Use SBCL Unix API to get the timestamp instead of CL functions.

[gaya-]

The main change is line 59 - 63. Everything else is minor indentation & co. fixes.

I was getting 0.6s difference on my system, which is pretty substantial...

[gaya-]

Within roslisp the two special variables *time-base* and *internal-time-base* are only used for this one function. I would get rid of them but someone from the outside might be using them even though they're not exported from the :roslisp namespace. Not sure how you best deprecate variables...

[daewok]

I've seen variable deprecations done with symbol macros before (can't remember where, though). Something like this would probably work:

(defvar *%time-base* (unix-time)
  "(Deprecated) Holds unix time (rounded to the nearest second) when roslisp was started")
(define-symbol-macro *time-base* (progn (ros-warn (roslisp time) "*time-base* is deprecated.") *%time-base*))

According to the Hyperspec though, the behavior of this will be undefined if a function has *time-base* declared as special.

[gaya-]

@daewok, thanks!

According to the Hyperspec though, the behavior of this will be undefined if a function has time-base declared as special.

As (declare (special *my-var*)) only makes sense inside of a lexical scope where *my-var* is the local variable name and one wants to turn it from a lexical variable to special variable, I don't see a point of using a name of an already existing special variable here. Especially, if that variable belongs to a different package. E.g. I can't see anyone writing (defun bla (roslisp::*time-base*) ...). Except maybe when the code is (in-package :roslisp), but if one goes so far as to mess with the internal roslisp implementation they might as well fix their variable names. Otherwise, SBCL will throw a compilation error, which isn't bad IMO.

[airballking]

I ran a quick sanity-test. It all compiles, runs, and makes sense to me.

Here is what I did:

• use_sim_time is false
• $ roscore on my local machine
• $ rosrun tf static_transform_publisher 1 2 3 0 0 0 a b 100 to have some publisher with a timestamp. NOTE: this is dated into the future by 100ms
• in the repl:
  • load roslisp and tf2_msgs
  • start a roslisp-node
  • define a callback function:

(defun from-msg (msg)
  (let ((now (ros-time)))
    (with-fields (transforms) msg
      (with-fields ((then (stamp header))) (elt transforms 0)
        (format t "~%now: ~a then: ~a diff: ~a~%" now then (- now then)))))

• subscribe: (defparameter *sub* (subscribe "/tf" "tf2_msgs/TFMessage" #'from-msg))

This prints something like this:
now: 1.42556563643949d9 stamp: 1.4255656365391152d9 diff: -0.0996251106262207d0

If I ask the static_transform_publisher to run with a period of 50ms I get:
now: 1.425566523690594d9 then: 1.4255665237398553d9 diff: -0.04926133155822754d0

So, I get what I expected: Almost the diff by which the static_transform_publisher future-dates. Cool! I tried this 3 times with recompiling and restarting. All fine.

I'd like to merge. @gaya- @moesenle Any final thoughts?

EDIT: If you wonder about the future-dating, it happens here:
https://github.com/ros/geometry/blob/indigo-devel/tf/src/static_transform_publisher.cpp#L72