Function: MAP-QUERY-PATH-TO-FILE

Documentation

Converts QUERY-PATH to a file on the local filesystem assuming the application is mapped to URL-BASE and lives in DIRECTORY. In other words: if query-path is "<URL-BASE><SOMETHING>" returns: "<DIRECTORY><SOMETHING>" (assuming said file exists), otherwise returns NIL.

Source

(defun map-query-path-to-file (query-path url-base directory)
  "Converts QUERY-PATH to a file on the local filesystem assuming
  the application is mapped to URL-BASE and lives in DIRECTORY.

In other words: if query-path is \"<URL-BASE><SOMETHING>\"
returns: \"<DIRECTORY><SOMETHING>\" (assuming said file
exists), otherwise returns NIL."
  ;; NB: We really could (and should) cache this function on
  ;; QUERY-PATH, but we need to figure out how to wipe the cache when
  ;; an application's url-prefix changes. considering how rarely that
  ;; happens it's sucks that we lose the spped increase this could
  ;; bring...
  (multiple-value-bind (starts-with <something>)
      (starts-with query-path url-base :return-suffix t)
    (if starts-with
        (let ((pathname (merge-pathnames <something> directory)))
          (if (probe-file pathname)
              pathname
              nil))
        nil)))