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