n3.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

/*
 * troff3.c
 * 
 * macro and string routines, storage allocation
 */

#include "tdef.h"
#include "fns.h"
#include "ext.h"

Tchar	*argtop;
int	pagech = '%';
int	strflg;

#define	MHASHSIZE	128	/* must be 2**n */
#define	MHASH(x)	((x>>6)^x) & (MHASHSIZE-1)
Contab	*mhash[MHASHSIZE];


Blockp	*blist;		/* allocated blocks for macros and strings */
int	nblist;		/* how many there are */
int	bfree = -1;	/* first (possible) free block in the list */

Contab *contabp = NULL;
#define MDELTA 500
int	nm = 0;

int savname;		/* name of macro/string being defined */
int savslot;		/* place in Contab of savname */
int freeslot = -1;	/* first (possible) free slot in contab */

void prcontab(Contab *p)
{
	int i;
	for (i = 0; i < nm; i++)
		if (p)
			if (p[i].rq != 0)
				fprintf(stderr, "slot %d, %-2.2s\n", i, unpair(p[i].rq));
			else
				fprintf(stderr, "slot %d empty\n", i);
		else
			fprintf(stderr, "slot %d empty\n", i);
}


void blockinit(void)
{
	blist = (Blockp *) calloc(NBLIST, sizeof(Blockp));
	if (blist == NULL) {
		ERROR "not enough room for %d blocks", NBLIST WARN;
		done2(1);
	}
	nblist = NBLIST;
	blist[0].nextoff = blist[1].nextoff = -1;
	blist[0].bp = (Tchar *) calloc(BLK, sizeof(Tchar));
	blist[1].bp = (Tchar *) calloc(BLK, sizeof(Tchar));
		/* -1 prevents blist[0] from being used; temporary fix */
		/* for a design botch: offset==0 is overloaded. */
		/* blist[1] reserved for .rd indicator -- also unused. */
		/* but someone unwittingly looks at these, so allocate something */
	bfree = 2;
}


char *grow(char *ptr, int num, int size)	/* make array bigger */
{
	char *p, new;

	if (ptr == NULL)
		p = (char *) calloc(num, size);
	else
		p = (char *) realloc(ptr, num * size);
	return p;
}

void mnspace(void)
{
	nm = sizeof(contab)/sizeof(Contab) + MDELTA;
	freeslot = sizeof(contab)/sizeof(Contab) + 1;
	contabp = (Contab *) grow((char *) contabp, nm, sizeof(Contab));
	if (contabp == NULL) {
		ERROR "not enough memory for namespace of %d marcos", nm WARN;
		exit(1);
	}
	contabp = (Contab *) memcpy((char *) contabp, (char *)contab,
							sizeof(contab));
	if (contabp == NULL) {
		ERROR "Cannot reinitialize macro/request name list" WARN;
		exit(1);
	}

}

void caseig(void)
{
	int i;
	Offset oldoff = offset;

	offset = 0;
	i = copyb();
	offset = oldoff;
	if (i != '.')
		control(i, 1);
}


void casern(void)
{
	int i, j, k;

	lgf++;
	skip();
	if ((i = getrq()) == 0 || (oldmn = findmn(i)) < 0)
		return;
	skip();
	clrmn(findmn(j = getrq()));
	if (j) {
		munhash(&contabp[oldmn]);
		contabp[oldmn].rq = j;
		maddhash(&contabp[oldmn]);
		if (dip != d )
			for (k = dilev; k; k--)
				if (d[k].curd == i)
					d[k].curd = j;
	}
}

void maddhash(Contab *rp)
{
	Contab **hp;

	if (rp->rq == 0)
		return;
	hp = &mhash[MHASH(rp->rq)];
	rp->link = *hp;
	*hp = rp;
}

void munhash(Contab *mp)
{	
	Contab *p;
	Contab **lp;

	if (mp->rq == 0)
		return;
	lp = &mhash[MHASH(mp->rq)];
	p = *lp;
	while (p) {
		if (p == mp) {
			*lp = p->link;
			p->link = 0;
			return;
		}
		lp = &p->link;
		p = p->link;
	}
}

void mrehash(void)
{
	Contab *p;
	int i;

	for (i=0; i < MHASHSIZE; i++)
		mhash[i] = 0;
	for (p=contabp; p < &contabp[nm]; p++)
		p->link = 0;
	for (p=contabp; p < &contabp[nm]; p++) {
		if (p->rq == 0)
			continue;
		i = MHASH(p->rq);
		p->link = mhash[i];
		mhash[i] = p;
	}
}

void caserm(void)
{
	int j;
	int k = 0;

	lgf++;
g0:
	while (!skip() && (j = getrq()) != 0) {
		if (dip != d)
			for (k = dilev; k; k--)
				if (d[k].curd == j) {
					ERROR "cannot remove diversion %s during definition",
								unpair(j) WARN;
					goto g0;
				}
		clrmn(findmn(j));
	}
	lgf--;
}


void caseas(void)
{
	app++;
	caseds();
}


void caseds(void)
{
	ds++;
	casede();
}


void caseam(void)
{
	app++;
	casede();
}


void casede(void)
{
	int i, req;
	Offset savoff;

	req = '.';
	lgf++;
	skip();
	if ((i = getrq()) == 0)
		goto de1;
	if ((offset = finds(i)) == 0)
		goto de1;
	if (newmn)
		savslot = newmn;
	else
		savslot = findmn(i);
	savname = i;
	if (ds)
		copys();
	else
		req = copyb();
	clrmn(oldmn);
	if (newmn) {
		if (contabp[newmn].rq)
			munhash(&contabp[newmn]);
		contabp[newmn].rq = i;
		maddhash(&contabp[newmn]);

	}
	if (apptr) {
		savoff = offset;
		offset = apptr;
		wbf((Tchar) IMP);
		offset = savoff;
	}
	offset = dip->op;
	if (req != '.')
		control(req, 1);
de1:
	ds = app = 0;
}


int findmn(int i)
{
	Contab *p;

	for (p = mhash[MHASH(i)]; p; p = p->link)
		if (i == p->rq)
			return(p - contabp);
	return(-1);
}


void clrmn(int i)
{
	if (i >= 0) {
		if (contabp[i].mx)
			ffree(contabp[i].mx);
		munhash(&contabp[i]);
		contabp[i].rq = 0;
		contabp[i].mx = 0;
		contabp[i].emx = 0;
		contabp[i].f = 0;
		if (contabp[i].divsiz != NULL) {
			free(contabp[i].divsiz);
			contabp[i].divsiz = NULL;
		}
		if (freeslot > i)
			freeslot = i;
	}
}

void growcontab(void)
{
	nm += MDELTA;
	contabp = (Contab *) grow((char *) contabp , nm, sizeof(Contab));
	if (contabp == NULL) {
		ERROR "Too many (%d) string/macro names", nm WARN;
		done2(02);
	} else {
		memset((char *)(contabp) + (nm - MDELTA) * sizeof(Contab),
						0, MDELTA * sizeof(Contab));
		mrehash();
	}
}


Offset finds(int mn)
{
	int i;
	Tchar j = IMP;
	Offset savip;

	oldmn = findmn(mn);
	newmn = 0;
	apptr = 0;
	if (app && oldmn >= 0 && contabp[oldmn].mx) {
		savip = ip;
		ip = contabp[oldmn].emx;
		oldmn = -1;
		apptr = ip;
		if (!diflg)
			ip = incoff(ip);
		nextb = ip;
		ip = savip;
	} else {
		for (i = freeslot; i < nm; i++) {
			if (contabp[i].rq == 0)
				break;
		}
		if (i == nm) 
			growcontab();
		freeslot = i + 1;
		if ((nextb = alloc()) == -1) {
			app = 0;
			if (macerr++ > 1)
				done2(02);
			if (nextb == 0)
				ERROR "Not enough space for string/macro names" WARN;
			edone(04);
			return(offset = 0);
		}
		contabp[i].mx = nextb;
		if (!diflg) {
			newmn = i;
			if (oldmn == -1)
				contabp[i].rq = -1;
		} else {
			contabp[i].rq = mn;
			maddhash(&contabp[i]);
		}
	}
	app = 0;
	return(offset = nextb);
}

int skip(void)
{
	Tchar i;

	while (cbits(i = getch()) == ' ' || ismot(i))
		;
	ch = i;
	return(nlflg);
}


int copyb(void)
{
	int i, j, state;
	Tchar ii;
	int req, k;
	Offset savoff;
	Uchar *p;

	if (skip() || !(j = getrq()))
		j = '.';
	req = j;
	p = unpair(j);
	/* was: k = j >> BYTE; j &= BYTEMASK; */
	j = p[0];
	k = p[1];
	copyf++;
	flushi();
	nlflg = 0;
	state = 1;

/* state 0	eat up
 * state 1	look for .
 * state 2	look for first char of end macro
 * state 3	look for second char of end macro
 */

	while (1) {
		i = cbits(ii = getch());
		if (state == 3) {
			if (i == k)
				break;
			if (!k) {
				ch = ii;
				i = getach();
				ch = ii;
				if (!i)
					break;
			}
			state = 0;
			goto c0;
		}
		if (i == '\n') {
			state = 1;
			nlflg = 0;
			goto c0;
		}
		if (state == 1 && i == '.') {
			state++;
			savoff = offset;
			goto c0;
		}
		if (state == 2 && i == j) {
			state++;
			goto c0;
		}
		state = 0;
c0:
		if (offset)
			wbf(ii);
	}
	if (offset) {
		offset = savoff;
		wbf((Tchar)0);
	}
	copyf--;
	return(req);
}


void copys(void)
{
	Tchar i;

	copyf++;
	if (skip())
		goto c0;
	if (cbits(i = getch()) != '"')
		wbf(i);
	while (cbits(i = getch()) != '\n')
		wbf(i);
c0:
	wbf((Tchar)0);
	copyf--;
}


Offset alloc(void)	/* return free Offset in nextb */
{
	int i, j;

	for (i = bfree; i < nblist; i++)
		if (blist[i].nextoff == 0)
			break;
	if (i == nblist) {
		blist = (Blockp *) realloc((char *) blist, 2 * nblist * sizeof(Blockp));
		if (blist == NULL) {
			ERROR "can't grow blist for string/macro defns" WARN;
			done2(2);
		}
		nblist *= 2;
		for (j = i; j < nblist; j++) {
			blist[j].nextoff = 0;
			blist[j].bp = 0;
		}
	}
	blist[i].nextoff = -1;	/* this block is the end */
	bfree = i + 1;
	if (blist[i].bp == 0)
		blist[i].bp = (Tchar *) calloc(BLK, sizeof(Tchar));
	if (blist[i].bp == NULL) {
		ERROR "can't allocate memory for string/macro definitions" WARN;
		done2(2);