  hb_count_bytes(input, counts);
  hb_scale_counts(counts, nodes);
  hb_output_counts(output, nodes);
  root_node = hb_build_tree(nodes);
  hb_convert_tree_to_code(nodes, codes, 0, 0, root_node);
  hb_compress_data(input, output, codes);
  free(counts);
  free(nodes);
  free(codes);
  FlushOutputBitFile(output);

  int compsize = VFtell(output->file) - original_pos;
  return compsize;
}

bool CZip::hb_ExpandFile(BITFILE *input, tVirtualFile *output) {
  tH0Node *nodes;
  int root_node;

  if ((nodes = (tH0Node *)malloc(514 * sizeof(tH0Node))) == NULL)
    return false;
  memset(nodes, 0, sizeof(tH0Node) * 514);
  hb_input_counts(input, nodes);
  root_node = hb_build_tree(nodes);
  hb_expand_data(input, output, nodes, root_node);
  free(nodes);
  return true;
}

void CZip::hb_output_counts(BITFILE *output, tH0Node *nodes) {
  int first, last, next, i;

  first = 0;
  while (first < 255 && nodes[first].count == 0)
    first++;

  for (; first < 256; first = next) {
    last = first + 1;
    for (;;) {
      for (; last < 256; last++)
        if (nodes[last].count == 0)
          break;
      last--;
      for (next = last + 1; next < 256; next++)
        if (nodes[next].count != 0)
          break;
      if (next > 255)
        break;
      if ((next - last) > 3)
        break;
      last = next;
    }

    if (VFputc(first, output->file) != first) {
      // fatal error
    }
    if (VFputc(last, output->file) != last) {
      // fatal error
    }
    for (i = first; i <= last; i++) {
      if (VFputc(nodes[i].count, output->file) != (int)nodes[i].count) {
        // fatal error
      }
    }
  }
  if (VFputc(0, output->file) != 0) {
    // fatal error
  }
}

void CZip::hb_input_counts(BITFILE *input, tH0Node *nodes) {
  int first;
  int last;
  int i;
  int c;

  for (i = 0; i < 256; i++)
    nodes[i].count = 0;
  if ((first = VFgetc(input->file)) == EOF) {
    //	fatal_error( "Error reading byte counts\n" );
  }
  if ((last = VFgetc(input->file)) == EOF) {
    // fatal_error( "Error reading byte counts\n" );
  }
  for (;;) {
    for (i = first; i <= last; i++)
      if ((c = VFgetc(input->file)) == EOF) {
        //	fatal_error( "Error reading byte counts\n" );
      } else
        nodes[i].count = (unsigned int)c;
    if ((first = VFgetc(input->file)) == EOF) {
      //   fatal_error( "Error reading byte counts\n" );
    }
    if (first == 0)
      break;
    if ((last = VFgetc(input->file)) == EOF) {
      //   fatal_error( "Error reading byte counts\n" );
    }
  }
  nodes[END_OF_STREAM].count = 1;
}

void CZip::hb_count_bytes(tVirtualFile *input, ulong *counts) {
  long input_marker;
  int c;

  input_marker = VFtell(input);
  while ((c = VFgetc(input)) != EOF)
    counts[c]++;
  VFseek(input, input_marker, SEEK_SET);
}

void CZip::hb_scale_counts(ulong *counts, tH0Node *nodes) {
  ulong max_count;
  int i;

  max_count = 0;
  for (i = 0; i < 256; i++)
    if (counts[i] > max_count)
      max_count = counts[i];
  if (max_count == 0) {
    counts[0] = 1;
    max_count = 1;
  }
  max_count = max_count / 255;
  max_count = max_count + 1;
  for (i = 0; i < 256; i++) {
    nodes[i].count = (uint)(counts[i] / max_count);
    if (nodes[i].count == 0 && counts[i] != 0)
      nodes[i].count = 1;
  }
  nodes[END_OF_STREAM].count = 1;
}

int CZip::hb_build_tree(tH0Node *nodes) {
  int next_free;
  int i;
  int min_1;
  int min_2;

  nodes[513].count = 0xffff;
  for (next_free = END_OF_STREAM + 1;; next_free++) {
    min_1 = 513;
    min_2 = 513;
    for (i = 0; i < next_free; i++)
      if (nodes[i].count != 0) {
        if (nodes[i].count < nodes[min_1].count) {
          min_2 = min_1;
          min_1 = i;
        } else if (nodes[i].count < nodes[min_2].count)
          min_2 = i;
      }
    if (min_2 == 513)
      break;

    nodes[next_free].count = nodes[min_1].count + nodes[min_2].count;
    nodes[min_1].saved_count = nodes[min_1].count;
    nodes[min_1].count = 0;
    nodes[min_2].saved_count = nodes[min_2].count;
    nodes[min_2].count = 0;
    nodes[next_free].child0 = min_1;
    nodes[next_free].child1 = min_2;
  }
  next_free--;
  nodes[next_free].saved_count = nodes[next_free].count;
  return (next_free);
}

void CZip::hb_convert_tree_to_code(tH0Node *nodes, tH0Code *codes, uint code_so_far, int bits, int node) {
  if (node <= END_OF_STREAM) {
    codes[node].code = code_so_far;
    codes[node].code_bits = bits;
    return;
  }

  code_so_far <<= 1;
  bits++;
  hb_convert_tree_to_code(nodes, codes, code_so_far, bits, nodes[node].child0);
  hb_convert_tree_to_code(nodes, codes, code_so_far | 1, bits, nodes[node].child1);
}

void CZip::hb_compress_data(tVirtualFile *input, BITFILE *output, tH0Code *codes) {
  int c;
  while ((c = VFgetc(input)) != EOF)
    OutputBits(output, (ulong)codes[c].code, codes[c].code_bits);
  OutputBits(output, (ulong)codes[END_OF_STREAM].code, codes[END_OF_STREAM].code_bits);
}

void CZip::hb_expand_data(BITFILE *input, tVirtualFile *output, tH0Node *nodes, int root_node) {
  int node;
  for (;;) {
    node = root_node;
    do {
      if (InputBit(input))
        node = nodes[node].child1;
      else
        node = nodes[node].child0;
    } while (node > END_OF_STREAM);
    if (node == END_OF_STREAM)
      break;
    if ((VFputc(node, output)) != node) {
      // fatal error
    }
  }
}