source: git/external/tcl/tclAlloc.c@ 952bbbc

/* 
 * 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.
 *
 * RCS: @(#) $Id: tclAlloc.c,v 1.1 2008-06-04 13:58:03 demin Exp $
 */

#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))

#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

/*
 *----------------------------------------------------------------------
 *
 * TclpAlloc --
 *
 *      Allocate more memory.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
TclpAlloc(
    unsigned int nbytes)        /* Number of bytes to allocate. */
{
    return (char*) malloc(nbytes);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFree --
 *
 *      Free memory.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

void
TclpFree(
    char *cp)           /* Pointer to memory to free. */
{   
    free(cp);
    return;
}


/*
 *----------------------------------------------------------------------
 *
 * TclpRealloc --
 *
 *      Reallocate memory.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
TclpRealloc(
    char *cp,                   /* Pointer to alloced block. */
    unsigned int nbytes)        /* New size of memory. */
{   
    return (char*) realloc(cp, nbytes);
}


/*
 *----------------------------------------------------------------------
 *
 * 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