Function deflateInit2

Picviewer CE+/dist.user.js:7460–7536

(strm, level, method, windowBits, memLevel, strategy)

function deflateInit2(strm, level, method, windowBits, memLevel, strategy) {
  if (!strm) { // === Z_NULL
    return Z_STREAM_ERROR;
  }
  var wrap = 1;

  if (level === Z_DEFAULT_COMPRESSION) {
    level = 6;
  }

  if (windowBits < 0) { /* suppress zlib wrapper */
    wrap = 0;
    windowBits = -windowBits;
  }

  else if (windowBits > 15) {
    wrap = 2;           /* write gzip wrapper instead */
    windowBits -= 16;
  }


  if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method !== Z_DEFLATED ||
    windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
    strategy < 0 || strategy > Z_FIXED) {
    return err(strm, Z_STREAM_ERROR);
  }


  if (windowBits === 8) {
    windowBits = 9;
  }
  /* until 256-byte window bug fixed */

  var s = new DeflateState();

  strm.state = s;
  s.strm = strm;

  s.wrap = wrap;
  s.gzhead = null;
  s.w_bits = windowBits;
  s.w_size = 1 << s.w_bits;
  s.w_mask = s.w_size - 1;

  s.hash_bits = memLevel + 7;
  s.hash_size = 1 << s.hash_bits;
  s.hash_mask = s.hash_size - 1;
  s.hash_shift = ~~((s.hash_bits + MIN_MATCH - 1) / MIN_MATCH);

  s.window = new utils.Buf8(s.w_size * 2);
  s.head = new utils.Buf16(s.hash_size);
  s.prev = new utils.Buf16(s.w_size);

  // Don't need mem init magic for JS.
  //s.high_water = 0;  /* nothing written to s->window yet */

  s.lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */