fdi.c

winNT技术操作系统,国外开放的原代码和LIUX一样

      /* selector 4 = fixed length of 3 */
      GET_SYMBOL(model4, sym);
      Q_READ_BITS(extra, CAB(q_extra_bits)[sym]);
      match_offset = CAB(q_position_base)[sym] + extra + 1;
      match_length = 3;
      break;

    case 5:
      /* selector 5 = fixed length of 4 */
      GET_SYMBOL(model5, sym);
      Q_READ_BITS(extra, CAB(q_extra_bits)[sym]);
      match_offset = CAB(q_position_base)[sym] + extra + 1;
      match_length = 4;
      break;

    case 6:
      /* selector 6 = variable length */
      GET_SYMBOL(model6len, sym);
      Q_READ_BITS(extra, CAB(q_length_extra)[sym]);
      match_length = CAB(q_length_base)[sym] + extra + 5;
      GET_SYMBOL(model6pos, sym);
      Q_READ_BITS(extra, CAB(q_extra_bits)[sym]);
      match_offset = CAB(q_position_base)[sym] + extra + 1;
      break;

    default:
      TRACE("Selector is bogus\n");
      return DECR_ILLEGALDATA;
    }

    /* if this is a match */
    if (selector >= 4) {
      rundest = window + window_posn;
      togo -= match_length;

      /* copy any wrapped around source data */
      if (window_posn >= match_offset) {
        /* no wrap */
        runsrc = rundest - match_offset;
      } else {
        runsrc = rundest + (window_size - match_offset);
        copy_length = match_offset - window_posn;
        if (copy_length < match_length) {
          match_length -= copy_length;
          window_posn += copy_length;
          while (copy_length-- > 0) *rundest++ = *runsrc++;
          runsrc = window;
        }
      }
      window_posn += match_length;

      /* copy match data - no worries about destination wraps */
      while (match_length-- > 0) *rundest++ = *runsrc++;
    }
  } /* while (togo > 0) */

  if (togo != 0) {
    TRACE("Frame overflow, this_run = %d\n", togo);
    return DECR_ILLEGALDATA;
  }

  memcpy(CAB(outbuf), window + ((!window_posn) ? window_size : window_posn) -
    outlen, outlen);

  QTM(window_posn) = window_posn;
  return DECR_OK;
}

/************************************************************
 * fdi_lzx_read_lens (internal)
 */
static int fdi_lzx_read_lens(cab_UBYTE *lens, cab_ULONG first, cab_ULONG last, struct lzx_bits *lb,
                  fdi_decomp_state *decomp_state) {
  cab_ULONG i,j, x,y;
  int z;

  register cab_ULONG bitbuf = lb->bb;
  register int bitsleft = lb->bl;
  cab_UBYTE *inpos = lb->ip;
  cab_UWORD *hufftbl;
  
  for (x = 0; x < 20; x++) {
    READ_BITS(y, 4);
    LENTABLE(PRETREE)[x] = y;
  }
  BUILD_TABLE(PRETREE);

  for (x = first; x < last; ) {
    READ_HUFFSYM(PRETREE, z);
    if (z == 17) {
      READ_BITS(y, 4); y += 4;
      while (y--) lens[x++] = 0;
    }
    else if (z == 18) {
      READ_BITS(y, 5); y += 20;
      while (y--) lens[x++] = 0;
    }
    else if (z == 19) {
      READ_BITS(y, 1); y += 4;
      READ_HUFFSYM(PRETREE, z);
      z = lens[x] - z; if (z < 0) z += 17;
      while (y--) lens[x++] = z;
    }
    else {
      z = lens[x] - z; if (z < 0) z += 17;
      lens[x++] = z;
    }
  }

  lb->bb = bitbuf;
  lb->bl = bitsleft;
  lb->ip = inpos;
  return 0;
}

/*******************************************************
 * LZXfdi_decomp(internal)
 */
static int LZXfdi_decomp(int inlen, int outlen, fdi_decomp_state *decomp_state) {
  cab_UBYTE *inpos  = CAB(inbuf);
  cab_UBYTE *endinp = inpos + inlen;
  cab_UBYTE *window = LZX(window);
  cab_UBYTE *runsrc, *rundest;
  cab_UWORD *hufftbl; /* used in READ_HUFFSYM macro as chosen decoding table */

  cab_ULONG window_posn = LZX(window_posn);
  cab_ULONG window_size = LZX(window_size);
  cab_ULONG R0 = LZX(R0);
  cab_ULONG R1 = LZX(R1);
  cab_ULONG R2 = LZX(R2);

  register cab_ULONG bitbuf;
  register int bitsleft;
  cab_ULONG match_offset, i,j,k; /* ijk used in READ_HUFFSYM macro */
  struct lzx_bits lb; /* used in READ_LENGTHS macro */

  int togo = outlen, this_run, main_element, aligned_bits;
  int match_length, copy_length, length_footer, extra, verbatim_bits;

  TRACE("(inlen == %d, outlen == %d)\n", inlen, outlen);

  INIT_BITSTREAM;

  /* read header if necessary */
  if (!LZX(header_read)) {
    i = j = 0;
    READ_BITS(k, 1); if (k) { READ_BITS(i,16); READ_BITS(j,16); }
    LZX(intel_filesize) = (i << 16) | j; /* or 0 if not encoded */
    LZX(header_read) = 1;
  }

  /* main decoding loop */
  while (togo > 0) {
    /* last block finished, new block expected */
    if (LZX(block_remaining) == 0) {
      if (LZX(block_type) == LZX_BLOCKTYPE_UNCOMPRESSED) {
        if (LZX(block_length) & 1) inpos++; /* realign bitstream to word */
        INIT_BITSTREAM;
      }

      READ_BITS(LZX(block_type), 3);
      READ_BITS(i, 16);
      READ_BITS(j, 8);
      LZX(block_remaining) = LZX(block_length) = (i << 8) | j;

      switch (LZX(block_type)) {
      case LZX_BLOCKTYPE_ALIGNED:
        for (i = 0; i < 8; i++) { READ_BITS(j, 3); LENTABLE(ALIGNED)[i] = j; }
        BUILD_TABLE(ALIGNED);
        /* rest of aligned header is same as verbatim */

      case LZX_BLOCKTYPE_VERBATIM:
        READ_LENGTHS(MAINTREE, 0, 256, fdi_lzx_read_lens);
        READ_LENGTHS(MAINTREE, 256, LZX(main_elements), fdi_lzx_read_lens);
        BUILD_TABLE(MAINTREE);
        if (LENTABLE(MAINTREE)[0xE8] != 0) LZX(intel_started) = 1;

        READ_LENGTHS(LENGTH, 0, LZX_NUM_SECONDARY_LENGTHS, fdi_lzx_read_lens);
        BUILD_TABLE(LENGTH);
        break;

      case LZX_BLOCKTYPE_UNCOMPRESSED:
        LZX(intel_started) = 1; /* because we can't assume otherwise */
        ENSURE_BITS(16); /* get up to 16 pad bits into the buffer */
        if (bitsleft > 16) inpos -= 2; /* and align the bitstream! */
        R0 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
        R1 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
        R2 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
        break;

      default:
        return DECR_ILLEGALDATA;
      }
    }

    /* buffer exhaustion check */
    if (inpos > endinp) {
      /* it's possible to have a file where the next run is less than
       * 16 bits in size. In this case, the READ_HUFFSYM() macro used
       * in building the tables will exhaust the buffer, so we should
       * allow for this, but not allow those accidentally read bits to
       * be used (so we check that there are at least 16 bits
       * remaining - in this boundary case they aren't really part of
       * the compressed data)
       */
      if (inpos > (endinp+2) || bitsleft < 16) return DECR_ILLEGALDATA;
    }

    while ((this_run = LZX(block_remaining)) > 0 && togo > 0) {
      if (this_run > togo) this_run = togo;
      togo -= this_run;
      LZX(block_remaining) -= this_run;

      /* apply 2^x-1 mask */
      window_posn &= window_size - 1;
      /* runs can't straddle the window wraparound */
      if ((window_posn + this_run) > window_size)
        return DECR_DATAFORMAT;

      switch (LZX(block_type)) {

      case LZX_BLOCKTYPE_VERBATIM:
        while (this_run > 0) {
          READ_HUFFSYM(MAINTREE, main_element);

          if (main_element < LZX_NUM_CHARS) {
            /* literal: 0 to LZX_NUM_CHARS-1 */
            window[window_posn++] = main_element;
            this_run--;
          }
          else {
            /* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
            main_element -= LZX_NUM_CHARS;
  
            match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
            if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
              READ_HUFFSYM(LENGTH, length_footer);
              match_length += length_footer;
            }
            match_length += LZX_MIN_MATCH;
  
            match_offset = main_element >> 3;
  
            if (match_offset > 2) {
              /* not repeated offset */
              if (match_offset != 3) {
                extra = CAB(extra_bits)[match_offset];
                READ_BITS(verbatim_bits, extra);
                match_offset = CAB(lzx_position_base)[match_offset] 
                               - 2 + verbatim_bits;
              }
              else {
                match_offset = 1;
              }
  
              /* update repeated offset LRU queue */
              R2 = R1; R1 = R0; R0 = match_offset;
            }
            else if (match_offset == 0) {
              match_offset = R0;
            }
            else if (match_offset == 1) {
              match_offset = R1;
              R1 = R0; R0 = match_offset;
            }
            else /* match_offset == 2 */ {
              match_offset = R2;
              R2 = R0; R0 = match_offset;
            }

            rundest = window + window_posn;
            this_run -= match_length;

            /* copy any wrapped around source data */
            if (window_posn >= match_offset) {
              /* no wrap */
              runsrc = rundest - match_offset;
            } else {
              runsrc = rundest + (window_size - match_offset);
              copy_length = match_offset - window_posn;
              if (copy_length < match_length) {
                match_length -= copy_length;
                window_posn += copy_length;
                while (copy_length-- > 0) *rundest++ = *runsrc++;
                runsrc = window;
              }
            }
            window_posn += match_length;

            /* copy match data - no worries about destination wraps */
            while (match_length-- > 0) *rundest++ = *runsrc++;
          }
        }
        break;

      case LZX_BLOCKTYPE_ALIGNED:
        while (this_run > 0) {
          READ_HUFFSYM(MAINTREE, main_element);
  
          if (main_element < LZX_NUM_CHARS) {
            /* literal: 0 to LZX_NUM_CHARS-1 */
            window[window_posn++] = main_element;
            this_run--;
          }
          else {
            /* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
            main_element -= LZX_NUM_CHARS;
  
            match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
            if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
              READ_HUFFSYM(LENGTH, length_footer);
              match_length += length_footer;
            }
            match_length += LZX_MIN_MATCH;
  
            match_offset = main_element >> 3;
  
            if (match_offset > 2) {
              /* not repeated offset */
              extra = CAB(extra_bits)[match_offset];
              match_offset = CAB(lzx_position_base)[match_offset] - 2;
              if (extra > 3) {
                /* verbatim and aligned bits */
                extra -= 3;
                READ_BITS(verbatim_bits, extra);
                match_offset += (verbatim_bits << 3);
                READ_HUFFSYM(ALIGNED, aligned_bits);
                match_offset += aligned_bits;
              }
              else if (extra == 3) {
                /* aligned bits only */
                READ_HUFFSYM(ALIGNED, aligned_bits);
                match_offset += aligned_bits;
              }
              else if (extra > 0) { /* extra==1, extra==2 */
                /* verbatim bits only */
                READ_BITS(verbatim_bits, extra);
                match_offset += verbatim_bits;
              }
              else /* extra == 0 */ {
                /* ??? */
                match_offset = 1;
              }
  
              /* update repeated offset LRU queue */
              R2 = R1; R1 = R0; R0 = match_offset;
            }
            else if (match_offset == 0) {
              match_offset = R0;
            }
            else if (match_offset == 1) {
              match_offset = R1;
              R1 = R0; R0 = match_offset;
            }
            else /* match_offset == 2 */ {
              match_offset = R2;
              R2 = R0; R0 = match_offset;
            }

            rundest = window + window_posn;
            this_run -= match_length;

            /* copy any wrapped around source data */
            if (window_posn >= match_offset) {
              /* no wrap */
              runsrc = rundest - match_offset;
            } else {
              runsrc = rundest + (window_size - match_offset);
              copy_length = match_offset - window_posn;
              if (copy_length < match_length) {
                match_length -= copy_length;
                window_posn += copy_length;
                while (copy_length-- > 0) *rundest++ = *runsrc++;
                runsrc = window;
              }
            }
            window_posn += match_length;

            /* copy match data - no worries about destination wraps */
            while (match_length-- > 0) *rundest++ = *runsrc++;
          }
        }
        break;

      case LZX_BLOCKTYPE_UNCOMPRESSED:
        if ((inpos + this_run) > endinp) return DECR_ILLEGALDATA;
        memcpy(window + window_posn,