422 lines
11 KiB
C
Executable File
422 lines
11 KiB
C
Executable File
/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
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/* All Rights Reserved */
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/* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */
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/* The copyright notice above does not evidence any */
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/* actual or intended publication of such source code. */
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#ident "@(#)alloc.c 1.3 94/10/14 SMI" /* SVr4.0 1.2 */
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/*******************************************************************
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PROPRIETARY NOTICE (Combined)
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This source code is unpublished proprietary information
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constituting, or derived under license from AT&T's UNIX(r) System V.
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In addition, portions of such source code were derived from Berkeley
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4.3 BSD under license from the Regents of the University of
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California.
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Copyright Notice
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Notice of copyright on this source code product does not indicate
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publication.
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(c) 1986,1987,1988,1989 Sun Microsystems, Inc
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(c) 1983,1984,1985,1986,1987,1988,1989 AT&T.
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All rights reserved.
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********************************************************************/
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/*
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* Copyright (c) 1983 Regents of the University of California.
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* All rights reserved. The Berkeley Software License Agreement
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* specifies the terms and conditions for redistribution.
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*/
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/*
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* UCB's version 5.3 in turn derived from their
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* malloc.c version 5.5 2/25/86.
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*/
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/*
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* malloc.c (Caltech) 2/21/82
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* Chris Kingsley, kingsley@cit-20.
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*
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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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/*
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* Use "#define OLDMALLOC" to include this code. Otherwise, the system's
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* malloc/free routines will be linked in.
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*/
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#include <sys/types.h>
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#define NULL 0
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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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/*
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* nmalloc[i] is the difference between the number of mallocs and frees
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* for a given block size.
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*/
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static u_int nmalloc[NBUCKETS];
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#if defined(DEBUG) || defined(RCHECK)
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#define ASSERT(p) if (!(p)) botch("p")
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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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printf("\r\nassertion botched: %s\r\n", s);
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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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char *
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malloc(nbytes)
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unsigned nbytes;
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{
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register union overhead *op;
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register int bucket, n;
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register unsigned amt;
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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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return (NULL);
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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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return (NULL);
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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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nmalloc[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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return ((char *)(op + 1));
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}
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/*
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* Allocate more memory to the indicated bucket.
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*/
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morecore(bucket)
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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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free(cp)
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char *cp;
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{
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register int size;
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register union overhead *op;
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if (cp == NULL)
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return;
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op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
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/*
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* The following botch is because csh tries to free a free block
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* when processing the =~ or !~ operators. -- layer@ucbmonet
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*/
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#ifdef CSHbotch /* was 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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return; /* sanity */
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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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nmalloc[size]--;
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}
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/*
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* When a program attempts "storage compaction" as mentioned in the
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* old malloc man page, it realloc's an already freed block. Usually
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* this is the last block it freed; occasionally it might be farther
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* back. We have to search all the free lists for the block in order
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* to determine its bucket: 1st we make one pass thru the lists
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* checking only the first block in each; if that fails we search
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* ``realloc_srchlen'' blocks in each list for a match (the variable
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* is extern so the caller can modify it). If that fails we just copy
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* however many bytes was given to realloc() and hope it's not huge.
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*/
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int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
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char *
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realloc(cp, nbytes)
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char *cp;
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unsigned nbytes;
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{
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register u_int onb;
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union overhead *op;
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char *res;
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int i, was_alloced = 0;
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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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was_alloced++;
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i = op->ov_index;
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} else {
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/*
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* Already free, doing "compaction".
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*
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* Search for the old block of memory on the
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* free list. First, check the most common
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* case (last element free'd), then (this failing)
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* the last ``realloc_srchlen'' items free'd.
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* If all lookups fail, then assume the size of
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* the memory block being realloc'd is the
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* largest possible (so that all "nbytes" of new
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* memory are copied into). Note that this could cause
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* a memory fault if the old area was tiny, and the moon
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* is gibbous. However, that is very unlikely.
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*/
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if ((i = findbucket(op, 1)) < 0 &&
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(i = findbucket(op, realloc_srchlen)) < 0)
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i = NBUCKETS;
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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 (was_alloced) {
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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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return(cp);
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} else
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free(cp);
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}
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if ((res = malloc(nbytes)) == NULL)
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return (NULL);
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if (cp != res) /* common optimization if "compacting" */
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bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
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return (res);
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}
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/*
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* Search ``srchlen'' elements of each free list for a block whose
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* header starts at ``freep''. If srchlen is -1 search the whole list.
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* Return bucket number, or -1 if not found.
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*/
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static
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findbucket(freep, srchlen)
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union overhead *freep;
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int srchlen;
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{
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register union overhead *p;
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register int i, j;
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for (i = 0; i < NBUCKETS; i++) {
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j = 0;
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for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
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if (p == freep)
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return (i);
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j++;
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}
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}
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return (-1);
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}
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/*
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* mstats - print out statistics about malloc
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*
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* Prints two lines of numbers, one showing the length of the free list
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* for each size category, the second showing the number of mallocs -
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* frees for each size category.
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*/
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showall(s)
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char **s;
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{
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#ifdef OLDMALLOC
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register int i, j;
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register union overhead *p;
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int totfree = 0,
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totused = 0;
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if (s[1])
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printf("Memory allocation statistics %s\nfree:", s[1]);
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for (i = 0; i < NBUCKETS; i++) {
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for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
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;
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if (s[1])
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printf(" %d", j);
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totfree += j * (1 << (i + 3));
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}
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if (s[1])
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printf("\nused:");
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for (i = 0; i < NBUCKETS; i++) {
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if (s[1])
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printf(" %d", nmalloc[i]);
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totused += nmalloc[i] * (1 << (i + 3));
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}
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if (s[1])
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printf("\n");
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printf("Total in use: %d, total free: %d\n", totused, totfree);
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#endif OLDMALLOC
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}
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