.PS
# 02Mar97: Cleaned up this file.  Removed a bunch of the tcpipiv2-only
#	   macros, and deleted those that were never used.
#
# This file defines the handy macros used in the document.
#
arrowwid = 0.0625	# This divisible by 2 (0.03125) has to be a "perfect"
			# size for ditroff.  This value is OK for TranScript on
			# on the LaserWriter (576 units/inch).
#arrowht = 0.125
arrowht = 0.09375
#arrowht = 0.0625
dash_off = 0.2		# default
gap_down = 0.12		# default downward distance in timeline gap
gap_side = 0.04		# default sidewards distance in timeline gap
basef = .375
maxwid = 5.416666
unusedfill = .1		# unused portions of structures
cbase = .256
cindent = .275
v6_hash	= 0.06

# Just remove "invis" to see the boxes
define	ibox { box invis }

# Client double arrow (left to right on top, right to left below)
define	Carrow	{
	arrow -> right 0.15 from $1 + (-0.15/2,  0.04) wid 0.03 ht 0.05
	arrow <- right 0.15 from $1 + (-0.15/2, -0.04) wid 0.03 ht 0.05
}

# Server double arrow (right to left on top, left to right below)
define	Sarrow	{
	arrow <- right 0.15 from $1 + (-0.15/2,  0.04) wid 0.03 ht 0.05
	arrow -> right 0.15 from $1 + (-0.15/2, -0.04) wid 0.03 ht 0.05
}

# Right arrow
define	Rarrow	{
	arrow -> right 0.15 from $1 + (-0.15/2,  0.00) wid 0.03 ht 0.05
}

# Left arrow
define	Larrow	{
	arrow <- right 0.15 from $1 + (-0.15/2,  0.00) wid 0.03 ht 0.05
}

#
# flowdef( <scale> )
# set up default for data flow pictures
define	flowdef X
	boxht = 0.2*$1
	boxwid = 0.8*$1
	ellipsewid = boxwid
	ellipseht = boxht*1.5
.ps 8
.vs 10
X

#
# memdef( <maxbytes>, <x-scale>, <y-scale>)
# set up default for memory layout pictures
define	memdef X
	boxht = .3*$3
	boxwid = (.95*maxwid)/$1*$2
	boff = boxwid/(2*$1)
	poff = boxht*.25
	arrowht = .09375*.8
	arrowwid = 0.0625*.8
	labelspace=.4		# used in by field2_a functions
.ps 8
.vs 10
X

#
# dsdef
# setup defaults for data structure pictures
define	dsdef X
	boxht = 0.15
	boxwid = boxht*6
	myboxrad = boxht/4
	ellipsewid = boxwid
	ellipseht = boxht*1.5
	arrowwid = 0.0625*.75
	arrowht = 0.09375*.75
	poff = .5*boxht
	# ellipse offset
	eoff = .5*poff
.ps 8
.vs 9
X

#
# text_span ( <left-corner>, <right-corner>, <text>, <text-wid>,
#					<height-of-text-above-corners> )
#
# For normal text, <height...> should be 0.15.
#
define	text_span X
Lab001:	$3 at 1/2 <$1, $2> + (0, $5)
	arrow from Lab001.c + (- $4/2, 0) to $1 + (0, $5)
	arrow from Lab001.c + (  $4/2, 0) to $2 + (0, $5)
X

#
# solid_box ( <sw-posn>, <ne-posn> )
#
# Draw a solid box, given 2 opposite corner positions.
# Note - unlike the dash_box macro below, we draw the box exactly from
# from the points specified - we don't offset the box by 0.2i from
# the given coordinates.
# The box is drawn in the order of the arguments, so that the command
# "... at last line.c below" will be positioned at the line from the
# se-posn to the sw-posn.
#
define	solid_box X
S0001: $1
S0002: $2
	line from S0001 to (S0001.x, S0002.y)
	line from last line.end to S0002
	line from last line.end to (S0002.x, S0001.y)
	line from last line.end to S0001
X

#
# dash_box ( <sw-posn>, <ne-posn> [ , <optional-dash-length> ] )
#
# Draw a dashed box, given the 2 opposite corner positions.
# The box is drawn in the order of the arguments, so that the command
# "... at last line.c below" will be positioned at the line from the
# se-posn to the sw-posn.
#
# Caller can set "dash_off = <value>" to change the default of 0.2 inches
# from all sides.  This has to be done before each call to the macro,
# as we reset it after each call.
#
# The <optional-dash-length> specifies the length of each dash and the
# length of the space between each dash.  The default is 0.05.
# Note this feature uses pic's substitution of the null string for any
# missing arguments in a macro call.
#
define	dash_box X
S001:	$1
S002:	$2
	line dashed $3 from S001 + (-dash_off, -dash_off) to \
		(S001.x, S002.y) + (-dash_off, dash_off)
	line dashed $3 from last line.end to \
		S002 + (dash_off, dash_off)
	line dashed $3 from last line.end to \
		(S002.x, S001.y) + (dash_off, -dash_off)
	line dashed $3 from last line.end to \
		S001 + (-dash_off, -dash_off)
dash_off = 0.2		# reset default
X

#
# left_brace ( <top>, <bottom> )
#
define	left_brace X
LB1:	$1
LB2:	$2
	arc from LB1 + (-0.09375, 0.00) to LB1 + (-0.15625, -0.0625) rad 0.0625
	line down (((LB1.y - LB2.y) - 0.125) / 2) - 0.03125
	line down  0.03125 left 0.03125
Bracept:line right 0.03125 down 0.03125
	line to LB2 + (-0.15625, 0.0625)
	arc from last line.end to LB2 + (-0.09375, 0.00) rad 0.0625
X

#
# right_brace ( <top>, <bottom> )
#
define	right_brace X
RB1:	$1
RB2:	$2
	arc cw from RB1 + (0.09375, 0.00) to RB1 + (0.15625, -0.0625) rad 0.0625
	line down (((RB1.y - RB2.y) - 0.125) / 2) - 0.03125
	line down 0.03125 right 0.03125
Bracept:line left 0.03125 down 0.03125
	line to RB2 + (0.15625, 0.0625)
	arc cw from last line.end to RB2 + (0.09375, 0.00) rad 0.0625
X

#
# bottom_brace ( <left>, <right> )
#
define	bottom_brace X
BB1:	$1
BB2:	$2
	arc from BB1 + (0.00, -0.09375) to BB1 + (0.0625, - 0.15625) rad 0.0625
	line right (((BB2.x - BB1.x) - 0.125) / 2) - 0.03125
	line right 0.03125 down 0.03125
Bracept:line up 0.03125 right 0.03125
	line to BB2 + (-0.0625, -0.15625)
	arc from last line.end to BB2 + (0, -0.09375) rad 0.0625
X

#
# top_brace ( <left>, <right> )
#
define	top_brace X
TB1:	$1
TB2:	$2
	arc cw from TB1 + (0.00, 0.09375) to TB1 + (0.0625, 0.15625) rad 0.0625
	line right (((TB2.x - TB1.x) - 0.125) / 2) - 0.03125
	line right 0.03125 up 0.03125
Bracept:line down 0.03125 right 0.03125
	line to TB2 + (-0.0625, 0.15625)
	arc cw from last line.end to TB2 + (0, 0.09375) rad 0.0625
X

#
# line_gap_down ( <top>, <bottom> )
#
define	line_gap_down X
Start:	$1
End:	$2

	line down ((Start.y - End.y) - gap_down)/2 from Start
	line right gap_side
	line left gap_side*2 down gap_down
	line right gap_side
	line to End
gap_down = 0.12		# reset default
gap_side = 0.04		# reset default
X

#
# line_gap_right ( <left>, <right> )
#
define	line_gap_right X
Start:	$1
End:	$2

	line right ((End.x - Start.x) - gap_down)/2 from Start
	line up gap_side
	line down gap_side*2 right gap_down
	line up gap_side
	line to End
gap_down = 0.12		# reset default
gap_side = 0.04		# reset default
X

#
# label_above( <sw-posn>, <se-posn>, <arrow-length>, <text> )
#
define	label_above X
P001:	$1 + (0, 0.1)
P002:	$2 + (0, 0.1)
	line up 0.2 from P001
	line up 0.2 from P002
	arrow <- right $3 from P001 + (0, 0.1)
	arrow <- left  $3 from P002 + (0, 0.1)
	$4 at 1/2 <2nd last arrow.start, last arrow.start>
X

#
# label_below( <sw-posn>, <se-posn>, <arrow-length>, <text> )
#
define	label_below X
P001:	$1 + (0, -0.1)
P002:	$2 + (0, -0.1)
	line down 0.2 from P001
	line down 0.2 from P002
	arrow <- right $3 from P001 + (0, -0.1)
	arrow <- left  $3 from P002 + (0, -0.1)
	$4 at 1/2 <2nd last arrow.start, last arrow.start>
X

#
# text_spanv ( <left-corner>, <right-corner>, <text>, <text-wid>,
#					<height-of-text-above-corners> )
# end points are in line with text
#
define	text_spanv X
Lab001:	$3 at 1/2 <$1, $2> 
	arrow from Lab001.c + (0, - $4/2) to $1
	arrow from Lab001.c + (0,  $4/2) to $2
X

#
# text_spanc ( <left-corner>, <right-corner>, <text>, <text-wid>,
#					<height-of-text-above-corners> )
# end points are in line with text
#
define	text_spanc X
Lab001:	$3 at 1/2 <$1, $2> 
	arrow from Lab001.c + (- $4/2, 0) to $1
	arrow from Lab001.c + (  $4/2, 0) to $2
X


#
# measureb ( sw-corner, se-corner, text, <text-wid>, <height>)
# Show the measurement below the object
define	measureb X
	Mleft: line from $1 + (0, -0.05) to $1 + (0, -($5 * 1.5) )
	Mright: line from $2 + (0, -0.05) to $2 + (0, -($5 * 1.5) )
	text_spanc( Mleft.c, Mright.c, $3, $4, $5)
X

#
# measurea ( sw-corner, se-corner, text, <text-wid>, <height>)
# Show the measurement above the object
define	measurea X
	Mleft: line from $1 + (0, 0.05) to $1 + (0, ($5 * 1.5) )
	Mright: line from $2 + (0, 0.05) to $2 + (0, ($5 * 1.5) )
	text_spanc( Mleft.c, Mright.c, $3, $4, $5)
X

#
# measurel ( nw-corner, sw-corner, text, <text-wid>, <height>)
# Show the measurement above the object
define	measurel X
	Mtop: line from $1 - (0.05, 0) to $1 - (($5 * 1.5),0 )
	Mbot: line from $2 - (0.05, 0) to $2 - (($5 * 1.5),0 )
	text_spanv( Mtop.c, Mbot.c, $3, $4, $5)
X

#
# measurer ( nw-corner, sw-corner, text, <text-wid>, <height>)
# Show the measurement above the object
define	measurer X
	Mtop: line from $1 + (0.05, 0) to $1 + (($5 * 1.5),0 )
	Mbot: line from $2 + (0.05, 0) to $2 + (($5 * 1.5),0 )
	text_spanv( Mtop.c, Mbot.c, $3, $4, $5)
X

#
# queue ( <start> )
#
define	queue X
$2: $1 - (.1,0)
$2exit: $1 + (0,.1)
	box wid 0.20 ht 0.05 with .nw at $2
	box wid 0.20 ht 0.05 with .nw at last box.sw
	box wid 0.20 ht 0.05 with .nw at last box.sw
	box wid 0.20 ht 0.05 with .nw at last box.sw
	line from last box.sw down 0.20
	line from last box.se down 0.20
$2entry: last box.s - 0,0.1
	move to $2
X

#
# pointer (from, to, sx, sy)
#
define	pointer X
# We want a 10% curve
Start: $1
End: $2
	dx = End.x - Start.x
	dy = End.y - Start.y
	incx = dx * $3; incy = dy * $4

	spline -> from $1 \
		to $1 + ( -incx, incy ) \
		to $2 + ( incx, -incy ) \
		to $2
X

#
# field_a( text, bytes, label, other)
# draw a box but label it above the field 
# leave room for other labels that may be there
define	field_a X
	$3: box wid (boxwid*$2)
		sprintf("%.0f", $2) below at last box.s
		spline <- from $3.n up (2+$4)*.4*boxht then right .1
		$1 at last spline.end ljust
		move to $3.e
X

#
# field_s(text, bytes, label)
# Draw a field with a slanted label
# leave room for other labels that may be there
define	field_s X
	$3: box wid (boxwid*$2)
		sprintf("%.0f", $2) below at last box.s
		line invis $1 ljust above aligned \
			from $3.ne + (-.75*boxwid,-.5*boxht) up boxht right boxwid 
		move to $3.e
X

#
# field2_ai( opts, text, sizetext, bytes, label, other)
# draw an box with options but label it above the field 
# leave room for other labels that may be there
# any text for the bottom is provided by sizetext
# additional box options can be provided in opts

define	field2_ai X
	$5: box $1 wid (boxwid*$4)
		spline <- from $5.n up (1.25+$6)*labelspace*boxht then right .1
		$2 at last spline.end ljust
		$3 below at $5.s
		move to $5.e
X

#
# field2_al( text, sizetext, bytes, label, other)
# draw a box but label it above the field but to the left
# leave room for other labels that may be there
# any text for the bottom is provided by sizetext

define	field2_al X
	$4: box wid (boxwid*$3)
		spline <- from $4.n up (1.25+$5)*labelspace*boxht then left .1
		right
		$1 at last spline.end rjust
		$2 below at $4.s
		move to $4.e
X

#
# field2_a( text, sizetext, bytes, label, other)
# draw a box but label it above the field 
# leave room for other labels that may be there
# any text for the bottom is provided by sizetext

define	field2_a X
	$4: box wid (boxwid*$3)
		spline <- from $4.n up (1.25+$5)*labelspace*boxht then right .1
		$1 at last spline.end ljust
		$2 below at $4.s
		move to $4.e
X

# draw a box and label it as a field within a packet
# field( boxtext, units, label )
define	field X
	$3: box $1 wid (boxwid*$2)
		move to $3.e
X

# draw a box and label it as a field within a packet
# the size in bytes appears below the box
# field2( boxtext, sizetext, units, boxlabel)
define	field2 X
	$4: box $1 wid (boxwid*$3)
		$2 below at last box.s
		move to $4.e
X

# Show field with internal tick marks
# fieldt( scale, text, units, label )
define	fieldt X
	fw = basef * $1
	fh = basef
	$4: box $2 wid (fw*$3) ht fh
	for t = fw to fw * ($3 - 1) by fw do {
		line from $4.nw + (t,0) to $4.sw + (t,0) dotted
	}
	move to $4.e
#	[ "$3" at $4.s below ]
X

define	inetsw X
Inetsw: box "-" with .c at $1; "0 " rjust at last box.w
"\fCinetsw[]\fP" above at last box.n
Iudp: box "UDP" with .n at last box.s; "1 " rjust at last box.w
Itcp: box "TCP" with .n at last box.s; "2 " rjust at last box.w
Iicmp: box "ICMP" with .n at last box.s; "3 " rjust at last box.w
Irip: box "raw IP" with .n at last box.s; "4 " rjust at last box.w
box "raw IP" with .n at last box.s; "5 " rjust at last box.w
X

#
# array( count, text, center0)
define	array X
A0: box with .nw at $3 ; $2 above at last box.n
for i = 2 to $1 do {
	Al: box with .n at last box.s;
}
X

#
# lnullp( start )
# draw the grounding end of a null pointer but on the left
define	lnullp X
	spline from $1+(poff,0) left 2*poff+boxht/2 then down boxht
	Mid: Here
	line from Mid - (boxht/2, 0) right boxht
	line from Mid - (boxht/4,.02) right boxht/2
	line from Mid - (boxht/8,.04) right boxht/4
	line from Mid - (boxht/16,.06) right boxht/8
	#pstart($1 + (poff,0))
X

#
# dnullp(start)
# draw the grounding end of a null pointer
define	dnullp X
	line from $1 down boxht
	Mid: Here
	line from Mid - (boxht/2, 0) right boxht
	line from Mid - (boxht/4,.02) right boxht/2
	line from Mid - (boxht/8,.04) right boxht/4
	line from Mid - (boxht/16,.06) right boxht/8
X

#
# nullp( start, horiz )
# draw the grounding end of a null pointer
define	nullp X
	if ($2 == 0) then {horiz=boxht/2} else { horiz=$2 }
	#horiz=$2
	spline from $1-(poff,0) right 2*poff+horiz then down boxht
	Mid: Here
	line from Mid - (boxht/2, 0) right boxht
	line from Mid - (boxht/4,.02) right boxht/2
	line from Mid - (boxht/8,.04) right boxht/4
	line from Mid - (boxht/16,.06) right boxht/8
	#pstart($1-(poff,0))
X

#
# vv_spline(top, bottom, offset, gap, arrow )
# Draw a V shaped spline from top to bottom.
define	vv_spline X
	initspline($1, $2, .5, .5, .25)
	line from Spline1 right $3
	spline from Spline1 then right $4 then to Spline2 $5
X
	
#
# vu_spline(top, bottom, off, off, gap, arrow, text)
# Connect top and bottom on the left
define	vu_spline X
	initspline($1, $2+($5,0), .5, .5, .25)
#		then up yrad then up dy-2*yrad then up yrad 
	spline from Spline1 then right dx-xrad then right xrad \
		then up dy \
		then left xrad then left dx-xrad $6
	if ($3 != 0 ) then { 
		line from Spline1 right $3 
		#circle fill 1 rad .015 with .c at last line.end
	}
	if ($4 != 0 ) then { 
		line from Spline2 right $4 
		#circle fill 1 rad .015 with .c at last line.end
	}
	line invis from $1 + ($5,0) then up dy $7
X

#
# hu_spline(left, right, off, off, gap, arrow, text)
# Connect left and right horizontally
define	hu_spline X
	Spline1: $1
	Spline2: $2
	dx = Spline2.x - Spline1.x
	spline from Spline1 then up $5 then right dx/2 \
		then to Spline2 + (0,$5) then to Spline2 $6
	if ($3 != 0 ) then { line from Spline1 up $3 }
	if ($4 != 0 ) then { line from Spline2 up $4 }
	line invis from $1 + (0,$5) then right dx $7
X

#
# initspline(p1, p2, scalex, scaley, scale_radius)
define	initspline X
	Spline1: $1
	Spline2: $2
	dx = Spline2.x - Spline1.x
	dy = Spline2.y - Spline1.y
	if (dx < 0 ) then { adx = -dx} else { adx = dx}
	if (dy < 0 ) then { ady = -dy} else { ady = dy }
	srad = max(min(adx*$3, ady*$4), boxht*$5)
	#srad = boxht/4
	xrad = srad
	yrad = srad
	#xrad = adx*$3
	#yrad = ady*$4
	#sprintf("dx %f dy %f srad %fxrad %f yrad %f", dx, dy, srad, xrad, yrad) \
	#	above at Spline1
	if (dx < 0 ) then { xrad = -srad }
	if (dy < 0 ) then { yrad = -srad }
	#if (dx < 0 ) then { xrad = -xrad }
	#if (dy < 0 ) then { yrad = -yrad }
X

#
# lr_spline(start, end, off, off, arrow, text, rad)
# Connect start and end in an l shape
define	lr_spline X
	initspline($1, $2, .2, .2, $7)
	spline from Spline1 \
		then up dy-yrad \
		then up yrad \
		then right xrad \
		then right dx-xrad $5
	if ($3 != 0 ) then { line from Spline1 up $3 }
	if ($4 != 0 ) then { line from Spline2 right $4 }
	line invis from $1 + (0,dy) then right dx $6
X

#
# l_spline(start, end, off, off, arrow, text)
# Connect start and end in an l shape
define	l_spline X
	initspline($1, $2, .2, .2, 1.25)
	spline from Spline1 \
		then up dy-yrad \
		then up yrad \
		then right xrad \
		then right dx-xrad $5
	if ($3 != 0 ) then { line from Spline1 up $3 }
	if ($4 != 0 ) then { line from Spline2 right $4 }
	line invis from $1 + (0,dy) then right dx $6
X

#
# vertical spline
# v_spline(p1, p2, off1, off2, arrow, turn)
#
define	v_spline X
	vz_spline($1, $2, $3, $4, $5, $6, .05)
#	initspline($1, $2, .2, .2)
#	spline from Spline1 \
#		then up (dy*$6)-yrad then up yrad \
#		then right dx then up yrad \
#		then up (dy*(1-$6))-yrad $5
#	if ($3 != 0 ) then { line from Spline1 down $3 }
#	if ($4 != 0 ) then { line from Spline2 up $4 }
X

#
# vertical Z spline
# vz2_spline(p1, p2, off1, off2, arrow, turn, overrun)
# same as hz_spline but with absolute measurement for turn
# instead of a percentage
#
define	vz2_spline X
	initspline($1, $2, .2, .2, .25)
	d1=$6
	d2=dy-$6
	overrun=$7
	span=min(min(.9*max(d1, -d1), .9*max(d2, -d2)), max($7, -$7))
	sign=dy/(max(dy,-dy))
	if (overrun < 0 ) then {
		overrun = -.5*span
	}
	spline from Spline1 \
		then up $6 - span*sign \
		then up span*sign + overrun*sign \
		then right dx up 2*overrun*sign \
		then up overrun*sign + span*sign \
		then to Spline2 $5
	if ($3 != 0 ) then { line from Spline1 down $3 }
	if ($4 != 0 ) then { line from Spline2 up $4 }
X

#
# vertical Z spline
# vz_spline(p1, p2, off1, off2, arrow, turn, overrun)
#
define	vz_spline X
	overrun=$7
	if (overrun == 0 ) then { overrun = .2 }
	initspline($1, $2, .2, .05, .25)
	spline from Spline1 \
		then up yrad then (dy*$6)+dy*overrun-yrad \
		then right dx down 2*dy*overrun \
		then up (dy*(1-$6))+dy*overrun-yrad then up yrad $5
	if ($3 != 0 ) then { line from Spline1 down $3 }
	if ($4 != 0 ) then { line from Spline2 up $4 }
X

#
# horizontal Z spline
# hz_spline(p1, p2, off1, off2, arrow, turn, overrun)
#
define	hz_spline X
	overrun=$7
	if (overrun == 0 ) then { overrun = .2 }
	initspline($1, $2, .2, .2, .25)
	spline from Spline1 \
		then right (dx*$6)+dx*overrun \
		then up dy left 2*dx*overrun \
		then right dx*(1-$6)+dx*overrun $5
	if ($3 != 0 ) then { line from Spline1 left $3 }
	if ($4 != 0 ) then { line from Spline2 right $4 }
X

#
# erase(center, fill, rad)
#
define	erase X
	if ( $3 == 0 ) then { erad = boxht/8 } else { erad = $3 }
	circle invis rad erad fill $2 with .c at $1
X

#
# target(center)
#
define	target X
	circle rad boxht/2 with .c at $1
X

# spline down and on the left
define	spline_dl {
Start:  $1
Dest:   $2
	line from Start to Start + ($3, 0)
        spline $5 from Start \
                then left $4 \
                then down $4 \
                then to Dest + (-$4, $4) \
                then to Dest + (-$4, 0) \
                then to Dest
}

# spline down and on the right
define	spline_dr {
Start:  $1
Dest:   $2
	line from Start to Start + ($3, 0)
        spline $5 from Start \
                then right $4 \
                then down $4 \
                then to Dest + ( $4, $4) \
                then to Dest + ( $4, 0) \
                then to Dest
}
 
# spline up and on the left
define	spline_ul {
Start:  $1
Dest:   $2
	line from Start to Start + ($3, 0)
        spline $5 from Start \
                then left $4 \
                then up $4 \
                then to Dest + (-$4, -$4) \
                then to Dest + (-$4, 0) \
                then to Dest
}
 
# spline up and on the right
define	spline_ur {
Start:  $1
Dest:   $2
	line from Start to Start + ($3, 0)
        spline $5 from Start \
                then right $4 \
                then up $4 \
                then to Dest + ( $4, -$4) \
                then to Dest + ( $4, 0) \
                then to Dest
}

# Spline right/up/right
define	spline_rur {
Start:	$1
End:	$2
	if ($4 == 0) then { dx = (End.x - Start.x) / 2 } else { dx = $4 }
	if ("$6" != "") then { turn1rad = $6 } else { turn1rad = 0.2 }
	if ("$7" != "") then { turn2rad = $7 } else { turn2rad = 0.2 }
Turn1:	(Start.x + dx, Start.y)
Turn2:	(Start.x + dx, End.y)
	line from Start to Start + ($3, 0)
	spline $5 from Start \
		to Turn1 + (-turn1rad, 0) \
		to Turn1 \
		to Turn1 + (0,  turn1rad) \
		to Turn2 + (0, -turn2rad) \
		to Turn2 \
		to Turn2 + ( turn2rad, 0) \
		to End
}

# Spline right/down/right
define	spline_rdr {
Start:	$1
End:	$2
	if ($4 == 0) then { dx = (End.x - Start.x) / 2 } else { dx = $4 }
	if ("$6" != "") then { turn1rad = $6 } else { turn1rad = 0.2 }
	if ("$7" != "") then { turn2rad = $7 } else { turn2rad = 0.2 }
Turn1:	(Start.x + dx, Start.y)
Turn2:	(Start.x + dx, End.y)
	line from Start to Start + ($3, 0)
	spline $5 from Start \
		to Turn1 + (-turn1rad, 0) \
		to Turn1 \
		to Turn1 + (0, -turn1rad) \
		to Turn2 + (0,  turn2rad) \
		to Turn2 \
		to Turn2 + ( turn2rad, 0) \
		to End
}

# Spline left/up/left
define	spline_lul {
Start:	$1
End:	$2
	if ($4 == 0) then { dx = (Start.x - End.x) / 2 } else { dx = $4 }
	if ("$6" != "") then { turn1rad = $6 } else { turn1rad = 0.2 }
	if ("$7" != "") then { turn2rad = $7 } else { turn2rad = 0.2 }
Turn1:	(Start.x - dx, Start.y)
Turn2:	(Start.x - dx, End.y)
	line from Start to Start + ($3, 0)
	spline $5 from Start \
		to Turn1 + ( turn1rad, 0) \
		to Turn1 \
		to Turn1 + (0,  turn1rad) \
		to Turn2 + (0, -turn2rad) \
		to Turn2 \
		to Turn2 + (-turn2rad, 0) \
		to End $5
}

# Spline left/down/left
define	spline_ldl {
Start:	$1
End:	$2
	if ($4 == 0) then { dx = (Start.x - End.x) / 2 } else { dx = $4 }
	if ("$6" != "") then { turn1rad = $6 } else { turn1rad = 0.2 }
	if ("$7" != "") then { turn2rad = $7 } else { turn2rad = 0.2 }
Turn1:	(Start.x - dx, Start.y)
Turn2:	(Start.x - dx, End.y)
	line from Start to Start + ($3, 0)
	spline $5 from Start \
		to Turn1 + ( turn1rad, 0) \
		to Turn1 \
		to Turn1 + (0, -turn1rad) \
		to Turn2 + (0,  turn2rad) \
		to Turn2 \
		to Turn2 + (-turn2rad, 0) \
		to End $5
}

# Place hash marks at the 32-bit boundaries of an IPv6 16-byte address.

define	ipv6_hash {
NW:	$1.nw
SE:	$1.se
mywid	= SE.x - NW.x
myht	= NW.y - SE.y
	line right v6_hash from NW + (0, -1*myht/4)
	line right v6_hash from NW + (0, -2*myht/4)
	line right v6_hash from NW + (0, -3*myht/4)
	line left  v6_hash from SE + (0,  1*myht/4)
	line left  v6_hash from SE + (0,  2*myht/4)
	line left  v6_hash from SE + (0,  3*myht/4)
v6_hash	= 0.06		# reset default
}

# Draw routers with rounded corners.
# Problem with boxes with rounded corners: .ne, .ne, .se, .sw now refer to
# the rounded portion, which screws things up.  Make invisible box without
# rounded corners for compass positions.
 
define  router {
	box invis $1 $2
	box rad 0.1 with .n at last box.n
}

# small15_text2(box_name, top_string, bottom_string)
#
# Text within a box is often "too big".  For example: box "top" "bottom"
# can have the string "top" too high in the box (with ascenders
# touching the top of the box) and the string "bottom" can be too low
# (with descenders touching the bottom of the box.
# But placing .ps and .vs commands within a picture is asking for trouble.
# The "right" way to do this is to make the string smaller with an inline
# \s-1 or \s-2, with a vertical motion before and after, then \s0.
#
# The "15" means the vertical motion is 0.15m and the "2" means two arguments.
#
# Note that when invoking this macro, do *not* put the arguments
# top_string and bottom_string in double quotes.  These two arguments
# may contain spaces (but not commas).

define	small15_text2 {
	box invis ht $1.ht wid $1.wid with .n at $1.n \
		"\v'0.15m'\s-1$2\s0\v'-0.15m'" "\v'-0.15m'\s-1$3\s0\v'0.15m'"
}

# Add invisible space to the right, normally to center picture.
 
define  right_space {
	box invis wid $2 with .w at $1
}

# Add invisible space to the right, normally to center picture.
 
define  left_space {
	box invis wid $2 with .e at $1
}

.PE