/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include "a.h" /* * 16. Conditional acceptance of input. * *	conditions are *		c - condition letter (o, e, t, n) *		!c - not c *		N - N>0 *		!N - N <= 0 *		'a'b' - if a==b *		!'a'b'	- if a!=b * *	\{xxx\} can be used for newline in bodies * *	.if .ie .el * */ int iftrue[20];int niftrue; voidstartbody(void){	int c;				while((c = getrune()) == ' ' || c == '\t')		;	ungetrune(c);} voidskipbody(void){	int c, cc, nbrace; 	nbrace = 0;	for(cc=0; (c = getrune()) >= 0; cc=c){		if(c == '\n' && nbrace <= 0)			break;		if(cc == '\\' && c == '{')			nbrace++;		if(cc == '\\' && c == '}')			nbrace--;	}} intifeval(void){	int c, cc, neg, nc;	Rune line[MaxLine], *p, *e, *q;	Rune *a;		while((c = getnext()) == ' ' || c == '\t')		;	neg = 0;	while(c == '!'){		neg = !neg;		c = getnext();	} 	if('0' <= c && c <= '9'){		ungetnext(c);		a = copyarg();		c = (eval(a)>0) ^ neg;		free(a);		return c;	}		switch(c){	case ' ':	case '\n':		ungetnext(c);		return !neg;	case 'o':	/* odd page */	case 't':	/* troff */	case 'h':	/* htmlroff */		while((c = getrune()) != ' ' && c != '\t' && c != '\n' && c >= 0)			;		return 1 ^ neg;	case 'n':	/* nroff */	case 'e':	/* even page */		while((c = getnext()) != ' ' && c != '\t' && c != '\n' && c >= 0)			;		return 0 ^ neg;	} 	/* string comparison 'string1'string2' */	p = line;	e = p+nelem(line);	nc = 0;	q = nil;	while((cc=getnext()) >= 0 && cc != '\n' && p<e){		if(cc == c){			if(++nc == 2)				break;			q = p;		}		*p++ = cc;	}	if(cc != c){		ungetnext(cc);		return 0;	}	if(nc < 2){		return 0;	}	*p = 0;	return (q-line == p-(q+1)		&& memcmp(line, q+1, (q-line)*sizeof(Rune))==0) ^ neg;}	voidr_if(Rune *name){	int n;		n = ifeval();	if(runestrcmp(name, L("ie")) == 0){		if(niftrue >= nelem(iftrue))			sysfatal("%Cie overflow", dot);		iftrue[niftrue++] = n;	}	if(n)		startbody();	else		skipbody();} voidr_el(Rune *name){	USED(name);		if(niftrue <= 0){		warn("%Cel underflow", dot);		return;	}	if(iftrue[--niftrue])		skipbody();	else		startbody();} voidt16init(void){	addraw(L("if"), r_if);	addraw(L("ie"), r_if);	addraw(L("el"), r_el);		addesc('{', e_nop, HtmlMode|ArgMode);	addesc('}', e_nop, HtmlMode|ArgMode);}