rosapps/dflat32/huffc.c

   1 /* ------------------- huffc.c -------------------- */
   2
   3 #include "dflat.h"
   4 #include "htree.h"
   5
   6 extern struct DfHTree *ht;
   7 extern int root;
   8 extern int treect;
   9 static int lastchar = '\n';
  10
  11 static void compress(FILE *, int, int);
  12 static void outbit(FILE *fo, int bit);
  13
  14 static int fgetcx(FILE *fi)
  15 {
  16     int c;
  17
  18     /* ------- bypass comments ------- */
  19     if ((c = fgetc(fi)) == ';' && lastchar == '\n')
  20         do    {
  21             while (c != '\n' && c != EOF)
  22                 c = fgetc(fi);
  23         } while (c == ';');
  24     lastchar = c;
  25     return c;
  26 }
  27
  28 void main(int argc, char *argv[])
  29 {
  30     FILE *fi, *fo;
  31     int c;
  32     DF_BYTECOUNTER bytectr = 0;
  33
  34     if (argc < 3)   {
  35         printf("\nusage: huffc infile outfile");
  36         exit(1);
  37     }
  38
  39     if ((fi = fopen(argv[1], "rb")) == NULL)    {
  40         printf("\nCannot open %s", argv[1]);
  41         exit(1);
  42     }
  43     if ((fo = fopen(argv[2], "wb")) == NULL)    {
  44         printf("\nCannot open %s", argv[2]);
  45         fclose(fi);
  46         exit(1);
  47     }
  48
  49     ht = calloc(256, sizeof(struct DfHTree));
  50
  51     /* - read the input file and count character frequency - */
  52     while ((c = fgetcx(fi)) != EOF)   {
  53         c &= 255;
  54         ht[c].cnt++;
  55         bytectr++;
  56     }
  57
  58     /* ---- build the huffman tree ---- */
  59     DfBuildTree();
  60
  61     /* --- write the byte count to the output file --- */
  62     fwrite(&bytectr, sizeof bytectr, 1, fo);
  63
  64     /* --- write the tree count to the output file --- */
  65     fwrite(&treect, sizeof treect, 1, fo);
  66
  67     /* --- write the root offset to the output file --- */
  68     fwrite(&root, sizeof root, 1, fo);
  69
  70     /* -- write the tree to the output file -- */
  71     for (c = 256; c < treect; c++)   {
  72         int lf = ht[c].left;
  73         int rt = ht[c].right;
  74         fwrite(&lf, sizeof lf, 1, fo);
  75         fwrite(&rt, sizeof rt, 1, fo);
  76     }
  77
  78     /* ------ compress the file ------ */
  79     fseek(fi, 0L, 0);
  80     while ((c = fgetcx(fi)) != EOF)
  81         compress(fo, (c & 255), 0);
  82     outbit(fo, -1);
  83     fclose(fi);
  84     fclose(fo);
  85     free(ht);
  86     exit(0);
  87 }
  88
  89 /* ---- compress a character value into a bit stream ---- */
  90 static void compress(FILE *fo, int h, int child)
  91 {
  92     if (ht[h].parent != -1)
  93         compress(fo, ht[h].parent, h);
  94     if (child)  {
  95         if (child == ht[h].right)
  96             outbit(fo, 0);
  97         else if (child == ht[h].left)
  98             outbit(fo, 1);
  99     }
 100 }
 101
 102 static char out8;
 103 static int ct8;
 104
 105 /* -- collect and write bits to the compressed output file -- */
 106 static void outbit(FILE *fo, int bit)
 107 {
 108     if (ct8 == 8 || bit == -1)  {
 109         while (ct8 < 8)    {
 110             out8 <<= 1;
 111             ct8++;
 112         }
 113         fputc(out8, fo);
 114         ct8 = 0;
 115     }
 116     out8 = (out8 << 1) | bit;
 117     ct8++;
 118 }