/usr/share/tcltk/tcllib1.16/debug/heartbeat.tcl is in tcllib 1.16-dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 | # -*- tcl -*
# Debug -- Heartbeat. Track operation of Tcl's eventloop.
# -- Colin McCormack / originally Wub server utilities
# # ## ### ##### ######## ############# #####################
## Requisites
package require Tcl 8.5
package require debug
namespace eval ::debug {
    namespace export heartbeat
    namespace ensemble create
}
# # ## ### ##### ######## ############# #####################
## API & Implementation
proc ::debug::heartbeat {{delta 500}} {
    variable duration $delta
    variable timer
    if {$duration > 0} {
	# stop a previous heartbeat before starting the next
	catch { after cancel $timer }
	on heartbeat
	every $duration {
	    debug.heartbeat {[debug::pulse]}
	}
    } else {
	catch { after cancel $timer }
	off heartbeat
    }
}
proc ::debug::every {ms body} {
    eval $body
    variable timer [after $ms [info level 0]]
    return
}
proc ::debug::pulse {} {
    variable duration
    variable hbtimer
    variable heartbeat
    set now  [::tcl::clock::milliseconds]
    set diff [expr {$now - $hbtimer - $duration}]
    set hbtimer $now
    return [list [incr heartbeat] $diff]
}
# # ## ### ##### ######## ############# #####################
namespace eval ::debug {
    variable duration  0 ; # milliseconds between heart-beats
    variable heartbeat 0 ; # beat counter
    variable hbtimer   [::tcl::clock::milliseconds]
    variable timer
}
# # ## ### ##### ######## ############# #####################
## Ready
package provide debug::heartbeat 1
return
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