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huf.c

/*$Source: /usr/home/dhesi/zoo/RCS/huf.c,v $*/
/*$Id: huf.c,v 1.9 91/07/09 01:39:55 dhesi Exp $*/
/***********************************************************
      huf.c -- static Huffman

Adapted from "ar" archiver written by Haruhiko Okumura.
***********************************************************/
#include "options.h"
#include "zoo.h"
#include "ar.h"
#include "lzh.h"
#include "errors.i"

extern void prterror();

#ifdef ANSI_HDRS
# include <stdlib.h>
#endif

#define NP (DICBIT + 1)
#define NT (CODE_BIT + 3)
#define PBIT 4  /* smallest integer such that (1U << PBIT) > NP */
#define TBIT 5  /* smallest integer such that (1U << TBIT) > NT */
#if NT > NP
# define NPT NT
#else
# define NPT NP
#endif

int decoded;            /* for use in decode.c */

ushort left[2 * NC - 1], right[2 * NC - 1];
static uchar *buf, c_len[NC], pt_len[NPT];
static uint   bufsiz = 0, blocksize;
static ushort c_freq[2 * NC - 1], c_table[4096], c_code[NC],
                    p_freq[2 * NP - 1], pt_table[256], pt_code[NPT],
                    t_freq[2 * NT - 1];

/***** encoding *****/

static void count_t_freq()
{
      int i, k, n, count;

      for (i = 0; i < NT; i++) t_freq[i] = 0;
      n = NC;
      while (n > 0 && c_len[n - 1] == 0) n--;
      i = 0;
      while (i < n) {
            k = c_len[i++];
            if (k == 0) {
                  count = 1;
                  while (i < n && c_len[i] == 0) {  i++;  count++;  }
                  if (count <= 2) t_freq[0] += count;
                  else if (count <= 18) t_freq[1]++;
                  else if (count == 19) {  t_freq[0]++;  t_freq[1]++;  }
                  else t_freq[2]++;
            } else t_freq[k + 2]++;
      }
}

static void write_pt_len(n, nbit, i_special)
int n;
int nbit;
int i_special;
{
      int i, k;

      while (n > 0 && pt_len[n - 1] == 0) n--;
      putbits(nbit, (uint) n);
      i = 0;
      while (i < n) {
            k = pt_len[i++];
            if (k <= 6) putbits(3, (uint) k);
            else putbits(k - 3, (uint) (((unsigned) 1 << (k - 3)) - 2));
            if (i == i_special) {
                  while (i < 6 && pt_len[i] == 0) i++;
                  putbits(2, (uint) ((i - 3) & 3));
            }
      }
}

static void write_c_len()
{
      int i, k, n, count;

      n = NC;
      while (n > 0 && c_len[n - 1] == 0) n--;
      putbits(CBIT, (uint) n);
      i = 0;
      while (i < n) {
            k = c_len[i++];
            if (k == 0) {
                  count = 1;
                  while (i < n && c_len[i] == 0) {  i++;  count++;  }
                  if (count <= 2) {
                        for (k = 0; k < count; k++)
                              putbits((int) pt_len[0], (uint) pt_code[0]);
                  } else if (count <= 18) {
                        putbits((int) pt_len[1], (uint) pt_code[1]);
                        putbits(4, (uint) (count - 3));
                  } else if (count == 19) {
                        putbits((int) pt_len[0], (uint) pt_code[0]);
                        putbits((int) pt_len[1], (uint) pt_code[1]);
                        putbits(4, 15);
                  } else {
                        putbits((int) pt_len[2], (uint) pt_code[2]);
                        putbits(CBIT, (uint) (count - 20));
                  }
            } else putbits((int) pt_len[k + 2], (uint) pt_code[k + 2]);
      }
}

static void encode_c(c)
int c;
{
      putbits((int) c_len[c], (uint) c_code[c]);
}

static void encode_p(p)
uint p;
{
      uint c, q;

      c = 0;  q = p;  while (q) {  q >>= 1;  c++;  }
      putbits((int) pt_len[c], (uint) pt_code[c]);
      if (c > 1) putbits((int) (c - 1), (uint) (p & ((unsigned) 0xFFFF >> (17 - c))));
}

static void send_block()
{
      uint i, k, flags, root, pos, size;

      root = make_tree(NC, c_freq, c_len, c_code);
      size = c_freq[root];
#if 0
      /*debug*/ (void) fprintf(stderr, "\nsize = %u\n", size);
#endif
      putbits(16, size);
      if (root >= NC) {
            count_t_freq();
            root = make_tree(NT, t_freq, pt_len, pt_code);
            if (root >= NT) {
                  write_pt_len(NT, TBIT, 3);
            } else {
                  putbits(TBIT, 0);  putbits(TBIT, root);
            }
            write_c_len();
      } else {
        putbits(TBIT, 0);  putbits(TBIT, 0);
            putbits(CBIT, 0);  putbits(CBIT, root);
      }
      root = make_tree(NP, p_freq, pt_len, pt_code);
      if (root >= NP) {
            write_pt_len(NP, PBIT, -1);
      } else {
            putbits(PBIT, 0);  putbits(PBIT, root);
      }
      pos = 0;
      for (i = 0; i < size; i++) {
            if (i % CHAR_BIT == 0) flags = buf[pos++];  else flags <<= 1;
            if (flags & ((unsigned) 1 << (CHAR_BIT - 1))) {
                  encode_c((int) (buf[pos++] + ((unsigned) 1 << CHAR_BIT)));
                  k = buf[pos++] << CHAR_BIT;  k += buf[pos++];
                  encode_p(k);
            } else encode_c((int) buf[pos++]);
            if (unpackable) return;
      }
      for (i = 0; i < NC; i++) c_freq[i] = 0;
      for (i = 0; i < NP; i++) p_freq[i] = 0;
}

static uint output_pos, output_mask;

void output(c, p)
uint c;
uint p;
{
      static uint cpos;

      if ((output_mask >>= 1) == 0) {
            output_mask = (unsigned) 1 << (CHAR_BIT - 1);
            if (output_pos >= bufsiz - 3 * CHAR_BIT) {
                  send_block();
                  if (unpackable) return;
                  output_pos = 0;
            }
            cpos = output_pos++;  buf[cpos] = 0;
      }
      buf[output_pos++] = (uchar) c;  c_freq[c]++;
      if (c >= ((unsigned) 1 << CHAR_BIT)) {
            buf[cpos] |= output_mask;
            buf[output_pos++] = (uchar)(p >> CHAR_BIT);
            buf[output_pos++] = (uchar) p;
            c = 0;  while (p) {  p >>= 1;  c++;  }
            p_freq[c]++;
      }
}

void huf_encode_start()
{
      int i;

      if (bufsiz == 0) {
            bufsiz = 16 * (unsigned) 1024;
            while ((buf = (uchar *) malloc(bufsiz)) == NULL) {
                  bufsiz = (bufsiz / (unsigned) 10) * (unsigned) 9;
                  if (bufsiz < 4 * (unsigned) 1024) 
                        prterror('f', no_memory);
            }
      }
      buf[0] = 0;
      for (i = 0; i < NC; i++) c_freq[i] = 0;
      for (i = 0; i < NP; i++) p_freq[i] = 0;
      output_pos = output_mask = 0;
      init_putbits();
}

void huf_encode_end()
{
      if (! unpackable) {
            send_block();
            putbits(CHAR_BIT - 1, 0);  /* flush remaining bits */
            putbits(16, 0);                     /* EOF marker */
      }
}

/***** decoding *****/

static void read_pt_len(nn, nbit, i_special)
int nn;
int nbit;
int i_special;
{
      int i, c, n;
      uint mask;

      n = getbits(nbit);
      if (n == 0) {
            c = getbits(nbit);
            for (i = 0; i < nn; i++) pt_len[i] = 0;
            for (i = 0; i < 256; i++) pt_table[i] = c;
      } else {
            i = 0;
            while (i < n) {
                  c = bitbuf >> (BITBUFSIZ - 3);
                  if (c == 7) {
                        mask = (unsigned) 1 << (BITBUFSIZ - 1 - 3);
                        while (mask & bitbuf) {  mask >>= 1;  c++;  }
                  }
                  fillbuf((c < 7) ? 3 : c - 3);
                  pt_len[i++] = c;
                  if (i == i_special) {
                        c = getbits(2);
                        while (--c >= 0) pt_len[i++] = 0;
                  }
            }
            while (i < nn) pt_len[i++] = 0;
            make_table(nn, pt_len, 8, pt_table);
      }
}

static void read_c_len()
{
      int i, c, n;
      uint mask;

      n = getbits(CBIT);
      if (n == 0) {
            c = getbits(CBIT);
            for (i = 0; i < NC; i++) c_len[i] = 0;
            for (i = 0; i < 4096; i++) c_table[i] = c;
      } else {
            i = 0;
            while (i < n) {
                  c = pt_table[bitbuf >> (BITBUFSIZ - 8)];
                  if (c >= NT) {
                        mask = (unsigned) 1 << (BITBUFSIZ - 1 - 8);
                        do {
                              if (bitbuf & mask) c = right[c];
                              else               c = left [c];
                              mask >>= 1;
                        } while (c >= NT);
                  }
                  fillbuf((int) pt_len[c]);
                  if (c <= 2) {
                        if      (c == 0) c = 1;
                        else if (c == 1) c = getbits(4) + 3;
                        else             c = getbits(CBIT) + 20;
                        while (--c >= 0) c_len[i++] = 0;
                  } else c_len[i++] = c - 2;
            }
            while (i < NC) c_len[i++] = 0;
            make_table(NC, c_len, 12, c_table);
      }
}

uint decode_c()
{
      uint j, mask;

      if (blocksize == 0) {
            blocksize = getbits(16);
            if (blocksize == 0) {
#if 0
                  (void) fprintf(stderr, "block size = 0, decoded\n");  /* debug */
#endif
                  decoded = 1;
                  return 0;
            }
            read_pt_len(NT, TBIT, 3);
            read_c_len();
            read_pt_len(NP, PBIT, -1);
      }
      blocksize--;
      j = c_table[bitbuf >> (BITBUFSIZ - 12)];
      if (j >= NC) {
            mask = (unsigned) 1 << (BITBUFSIZ - 1 - 12);
            do {
                  if (bitbuf & mask) j = right[j];
                  else               j = left [j];
                  mask >>= 1;
            } while (j >= NC);
      }
      fillbuf((int) c_len[j]);
      return j;
}

uint decode_p()
{
      uint j, mask;

      j = pt_table[bitbuf >> (BITBUFSIZ - 8)];
      if (j >= NP) {
            mask = (unsigned) 1 << (BITBUFSIZ - 1 - 8);
            do {
                  if (bitbuf & mask) j = right[j];
                  else               j = left [j];
                  mask >>= 1;
            } while (j >= NP);
      }
      fillbuf((int) pt_len[j]);
      if (j != 0) j = ((unsigned) 1 << (j - 1)) + getbits((int) (j - 1));
      return j;
}

void huf_decode_start()
{
      init_getbits();  blocksize = 0;
}

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