stak.c revision 5976:b177556d43c5 
1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 */
25
26/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
27/*	  All Rights Reserved  	*/
28
29#pragma ident	"%Z%%M%	%I%	%E% SMI"
30/*
31 * UNIX shell
32 */
33
34#include	"defs.h"
35
36
37/* ========	storage allocation	======== */
38
39unsigned char *
40getstak(asize)			/* allocate requested stack */
41int	asize;
42{
43	unsigned char	*oldstak;
44	int		size;
45
46	size = round(asize, BYTESPERWORD);
47	oldstak = stakbot;
48	staktop = stakbot += size;
49	if (staktop >= brkend)
50		growstak(staktop);
51	return(oldstak);
52}
53
54/*
55 * set up stack for local use
56 * should be followed by `endstak'
57 */
58unsigned char *
59locstak()
60{
61	if (brkend - stakbot < BRKINCR)
62	{
63		if (setbrk(brkincr) == -1)
64			error(nostack);
65		if (brkincr < BRKMAX)
66			brkincr += 256;
67	}
68	return(stakbot);
69}
70
71void
72growstak(newtop)
73unsigned char	*newtop;
74{
75	unsigned	incr;
76
77	incr = (unsigned)round(newtop - brkend + 1, BYTESPERWORD);
78	if (brkincr > incr)
79		incr = brkincr;
80	if (setbrk(incr) == -1)
81		error(nospace);
82}
83
84unsigned char *
85savstak()
86{
87	assert(staktop == stakbot);
88	return(stakbot);
89}
90
91unsigned char *
92endstak(unsigned char *argp)		/* tidy up after `locstak' */
93{
94	unsigned char	*oldstak;
95
96	if (argp >= brkend)
97		growstak(argp);
98	*argp++ = 0;
99	oldstak = stakbot;
100	stakbot = staktop = (unsigned char *)round(argp, BYTESPERWORD);
101	if (staktop >= brkend)
102		growstak(staktop);
103	return(oldstak);
104}
105
106void
107tdystak(unsigned char	*x)		/* try to bring stack back to x */
108{
109	struct blk *next;
110
111	while ((unsigned char *)stakbsy > x)
112	{
113		next = stakbsy->word;
114		free(stakbsy);
115		stakbsy = next;
116	}
117	staktop = stakbot = max(x, stakbas);
118	rmtemp(x);
119}
120
121void
122stakchk(void)
123{
124	if ((brkend - stakbas) > BRKINCR + BRKINCR)
125		setbrk(-BRKINCR);
126}
127
128unsigned char *
129cpystak(x)
130unsigned char	*x;
131{
132	return(endstak(movstrstak(x, locstak())));
133}
134
135unsigned char *
136movstrstak(unsigned char *a, unsigned char *b)
137{
138	do
139	{
140		if (b >= brkend)
141			growstak(b);
142	}
143	while (*b++ = *a++);
144	return(--b);
145}
146
147/*
148 * Copy s2 to s1, always copy n bytes.
149 * Return s1
150 */
151unsigned char *
152memcpystak(unsigned char *s1, unsigned char *s2, int n)
153{
154	unsigned char *os1 = s1;
155
156	while (--n >= 0) {
157		if (s1 >= brkend)
158			growstak(s1);
159		*s1++ = *s2++;
160	}
161	return (os1);
162}
163