 jas_stream_t *jas_stream_fopen(const char *filename, const char *mode)
 {
 	jas_stream_t *stream;
	jas_stream_fileobj_t *obj;
	int openflags;

	/* Allocate a stream object. */
	if (!(stream = jas_stream_create())) {
		return 0;
	}

	/* Parse the mode string. */
	stream->openmode_ = jas_strtoopenmode(mode);

	/* Determine the correct flags to use for opening the file. */
	if ((stream->openmode_ & JAS_STREAM_READ) &&
	  (stream->openmode_ & JAS_STREAM_WRITE)) {
		openflags = O_RDWR;
	} else if (stream->openmode_ & JAS_STREAM_READ) {
		openflags = O_RDONLY;
	} else if (stream->openmode_ & JAS_STREAM_WRITE) {
		openflags = O_WRONLY;
	} else {
		openflags = 0;
	}
	if (stream->openmode_ & JAS_STREAM_APPEND) {
		openflags |= O_APPEND;
	}
	if (stream->openmode_ & JAS_STREAM_BINARY) {
		openflags |= O_BINARY;
	}
	if (stream->openmode_ & JAS_STREAM_CREATE) {
		openflags |= O_CREAT | O_TRUNC;
	}

	/* Allocate space for the underlying file stream object. */
	if (!(obj = jas_malloc(sizeof(jas_stream_fileobj_t)))) {
		jas_stream_destroy(stream);
		return 0;
	}
	obj->fd = -1;
	obj->flags = 0;
	obj->pathname[0] = '\0';
	stream->obj_ = (void *) obj;

	/* Select the operations for a file stream object. */
	stream->ops_ = &jas_stream_fileops;

	/* Open the underlying file. */
	if ((obj->fd = open(filename, openflags, JAS_STREAM_PERMS)) < 0) {
		jas_free(obj);
		jas_stream_destroy(stream);
		return 0;
	}

	/* By default, use full buffering for this type of stream. */
	jas_stream_initbuf(stream, JAS_STREAM_FULLBUF, 0, 0);

	return stream;
}

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.