run.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

			do
				s++;
			while (*s!=' ' && *s!='\t' && *s!='\n' && *s!='\0');
			temp = *s;
			*s = '\0';
			sprintf(num, "%d", n);
			if (is_number(t))
				setsymtab(num, t, atof(t), STR|NUM, (Array *) ap->sval);
			else
				setsymtab(num, t, 0.0, STR, (Array *) ap->sval);
			*s = temp;
			if (*s != 0)
				s++;
		}
	} else if (sep == 0) {	/* new: split(s, a, "") => 1 char/elem */
		for (n = 0; *s != 0; s++) {
			char buf[2];
			n++;
			sprintf(num, "%d", n);
			buf[0] = *s;
			buf[1] = 0;
			if (isdigit(buf[0]))
				setsymtab(num, buf, atof(buf), STR|NUM, (Array *) ap->sval);
			else
				setsymtab(num, buf, 0.0, STR, (Array *) ap->sval);
		}
	} else if (*s != 0) {
		for (;;) {
			n++;
			t = s;
			while (*s != sep && *s != '\n' && *s != '\0')
				s++;
			temp = *s;
			*s = '\0';
			sprintf(num, "%d", n);
			if (is_number(t))
				setsymtab(num, t, atof(t), STR|NUM, (Array *) ap->sval);
			else
				setsymtab(num, t, 0.0, STR, (Array *) ap->sval);
			*s = temp;
			if (*s++ == 0)
				break;
		}
	}
	tempfree(ap);
	tempfree(y);
	if (a[2] != 0 && arg3type == STRING)
		tempfree(x);
	x = gettemp();
	x->tval = NUM;
	x->fval = n;
	return(x);
}

Cell *condexpr(Node **a, int n)	/* a[0] ? a[1] : a[2] */
{
	Cell *x;

	x = execute(a[0]);
	if (istrue(x)) {
		tempfree(x);
		x = execute(a[1]);
	} else {
		tempfree(x);
		x = execute(a[2]);
	}
	return(x);
}

Cell *ifstat(Node **a, int n)	/* if (a[0]) a[1]; else a[2] */
{
	Cell *x;

	x = execute(a[0]);
	if (istrue(x)) {
		tempfree(x);
		x = execute(a[1]);
	} else if (a[2] != 0) {
		tempfree(x);
		x = execute(a[2]);
	}
	return(x);
}

Cell *whilestat(Node **a, int n)	/* while (a[0]) a[1] */
{
	Cell *x;

	for (;;) {
		x = execute(a[0]);
		if (!istrue(x))
			return(x);
		tempfree(x);
		x = execute(a[1]);
		if (isbreak(x)) {
			x = True;
			return(x);
		}
		if (isnext(x) || isexit(x) || isret(x))
			return(x);
		tempfree(x);
	}
}

Cell *dostat(Node **a, int n)	/* do a[0]; while(a[1]) */
{
	Cell *x;

	for (;;) {
		x = execute(a[0]);
		if (isbreak(x))
			return True;
		if (isnext(x) || isnextfile(x) || isexit(x) || isret(x))
			return(x);
		tempfree(x);
		x = execute(a[1]);
		if (!istrue(x))
			return(x);
		tempfree(x);
	}
}

Cell *forstat(Node **a, int n)	/* for (a[0]; a[1]; a[2]) a[3] */
{
	Cell *x;

	x = execute(a[0]);
	tempfree(x);
	for (;;) {
		if (a[1]!=0) {
			x = execute(a[1]);
			if (!istrue(x)) return(x);
			else tempfree(x);
		}
		x = execute(a[3]);
		if (isbreak(x))		/* turn off break */
			return True;
		if (isnext(x) || isexit(x) || isret(x))
			return(x);
		tempfree(x);
		x = execute(a[2]);
		tempfree(x);
	}
}

Cell *instat(Node **a, int n)	/* for (a[0] in a[1]) a[2] */
{
	Cell *x, *vp, *arrayp, *cp, *ncp;
	Array *tp;
	int i;

	vp = execute(a[0]);
	arrayp = execute(a[1]);
	if (!isarr(arrayp)) {
		return True;
	}
	tp = (Array *) arrayp->sval;
	tempfree(arrayp);
	for (i = 0; i < tp->size; i++) {	/* this routine knows too much */
		for (cp = tp->tab[i]; cp != NULL; cp = ncp) {
			setsval(vp, cp->nval);
			ncp = cp->cnext;
			x = execute(a[2]);
			if (isbreak(x)) {
				tempfree(vp);
				return True;
			}
			if (isnext(x) || isexit(x) || isret(x)) {
				tempfree(vp);
				return(x);
			}
			tempfree(x);
		}
	}
	return True;
}

Cell *bltin(Node **a, int n)	/* builtin functions. a[0] is type, a[1] is arg list */
{
	Cell *x, *y;
	Awkfloat u;
	int t;
	wchar_t wc;
	char *p, *buf;
	char mbc[50];
	Node *nextarg;
	FILE *fp;

	t = ptoi(a[0]);
	x = execute(a[1]);
	nextarg = a[1]->nnext;
	switch (t) {
	case FLENGTH:
		p = getsval(x);
		u = (Awkfloat) countposn(p, strlen(p)); break;
	case FLOG:
		u = errcheck(log(getfval(x)), "log"); break;
	case FINT:
		modf(getfval(x), &u); break;
	case FEXP:
		u = errcheck(exp(getfval(x)), "exp"); break;
	case FSQRT:
		u = errcheck(sqrt(getfval(x)), "sqrt"); break;
	case FSIN:
		u = sin(getfval(x)); break;
	case FCOS:
		u = cos(getfval(x)); break;
	case FATAN:
		if (nextarg == 0) {
			WARNING("atan2 requires two arguments; returning 1.0");
			u = 1.0;
		} else {
			y = execute(a[1]->nnext);
			u = atan2(getfval(x), getfval(y));
			tempfree(y);
			nextarg = nextarg->nnext;
		}
		break;
	case FSYSTEM:
		fflush(stdout);		/* in case something is buffered already */
		u = (Awkfloat) system(getsval(x)) / 256;   /* 256 is unix-dep */
		break;
	case FRAND:
		/* in principle, rand() returns something in 0..RAND_MAX */
		u = (Awkfloat) (rand() % RAND_MAX) / RAND_MAX;
		break;
	case FSRAND:
		if (isrec(x))	/* no argument provided */
			u = time((time_t *)0);
		else
			u = getfval(x);
		srand((unsigned int) u);
		break;
	case FTOUPPER:
	case FTOLOWER:
		buf = tostring(getsval(x));
		if (t == FTOUPPER) {
			for (p = buf; *p; p++)
				if (islower(*p))
					*p = toupper(*p);
		} else {
			for (p = buf; *p; p++)
				if (isupper(*p))
					*p = tolower(*p);
		}
		tempfree(x);
		x = gettemp();
		setsval(x, buf);
		free(buf);
		return x;
	case FFLUSH:
		if ((fp = openfile(FFLUSH, getsval(x))) == NULL)
			u = EOF;
		else
			u = fflush(fp);
		break;
	case FUTF:
		wc = (int)getfval(x);
		mbc[wctomb(mbc, wc)] = 0;
		tempfree(x);
		x = gettemp();
		setsval(x, mbc);
		return x;
	default:	/* can't happen */
		FATAL("illegal function type %d", t);
		break;
	}
	tempfree(x);
	x = gettemp();
	setfval(x, u);
	if (nextarg != 0) {
		WARNING("warning: function has too many arguments");
		for ( ; nextarg; nextarg = nextarg->nnext)
			execute(nextarg);
	}
	return(x);
}

Cell *printstat(Node **a, int n)	/* print a[0] */
{
	int r;
	Node *x;
	Cell *y;
	FILE *fp;

	if (a[1] == 0)	/* a[1] is redirection operator, a[2] is file */
		fp = stdout;
	else
		fp = redirect(ptoi(a[1]), a[2]);
	for (x = a[0]; x != NULL; x = x->nnext) {
		y = execute(x);
		fputs(getsval(y), fp);
		tempfree(y);
		if (x->nnext == NULL)
			r = fputs(*ORS, fp);
		else
			r = fputs(*OFS, fp);
		if (r == EOF)
			FATAL("write error on %s", filename(fp));
	}
	if (a[1] != 0)
		if (fflush(fp) == EOF)
			FATAL("write error on %s", filename(fp));
	return(True);
}

Cell *nullproc(Node **a, int n)
{
	n = n;
	a = a;
	return 0;
}


FILE *redirect(int a, Node *b)	/* set up all i/o redirections */
{
	FILE *fp;
	Cell *x;
	char *fname;

	x = execute(b);
	fname = getsval(x);
	fp = openfile(a, fname);
	if (fp == NULL)
		FATAL("can't open file %s", fname);
	tempfree(x);
	return fp;
}

struct files {
	FILE	*fp;
	char	*fname;
	int	mode;	/* '|', 'a', 'w' => LE/LT, GT */
} files[FOPEN_MAX] ={
	{ NULL,  "/dev/stdin",  LT },	/* watch out: don't free this! */
	{ NULL, "/dev/stdout", GT },
	{ NULL, "/dev/stderr", GT }
};

void stdinit(void)	/* in case stdin, etc., are not constants */
{
	files[0].fp = stdin;
	files[1].fp = stdout;
	files[2].fp = stderr;
}

FILE *openfile(int a, char *us)
{
	char *s = us;
	int i, m;
	FILE *fp = 0;

	if (*s == '\0')
		FATAL("null file name in print or getline");
	for (i=0; i < FOPEN_MAX; i++)
		if (files[i].fname && strcmp(s, files[i].fname) == 0) {
			if (a == files[i].mode || (a==APPEND && files[i].mode==GT))
				return files[i].fp;
			if (a == FFLUSH)
				return files[i].fp;
		}
	if (a == FFLUSH)	/* didn't find it, so don't create it! */
		return NULL;

	for (i=0; i < FOPEN_MAX; i++)
		if (files[i].fp == 0)
			break;
	if (i >= FOPEN_MAX)
		FATAL("%s makes too many open files", s);
	fflush(stdout);	/* force a semblance of order */
	m = a;
	if (a == GT) {
		fp = fopen(s, "w");
	} else if (a == APPEND) {
		fp = fopen(s, "a");
		m = GT;	/* so can mix > and >> */
	} else if (a == '|') {	/* output pipe */
		fp = popen(s, "w");
	} else if (a == LE) {	/* input pipe */
		fp = popen(s, "r");
	} else if (a == LT) {	/* getline <file */
		fp = strcmp(s, "-") == 0 ? stdin : fopen(s, "r");	/* "-" is stdin */
	} else	/* can't happen */
		FATAL("illegal redirection %d", a);
	if (fp != NULL) {
		files[i].fname = tostring(s);
		files[i].fp = fp;
		files[i].mode = m;
	}
	return fp;
}

char *filename(FILE *fp)
{
	int i;

	for (i = 0; i < FOPEN_MAX; i++)
		if (fp == files[i].fp)
			return files[i].fname;
	return "???";
}

Cell *closefile(Node **a, int n)
{
	Cell *x;
	int i, stat;

	n = n;
	x = execute(a[0]);
	getsval(x);
	for (i = 0; i < FOPEN_MAX; i++)
		if (files[i].fname && strcmp(x->sval, files[i].fname) == 0) {
			if (ferror(files[i].fp))
				WARNING( "i/o error occurred on %s", files[i].fname );
			if (files[i].mode == '|' || files[i].mode == LE)
				stat = pclose(files[i].fp);
			else
				stat = fclose(files[i].fp);
			if (stat == EOF)
				WARNING( "i/o error occurred closing %s", files[i].fname );
			if (i > 2)	/* don't do /dev/std... */
				xfree(files[i].fname);
			files[i].fname = NULL;	/* watch out for ref thru this */
			files[i].fp = NULL;
		}
	tempfree(x);
	return(True);
}

void closeall(void)
{
	int i, stat;

	for (i = 0; i < FOPEN_MAX; i++)
		if (files[i].fp) {
			if (ferror(files[i].fp))
				WARNING( "i/o error occurred on %s", files[i].fname );
			if (files[i].mode == '|' || files[i].mode == LE)
				stat = pclose(files[i].fp);
			else
				stat = fclose(files[i].fp);
			if (stat == EOF)
				WARNING( "i/o error occurred while closing %s", files[i].fname );
		}
}

void backsub(char **pb_ptr, char **sptr_ptr);

Cell *sub(Node **a, int nnn)	/* substitute command */
{
	char *sptr, *pb, *q;
	Cell *x, *y, *result;
	char *t, *buf;
	void *p;
	int bufsz = recsize;

	if ((buf = (char *) malloc(bufsz)) == NULL)
		FATAL("out of memory in sub");
	x = execute(a[3]);	/* target string */
	t = getsval(x);
	if (a[0] == 0)		/* 0 => a[1] is already-compiled regexpr */
		p = (void *) a[1];	/* regular expression */
	else {
		y = execute(a[1]);
		p = compre(getsval(y));
		tempfree(y);
	}
	y = execute(a[2]);	/* replacement string */
	result = False;
	if (pmatch(p, t, t)) {
		sptr = t;
		adjbuf(&buf, &bufsz, 1+patbeg-sptr, recsize, 0, "sub");
		pb = buf;
		while (sptr < patbeg)
			*pb++ = *sptr++;
		sptr = getsval(y);
		while (*sptr != 0) {
			adjbuf(&buf, &bufsz, 5+pb-buf, recsize, &pb, "sub");
			if (*sptr == '\\') {
				backsub(&pb, &sptr);
			} else if (*sptr == '&') {
				sptr++;
				adjbuf(&buf, &bufsz, 1+patlen+pb-buf, recsize, &pb, "sub");
				for (q = patbeg; q < patbeg+patlen; )
					*pb++ = *q++;
			} else
				*pb++ = *sptr++;
		}
		*pb = '\0';
		if (pb > buf + bufsz)
			FATAL("sub result1 %.30s too big; can't happen", buf);
		sptr = patbeg + patlen;
		if ((patlen == 0 && *patbeg) || (patlen && *(sptr-1))) {
			adjbuf(&buf, &bufsz, 1+strlen(sptr)+pb-buf, 0, &pb, "sub");
			while ((*pb++ = *sptr++) != 0)
				;
		}
		if (pb > buf + bufsz)
			FATAL("sub result2 %.30s too big; can't happen", buf);
		setsval(x, buf);	/* BUG: should be able to avoid copy */
		result = True;;
	}
	tempfree(x);
	tempfree(y);
	free(buf);
	return result;
}

Cell *gsub(Node **a, int nnn)	/* global substitute */
{
	Cell *x, *y;
	char *rptr, *sptr, *t, *pb, *c;
	char *buf;
	void *p;
	int mflag, num;
	int bufsz = recsize;

	if ((buf = (char *)malloc(bufsz)) == NULL)
		FATAL("out of memory in gsub");
	mflag = 0;	/* if mflag == 0, can replace empty string */
	num = 0;
	x = execute(a[3]);	/* target string */
	c = t = getsval(x);
	if (a[0] == 0)		/* 0 => a[1] is already-compiled regexpr */
		p = (void *) a[1];	/* regular expression */
	else {
		y = execute(a[1]);
		p = compre(getsval(y));
		tempfree(y);
	}
	y = execute(a[2]);	/* replacement string */
	if (pmatch(p, t, c)) {
		pb = buf;
		rptr = getsval(y);
		do {
			if (patlen == 0 && *patbeg != 0) {	/* matched empty string */
				if (mflag == 0) {	/* can replace empty */
					num++;
					sptr = rptr;
					while (*sptr != 0) {
						adjbuf(&buf, &bufsz, 5+pb-buf, recsize, &pb, "gsub");
						if (*sptr == '\\') {
							backsub(&pb, &sptr);
						} else if (*sptr == '&') {
							char *q;
							sptr++;
							adjbuf(&buf, &bufsz, 1+patlen+pb-buf, recsize, &pb, "gsub");
							for (q = patbeg; q < patbeg+patlen; )
								*pb++ = *q++;
						} else
							*pb++ = *sptr++;
					}
				}
				if (*c == 0)	/* at end */
					goto done;
				adjbuf(&buf, &bufsz, 2+pb-buf, recsize, &pb, "gsub");
				*pb++ = *c++;
				if (pb > buf + bufsz)	/* BUG: not sure of this test */
					FATAL("gsub result0 %.30s too big; can't happen", buf);
				mflag = 0;
			}
			else {	/* matched nonempty string */
				num++;
				sptr = c;
				adjbuf(&buf, &bufsz, 1+(patbeg-sptr)+pb-buf, recsize, &pb, "gsub");
				while (sptr < patbeg)
					*pb++ = *sptr++;
				sptr = rptr;
				while (*sptr != 0) {
					adjbuf(&buf, &bufsz, 5+pb-buf, recsize, &pb, "gsub");
					if (*sptr == '\\') {
						backsub(&pb, &sptr);
					} else if (*sptr == '&') {
						char *q;
						sptr++;
						adjbuf(&buf, &bufsz, 1+patlen+pb-buf, recsize, &pb, "gsub");
						for (q = patbeg; q < patbeg+patlen; )
							*pb++ = *q++;
					} else
						*pb++ = *sptr++;
				}
				c = patbeg + patlen;
				if ((c[-1] == 0) || (*c == 0))
					goto done;
				if (pb > buf + bufsz)
					FATAL("gsub result1 %.30s too big; can't happen", buf);
				mflag = 1;
			}
		} while (pmatch(p, t, c));
		sptr = c;
		adjbuf(&buf, &bufsz, 1+strlen(sptr)+pb-buf, 0, &pb, "gsub");
		while ((*pb++ = *sptr++) != 0)
			;
	done:	if (pb > buf + bufsz)
			FATAL("gsub result2 %.30s too big; can't happen", buf);
		*pb = '\0';
		setsval(x, buf);	/* BUG: should be able to avoid copy + free */
	}
	tempfree(x);
	tempfree(y);
	x = gettemp();
	x->tval = NUM;
	x->fval = num;
	free(buf);
	return(x);
}

void backsub(char **pb_ptr, char **sptr_ptr)	/* handle \\& variations */
{						/* sptr[0] == '\\' */
	char *pb = *pb_ptr, *sptr = *sptr_ptr;

	if (sptr[1] == '\\') {
		if (sptr[2] == '\\' && sptr[3] == '&') { /* \\\& -> \& */
			*pb++ = '\\';
			*pb++ = '&';
			sptr += 4;
		} else if (sptr[2] == '&') {	/* \\& -> \ + matched */
			*pb++ = '\\';
			sptr += 2;
		} else {			/* \\x -> \\x */
			*pb++ = *sptr++;
			*pb++ = *sptr++;
		}
	} else if (sptr[1] == '&') {	/* literal & */
		sptr++;
		*pb++ = *sptr++;
	} else				/* literal \ */
		*pb++ = *sptr++;

	*pb_ptr = pb;
	*sptr_ptr = sptr;
}