362 lines
9.7 KiB
C
362 lines
9.7 KiB
C
/* ==== malloc.c ============================================================
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* Copyright (c) 1983 Regents of the University of California.
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* Copyright (c) 1993, 1994 by Chris Provenzano, proven@mit.edu
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Description : Malloc functions.
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* This is a very fast storage allocator. It allocates blocks of a small
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* number of different sizes, and keeps free lists of each size. Blocks that
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* don't exactly fit are passed up to the next larger size. In this
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* implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
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* This is designed for use in a virtual memory environment.
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*
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* 0.00 82/02/21 Chris Kingsley kingsley@cit-20
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*
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* 1.00 93/11/06 proven
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* -Modified BSD libc malloc to be threadsafe.
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*
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*/
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#ifndef lint
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static const char rcsid[] = "$Id: malloc.c,v 1.4 1994/02/07 22:04:20 proven Exp $ $provenid: malloc.c,v 1.16 1994/02/07 02:19:00 proven Exp $";
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#endif
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#include <pthread.h>
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#include <sys/types.h>
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#include <string.h>
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#include <pthread/posix.h>
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/*
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* The overhead on a block is at least 4 bytes. When free, this space
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* contains a pointer to the next free block, and the bottom two bits must
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* be zero. When in use, the first byte is set to MAGIC, and the second
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* byte is the size index. The remaining bytes are for alignment.
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* If range checking is enabled then a second word holds the size of the
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* requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
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* The order of elements is critical: ov_magic must overlay the low order
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* bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
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*/
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union overhead {
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union overhead *ov_next; /* when free */
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struct {
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u_char ovu_magic; /* magic number */
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u_char ovu_index; /* bucket # */
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#ifdef RCHECK
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u_short ovu_rmagic; /* range magic number */
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u_int ovu_size; /* actual block size */
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#endif
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} ovu;
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#define ov_magic ovu.ovu_magic
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#define ov_index ovu.ovu_index
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#define ov_rmagic ovu.ovu_rmagic
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#define ov_size ovu.ovu_size
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};
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#define MAGIC 0xef /* magic # on accounting info */
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#define RMAGIC 0x5555 /* magic # on range info */
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#ifdef RCHECK
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#define RSLOP sizeof (u_short)
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#else
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#define RSLOP 0
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#endif
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/*
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* nextf[i] is the pointer to the next free block of size 2^(i+3). The
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* smallest allocatable block is 8 bytes. The overhead information
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* precedes the data area returned to the user.
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*/
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#define NBUCKETS 30
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static union overhead *nextf[NBUCKETS];
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extern char *sbrk();
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static int pagesz; /* page size */
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static int pagebucket; /* page size bucket */
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static semaphore malloc_lock = SEMAPHORE_CLEAR;
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#if defined(DEBUG) || defined(RCHECK)
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#define ASSERT(p) if (!(p)) botch("p")
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#include <stdio.h>
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static
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botch(s)
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char *s;
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{
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fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
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(void) fflush(stderr); /* just in case user buffered it */
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abort();
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}
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#else
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#define ASSERT(p)
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#endif
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/* ==========================================================================
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* morecore()
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*
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* Allocate more memory to the indicated bucket
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*/
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static inline void morecore(int bucket)
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{
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register union overhead *op;
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register int sz; /* size of desired block */
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int amt; /* amount to allocate */
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int nblks; /* how many blocks we get */
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/*
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* sbrk_size <= 0 only for big, FLUFFY, requests (about
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* 2^30 bytes on a VAX, I think) or for a negative arg.
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*/
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sz = 1 << (bucket + 3);
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#ifdef DEBUG
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ASSERT(sz > 0);
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#else
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if (sz <= 0)
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return;
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#endif
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if (sz < pagesz) {
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amt = pagesz;
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nblks = amt / sz;
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} else {
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amt = sz + pagesz;
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nblks = 1;
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}
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op = (union overhead *)sbrk(amt);
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/* no more room! */
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if ((int)op == -1)
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return;
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/*
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* Add new memory allocated to that on
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* free list for this hash bucket.
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*/
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nextf[bucket] = op;
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while (--nblks > 0) {
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op->ov_next = (union overhead *)((caddr_t)op + sz);
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op = (union overhead *)((caddr_t)op + sz);
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}
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}
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/* ==========================================================================
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* malloc()
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*/
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void *malloc(size_t nbytes)
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{
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union overhead *op;
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unsigned int amt;
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int bucket, n;
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semaphore *lock;
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lock = &malloc_lock;
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while(SEMAPHORE_TEST_AND_SET(lock)) {
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pthread_yield();
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}
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/*
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* First time malloc is called, setup page size and
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* align break pointer so all data will be page aligned.
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*/
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if (pagesz == 0) {
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pagesz = n = getpagesize();
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op = (union overhead *)sbrk(0);
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n = n - sizeof (*op) - ((int)op & (n - 1));
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if (n < 0)
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n += pagesz;
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if (n) {
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if (sbrk(n) == (char *)-1)
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return (NULL);
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}
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bucket = 0;
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amt = 8;
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while (pagesz > amt) {
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amt <<= 1;
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bucket++;
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}
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pagebucket = bucket;
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}
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/*
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* Convert amount of memory requested into closest block size
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* stored in hash buckets which satisfies request.
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* Account for space used per block for accounting.
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*/
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if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
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#ifndef RCHECK
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amt = 8; /* size of first bucket */
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bucket = 0;
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#else
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amt = 16; /* size of first bucket */
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bucket = 1;
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#endif
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n = -(sizeof (*op) + RSLOP);
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} else {
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amt = pagesz;
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bucket = pagebucket;
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}
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while (nbytes > amt + n) {
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amt <<= 1;
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if (amt == 0) {
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SEMAPHORE_RESET(lock);
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return (NULL);
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}
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bucket++;
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}
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/*
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* If nothing in hash bucket right now,
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* request more memory from the system.
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*/
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if ((op = nextf[bucket]) == NULL) {
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morecore(bucket);
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if ((op = nextf[bucket]) == NULL) {
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SEMAPHORE_RESET(lock);
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return (NULL);
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}
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}
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/* remove from linked list */
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nextf[bucket] = op->ov_next;
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op->ov_magic = MAGIC;
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op->ov_index = bucket;
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#ifdef RCHECK
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/*
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* Record allocated size of block and
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* bound space with magic numbers.
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*/
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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op->ov_rmagic = RMAGIC;
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*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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SEMAPHORE_RESET(lock);
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return ((char *)(op + 1));
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}
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/* ==========================================================================
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* free()
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*/
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void free(void *cp)
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{
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union overhead *op;
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semaphore *lock;
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int size;
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lock = &malloc_lock;
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while(SEMAPHORE_TEST_AND_SET(lock)) {
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pthread_yield();
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}
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if (cp == NULL) {
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SEMAPHORE_RESET(lock);
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return;
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}
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op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
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#ifdef DEBUG
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ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
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#else
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if (op->ov_magic != MAGIC) {
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SEMAPHORE_RESET(lock);
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return; /* sanity */
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}
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#endif
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#ifdef RCHECK
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ASSERT(op->ov_rmagic == RMAGIC);
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ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
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#endif
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size = op->ov_index;
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ASSERT(size < NBUCKETS);
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op->ov_next = nextf[size]; /* also clobbers ov_magic */
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nextf[size] = op;
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SEMAPHORE_RESET(lock);
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}
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/* ==========================================================================
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* realloc()
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*
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* Storage compaction is no longer supported, fix program and try again.
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*/
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void *realloc(void *cp, size_t nbytes)
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{
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u_int onb;
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int i;
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semaphore *lock;
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union overhead *op;
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char *res;
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if (cp == NULL)
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return (malloc(nbytes));
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op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
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if (op->ov_magic == MAGIC) {
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i = op->ov_index;
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} else {
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/*
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* This will cause old programs using storage compaction feature of
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* realloc to break in a pseudo resonable way that is easy to debug.
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* Returning a malloced buffer without the copy may cause
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* indeterministic behavior.
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*/
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return(NULL);
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}
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lock = &malloc_lock;
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while(SEMAPHORE_TEST_AND_SET(lock)) {
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pthread_yield();
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}
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onb = 1 << (i + 3);
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if (onb < pagesz)
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onb -= sizeof (*op) + RSLOP;
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else
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onb += pagesz - sizeof (*op) - RSLOP;
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/* avoid the copy if same size block */
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if (i) {
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i = 1 << (i + 2);
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if (i < pagesz)
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i -= sizeof (*op) + RSLOP;
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else
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i += pagesz - sizeof (*op) - RSLOP;
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}
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if (nbytes <= onb && nbytes > i) {
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#ifdef RCHECK
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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SEMAPHORE_RESET(lock);
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return(cp);
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}
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SEMAPHORE_RESET(lock);
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if ((res = malloc(nbytes)) == NULL) {
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free(cp);
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return (NULL);
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}
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bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
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free(cp);
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return (res);
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}
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