Function _tr_flush_block

Picviewer CE+/dist.user.js:11424–11505

(s, buf, stored_len, last)

 * trees or store, and output the encoded block to the zip file.
 */
function _tr_flush_block(s, buf, stored_len, last)
//DeflateState *s;
//charf *buf;       /* input block, or NULL if too old */
//ulg stored_len;   /* length of input block */
//int last;         /* one if this is the last block for a file */
{
  var opt_lenb, static_lenb;  /* opt_len and static_len in bytes */
  var max_blindex = 0;        /* index of last bit length code of non zero freq */

  /* Build the Huffman trees unless a stored block is forced */
  if (s.level > 0) {

    /* Check if the file is binary or text */
    if (s.strm.data_type === Z_UNKNOWN) {
      s.strm.data_type = detect_data_type(s);
    }

    /* Construct the literal and distance trees */
    build_tree(s, s.l_desc);
    // Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
    //        s->static_len));

    build_tree(s, s.d_desc);
    // Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
    //        s->static_len));
    /* At this point, opt_len and static_len are the total bit lengths of
     * the compressed block data, excluding the tree representations.
     */

    /* Build the bit length tree for the above two trees, and get the index
     * in bl_order of the last bit length code to send.
     */
    max_blindex = build_bl_tree(s);

    /* Determine the best encoding. Compute the block lengths in bytes. */
    opt_lenb = (s.opt_len + 3 + 7) >>> 3;
    static_lenb = (s.static_len + 3 + 7) >>> 3;

    // Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
    //        opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
    //        s->last_lit));

    if (static_lenb <= opt_lenb) { opt_lenb = static_lenb; }

  } else {
    // Assert(buf != (char*)0, "lost buf");
    opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
  }

  if ((stored_len + 4 <= opt_lenb) && (buf !== -1)) {
    /* 4: two words for the lengths */

    /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
     * Otherwise we can't have processed more than WSIZE input bytes since
     * the last block flush, because compression would have been
     * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
     * transform a block into a stored block.
     */