delay.4th revision 281843 
1\ Copyright (c) 2008-2015 Devin Teske <dteske@FreeBSD.org>
2\ All rights reserved.
3\ 
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25\ $FreeBSD: stable/10/sys/boot/forth/delay.4th 281843 2015-04-22 01:08:40Z dteske $
26
27marker task-delay.4th
28
29vocabulary delay-processing
30only forth also delay-processing definitions
31
322  constant delay_default \ Default delay (in seconds)
333  constant etx_key       \ End-of-Text character produced by Ctrl+C
3413 constant enter_key     \ Carriage-Return character produce by ENTER
3527 constant esc_key       \ Escape character produced by ESC or Ctrl+[
36
37variable delay_tstart     \ state variable used for delay timing
38variable delay_delay      \ determined configurable delay duration
39variable delay_cancelled  \ state variable for user cancellation
40variable delay_showdots   \ whether continually print dots while waiting
41
42only forth definitions also delay-processing
43
44: delay_execute ( -- )
45
46	\ make sure that we have a command to execute
47	s" delay_command" getenv dup -1 = if
48		drop exit 
49	then
50
51	\ read custom time-duration (if set)
52	s" loader_delay" getenv dup -1 = if
53		drop          \ no custom duration (remove dup'd bunk -1)
54		delay_default \ use default setting (replacing bunk -1)
55	else
56		\ make sure custom duration is a number
57		?number 0= if
58			delay_default \ use default if otherwise
59		then
60	then
61
62	\ initialize state variables
63	delay_delay !          \ stored value is on the stack from above
64	seconds delay_tstart ! \ store the time we started
65	0 delay_cancelled !    \ boolean flag indicating user-cancelled event
66
67	false delay_showdots ! \ reset to zero and read from environment
68	s" delay_showdots" getenv dup -1 <> if
69		2drop \ don't need the value, just existance
70		true delay_showdots !
71	else
72		drop
73	then
74
75	\ Loop until we have exceeded the desired time duration
76	begin
77		25 ms \ sleep for 25 milliseconds (40 iterations/sec)
78
79		\ throw some dots up on the screen if desired
80		delay_showdots @ if
81			." ." \ dots visually aid in the perception of time
82		then
83
84		\ was a key depressed?
85		key? if
86			key \ obtain ASCII value for keystroke
87			dup enter_key = if
88				-1 delay_delay ! \ break loop
89			then
90			dup etx_key = swap esc_key = OR if
91				-1 delay_delay !     \ break loop
92				-1 delay_cancelled ! \ set cancelled flag
93			then
94		then
95
96		\ if the time duration is set to zero, loop forever
97		\ waiting for either ENTER or Ctrl-C/Escape to be pressed
98		delay_delay @ 0> if
99			\ calculate elapsed time
100			seconds delay_tstart @ - delay_delay @ >
101		else
102			-1 \ break loop
103		then
104	until
105
106	\ if we were throwing up dots, throw up a line-break
107	delay_showdots @ if
108		cr
109	then
110
111	\ did the user press either Ctrl-C or Escape?
112	delay_cancelled @ if
113		2drop \ we don't need the command string anymore
114	else
115		evaluate \ evaluate/execute the command string
116 	then
117;
118
119only forth definitions
120