dc.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <bio.h>

typedef	void*	pointer;
#pragma	varargck	type	"lx"	pointer

#define FATAL 0
#define NFATAL 1
#define BLK sizeof(Blk)
#define PTRSZ sizeof(int*)
#define HEADSZ 1024
#define STKSZ 100
#define RDSKSZ 100
#define TBLSZ 256
#define ARRAYST 221
#define MAXIND 2048
#define NL 1
#define NG 2
#define NE 3
#define length(p)	((p)->wt-(p)->beg)
#define rewind(p)	(p)->rd=(p)->beg
#define create(p)	(p)->rd = (p)->wt = (p)->beg
#define fsfile(p)	(p)->rd = (p)->wt
#define truncate(p)	(p)->wt = (p)->rd
#define sfeof(p)	(((p)->rd==(p)->wt)?1:0)
#define sfbeg(p)	(((p)->rd==(p)->beg)?1:0)
#define sungetc(p,c)	*(--(p)->rd)=c
#define sgetc(p)	(((p)->rd==(p)->wt)?-1:*(p)->rd++)
#define skipc(p)	{if((p)->rd<(p)->wt)(p)->rd++;}
#define slookc(p)	(((p)->rd==(p)->wt)?-1:*(p)->rd)
#define sbackc(p)	(((p)->rd==(p)->beg)?-1:*(--(p)->rd))
#define backc(p)	{if((p)->rd>(p)->beg) --(p)->rd;}
#define sputc(p,c)	{if((p)->wt==(p)->last)more(p);\
				*(p)->wt++ = c; }
#define salterc(p,c)	{if((p)->rd==(p)->last)more(p);\
				*(p)->rd++ = c;\
				if((p)->rd>(p)->wt)(p)->wt=(p)->rd;}
#define sunputc(p)	(*((p)->rd = --(p)->wt))
#define sclobber(p)	((p)->rd = --(p)->wt)
#define zero(p)		for(pp=(p)->beg;pp<(p)->last;)\
				*pp++='\0'
#define OUTC(x)		{Bputc(&bout,x); if(--count == 0){Bprint(&bout,"\\\n"); count=ll;} }
#define TEST2		{if((count -= 2) <=0){Bprint(&bout,"\\\n");count=ll;}}
#define EMPTY		if(stkerr != 0){Bprint(&bout,"stack empty\n"); continue; }
#define EMPTYR(x)	if(stkerr!=0){pushp(x);Bprint(&bout,"stack empty\n");continue;}
#define EMPTYS		if(stkerr != 0){Bprint(&bout,"stack empty\n"); return(1);}
#define EMPTYSR(x)	if(stkerr !=0){Bprint(&bout,"stack empty\n");pushp(x);return(1);}
#define error(p)	{Bprint(&bout,p); continue; }
#define errorrt(p)	{Bprint(&bout,p); return(1); }
#define LASTFUN 026

typedef	struct	Blk	Blk;
struct	Blk
{
	char	*rd;
	char	*wt;
	char	*beg;
	char	*last;
};
typedef	struct	Sym	Sym;
struct	Sym
{
	Sym	*next;
	Blk	*val;
};
typedef	struct	Wblk	Wblk;
struct	Wblk
{
	Blk	**rdw;
	Blk	**wtw;
	Blk	**begw;
	Blk	**lastw;
};

Biobuf	*curfile, *fsave;
Blk	*arg1, *arg2;
uchar	savk;
int	dbg;
int	ifile;
Blk	*scalptr, *basptr, *tenptr, *inbas;
Blk	*sqtemp, *chptr, *strptr, *divxyz;
Blk	*stack[STKSZ];
Blk	**stkptr,**stkbeg;
Blk	**stkend;
Blk	*hfree;
int	stkerr;
int	lastchar;
Blk	*readstk[RDSKSZ];
Blk	**readptr;
Blk	*rem;
int	k;
Blk	*irem;
int	skd,skr;
int	neg;
Sym	symlst[TBLSZ];
Sym	*stable[TBLSZ];
Sym	*sptr, *sfree;
long	rel;
long	nbytes;
long	all;
long	headmor;
long	obase;
int	fw,fw1,ll;
void	(*outdit)(Blk *p, int flg);
int	logo;
int	logten;
int	count;
char	*pp;
char	*dummy;
long	longest, maxsize, active;
int	lall, lrel, lcopy, lmore, lbytes;
int	inside;
Biobuf	bin;
Biobuf	bout;

void	main(int argc, char *argv[]);
void	commnds(void);
Blk*	readin(void);
Blk*	div(Blk *ddivd, Blk *ddivr);
int	dscale(void);
Blk*	removr(Blk *p, int n);
Blk*	dcsqrt(Blk *p);
void	init(int argc, char *argv[]);
void	onintr(void);
void	pushp(Blk *p);
Blk*	pop(void);
Blk*	readin(void);
Blk*	add0(Blk *p, int ct);
Blk*	mult(Blk *p, Blk *q);
void	chsign(Blk *p);
int	readc(void);
void	unreadc(char c);
void	binop(char c);
void	dcprint(Blk *hptr);
Blk*	dcexp(Blk *base, Blk *ex);
Blk*	getdec(Blk *p, int sc);
void	tenot(Blk *p, int sc);
void	oneot(Blk *p, int sc, char ch);
void	hexot(Blk *p, int flg);
void	bigot(Blk *p, int flg);
Blk*	add(Blk *a1, Blk *a2);
int	eqk(void);
Blk*	removc(Blk *p, int n);
Blk*	scalint(Blk *p);
Blk*	scale(Blk *p, int n);
int	subt(void);
int	command(void);
int	cond(char c);
void	load(void);
int	log2(long n);
Blk*	salloc(int size);
Blk*	morehd(void);
Blk*	copy(Blk *hptr, int size);
void	sdump(char *s1, Blk *hptr);
void	seekc(Blk *hptr, int n);
void	salterwd(Blk *hptr, Blk *n);
void	more(Blk *hptr);
void	ospace(char *s);
void	garbage(char *s);
void	release(Blk *p);
Blk*	dcgetwd(Blk *p);
void	putwd(Blk *p, Blk *c);
Blk*	lookwd(Blk *p);
char*	nalloc(char *p, unsigned nbytes);
int	getstk(void);

/********debug only**/
void
tpr(char *cp, Blk *bp)
{
	print("%s-> ", cp);
	print("beg: %lx rd: %lx wt: %lx last: %lx\n", bp->beg, bp->rd,
		bp->wt, bp->last);
	for (cp = bp->beg; cp != bp->wt; cp++) {
		print("%d", *cp);
		if (cp != bp->wt-1)
			print("/");
	}
	print("\n");
}
/************/

void
main(int argc, char *argv[])
{
	Binit(&bin, 0, OREAD);
	Binit(&bout, 1, OWRITE);
	init(argc,argv);
	commnds();
	exits(0);
}

void
commnds(void)
{
	Blk *p, *q, **ptr, *s, *t;
	long l;
	Sym *sp;
	int sk, sk1, sk2, c, sign, n, d;

	while(1) {
		Bflush(&bout);
		if(((c = readc())>='0' && c <= '9') ||
		    (c>='A' && c <='F') || c == '.') {
			unreadc(c);
			p = readin();
			pushp(p);
			continue;
		}
		switch(c) {
		case ' ':
		case '\n':
		case -1:
			continue;
		case 'Y':
			sdump("stk",*stkptr);
			Bprint(&bout, "all %ld rel %ld headmor %ld\n",all,rel,headmor);
			Bprint(&bout, "nbytes %ld\n",nbytes);
			Bprint(&bout, "longest %ld active %ld maxsize %ld\n", longest,
				active, maxsize);
			Bprint(&bout, "new all %d rel %d copy %d more %d lbytes %d\n",
				lall, lrel, lcopy, lmore, lbytes);
			lall = lrel = lcopy = lmore = lbytes = 0;
			continue;
		case '_':
			p = readin();
			savk = sunputc(p);
			chsign(p);
			sputc(p,savk);
			pushp(p);
			continue;
		case '-':
			subt();
			continue;
		case '+':
			if(eqk() != 0)
				continue;
			binop('+');
			continue;
		case '*':
			arg1 = pop();
			EMPTY;
			arg2 = pop();
			EMPTYR(arg1);
			sk1 = sunputc(arg1);
			sk2 = sunputc(arg2);
			savk = sk1+sk2;
			binop('*');
			p = pop();
			if(savk>k && savk>sk1 && savk>sk2) {
				sclobber(p);
				sk = sk1;
				if(sk<sk2)
					sk = sk2;
				if(sk<k)
					sk = k;
				p = removc(p,savk-sk);
				savk = sk;
				sputc(p,savk);
			}
			pushp(p);
			continue;
		case '/':
		casediv:
			if(dscale() != 0)
				continue;
			binop('/');
			if(irem != 0)
				release(irem);
			release(rem);
			continue;
		case '%':
			if(dscale() != 0)
				continue;
			binop('/');
			p = pop();
			release(p);
			if(irem == 0) {
				sputc(rem,skr+k);
				pushp(rem);
				continue;
			}
			p = add0(rem,skd-(skr+k));
			q = add(p,irem);
			release(p);
			release(irem);
			sputc(q,skd);
			pushp(q);
			continue;
		case 'v':
			p = pop();
			EMPTY;
			savk = sunputc(p);
			if(length(p) == 0) {
				sputc(p,savk);
				pushp(p);
				continue;
			}
			if(sbackc(p)<0) {
				error("sqrt of neg number\n");
			}
			if(k<savk)
				n = savk;
			else {
				n = k*2-savk;
				savk = k;
			}
			arg1 = add0(p,n);
			arg2 = dcsqrt(arg1);
			sputc(arg2,savk);
			pushp(arg2);
			continue;

		case '^':
			neg = 0;
			arg1 = pop();
			EMPTY;
			if(sunputc(arg1) != 0)
				error("exp not an integer\n");
			arg2 = pop();
			EMPTYR(arg1);
			if(sfbeg(arg1) == 0 && sbackc(arg1)<0) {
				neg++;
				chsign(arg1);
			}
			if(length(arg1)>=3) {
				error("exp too big\n");
			}
			savk = sunputc(arg2);
			p = dcexp(arg2,arg1);
			release(arg2);
			rewind(arg1);
			c = sgetc(arg1);
			if(c == -1)
				c = 0;
			else
			if(sfeof(arg1) == 0)
				c = sgetc(arg1)*100 + c;
			d = c*savk;
			release(arg1);
		/*	if(neg == 0) {		removed to fix -exp bug*/
				if(k>=savk)
					n = k;
				else
					n = savk;
				if(n<d) {
					q = removc(p,d-n);
					sputc(q,n);
					pushp(q);
				} else {
					sputc(p,d);
					pushp(p);
				}
		/*	} else { this is disaster for exp <-127 */
		/*		sputc(p,d);		*/
		/*		pushp(p);		*/
		/*	}				*/
			if(neg == 0)
				continue;
			p = pop();
			q = salloc(2);
			sputc(q,1);
			sputc(q,0);
			pushp(q);
			pushp(p);
			goto casediv;
		case 'z':
			p = salloc(2);
			n = stkptr - stkbeg;
			if(n >= 100) {
				sputc(p,n/100);
				n %= 100;
			}
			sputc(p,n);
			sputc(p,0);
			pushp(p);
			continue;
		case 'Z':
			p = pop();
			EMPTY;
			n = (length(p)-1)<<1;
			fsfile(p);
			backc(p);
			if(sfbeg(p) == 0) {
				if((c = sbackc(p))<0) {
					n -= 2;
					if(sfbeg(p) == 1)
						n++;
					else {
						if((c = sbackc(p)) == 0)
							n++;
						else
						if(c > 90)
							n--;
					}
				} else
				if(c < 10)
					n--;
			}
			release(p);
			q = salloc(1);
			if(n >= 100) {
				sputc(q,n%100);
				n /= 100;
			}
			sputc(q,n);
			sputc(q,0);
			pushp(q);
			continue;
		case 'i':
			p = pop();
			EMPTY;
			p = scalint(p);
			release(inbas);
			inbas = p;
			continue;
		case 'I':
			p = copy(inbas,length(inbas)+1);
			sputc(p,0);
			pushp(p);
			continue;
		case 'o':
			p = pop();
			EMPTY;
			p = scalint(p);
			sign = 0;
			n = length(p);
			q = copy(p,n);
			fsfile(q);
			l = c = sbackc(q);
			if(n != 1) {
				if(c<0) {
					sign = 1;
					chsign(q);
					n = length(q);
					fsfile(q);
					l = c = sbackc(q);
				}
				if(n != 1) {
					while(sfbeg(q) == 0)
						l = l*100+sbackc(q);
				}
			}
			logo = log2(l);
			obase = l;
			release(basptr);
			if(sign == 1)
				obase = -l;
			basptr = p;
			outdit = bigot;
			if(n == 1 && sign == 0) {
				if(c <= 16) {
					outdit = hexot;
					fw = 1;
					fw1 = 0;
					ll = 70;
					release(q);
					continue;
				}
			}
			n = 0;
			if(sign == 1)
				n++;
			p = salloc(1);
			sputc(p,-1);
			t = add(p,q);
			n += length(t)*2;
			fsfile(t);
			if(sbackc(t)>9)
				n++;
			release(t);
			release(q);
			release(p);
			fw = n;
			fw1 = n-1;
			ll = 70;
			if(fw>=ll)
				continue;
			ll = (70/fw)*fw;
			continue;
		case 'O':
			p = copy(basptr,length(basptr)+1);
			sputc(p,0);
			pushp(p);
			continue;
		case '[':
			n = 0;
			p = salloc(0);
			for(;;) {
				if((c = readc()) == ']') {
					if(n == 0)
						break;
					n--;
				}
				sputc(p,c);
				if(c == '[')
					n++;
			}
			pushp(p);
			continue;
		case 'k':
			p = pop();
			EMPTY;
			p = scalint(p);
			if(length(p)>1) {
				error("scale too big\n");
			}
			rewind(p);
			k = 0;
			if(!sfeof(p))
				k = sgetc(p);
			release(scalptr);
			scalptr = p;
			continue;
		case 'K':
			p = copy(scalptr,length(scalptr)+1);
			sputc(p,0);
			pushp(p);
			continue;
		case 'X':
			p = pop();
			EMPTY;
			fsfile(p);
			n = sbackc(p);
			release(p);
			p = salloc(2);
			sputc(p,n);
			sputc(p,0);
			pushp(p);
			continue;
		case 'Q':
			p = pop();
			EMPTY;
			if(length(p)>2) {
				error("Q?\n");
			}
			rewind(p);
			if((c =  sgetc(p))<0) {
				error("neg Q\n");
			}
			release(p);
			while(c-- > 0) {
				if(readptr == &readstk[0]) {
					error("readstk?\n");
				}
				if(*readptr != 0)
					release(*readptr);
				readptr--;
			}
			continue;
		case 'q':
			if(readptr <= &readstk[1])
				exits(0);
			if(*readptr != 0)
				release(*readptr);
			readptr--;
			if(*readptr != 0)
				release(*readptr);
			readptr--;
			continue;
		case 'f':
			if(stkptr == &stack[0])
				Bprint(&bout,"empty stack\n");
			else {
				for(ptr = stkptr; ptr > &stack[0];) {
					dcprint(*ptr--);
				}
			}
			continue;
		case 'p':
			if(stkptr == &stack[0])
				Bprint(&bout,"empty stack\n");
			else {
				dcprint(*stkptr);
			}
			continue;
		case 'P':
			p = pop();
			EMPTY;
			sputc(p,0);
			Bprint(&bout,"%s",p->beg);
			release(p);
			continue;
		case 'd':
			if(stkptr == &stack[0]) {
				Bprint(&bout,"empty stack\n");
				continue;
			}
			q = *stkptr;
			n = length(q);
			p = copy(*stkptr,n);
			pushp(p);
			continue;
		case 'c':
			while(stkerr == 0) {
				p = pop();
				if(stkerr == 0)
					release(p);
			}
			continue;
		case 'S':
			if(stkptr == &stack[0]) {
				error("save: args\n");
			}
			c = getstk() & 0377;
			sptr = stable[c];
			sp = stable[c] = sfree;
			sfree = sfree->next;
			if(sfree == 0)
				goto sempty;
			sp->next = sptr;
			p = pop();
			EMPTY;
			if(c >= ARRAYST) {
				q = copy(p,length(p)+PTRSZ);
				for(n = 0;n < PTRSZ;n++) {
					sputc(q,0);
				}
				release(p);
				p = q;
			}
			sp->val = p;
			continue;
		sempty:
			error("symbol table overflow\n");
		case 's':
			if(stkptr == &stack[0]) {
				error("save:args\n");
			}
			c = getstk() & 0377;
			sptr = stable[c];
			if(sptr != 0) {
				p = sptr->val;
				if(c >= ARRAYST) {
					rewind(p);
					while(sfeof(p) == 0)
						release(dcgetwd(p));
				}
				release(p);
			} else {
				sptr = stable[c] = sfree;
				sfree = sfree->next;
				if(sfree == 0)
					goto sempty;
				sptr->next = 0;
			}
			p = pop();
			sptr->val = p;
			continue;
		case 'l':
			load();
			continue;
		case 'L':
			c = getstk() & 0377;
			sptr = stable[c];
			if(sptr == 0) {
				error("L?\n");
			}
			stable[c] = sptr->next;
			sptr->next = sfree;
			sfree = sptr;
			p = sptr->val;
			if(c >= ARRAYST) {
				rewind(p);
				while(sfeof(p) == 0) {
					q = dcgetwd(p);
					if(q != 0)
						release(q);
				}
			}
			pushp(p);
			continue;
		case ':':
			p = pop();
			EMPTY;
			q = scalint(p);
			fsfile(q);
			c = 0;
			if((sfbeg(q) == 0) && ((c = sbackc(q))<0)) {
				error("neg index\n");
			}
			if(length(q)>2) {
				error("index too big\n");
			}
			if(sfbeg(q) == 0)
				c = c*100+sbackc(q);
			if(c >= MAXIND) {
				error("index too big\n");
			}
			release(q);
			n = getstk() & 0377;
			sptr = stable[n];
			if(sptr == 0) {
				sptr = stable[n] = sfree;
				sfree = sfree->next;
				if(sfree == 0)
					goto sempty;
				sptr->next = 0;
				p = salloc((c+PTRSZ)*PTRSZ);
				zero(p);
			} else {
				p = sptr->val;
				if(length(p)-PTRSZ < c*PTRSZ) {
					q = copy(p,(c+PTRSZ)*PTRSZ);
					release(p);
					p = q;
				}
			}
			seekc(p,c*PTRSZ);
			q = lookwd(p);
			if(q!=0)
				release(q);
			s = pop();
			EMPTY;
			salterwd(p, s);
			sptr->val = p;
			continue;
		case ';':
			p = pop();
			EMPTY;
			q = scalint(p);
			fsfile(q);
			c = 0;
			if((sfbeg(q) == 0) && ((c = sbackc(q))<0)) {
				error("neg index\n");
			}
			if(length(q)>2) {
				error("index too big\n");
			}
			if(sfbeg(q) == 0)
				c = c*100+sbackc(q);
			if(c >= MAXIND) {
				error("index too big\n");
			}
			release(q);
			n = getstk() & 0377;
			sptr = stable[n];
			if(sptr != 0){
				p = sptr->val;
				if(length(p)-PTRSZ >= c*PTRSZ) {
					seekc(p,c*PTRSZ);
					s = dcgetwd(p);
					if(s != 0) {
						q = copy(s,length(s));
						pushp(q);
						continue;
					}
				}
			}
			q = salloc(1);	/*so uninitialized array elt prints as 0*/
			sputc(q, 0);
			pushp(q);
			continue;
		case 'x':
		execute:
			p = pop();
			EMPTY;
			if((readptr != &readstk[0]) && (*readptr != 0)) {
				if((*readptr)->rd == (*readptr)->wt)
					release(*readptr);
				else {
					if(readptr++ == &readstk[RDSKSZ]) {
						error("nesting depth\n");
					}
				}
			} else