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+/*
+ * tclAlloc.c --
+ *
+ * This is a very fast storage allocator. It allocates blocks of a
+ * small number of different sizes, and keeps free lists of each size.
+ * Blocks that don't exactly fit are passed up to the next larger size.
+ * Blocks over a certain size are directly allocated from the system.
+ *
+ * Copyright (c) 1983 Regents of the University of California.
+ * Copyright (c) 1996-1997 Sun Microsystems, Inc.
+ *
+ * Portions contributed by Chris Kingsley, Jack Jansen and Ray Johnson.
+ *
+ * See the file "license.terms" for information on usage and redistribution
+ * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+ *
+ * SCCS: @(#) tclAlloc.c 1.4 97/08/11 18:45:38
+ */
+
+#include "tclInt.h"
+#include "tclPort.h"
+
+#ifdef TCL_DEBUG
+# define DEBUG
+/* #define MSTATS */
+# define RCHECK
+#endif
+
+typedef unsigned long caddr_t;
+
+/*
+ * The overhead on a block is at least 4 bytes. When free, this space
+ * contains a pointer to the next free block, and the bottom two bits must
+ * be zero. When in use, the first byte is set to MAGIC, and the second
+ * byte is the size index. The remaining bytes are for alignment.
+ * If range checking is enabled then a second word holds the size of the
+ * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
+ * The order of elements is critical: ov_magic must overlay the low order
+ * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
+ */
+
+union overhead {
+ union overhead *ov_next; /* when free */
+ struct {
+ unsigned char ovu_magic0; /* magic number */
+ unsigned char ovu_index; /* bucket # */
+ unsigned char ovu_unused; /* unused */
+ unsigned char ovu_magic1; /* other magic number */
+#ifdef RCHECK
+ unsigned short ovu_rmagic; /* range magic number */
+ unsigned long ovu_size; /* actual block size */
+#endif
+ } ovu;
+#define ov_magic0 ovu.ovu_magic0
+#define ov_magic1 ovu.ovu_magic1
+#define ov_index ovu.ovu_index
+#define ov_rmagic ovu.ovu_rmagic
+#define ov_size ovu.ovu_size
+};
+
+
+#define MAGIC 0xef /* magic # on accounting info */
+#define RMAGIC 0x5555 /* magic # on range info */
+
+#ifdef RCHECK
+#define RSLOP sizeof (unsigned short)
+#else
+#define RSLOP 0
+#endif
+
+#define OVERHEAD (sizeof(union overhead) + RSLOP)
+
+/*
+ * nextf[i] is the pointer to the next free block of size 2^(i+3). The
+ * smallest allocatable block is 8 bytes. The overhead information
+ * precedes the data area returned to the user.
+ */
+
+#define NBUCKETS 13
+#define MAXMALLOC (1<<(NBUCKETS+2))
+static union overhead *nextf[NBUCKETS];
+
+#ifdef MSTATS
+
+/*
+ * nmalloc[i] is the difference between the number of mallocs and frees
+ * for a given block size.
+ */
+
+static unsigned int nmalloc[NBUCKETS+1];
+#include <stdio.h>
+#endif
+
+#if defined(DEBUG) || defined(RCHECK)
+#define ASSERT(p) if (!(p)) panic(# p)
+#define RANGE_ASSERT(p) if (!(p)) panic(# p)
+#else
+#define ASSERT(p)
+#define RANGE_ASSERT(p)
+#endif
+
+/*
+ * Prototypes for functions used only in this file.
+ */
+
+static void MoreCore _ANSI_ARGS_((int bucket));
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclpAlloc --
+ *
+ * Allocate more memory.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+char *
+TclpAlloc(
+ unsigned int nbytes) /* Number of bytes to allocate. */
+{
+ register union overhead *op;
+ register long bucket;
+ register unsigned amt;
+
+ /*
+ * First the simple case: we simple allocate big blocks directly
+ */
+ if (nbytes + OVERHEAD >= MAXMALLOC) {
+ op = (union overhead *)TclpSysAlloc(nbytes+OVERHEAD, 0);
+ if (op == NULL) {
+ return NULL;
+ }
+ op->ov_magic0 = op->ov_magic1 = MAGIC;
+ op->ov_index = 0xff;
+#ifdef MSTATS
+ nmalloc[NBUCKETS]++;
+#endif
+#ifdef RCHECK
+ /*
+ * Record allocated size of block and
+ * bound space with magic numbers.
+ */
+ op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
+ op->ov_rmagic = RMAGIC;
+ *(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
+#endif
+ return (void *)(op+1);
+ }
+ /*
+ * Convert amount of memory requested into closest block size
+ * stored in hash buckets which satisfies request.
+ * Account for space used per block for accounting.
+ */
+#ifndef RCHECK
+ amt = 8; /* size of first bucket */
+ bucket = 0;
+#else
+ amt = 16; /* size of first bucket */
+ bucket = 1;
+#endif
+ while (nbytes + OVERHEAD > amt) {
+ amt <<= 1;
+ if (amt == 0) {
+ return (NULL);
+ }
+ bucket++;
+ }
+ ASSERT( bucket < NBUCKETS );
+
+ /*
+ * If nothing in hash bucket right now,
+ * request more memory from the system.
+ */
+ if ((op = nextf[bucket]) == NULL) {
+ MoreCore(bucket);
+ if ((op = nextf[bucket]) == NULL) {
+ return (NULL);
+ }
+ }
+ /*
+ * Remove from linked list
+ */
+ nextf[bucket] = op->ov_next;
+ op->ov_magic0 = op->ov_magic1 = MAGIC;
+ op->ov_index = (unsigned char) bucket;
+#ifdef MSTATS
+ nmalloc[bucket]++;
+#endif
+#ifdef RCHECK
+ /*
+ * Record allocated size of block and
+ * bound space with magic numbers.
+ */
+ op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
+ op->ov_rmagic = RMAGIC;
+ *(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
+#endif
+ return ((char *)(op + 1));
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * MoreCore --
+ *
+ * Allocate more memory to the indicated bucket.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * Attempts to get more memory from the system.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+MoreCore(
+ int bucket) /* What bucket to allocat to. */
+{
+ register union overhead *op;
+ register long sz; /* size of desired block */
+ long amt; /* amount to allocate */
+ int nblks; /* how many blocks we get */
+
+ /*
+ * sbrk_size <= 0 only for big, FLUFFY, requests (about
+ * 2^30 bytes on a VAX, I think) or for a negative arg.
+ */
+ sz = 1 << (bucket + 3);
+ ASSERT(sz > 0);
+
+ amt = MAXMALLOC;
+ nblks = amt / sz;
+ ASSERT(nblks*sz == amt);
+
+ op = (union overhead *)TclpSysAlloc(amt, 1);
+ /* no more room! */
+ if (op == NULL) {
+ return;
+ }
+
+ /*
+ * Add new memory allocated to that on
+ * free list for this hash bucket.
+ */
+ nextf[bucket] = op;
+ while (--nblks > 0) {
+ op->ov_next = (union overhead *)((caddr_t)op + sz);
+ op = (union overhead *)((caddr_t)op + sz);
+ }
+ op->ov_next = (union overhead *)NULL;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclpFree --
+ *
+ * Free memory.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+TclpFree(
+ char *cp) /* Pointer to memory to free. */
+{
+ register long size;
+ register union overhead *op;
+
+ if (cp == NULL) {
+ return;
+ }
+
+ op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
+
+ ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
+ ASSERT(op->ov_magic1 == MAGIC);
+ if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
+ return;
+ }
+
+ RANGE_ASSERT(op->ov_rmagic == RMAGIC);
+ RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
+ size = op->ov_index;
+ if ( size == 0xff ) {
+#ifdef MSTATS
+ nmalloc[NBUCKETS]--;
+#endif
+ TclpSysFree(op);
+ return;
+ }
+ ASSERT(size < NBUCKETS);
+ op->ov_next = nextf[size]; /* also clobbers ov_magic */
+ nextf[size] = op;
+#ifdef MSTATS
+ nmalloc[size]--;
+#endif
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclpRealloc --
+ *
+ * Reallocate memory.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+char *
+TclpRealloc(
+ char *cp, /* Pointer to alloced block. */
+ unsigned int nbytes) /* New size of memory. */
+{
+ int i;
+ union overhead *op;
+ int expensive;
+ unsigned long maxsize;
+
+ if (cp == NULL) {
+ return (TclpAlloc(nbytes));
+ }
+
+ op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
+
+ ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
+ ASSERT(op->ov_magic1 == MAGIC);
+ if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
+ return NULL;
+ }
+
+ RANGE_ASSERT(op->ov_rmagic == RMAGIC);
+ RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
+ i = op->ov_index;
+
+ /*
+ * If the block isn't in a bin, just realloc it.
+ */
+
+ if (i == 0xff) {
+ op = (union overhead *) TclpSysRealloc(op, nbytes+OVERHEAD);
+ if (op == NULL) {
+ return NULL;
+ }
+#ifdef MSTATS
+ nmalloc[NBUCKETS]++;
+#endif
+#ifdef RCHECK
+ /*
+ * Record allocated size of block and update magic number bounds.
+ */
+
+ op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
+ *(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
+#endif
+ return (char *)(op+1);
+ }
+ maxsize = 1 << (i+3);
+ expensive = 0;
+ if ( nbytes + OVERHEAD > maxsize ) {
+ expensive = 1;
+ } else if ( i > 0 && nbytes + OVERHEAD < (maxsize/2) ) {
+ expensive = 1;
+ }
+
+ if (expensive) {
+ void *newp;
+
+ newp = TclpAlloc(nbytes);
+ if ( newp == NULL ) {
+ return NULL;
+ }
+ maxsize -= OVERHEAD;
+ if ( maxsize < nbytes )
+ nbytes = maxsize;
+ memcpy((VOID *) newp, (VOID *) cp, (size_t) nbytes);
+ TclpFree(cp);
+ return newp;
+ }
+
+ /*
+ * Ok, we don't have to copy, it fits as-is
+ */
+#ifdef RCHECK
+ op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
+ *(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
+#endif
+ return(cp);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * mstats --
+ *
+ * Prints two lines of numbers, one showing the length of the
+ * free list for each size category, the second showing the
+ * number of mallocs - frees for each size category.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+#ifdef MSTATS
+void
+mstats(
+ char *s) /* Where to write info. */
+{
+ register int i, j;
+ register union overhead *p;
+ int totfree = 0,
+ totused = 0;
+
+ fprintf(stderr, "Memory allocation statistics %s\nTclpFree:\t", s);
+ for (i = 0; i < NBUCKETS; i++) {
+ for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
+ fprintf(stderr, " %d", j);
+ totfree += j * (1 << (i + 3));
+ }
+ fprintf(stderr, "\nused:\t");
+ for (i = 0; i < NBUCKETS; i++) {
+ fprintf(stderr, " %d", nmalloc[i]);
+ totused += nmalloc[i] * (1 << (i + 3));
+ }
+ fprintf(stderr, "\n\tTotal small in use: %d, total free: %d\n",
+ totused, totfree);
+ fprintf(stderr, "\n\tNumber of big (>%d) blocks in use: %d\n",
+ MAXMALLOC, nmalloc[NBUCKETS]);
+}
+#endif