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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 1987 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include "mallint.h"
#include <errno.h>
extern int errno;
/*
* memalign(align,nbytes)
*
* Description:
* Returns a block of specified size on a specified alignment boundary.
*
* Algorithm:
* Malloc enough to ensure that a block can be aligned correctly.
* Find the alignment point and return the fragments
* before and after the block.
*
* Errors:
* Returns NULL and sets errno as follows:
* [EINVAL]
* if nbytes = 0,
* or if alignment is misaligned,
* or if the heap has been detectably corrupted.
* [ENOMEM]
* if the requested memory could not be allocated.
*/
char *
memalign(align, nbytes)
uint align;
uint nbytes;
{
uint reqsize; /* Num of bytes to get from malloc() */
register char *p; /* Ptr returned from malloc() */
register Dblk blk; /* For addressing fragment blocks */
register uint blksize; /* Current (shrinking) block size */
register char *alignedp; /* Ptr to properly aligned boundary */
register Dblk aligned_blk; /* The block to be returned */
register uint frag_size; /* size of fragments fore and aft */
uint x; /* ccom can't do (char*)(uint/uint) */
/*
* check for valid size and alignment parameters
*/
if (nbytes == 0 || misaligned(align)) {
errno = EINVAL;
return NULL;
}
/*
* Malloc enough memory to guarantee that the result can be
* aligned correctly. The worst case is when malloc returns
* a block so close to the next alignment boundary that a
* fragment of minimum size cannot be created.
*/
nbytes = roundup(nbytes, ALIGNSIZ);
reqsize = nbytes + align + SMALLEST_BLK;
p = malloc(reqsize);
if (p == NULL) {
return NULL;
}
/*
* get size of the entire block (overhead and all)
*/
blk = (Dblk)(p - ALIGNSIZ); /* back up to get length word */
blksize = blk->size;
/*
* locate the proper alignment boundary within the block.
*/
x = roundup((uint)p, align); /* ccom work-around */
alignedp = (char *)x;
aligned_blk = (Dblk)(alignedp - ALIGNSIZ);
/*
* Check out the space to the left of the alignment
* boundary, and split off a fragment if necessary.
*/
frag_size = (uint)aligned_blk - (uint)blk;
if (frag_size != 0) {
/*
* Create a fragment to the left of the aligned block.
*/
if ( frag_size < SMALLEST_BLK ) {
/*
* Not enough space. So make the split
* at the other end of the alignment unit.
*/
frag_size += align;
aligned_blk = nextblk(aligned_blk,align);
}
blk->size = frag_size;
blksize -= frag_size;
aligned_blk->size = blksize;
free(blk->data);
}
/*
* Is there a (sufficiently large) fragment to the
* right of the aligned block?
*/
nbytes += ALIGNSIZ;
frag_size = blksize - nbytes;
if (frag_size > SMALLEST_BLK) {
/*
* split and free a fragment on the right
*/
blk = nextblk(aligned_blk, nbytes);
blk->size = frag_size;
aligned_blk->size -= frag_size;
free(blk->data);
}
return(aligned_blk->data);
}
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