1*0Sstevel@tonic-gate /*
2*0Sstevel@tonic-gate * CDDL HEADER START
3*0Sstevel@tonic-gate *
4*0Sstevel@tonic-gate * The contents of this file are subject to the terms of the
5*0Sstevel@tonic-gate * Common Development and Distribution License, Version 1.0 only
6*0Sstevel@tonic-gate * (the "License"). You may not use this file except in compliance
7*0Sstevel@tonic-gate * with the License.
8*0Sstevel@tonic-gate *
9*0Sstevel@tonic-gate * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10*0Sstevel@tonic-gate * or http://www.opensolaris.org/os/licensing.
11*0Sstevel@tonic-gate * See the License for the specific language governing permissions
12*0Sstevel@tonic-gate * and limitations under the License.
13*0Sstevel@tonic-gate *
14*0Sstevel@tonic-gate * When distributing Covered Code, include this CDDL HEADER in each
15*0Sstevel@tonic-gate * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16*0Sstevel@tonic-gate * If applicable, add the following below this CDDL HEADER, with the
17*0Sstevel@tonic-gate * fields enclosed by brackets "[]" replaced with your own identifying
18*0Sstevel@tonic-gate * information: Portions Copyright [yyyy] [name of copyright owner]
19*0Sstevel@tonic-gate *
20*0Sstevel@tonic-gate * CDDL HEADER END
21*0Sstevel@tonic-gate */
22*0Sstevel@tonic-gate /*
23*0Sstevel@tonic-gate * Copyright 1987 Sun Microsystems, Inc. All rights reserved.
24*0Sstevel@tonic-gate * Use is subject to license terms.
25*0Sstevel@tonic-gate */
26*0Sstevel@tonic-gate
27*0Sstevel@tonic-gate #pragma ident "%Z%%M% %I% %E% SMI"
28*0Sstevel@tonic-gate
29*0Sstevel@tonic-gate #include "mallint.h"
30*0Sstevel@tonic-gate #include <errno.h>
31*0Sstevel@tonic-gate
32*0Sstevel@tonic-gate extern int errno;
33*0Sstevel@tonic-gate
34*0Sstevel@tonic-gate /*
35*0Sstevel@tonic-gate * memalign(align,nbytes)
36*0Sstevel@tonic-gate *
37*0Sstevel@tonic-gate * Description:
38*0Sstevel@tonic-gate * Returns a block of specified size on a specified alignment boundary.
39*0Sstevel@tonic-gate *
40*0Sstevel@tonic-gate * Algorithm:
41*0Sstevel@tonic-gate * Malloc enough to ensure that a block can be aligned correctly.
42*0Sstevel@tonic-gate * Find the alignment point and return the fragments
43*0Sstevel@tonic-gate * before and after the block.
44*0Sstevel@tonic-gate *
45*0Sstevel@tonic-gate * Errors:
46*0Sstevel@tonic-gate * Returns NULL and sets errno as follows:
47*0Sstevel@tonic-gate * [EINVAL]
48*0Sstevel@tonic-gate * if nbytes = 0,
49*0Sstevel@tonic-gate * or if alignment is misaligned,
50*0Sstevel@tonic-gate * or if the heap has been detectably corrupted.
51*0Sstevel@tonic-gate * [ENOMEM]
52*0Sstevel@tonic-gate * if the requested memory could not be allocated.
53*0Sstevel@tonic-gate */
54*0Sstevel@tonic-gate
55*0Sstevel@tonic-gate char *
memalign(align,nbytes)56*0Sstevel@tonic-gate memalign(align, nbytes)
57*0Sstevel@tonic-gate uint align;
58*0Sstevel@tonic-gate uint nbytes;
59*0Sstevel@tonic-gate {
60*0Sstevel@tonic-gate uint reqsize; /* Num of bytes to get from malloc() */
61*0Sstevel@tonic-gate register char *p; /* Ptr returned from malloc() */
62*0Sstevel@tonic-gate register Dblk blk; /* For addressing fragment blocks */
63*0Sstevel@tonic-gate register uint blksize; /* Current (shrinking) block size */
64*0Sstevel@tonic-gate register char *alignedp; /* Ptr to properly aligned boundary */
65*0Sstevel@tonic-gate register Dblk aligned_blk; /* The block to be returned */
66*0Sstevel@tonic-gate register uint frag_size; /* size of fragments fore and aft */
67*0Sstevel@tonic-gate uint x; /* ccom can't do (char*)(uint/uint) */
68*0Sstevel@tonic-gate
69*0Sstevel@tonic-gate /*
70*0Sstevel@tonic-gate * check for valid size and alignment parameters
71*0Sstevel@tonic-gate */
72*0Sstevel@tonic-gate if (nbytes == 0 || misaligned(align)) {
73*0Sstevel@tonic-gate errno = EINVAL;
74*0Sstevel@tonic-gate return NULL;
75*0Sstevel@tonic-gate }
76*0Sstevel@tonic-gate
77*0Sstevel@tonic-gate /*
78*0Sstevel@tonic-gate * Malloc enough memory to guarantee that the result can be
79*0Sstevel@tonic-gate * aligned correctly. The worst case is when malloc returns
80*0Sstevel@tonic-gate * a block so close to the next alignment boundary that a
81*0Sstevel@tonic-gate * fragment of minimum size cannot be created.
82*0Sstevel@tonic-gate */
83*0Sstevel@tonic-gate nbytes = roundup(nbytes, ALIGNSIZ);
84*0Sstevel@tonic-gate reqsize = nbytes + align + SMALLEST_BLK;
85*0Sstevel@tonic-gate p = malloc(reqsize);
86*0Sstevel@tonic-gate if (p == NULL) {
87*0Sstevel@tonic-gate return NULL;
88*0Sstevel@tonic-gate }
89*0Sstevel@tonic-gate
90*0Sstevel@tonic-gate /*
91*0Sstevel@tonic-gate * get size of the entire block (overhead and all)
92*0Sstevel@tonic-gate */
93*0Sstevel@tonic-gate blk = (Dblk)(p - ALIGNSIZ); /* back up to get length word */
94*0Sstevel@tonic-gate blksize = blk->size;
95*0Sstevel@tonic-gate
96*0Sstevel@tonic-gate /*
97*0Sstevel@tonic-gate * locate the proper alignment boundary within the block.
98*0Sstevel@tonic-gate */
99*0Sstevel@tonic-gate x = roundup((uint)p, align); /* ccom work-around */
100*0Sstevel@tonic-gate alignedp = (char *)x;
101*0Sstevel@tonic-gate aligned_blk = (Dblk)(alignedp - ALIGNSIZ);
102*0Sstevel@tonic-gate
103*0Sstevel@tonic-gate /*
104*0Sstevel@tonic-gate * Check out the space to the left of the alignment
105*0Sstevel@tonic-gate * boundary, and split off a fragment if necessary.
106*0Sstevel@tonic-gate */
107*0Sstevel@tonic-gate frag_size = (uint)aligned_blk - (uint)blk;
108*0Sstevel@tonic-gate if (frag_size != 0) {
109*0Sstevel@tonic-gate /*
110*0Sstevel@tonic-gate * Create a fragment to the left of the aligned block.
111*0Sstevel@tonic-gate */
112*0Sstevel@tonic-gate if ( frag_size < SMALLEST_BLK ) {
113*0Sstevel@tonic-gate /*
114*0Sstevel@tonic-gate * Not enough space. So make the split
115*0Sstevel@tonic-gate * at the other end of the alignment unit.
116*0Sstevel@tonic-gate */
117*0Sstevel@tonic-gate frag_size += align;
118*0Sstevel@tonic-gate aligned_blk = nextblk(aligned_blk,align);
119*0Sstevel@tonic-gate }
120*0Sstevel@tonic-gate blk->size = frag_size;
121*0Sstevel@tonic-gate blksize -= frag_size;
122*0Sstevel@tonic-gate aligned_blk->size = blksize;
123*0Sstevel@tonic-gate free(blk->data);
124*0Sstevel@tonic-gate }
125*0Sstevel@tonic-gate
126*0Sstevel@tonic-gate /*
127*0Sstevel@tonic-gate * Is there a (sufficiently large) fragment to the
128*0Sstevel@tonic-gate * right of the aligned block?
129*0Sstevel@tonic-gate */
130*0Sstevel@tonic-gate nbytes += ALIGNSIZ;
131*0Sstevel@tonic-gate frag_size = blksize - nbytes;
132*0Sstevel@tonic-gate if (frag_size > SMALLEST_BLK) {
133*0Sstevel@tonic-gate /*
134*0Sstevel@tonic-gate * split and free a fragment on the right
135*0Sstevel@tonic-gate */
136*0Sstevel@tonic-gate blk = nextblk(aligned_blk, nbytes);
137*0Sstevel@tonic-gate blk->size = frag_size;
138*0Sstevel@tonic-gate aligned_blk->size -= frag_size;
139*0Sstevel@tonic-gate free(blk->data);
140*0Sstevel@tonic-gate }
141*0Sstevel@tonic-gate return(aligned_blk->data);
142*0Sstevel@tonic-gate }
143