Function inflateInit2

src/Setup/unzip.cpp:2381–2442

int inflateInit2(z_streamp z)
{ const char *version = ZLIB_VERSION; int stream_size = sizeof(z_stream);
  if (version == Z_NULL || version[0] != ZLIB_VERSION[0] || stream_size != sizeof(z_stream)) return Z_VERSION_ERROR;

  int w = -15; // MAX_WBITS: 32K LZ77 window.
  // Warning: reducing MAX_WBITS makes minigzip unable to extract .gz files created by gzip.
  // The memory requirements for deflate are (in bytes):
  //            (1 << (windowBits+2)) +  (1 << (memLevel+9))
  // that is: 128K for windowBits=15  +  128K for memLevel = 8  (default values)
  // plus a few kilobytes for small objects. For example, if you want to reduce
  // the default memory requirements from 256K to 128K, compile with
  //     make CFLAGS="-O -DMAX_WBITS=14 -DMAX_MEM_LEVEL=7"
  // Of course this will generally degrade compression (there's no free lunch).
  //
  //   The memory requirements for inflate are (in bytes) 1 << windowBits
  // that is, 32K for windowBits=15 (default value) plus a few kilobytes
  // for small objects.

  // initialize state
  if (z == Z_NULL) return Z_STREAM_ERROR;
  z->msg = Z_NULL;
  if (z->zalloc == Z_NULL)
  {
    z->zalloc = zcalloc;
    z->opaque = (voidpf)0;
  }
  if (z->zfree == Z_NULL) z->zfree = zcfree;
  if ((z->state = (struct internal_state *)
       ZALLOC(z,1,sizeof(struct internal_state))) == Z_NULL)
    return Z_MEM_ERROR;
  z->state->blocks = Z_NULL;

  // handle undocumented nowrap option (no zlib header or check)
  z->state->nowrap = 0;
  if (w < 0)
  {
    w = - w;
    z->state->nowrap = 1;
  }

  // set window size
  if (w < 8 || w > 15)
  {
    inflateEnd(z);
    return Z_STREAM_ERROR;
  }
  z->state->wbits = (uInt)w;

  // create inflate_blocks state
  if ((z->state->blocks =
      inflate_blocks_new(z, z->state->nowrap ? Z_NULL : adler32, (uInt)1 << w))
      == Z_NULL)
  {
    inflateEnd(z);
    return Z_MEM_ERROR;
  }
  LuTracev((stderr, "inflate: allocated\n"));