/*
 * main.c
 * Facility: m4 macro processor
 * by: oz
 */

#include "mdef.h"

/*
 * m4 - macro processor
 *
 * PD m4 is based on the macro tool distributed with the software 
 * tools (VOS) package, and described in the "SOFTWARE TOOLS" and 
 * "SOFTWARE TOOLS IN PASCAL" books. It has been expanded to include 
 * most of the command set of SysV m4, the standard UN*X macro processor.
 *
 * Since both PD m4 and UN*X m4 are based on SOFTWARE TOOLS macro,
 * there may be certain implementation similarities between
 * the two. The PD m4 was produced without ANY references to m4
 * sources.
 *
 * References:
 *
 *	Software Tools distribution: macro
 *
 *	Kernighan, Brian W. and P. J. Plauger, SOFTWARE
 *	TOOLS IN PASCAL, Addison-Wesley, Mass. 1981
 *
 *	Kernighan, Brian W. and P. J. Plauger, SOFTWARE
 *	TOOLS, Addison-Wesley, Mass. 1976
 *
 *	Kernighan, Brian W. and Dennis M. Ritchie,
 *	THE M4 MACRO PROCESSOR, Unix Programmer's Manual,
 *	Seventh Edition, Vol. 2, Bell Telephone Labs, 1979
 *
 *	System V man page for M4
 *
 * Modification History:
 *
 * Jan 28 1986 Oz	Break the whole thing into little
 *			pieces, for easier (?) maintenance.
 *
 * Dec 12 1985 Oz	Optimize the code, try to squeeze
 *			few microseconds out..
 *
 * Dec 05 1985 Oz	Add getopt interface, define (-D),
 *			undefine (-U) options.
 *
 * Oct 21 1985 Oz	Clean up various bugs, add comment handling.
 *
 * June 7 1985 Oz	Add some of SysV m4 stuff (m4wrap, pushdef,
 *			popdef, decr, shift etc.).
 *
 * June 5 1985 Oz	Initial cut.
 *
 * Implementation Notes:
 *
 * [1]	PD m4 uses a different (and simpler) stack mechanism than the one 
 *	described in Software Tools and Software Tools in Pascal books. 
 *	The triple stack nonsense is replaced with a single stack containing 
 *	the call frames and the arguments. Each frame is back-linked to a 
 * 	previous stack frame, which enables us to rewind the stack after 
 * 	each nested call is completed. Each argument is a character pointer 
 *	to the beginning of the argument string within the string space.
 *	The only exceptions to this are (*) arg 0 and arg 1, which are
 * 	the macro definition and macro name strings, stored dynamically
 *	for the hash table.
 *
 *	    .					   .
 *	|   .	|  <-- sp			|  .  |
 *	+-------+				+-----+
 *	| arg 3 ------------------------------->| str |
 *	+-------+				|  .  |
 *	| arg 2 --------------+ 		   .
 *	+-------+	      |
 *	    *		      |			|     |
 *	+-------+	      | 		+-----+
 *	| plev	|  <-- fp     +---------------->| str |
 *	+-------+				|  .  |
 *	| type	|				   .
 *	+-------+
 *	| prcf	-----------+		plev: paren level
 *	+-------+  	   |		type: call type
 *	|   .	| 	   |		prcf: prev. call frame
 *	    .	   	   |
 *	+-------+	   |
 *	|	<----------+
 *	+-------+
 *
 * [2]	We have three types of null values:
 *
 *		nil  - nodeblock pointer type 0
 *		null - null string ("")
 *		NULL - Stdio-defined NULL
 *
 */

ndptr hashtab[HASHSIZE];	/* hash table for macros etc.  */
char buf[BUFSIZE];		/* push-back buffer	       */
char *bp = buf; 		/* first available character   */
char *endpbb = buf+BUFSIZE;	/* end of push-back buffer     */
stae mstack[STACKMAX+1]; 	/* stack of m4 machine         */
char strspace[STRSPMAX+1];	/* string space for evaluation */
char *ep = strspace;		/* first free char in strspace */
char *endest= strspace+STRSPMAX;/* end of string space	       */
int sp; 			/* current m4  stack pointer   */
int fp; 			/* m4 call frame pointer       */
FILE *infile[MAXINP];		/* input file stack (0=stdin)  */
FILE *outfile[MAXOUT];		/* diversion array(0=bitbucket)*/
FILE *active;			/* active output file pointer  */
char *m4temp;			/* filename for diversions     */
int ilevel = 0; 		/* input file stack pointer    */
int oindex = 0; 		/* diversion index..	       */
char *null = "";                /* as it says.. just a null..  */
char *m4wraps = "";             /* m4wrap string default..     */
char lquote = LQUOTE;		/* left quote character  (`)   */
char rquote = RQUOTE;		/* right quote character (')   */
char scommt = SCOMMT;		/* start character for comment */
char ecommt = ECOMMT;		/* end character for comment   */
struct keyblk keywrds[] = {	/* m4 keywords to be installed */
	"include",      INCLTYPE,
	"sinclude",     SINCTYPE,
	"define",       DEFITYPE,
	"defn",         DEFNTYPE,
	"divert",       DIVRTYPE,
	"expr",         EXPRTYPE,
	"eval",         EXPRTYPE,
	"substr",       SUBSTYPE,
	"ifelse",       IFELTYPE,
	"ifdef",        IFDFTYPE,
	"len",          LENGTYPE,
	"incr",         INCRTYPE,
	"decr",         DECRTYPE,
	"dnl",          DNLNTYPE,
	"changequote",  CHNQTYPE,
	"changecom",    CHNCTYPE,
	"index",        INDXTYPE,
#ifdef EXTENDED
	"paste",        PASTTYPE,
	"spaste",       SPASTYPE,
#endif
	"popdef",       POPDTYPE,
	"pushdef",      PUSDTYPE,
	"dumpdef",      DUMPTYPE,
	"shift",        SHIFTYPE,
	"translit",     TRNLTYPE,
	"undefine",     UNDFTYPE,
	"undivert",     UNDVTYPE,
	"divnum",       DIVNTYPE,
	"maketemp",     MKTMTYPE,
	"errprint",     ERRPTYPE,
	"m4wrap",       M4WRTYPE,
	"m4exit",       EXITTYPE,
#if unix || vms
	"syscmd",       SYSCTYPE,
	"sysval",       SYSVTYPE,
#endif
#if unix
	"unix",         MACRTYPE,
#else
#if vms
	"vms",          MACRTYPE,
#endif
#endif
};

#define MAXKEYS	(sizeof(keywrds)/sizeof(struct keyblk))

extern int optind;
extern char *optarg;

int main(argc,argv)
int argc;
char *argv[];
{
	register int c;
	register int n;
	char *p;
	static char divnam[] = DIVNAM;

	if (signal(SIGINT, SIG_IGN) != SIG_IGN)
		signal(SIGINT, onintr);
#ifdef NONZEROPAGES
	initm4();
#endif
	initkwds();

	while ((c = getopt(argc, argv, "tD:U:o:")) != EOF) {
		switch(c) {

		case 'D':               /* define something..*/
			for (p = optarg; *p; p++)
				if (*p == '=')
					break;
			if (*p)
				*p++ = EOS;
			dodefine(optarg, p);
			break;
		case 'U':               /* undefine...       */
			remhash(optarg, TOP);
			break;
		case 'o':		/* specific output   */
		case '?':
		default:
			usage();
		}
	}

	argc -= optind;
	argv += optind;

	if(argc > 1) { usage(); }
	infile[0] = stdin;		/* default input (naturally) */
	if(argc == 1) {
		if(!(infile[0] = fopen(argv[0], "r"))) {
			perror(argv[0]);
			return 1;
		}
	}

	active = stdout;		/* default active output     */
	m4temp = mktemp(divnam);	/* filename for diversions   */

	sp = -1;			/* stack pointer initialized */
	fp = 0; 			/* frame pointer initialized */

	macro();			/* get some work done here   */

	if (*m4wraps) { 		/* anything for rundown ??   */
		ilevel = 0;		/* in case m4wrap includes.. */
		putback(EOF);		/* eof is a must !!	     */
		pbstr(m4wraps); 	/* user-defined wrapup act   */
		macro();		/* last will and testament   */
	}
	else				/* default wrap-up: undivert */
		for (n = 1; n < MAXOUT; n++)
			if (outfile[n] != NULL)
				getdiv(n);

					/* remove bitbucket if used  */
	if (outfile[0] != NULL) {
		(void) fclose(outfile[0]);
		m4temp[UNIQUE] = '0';
#if vms
		(void) remove(m4temp);
#else
		(void) unlink(m4temp);
#endif
	}

	exit(0);
}

/*
 * macro - the work horse..
 *
 */
void macro() {
	char token[MAXTOK];
	register char *s;
	register int t, l;
	register ndptr p;
	register int  nlpar;

	cycle {
		if ((t = gpbc()) == '_' || isalpha(t)) {
			putback(t);
			if ((p = inspect(s = token)) == nil) {
				if (sp < 0)
					while (*s)
						putc(*s++, active);
				else
					while (*s)
						chrsave(*s++);
			}
			else {
		/*
		 * real thing.. First build a call frame:
		 *
		 */
				pushf(fp);	/* previous call frm */
				pushf(p->type); /* type of the call  */
				pushf(0);	/* parenthesis level */
				fp = sp;	/* new frame pointer */
		/*
		 * now push the string arguments:
		 *
		 */
				pushs(p->defn);	      /* defn string */
				pushs(p->name);	      /* macro name  */
				pushs(ep);	      /* start next..*/

				putback(l = gpbc());
				if (l != LPAREN)  {   /* add bracks  */
					putback(RPAREN);
					putback(LPAREN);
				}
			}
		}
		else if (t == EOF) {
			if (sp > -1)
				error("m4: unexpected end of input");
			if (--ilevel < 0)
				break;			/* all done thanks.. */
			(void) fclose(infile[ilevel+1]);
			continue;
		}
	/*
	 * non-alpha single-char token seen..
	 * [the order of else if .. stmts is
	 * important.]
	 *
	 */
		else if (t == lquote) { 		/* strip quotes */
			nlpar = 1;
			do {
				if ((l = gpbc()) == rquote)
					nlpar--;
				else if (l == lquote)
					nlpar++;
				else if (l == EOF)
					error("m4: missing right quote");
				if (nlpar > 0) {
					if (sp < 0)
						putc(l, active);
					else
						chrsave(l);
				}
			}
			while (nlpar != 0);
		}

		else if (sp < 0) {		/* not in a macro at all */
			if (t == scommt) {	/* comment handling here */
				putc(t, active);
				while ((t = gpbc()) != ecommt)
					putc(t, active);
			}
			putc(t, active);	/* output directly..	 */
		}

		else switch(t) {

		case LPAREN:
			if (PARLEV > 0)
				chrsave(t);
			while (isspace(l = gpbc()))
				;		/* skip blank, tab, nl.. */
			putback(l);
			PARLEV++;
			break;

		case RPAREN:
			if (--PARLEV > 0)
				chrsave(t);
			else {			/* end of argument list */
				chrsave(EOS);

				if (sp == STACKMAX)
					error("m4: internal stack overflow");

				if (CALTYP == MACRTYPE)
					expand((char**)mstack+fp+1,(int)sp-fp);
				else
					eval((char**)mstack+fp+1,sp-fp,CALTYP);

				ep = PREVEP;	/* flush strspace */
				sp = PREVSP;	/* previous sp..  */
				fp = PREVFP;	/* rewind stack...*/
			}
			break;

		case COMMA:
			if (PARLEV == 1)	{
				chrsave(EOS);		/* new argument   */
				while (isspace(l = gpbc()))
					;
				putback(l);
				pushs(ep);
			}
			break;
		default:
			chrsave(t);			/* stack the char */
			break;
		}
	}
}


/*
 * build an input token..
 * consider only those starting with _ or A-Za-z. This is a
 * combo with lookup to speed things up.
 */
ndptr
inspect(tp) 
register char *tp;
{
	register int h = 0;
	register char c;
	register char *name = tp;
	register char *etp = tp+MAXTOK;
	register ndptr p;

	while (tp < etp && (isalnum(c = gpbc()) || c == '_'))
		h += (*tp++ = c);
	putback(c);
	if (tp == etp)
		error("m4: token too long");
	*tp = EOS;
	for (p = hashtab[h%HASHSIZE]; p != nil; p = p->nxtptr)
		if (strcmp(name, p->name) == 0)
			break;
	return(p);
}

#ifdef NONZEROPAGES
/*
 * initm4 - initialize various tables. Useful only if your system 
 * does not know anything about demand-zero pages.
 *
 */
void initm4()
{
	register int i;

	for (i = 0; i < HASHSIZE; i++)
		hashtab[i] = nil;
	for (i = 0; i < MAXOUT; i++)
		outfile[i] = NULL;
}
#endif

/*
 * initkwds - initialise m4 keywords as fast as possible. 
 * This very similar to install, but without certain overheads,
 * such as calling lookup. Malloc is not used for storing the 
 * keyword strings, since we simply use the static  pointers
 * within keywrds block. We also assume that there is enough memory 
 * to at least install the keywords (i.e. malloc won't fail).
 *
 */
void initkwds() {
	register int i;
	register int h;
	register ndptr p;

	for (i = 0; i < MAXKEYS; i++) {
		h = hash(keywrds[i].knam);
		p = (ndptr) malloc(sizeof(struct ndblock));
		p->nxtptr = hashtab[h];
		hashtab[h] = p;
		p->name = keywrds[i].knam;
		p->defn = null;
		p->type = keywrds[i].ktyp | STATIC;
	}
}
