getdecode.cpp

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/*
NOTICE

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Software solely for the purpose of accessing the MOC Data; (ii) to modify
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of accessing the MOC Data.  In addition, you may distribute the Software,
including any modifications thereof, solely for use with the MOC Data,
provided that (i) you must include this notice with all copies of the
Software to be distributed; (ii) you may not remove or alter any
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third party for the Software; and (iv) you will not export the Software
without the appropriate United States and foreign government licenses.

You acknowledge that no title to the intellectual property in the Software
is transferred to you.  You further acknowledge that title and full
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Copyright (C) 1999 Malin Space Science Systems.  All Rights Reserved.
*/
//static char *sccsid = "@(#)getdecode.c  1.1 10/04/99";

/*
    Huffman code tree module
    Mike Caplinger, MOC GDS Design Scientist
    SCCS @(#)getdecode.c  1.1 11/19/91

    This module manages the Ligocki-style Huffman decoding trees for
    the predictive decompressor.  It is a little roundabout in that
    it builds a Huffman code tree in node form from the flight software
    encoding tables and then "tablefies" it; that way, separate decoding
    tables don't have to be maintained.  One can also just load an
    existing decode file in (for testing.)

    This will probably all go away if the clean canonical decompressor
    is ever written.
*/

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

#include "fs.h"

#define DEFINE_CODE_TABLES
#include "fs.h"
#include "predcode.h"

typedef struct ht_node {
  int value;
  struct ht_node *zero, *one;
} Huffman_node;

/* in TJL terminology, left is 0 and right is 1. */
extern uint8 code[], left[], right[];

void decodeLoad(char *decodefile)
{
  unsigned int decodeSize;
  FILE *fd;

  if((fd = fopen(decodefile, "r")) == NULL) {
    (void)fprintf(stderr, "Unable to open '%s' for reading\n",
                  decodefile);
    exit(1);
  }

  if(fread((char *)(&decodeSize), sizeof(decodeSize), 1, fd) != 1) {
    fprintf(stderr, "Unable to read decode file, '%s'\n", decodefile);
    exit(1);
  }

  if(fread(code, sizeof(code[0]), decodeSize, fd) != decodeSize) {
    fprintf(stderr, "Unable to read decode file, '%s'\n", decodefile);
    exit(1);
  }

  if(fread(left, sizeof(left[0]), decodeSize, fd) != decodeSize) {
    fprintf(stderr, "Unable to read decode file, '%s'\n", decodefile);
    exit(1);
  }

  if(fread(right, sizeof(right[0]), decodeSize, fd) != decodeSize) {
    fprintf(stderr, "Unable to read decode file, '%s'\n", decodefile);
    exit(1);
  }

  (void)fclose(fd);
}

Huffman_node *ht_insert(Huffman_node *root, int value, int code, int len)
{
  int bit;
  Huffman_node **branch;

  if(!root) {
    root = (Huffman_node *) malloc(sizeof(Huffman_node));
    root->value = 0;
    root->zero = root->one = NULL;
  }

  if(len == 0) {
    root->value = value;
  }
  else {
    bit = code & 0x1;
    if(bit == 0) branch = &root->zero;
    else branch = &root->one;

    if(*branch == 0) {
      *branch = (Huffman_node *) malloc(sizeof(Huffman_node));
      (*branch)->value = 0;
      (*branch)->zero = 0;
      (*branch)->one = 0;
    }
    ht_insert(*branch, value, code >> 1, len - 1);
  }
  return root;
}

int ht_lookup(Huffman_node *root, int code, int len)
{
  int bit;

  if(root->zero == 0 && root->one == 0) return root->value;
  bit = code & 1;
  if(bit == 0) return ht_lookup(root->zero, code >> 1, len - 1);
  else return ht_lookup(root->one, code >> 1, len - 1);
}

void ht_dump(Huffman_node *root, int code, int len)
{
  if(root->zero == 0 && root->one == 0) {
    printf("%d %x(%d)\n", root->value, code, len);
  }
  else {
    if(root->zero) {
      ht_dump(root->zero, code, len + 1);
    }
    if(root->one) {
      ht_dump(root->one, code | (1 << len), len + 1);
    }
  }
}

#define ZERO (1<<0)
#define ONE (1<<1)

/*
    Convert a Huffman tree to TJL table form. Call initially
    with index = 0.
*/
int ht_tablefy(Huffman_node *root, unsigned char *flags, unsigned char *zero, unsigned char *one, unsigned char *index)
{
  int local_index = (int)(long)(index);

  if(root->zero) {
    if(root->zero->zero == 0 && root->zero->one == 0) {
      flags[(int)(long)index] &= ~ZERO;
      zero[(int)(long)index] = root->zero->value;
    }
    else {
      flags[local_index] |= ZERO;
      index += 1;
      zero[local_index] = (char)(long)index;
      index = (unsigned char*)(long)ht_tablefy(root->zero, flags, zero, one, index);
    }
  }
  if(root->one) {
    if(root->one->zero == 0 && root->one->one == 0) {
      flags[local_index] &= ~ONE;
      one[local_index] = root->one->value;
    }
    else {
      flags[local_index] |= ONE;
      index += 1;
      one[local_index] = (char)(long)index;
      index = (unsigned char*)(long)ht_tablefy(root->one, flags, zero, one, index);
    }
  }
  return (int)(long)index;
}

Huffman_node *ht_tree_gen(int i)
{
  Huffman_node *tree = 0;
  uint16 *code;
  uint8 *len;
  uint8 *requant;

  code = CodeBitsVec[i];
  len = CodeLenVec[i];
  requant = CodeRequantVec[i];

  tree = ht_insert(tree, requant[0], code[0], len[0]);

  for(i = 1; i < 128; i++) {
    if(requant[i] != requant[i-1])
      tree = ht_insert(tree, requant[i], code[i], len[i]);
  }

  tree = ht_insert(tree, requant[255], code[255], len[255]);

  for(i = 254; i >= 128; i--) {
    if(requant[i] != requant[i+1])
      tree = ht_insert(tree, requant[i], code[i], len[i]);
  }
  return tree;
}

void ht_free(Huffman_node *root)
{
  if(root->zero) ht_free(root->zero);
  if(root->one) ht_free(root->one);
  free(root);
}

void decodeInit(int n) {
  Huffman_node *tree = 0;
//  uint8 flags[256], zero[256], one[256];

  tree = ht_tree_gen(n);
  /* i is the # of slots actually used... */
  ht_tablefy(tree, code, left, right, 0);
  ht_free(tree);
}