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#include <u.h>
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#include <libc.h>
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#include <bio.h>
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#include "String.h"
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struct Sinstack{
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	int	depth;
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	Biobuf	*fp[32];	/* hard limit to avoid infinite recursion */
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};
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/* initialize */
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extern Sinstack *
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s_allocinstack(char *file)
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{
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	Sinstack *sp;
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	Biobuf *fp;
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	fp = Bopen(file, OREAD);
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	if(fp == nil)
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		return nil;
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	sp = malloc(sizeof *sp);
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	sp->depth = 0;
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	sp->fp[0] = fp;
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	return sp;
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}
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extern void
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s_freeinstack(Sinstack *sp)
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{
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	while(sp->depth >= 0)
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		Bterm(sp->fp[sp->depth--]);
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	free(sp);
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}
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/*  Append an input line to a String.
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 *
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 *  Empty lines and leading whitespace are removed.
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 */
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static char *
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rdline(Biobuf *fp, String *to)
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{
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	int c;
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	int len = 0;
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	c = Bgetc(fp);
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	/* eat leading white */
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	while(c==' ' || c=='\t' || c=='\n' || c=='\r')
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		c = Bgetc(fp);
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	if(c < 0)
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		return 0;
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	for(;;){
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		switch(c) {
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		case -1:
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			goto out;
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		case '\\':
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			c = Bgetc(fp);
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			if (c != '\n') {
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				s_putc(to, '\\');
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				s_putc(to, c);
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				len += 2;
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			}
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			break;
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		case '\r':
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			break;
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		case '\n':
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			if(len != 0)
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				goto out;
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			break;
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		default:
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			s_putc(to, c);
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			len++;
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			break;
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		}
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		c = Bgetc(fp);
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	}
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out:
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	s_terminate(to);
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	return to->ptr - len;
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}
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/* Append an input line to a String.
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 *
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 * Returns a pointer to the character string (or 0).
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 * Leading whitespace and newlines are removed.
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 * Lines starting with #include cause us to descend into the new file.
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 * Empty lines and other lines starting with '#' are ignored.
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 */
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extern char *
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s_rdinstack(Sinstack *sp, String *to)
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{
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	char *p;
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	Biobuf *fp, *nfp;
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	s_terminate(to);
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	fp = sp->fp[sp->depth];
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	for(;;){
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		p = rdline(fp, to);
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		if(p == nil){
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			if(sp->depth == 0)
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				break;
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			Bterm(fp);
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			sp->depth--;
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			return s_rdinstack(sp, to);
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		}
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		if(strncmp(p, "#include", 8) == 0 && (p[8] == ' ' || p[8] == '\t')){
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			to->ptr = p;
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			p += 8;
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			/* sanity (and looping) */
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			if(sp->depth >= nelem(sp->fp))
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				sysfatal("s_recgetline: includes too deep");
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			/* skip white */
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			while(*p == ' ' || *p == '\t')
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				p++;
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			nfp = Bopen(p, OREAD);
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			if(nfp == nil)
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				continue;
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			sp->depth++;
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			sp->fp[sp->depth] = nfp;
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			return s_rdinstack(sp, to);
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		}
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		/* got milk? */
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		if(*p != '#')
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			break;
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		/* take care of comments */
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		to->ptr = p;
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		s_terminate(to);
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	}
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	return p;
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}