int jp2_validate(jas_stream_t *in)
{
	char buf[JP2_VALIDATELEN];
	int i;
	int n;
#if 0
	jas_stream_t *tmpstream;
	jp2_box_t *box;
#endif

	assert(JAS_STREAM_MAXPUTBACK >= JP2_VALIDATELEN);

	/* Read the validation data (i.e., the data used for detecting
	  the format). */
	if ((n = jas_stream_read(in, buf, JP2_VALIDATELEN)) < 0) {
		return -1;
	}

	/* Put the validation data back onto the stream, so that the
	  stream position will not be changed. */
	for (i = n - 1; i >= 0; --i) {
		if (jas_stream_ungetc(in, buf[i]) == EOF) {
			return -1;
		}
	}

	/* Did we read enough data? */
	if (n < JP2_VALIDATELEN) {
		return -1;
	}

	/* Is the box type correct? */
	if (((buf[4] << 24) | (buf[5] << 16) | (buf[6] << 8) | buf[7]) !=
	  JP2_BOX_JP)
	{
		return -1;
	}

	return 0;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.