Reformatting a long string so each line is at the most 78 characters and end with \?

Is there a way to re-indent and re-wrap a long string, i.e. a paragraph of text with double quotation marks on each end, such that each line 1) has at the most a pre-defined number of characters, e.g. 78 characters, for better readability in editor windows, and 2) end with  \ so it is still a long string without line breaks?