int pgx_validate(jas_stream_t *in)
{
	uchar buf[PGX_MAGICLEN];
	uint_fast32_t magic;
	int i;
	int n;

	assert(JAS_STREAM_MAXPUTBACK >= PGX_MAGICLEN);

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

	/* Compute the signature value. */
	magic = (buf[0] << 8) | buf[1];

	/* Ensure that the signature is correct for this format. */
	if (magic != PGX_MAGIC) {
		return -1;
	}

	return 0;
}
The software 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 can introduce other weaknesses when the calculation is used for resource management or execution control.