[perl5.git] / malloc.c

/*    malloc.c
 *
 */

#ifndef NO_FANCY_MALLOC
#  ifndef SMALL_BUCKET_VIA_TABLE
#    define SMALL_BUCKET_VIA_TABLE
#  endif 
#  ifndef BUCKETS_ROOT2
#    define BUCKETS_ROOT2
#  endif 
#  ifndef IGNORE_SMALL_BAD_FREE
#    define IGNORE_SMALL_BAD_FREE
#  endif 
#endif 

#ifndef PLAIN_MALLOC			/* Bulk enable features */
#  ifndef PACK_MALLOC
#      define PACK_MALLOC
#  endif 
#  ifndef TWO_POT_OPTIMIZE
#    define TWO_POT_OPTIMIZE
#  endif 
#  if defined(PERL_CORE) && !defined(PERL_EMERGENCY_SBRK)
#    define PERL_EMERGENCY_SBRK
#  endif 
#  if defined(PERL_CORE) && !defined(DEBUGGING_MSTATS)
#    define DEBUGGING_MSTATS
#  endif 
#endif

#define MIN_BUC_POW2 (sizeof(void*) > 4 ? 3 : 2) /* Allow for 4-byte arena. */
#define MIN_BUCKET (MIN_BUC_POW2 * BUCKETS_PER_POW2)

#if !(defined(I286) || defined(atarist))
	/* take 2k unless the block is bigger than that */
#  define LOG_OF_MIN_ARENA 11
#else
	/* take 16k unless the block is bigger than that 
	   (80286s like large segments!), probably good on the atari too */
#  define LOG_OF_MIN_ARENA 14
#endif

#ifndef lint
#  if defined(DEBUGGING) && !defined(NO_RCHECK)
#    define RCHECK
#  endif
#  if defined(RCHECK) && defined(IGNORE_SMALL_BAD_FREE)
#    undef IGNORE_SMALL_BAD_FREE
#  endif 
/*
 * malloc.c (Caltech) 2/21/82
 * Chris Kingsley, kingsley@cit-20.
 *
 * 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.  In this 
 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
 * If PACK_MALLOC is defined, small blocks are 2^n bytes long.
 * This is designed for use in a program that uses vast quantities of memory,
 * but bombs when it runs out. 
 */

#ifdef PERL_CORE
#  include "EXTERN.h"
#  include "perl.h"
#else
#  ifdef PERL_FOR_X2P
#    include "../EXTERN.h"
#    include "../perl.h"
#  else
#    include <stdlib.h>
#    include <stdio.h>
#    include <memory.h>
#    define _(arg) arg
#    ifndef Malloc_t
#      define Malloc_t void *
#    endif
#    ifndef MEM_SIZE
#      define MEM_SIZE unsigned long
#    endif
#    ifndef LONG_MAX
#      define LONG_MAX 0x7FFFFFFF
#    endif
#    ifndef UV
#      define UV unsigned long
#    endif
#    ifndef caddr_t
#      define caddr_t char *
#    endif
#    ifndef Free_t
#      define Free_t void
#    endif
#    define Copy(s,d,n,t) (void)memcpy((char*)(d),(char*)(s), (n) * sizeof(t))
#    define PerlEnv_getenv getenv
#    define PerlIO_printf fprintf
#    define PerlIO_stderr() stderr
#  endif
#  ifndef croak				/* make depend */
#    define croak(mess, arg) warn((mess), (arg)); exit(1);
#  endif 
#  ifndef warn
#    define warn(mess, arg) fprintf(stderr, (mess), (arg));
#  endif 
#  ifdef DEBUG_m
#    undef DEBUG_m
#  endif 
#  define DEBUG_m(a)
#  ifdef DEBUGGING
#     undef DEBUGGING
#  endif
#endif

#ifndef MUTEX_LOCK
#  define MUTEX_LOCK(l)
#endif 

#ifndef MUTEX_UNLOCK
#  define MUTEX_UNLOCK(l)
#endif 

#ifdef DEBUGGING
#  undef DEBUG_m
#  define DEBUG_m(a)  if (debug & 128)   a
#endif

/* I don't much care whether these are defined in sys/types.h--LAW */

#define u_char unsigned char
#define u_int unsigned int

#ifdef HAS_QUAD
#  define u_bigint UV			/* Needs to eat *void. */
#else  /* needed? */
#  define u_bigint unsigned long	/* Needs to eat *void. */
#endif

#define u_short unsigned short

/* 286 and atarist like big chunks, which gives too much overhead. */
#if (defined(RCHECK) || defined(I286) || defined(atarist)) && defined(PACK_MALLOC)
#  undef PACK_MALLOC
#endif 

/*
 * The description below is applicable if PACK_MALLOC is not defined.
 *
 * 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 and the size of the block fits
 * in two bytes, then the top two bytes hold the size of the requested block
 * plus the range checking words, and the header word MINUS ONE.
 */
union	overhead {
	union	overhead *ov_next;	/* when free */
#if MEM_ALIGNBYTES > 4
	double	strut;			/* alignment problems */
#endif
	struct {
		u_char	ovu_magic;	/* magic number */
		u_char	ovu_index;	/* bucket # */
#ifdef RCHECK
		u_short	ovu_size;	/* actual block size */
		u_int	ovu_rmagic;	/* range magic number */
#endif
	} ovu;
#define	ov_magic	ovu.ovu_magic
#define	ov_index	ovu.ovu_index
#define	ov_size		ovu.ovu_size
#define	ov_rmagic	ovu.ovu_rmagic
};

#ifdef DEBUGGING
static void botch _((char *diag, char *s));
#endif
static void morecore _((int bucket));
static int findbucket _((union overhead *freep, int srchlen));

#define	MAGIC		0xff		/* magic # on accounting info */
#define RMAGIC		0x55555555	/* magic # on range info */
#define RMAGIC_C	0x55		/* magic # on range info */

#ifdef RCHECK
#  define	RSLOP		sizeof (u_int)
#  ifdef TWO_POT_OPTIMIZE
#    define MAX_SHORT_BUCKET (12 * BUCKETS_PER_POW2)
#  else
#    define MAX_SHORT_BUCKET (13 * BUCKETS_PER_POW2)
#  endif 
#else
#  define	RSLOP		0
#endif

#if !defined(PACK_MALLOC) && defined(BUCKETS_ROOT2)
#  undef BUCKETS_ROOT2
#endif 

#ifdef BUCKETS_ROOT2
#  define BUCKET_TABLE_SHIFT 2
#  define BUCKET_POW2_SHIFT 1
#  define BUCKETS_PER_POW2 2
#else
#  define BUCKET_TABLE_SHIFT MIN_BUC_POW2
#  define BUCKET_POW2_SHIFT 0
#  define BUCKETS_PER_POW2 1
#endif 

#ifdef BUCKETS_ROOT2
#  define MAX_BUCKET_BY_TABLE 13
static u_short buck_size[MAX_BUCKET_BY_TABLE + 1] = 
  { 
      0, 0, 0, 0, 4, 4, 8, 12, 16, 24, 32, 48, 64, 80,
  };
#  define BUCKET_SIZE(i) ((i) % 2 ? buck_size[i] : (1 << ((i) >> BUCKET_POW2_SHIFT)))
#  define BUCKET_SIZE_REAL(i) ((i) <= MAX_BUCKET_BY_TABLE		\
			       ? buck_size[i] 				\
			       : ((1 << ((i) >> BUCKET_POW2_SHIFT))	\
				  - MEM_OVERHEAD(i)			\
				  + POW2_OPTIMIZE_SURPLUS(i)))
#else
#  define BUCKET_SIZE(i) (1 << ((i) >> BUCKET_POW2_SHIFT))
#  define BUCKET_SIZE_REAL(i) (BUCKET_SIZE(i) - MEM_OVERHEAD(i) + POW2_OPTIMIZE_SURPLUS(i))
#endif 


#ifdef PACK_MALLOC
/* In this case it is assumed that if we do sbrk() in 2K units, we
 * will get 2K aligned arenas (at least after some initial
 * alignment). The bucket number of the given subblock is on the start
 * of 2K arena which contains the subblock.  Several following bytes
 * contain the magic numbers for the subblocks in the block.
 *
 * Sizes of chunks are powers of 2 for chunks in buckets <=
 * MAX_PACKED, after this they are (2^n - sizeof(union overhead)) (to
 * get alignment right).
 *
 * Consider an arena for 2^n with n>MAX_PACKED.  We suppose that
 * starts of all the chunks in a 2K arena are in different
 * 2^n-byte-long chunks.  If the top of the last chunk is aligned on a
 * boundary of 2K block, this means that sizeof(union
 * overhead)*"number of chunks" < 2^n, or sizeof(union overhead)*2K <
 * 4^n, or n > 6 + log2(sizeof()/2)/2, since a chunk of size 2^n -
 * overhead is used.  Since this rules out n = 7 for 8 byte alignment,
 * we specialcase allocation of the first of 16 128-byte-long chunks.
 *
 * Note that with the above assumption we automatically have enough
 * place for MAGIC at the start of 2K block.  Note also that we
 * overlay union overhead over the chunk, thus the start of small chunks
 * is immediately overwritten after freeing.  */
#  define MAX_PACKED_POW2 6
#  define MAX_PACKED (MAX_PACKED_POW2 * BUCKETS_PER_POW2 + BUCKET_POW2_SHIFT)
#  define MAX_POW2_ALGO ((1<<(MAX_PACKED_POW2 + 1)) - M_OVERHEAD)
#  define TWOK_MASK ((1<<LOG_OF_MIN_ARENA) - 1)
#  define TWOK_MASKED(x) ((u_bigint)(x) & ~TWOK_MASK)
#  define TWOK_SHIFT(x) ((u_bigint)(x) & TWOK_MASK)
#  define OV_INDEXp(block) ((u_char*)(TWOK_MASKED(block)))
#  define OV_INDEX(block) (*OV_INDEXp(block))
#  define OV_MAGIC(block,bucket) (*(OV_INDEXp(block) +			\
				    (TWOK_SHIFT(block)>>		\
				     (bucket>>BUCKET_POW2_SHIFT)) +	\
				    (bucket >= MIN_NEEDS_SHIFT ? 1 : 0)))
    /* A bucket can have a shift smaller than it size, we need to
       shift its magic number so it will not overwrite index: */
#  ifdef BUCKETS_ROOT2
#    define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2 - 1) /* Shift 80 greater than chunk 64. */
#  else
#    define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2) /* Shift 128 greater than chunk 32. */
#  endif 
#  define CHUNK_SHIFT 0

/* Number of active buckets of given ordinal. */
#ifdef IGNORE_SMALL_BAD_FREE
#define FIRST_BUCKET_WITH_CHECK (6 * BUCKETS_PER_POW2) /* 64 */
#  define N_BLKS(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK 		\
			 ? ((1<<LOG_OF_MIN_ARENA) - 1)/BUCKET_SIZE(bucket) \
			 : n_blks[bucket] )
#else
#  define N_BLKS(bucket) n_blks[bucket]
#endif 

static u_short n_blks[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] = 
  {
#  if BUCKETS_PER_POW2==1
      0, 0,
      (MIN_BUC_POW2==2 ? 384 : 0),
      224, 120, 62, 31, 16, 8, 4, 2
#  else
      0, 0, 0, 0,
      (MIN_BUC_POW2==2 ? 384 : 0), (MIN_BUC_POW2==2 ? 384 : 0),	/* 4, 4 */
      224, 149, 120, 80, 62, 41, 31, 25, 16, 16, 8, 8, 4, 4, 2, 2
#  endif
  };

/* Shift of the first bucket with the given ordinal inside 2K chunk. */
#ifdef IGNORE_SMALL_BAD_FREE
#  define BLK_SHIFT(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK 	\
			      ? ((1<<LOG_OF_MIN_ARENA)			\
				 - BUCKET_SIZE(bucket) * N_BLKS(bucket)) \
			      : blk_shift[bucket])
#else
#  define BLK_SHIFT(bucket) blk_shift[bucket]
#endif 

static u_short blk_shift[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] = 
  { 
#  if BUCKETS_PER_POW2==1
      0, 0,
      (MIN_BUC_POW2==2 ? 512 : 0),
      256, 128, 64, 64,			/* 8 to 64 */
      16*sizeof(union overhead), 
      8*sizeof(union overhead), 
      4*sizeof(union overhead), 
      2*sizeof(union overhead), 
#  else
      0, 0, 0, 0,
      (MIN_BUC_POW2==2 ? 512 : 0), (MIN_BUC_POW2==2 ? 512 : 0),
      256, 260, 128, 128, 64, 80, 64, 48, /* 8 to 96 */
      16*sizeof(union overhead), 16*sizeof(union overhead), 
      8*sizeof(union overhead), 8*sizeof(union overhead), 
      4*sizeof(union overhead), 4*sizeof(union overhead), 
      2*sizeof(union overhead), 2*sizeof(union overhead), 
#  endif 
  };

#else  /* !PACK_MALLOC */

#  define OV_MAGIC(block,bucket) (block)->ov_magic
#  define OV_INDEX(block) (block)->ov_index
#  define CHUNK_SHIFT 1
#  define MAX_PACKED -1
#endif /* !PACK_MALLOC */

#define M_OVERHEAD (sizeof(union overhead) + RSLOP)

#ifdef PACK_MALLOC
#  define MEM_OVERHEAD(bucket) \
  (bucket <= MAX_PACKED ? 0 : M_OVERHEAD)
#  ifdef SMALL_BUCKET_VIA_TABLE
#    define START_SHIFTS_BUCKET ((MAX_PACKED_POW2 + 1) * BUCKETS_PER_POW2)
#    define START_SHIFT MAX_PACKED_POW2
#    ifdef BUCKETS_ROOT2		/* Chunks of size 3*2^n. */
#      define SIZE_TABLE_MAX 80
#    else
#      define SIZE_TABLE_MAX 64
#    endif 
static char bucket_of[] =
  {
#    ifdef BUCKETS_ROOT2		/* Chunks of size 3*2^n. */
      /* 0 to 15 in 4-byte increments. */
      (sizeof(void*) > 4 ? 6 : 5),	/* 4/8, 5-th bucket for better reports */
      6,				/* 8 */
      7, 8,				/* 12, 16 */
      9, 9, 10, 10,			/* 24, 32 */
      11, 11, 11, 11,			/* 48 */
      12, 12, 12, 12,			/* 64 */
      13, 13, 13, 13,			/* 80 */
      13, 13, 13, 13			/* 80 */
#    else /* !BUCKETS_ROOT2 */
      /* 0 to 15 in 4-byte increments. */
      (sizeof(void*) > 4 ? 3 : 2),
      3, 
      4, 4, 
      5, 5, 5, 5,
      6, 6, 6, 6,
      6, 6, 6, 6
#    endif /* !BUCKETS_ROOT2 */
  };
#  else  /* !SMALL_BUCKET_VIA_TABLE */
#    define START_SHIFTS_BUCKET MIN_BUCKET
#    define START_SHIFT (MIN_BUC_POW2 - 1)
#  endif /* !SMALL_BUCKET_VIA_TABLE */
#else  /* !PACK_MALLOC */
#  define MEM_OVERHEAD(bucket) M_OVERHEAD
#  ifdef SMALL_BUCKET_VIA_TABLE
#    undef SMALL_BUCKET_VIA_TABLE
#  endif 
#  define START_SHIFTS_BUCKET MIN_BUCKET
#  define START_SHIFT (MIN_BUC_POW2 - 1)
#endif /* !PACK_MALLOC */

/*
 * Big allocations are often of the size 2^n bytes. To make them a
 * little bit better, make blocks of size 2^n+pagesize for big n.
 */

#ifdef TWO_POT_OPTIMIZE

#  ifndef PERL_PAGESIZE
#    define PERL_PAGESIZE 4096
#  endif 
#  ifndef FIRST_BIG_POW2
#    define FIRST_BIG_POW2 15	/* 32K, 16K is used too often. */
#  endif
#  define FIRST_BIG_BLOCK (1<<FIRST_BIG_POW2)
/* If this value or more, check against bigger blocks. */
#  define FIRST_BIG_BOUND (FIRST_BIG_BLOCK - M_OVERHEAD)
/* If less than this value, goes into 2^n-overhead-block. */
#  define LAST_SMALL_BOUND ((FIRST_BIG_BLOCK>>1) - M_OVERHEAD)

#  define POW2_OPTIMIZE_ADJUST(nbytes)				\
   ((nbytes >= FIRST_BIG_BOUND) ? nbytes -= PERL_PAGESIZE : 0)
#  define POW2_OPTIMIZE_SURPLUS(bucket)				\
   ((bucket >= FIRST_BIG_POW2 * BUCKETS_PER_POW2) ? PERL_PAGESIZE : 0)

#else  /* !TWO_POT_OPTIMIZE */
#  define POW2_OPTIMIZE_ADJUST(nbytes)
#  define POW2_OPTIMIZE_SURPLUS(bucket) 0
#endif /* !TWO_POT_OPTIMIZE */

#if defined(HAS_64K_LIMIT) && defined(PERL_CORE)
#  define BARK_64K_LIMIT(what,nbytes,size)				\
	if (nbytes > 0xffff) {						\
		PerlIO_printf(PerlIO_stderr(),				\
			      "%s too large: %lx\n", what, size);	\
		my_exit(1);						\
	}
#else /* !HAS_64K_LIMIT || !PERL_CORE */
#  define BARK_64K_LIMIT(what,nbytes,size)
#endif /* !HAS_64K_LIMIT || !PERL_CORE */

#ifndef MIN_SBRK
#  define MIN_SBRK 2048
#endif 

#ifndef FIRST_SBRK
#  define FIRST_SBRK (48*1024)
#endif 

/* Minimal sbrk in percents of what is already alloced. */
#ifndef MIN_SBRK_FRAC
#  define MIN_SBRK_FRAC 3
#endif 

#ifndef SBRK_ALLOW_FAILURES
#  define SBRK_ALLOW_FAILURES 3
#endif 

#ifndef SBRK_FAILURE_PRICE
#  define SBRK_FAILURE_PRICE 50
#endif 

#if defined(PERL_EMERGENCY_SBRK) && defined(PERL_CORE)

#  ifndef BIG_SIZE
#    define BIG_SIZE (1<<16)		/* 64K */
#  endif 

static char *emergency_buffer;
static MEM_SIZE emergency_buffer_size;

static Malloc_t
emergency_sbrk(size)
    MEM_SIZE size;
{
    if (size >= BIG_SIZE) {
	/* Give the possibility to recover: */
	MUTEX_UNLOCK(&malloc_mutex);
	croak("Out of memory during \"large\" request for %i bytes", size);
    }

    if (!emergency_buffer) {		
	dTHR;
	/* First offense, give a possibility to recover by dieing. */
	/* No malloc involved here: */
	GV **gvp = (GV**)hv_fetch(defstash, "^M", 2, 0);
	SV *sv;
	char *pv;

	if (!gvp) gvp = (GV**)hv_fetch(defstash, "\015", 1, 0);
	if (!gvp || !(sv = GvSV(*gvp)) || !SvPOK(sv) 
	    || (SvLEN(sv) < (1<<LOG_OF_MIN_ARENA) - M_OVERHEAD)) 
	    return (char *)-1;		/* Now die die die... */

	/* Got it, now detach SvPV: */
	pv = SvPV(sv, na);
	/* Check alignment: */
	if (((u_bigint)(pv - M_OVERHEAD)) & ((1<<LOG_OF_MIN_ARENA) - 1)) {
	    PerlIO_puts(PerlIO_stderr(),"Bad alignment of $^M!\n");
	    return (char *)-1;		/* die die die */
	}

	emergency_buffer = pv - M_OVERHEAD;
	emergency_buffer_size = SvLEN(sv) + M_OVERHEAD;
	SvPOK_off(sv);
	SvREADONLY_on(sv);
	MUTEX_UNLOCK(&malloc_mutex);
	croak("Out of memory during request for %i bytes", size);
    }
    else if (emergency_buffer_size >= size) {
	emergency_buffer_size -= size;
	return emergency_buffer + emergency_buffer_size;
    }
    
    return (char *)-1;			/* poor guy... */
}

#else /* !(defined(PERL_EMERGENCY_SBRK) && defined(PERL_CORE)) */
#  define emergency_sbrk(size)	-1
#endif /* !(defined(PERL_EMERGENCY_SBRK) && defined(PERL_CORE)) */

/*
 * nextf[i] is the pointer to the next free block of size 2^i.  The
 * smallest allocatable block is 8 bytes.  The overhead information
 * precedes the data area returned to the user.
 */
#define	NBUCKETS (32*BUCKETS_PER_POW2 + 1)
static	union overhead *nextf[NBUCKETS];

#ifdef USE_PERL_SBRK
#define sbrk(a) Perl_sbrk(a)
Malloc_t Perl_sbrk _((int size));
#else 
#ifdef DONT_DECLARE_STD
#ifdef I_UNISTD
#include <unistd.h>
#endif
#else
extern	Malloc_t sbrk(int);
#endif
#endif

#ifdef DEBUGGING_MSTATS
/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static	u_int nmalloc[NBUCKETS];
static  u_int sbrk_slack;
static  u_int start_slack;
#endif

static	u_int goodsbrk;

#ifdef DEBUGGING
#define	ASSERT(p,diag)   if (!(p)) botch(diag,STRINGIFY(p));  else
static void
botch(char *diag, char *s)
{
	PerlIO_printf(PerlIO_stderr(), "assertion botched (%s?): %s\n", diag, s);
	PerlProc_abort();
}
#else
#define	ASSERT(p, diag)
#endif

Malloc_t
malloc(register size_t nbytes)
{
  	register union overhead *p;
  	register int bucket;
  	register MEM_SIZE shiftr;

#if defined(DEBUGGING) || defined(RCHECK)
	MEM_SIZE size = nbytes;
#endif

	BARK_64K_LIMIT("Allocation",nbytes,nbytes);
#ifdef DEBUGGING
	if ((long)nbytes < 0)
		croak("%s", "panic: malloc");
#endif

	MUTEX_LOCK(&malloc_mutex);
	/*
	 * Convert amount of memory requested into
	 * closest block size stored in hash buckets
	 * which satisfies request.  Account for
	 * space used per block for accounting.
	 */
#ifdef PACK_MALLOC
#  ifdef SMALL_BUCKET_VIA_TABLE
	if (nbytes == 0)
	    bucket = MIN_BUCKET;
	else if (nbytes <= SIZE_TABLE_MAX) {
	    bucket = bucket_of[(nbytes - 1) >> BUCKET_TABLE_SHIFT];
	} else
#  else
	if (nbytes == 0)
	    nbytes = 1;
	if (nbytes <= MAX_POW2_ALGO) goto do_shifts;
	else
#  endif
#endif 
	{
	    POW2_OPTIMIZE_ADJUST(nbytes);
	    nbytes += M_OVERHEAD;
	    nbytes = (nbytes + 3) &~ 3; 
	  do_shifts:
	    shiftr = (nbytes - 1) >> START_SHIFT;
	    bucket = START_SHIFTS_BUCKET;
	    /* apart from this loop, this is O(1) */
	    while (shiftr >>= 1)
  		bucket += BUCKETS_PER_POW2;
	}
	/*
	 * If nothing in hash bucket right now,
	 * request more memory from the system.
	 */
  	if (nextf[bucket] == NULL)    
  		morecore(bucket);
  	if ((p = nextf[bucket]) == NULL) {
		MUTEX_UNLOCK(&malloc_mutex);
#ifdef PERL_CORE
		if (!nomemok) {
		    PerlIO_puts(PerlIO_stderr(),"Out of memory!\n");
		    my_exit(1);
		}
#else
  		return (NULL);
#endif
	}

	DEBUG_m(PerlIO_printf(Perl_debug_log,
			      "0x%lx: (%05lu) malloc %ld bytes\n",
			      (unsigned long)(p+1), (unsigned long)(an++),
			      (long)size));

	/* remove from linked list */
#ifdef RCHECK
	if (*((int*)p) & (sizeof(union overhead) - 1))
	    PerlIO_printf(PerlIO_stderr(), "Corrupt malloc ptr 0x%lx at 0x%lx\n",
		(unsigned long)*((int*)p),(unsigned long)p);
#endif
  	nextf[bucket] = p->ov_next;
#ifdef IGNORE_SMALL_BAD_FREE
	if (bucket >= FIRST_BUCKET_WITH_CHECK)
#endif 
	    OV_MAGIC(p, bucket) = MAGIC;
#ifndef PACK_MALLOC
	OV_INDEX(p) = bucket;
#endif
#ifdef RCHECK
	/*
	 * Record allocated size of block and
	 * bound space with magic numbers.
	 */
	p->ov_rmagic = RMAGIC;
	if (bucket <= MAX_SHORT_BUCKET) {
	    int i;
	    
	    nbytes = size + M_OVERHEAD; 
	    p->ov_size = nbytes - 1;
	    if ((i = nbytes & 3)) {
		i = 4 - i;
		while (i--)
		    *((char *)((caddr_t)p + nbytes - RSLOP + i)) = RMAGIC_C;
	    }
	    nbytes = (nbytes + 3) &~ 3; 
	    *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
	}
#endif
	MUTEX_UNLOCK(&malloc_mutex);
  	return ((Malloc_t)(p + CHUNK_SHIFT));
}

static char *last_sbrk_top;
static char *last_op;			/* This arena can be easily extended. */
static int sbrked_remains;
static int sbrk_good = SBRK_ALLOW_FAILURES * SBRK_FAILURE_PRICE;

#ifdef DEBUGGING_MSTATS
static int sbrks;
#endif 

struct chunk_chain_s {
    struct chunk_chain_s *next;
    MEM_SIZE size;
};
static struct chunk_chain_s *chunk_chain;
static int n_chunks;
static char max_bucket;

/* Cutoff a piece of one of the chunks in the chain.  Prefer smaller chunk. */
static void *
get_from_chain(MEM_SIZE size)
{
    struct chunk_chain_s *elt = chunk_chain, **oldp = &chunk_chain;
    struct chunk_chain_s **oldgoodp = NULL;
    long min_remain = LONG_MAX;

    while (elt) {
	if (elt->size >= size) {
	    long remains = elt->size - size;
	    if (remains >= 0 && remains < min_remain) {
		oldgoodp = oldp;
		min_remain = remains;
	    }
	    if (remains == 0) {
		break;
	    }
	}
	oldp = &( elt->next );
	elt = elt->next;
    }
    if (!oldgoodp) return NULL;
    if (min_remain) {
	void *ret = *oldgoodp;
	struct chunk_chain_s *next = (*oldgoodp)->next;
	
	*oldgoodp = (struct chunk_chain_s *)((char*)ret + size);
	(*oldgoodp)->size = min_remain;
	(*oldgoodp)->next = next;
	return ret;
    } else {
	void *ret = *oldgoodp;
	*oldgoodp = (*oldgoodp)->next;
	n_chunks--;
	return ret;
    }
}

static void
add_to_chain(void *p, MEM_SIZE size, MEM_SIZE chip)
{
    struct chunk_chain_s *next = chunk_chain;
    char *cp = (char*)p;
    
    cp += chip;
    chunk_chain = (struct chunk_chain_s *)cp;
    chunk_chain->size = size - chip;
    chunk_chain->next = next;
    n_chunks++;
}

static void *
get_from_bigger_buckets(int bucket, MEM_SIZE size)
{
    int price = 1;
    static int bucketprice[NBUCKETS];
    while (bucket <= max_bucket) {
	/* We postpone stealing from bigger buckets until we want it
	   often enough. */
	if (nextf[bucket] && bucketprice[bucket]++ >= price) {
	    /* Steal it! */
	    void *ret = (void*)(nextf[bucket] - 1 + CHUNK_SHIFT);
	    bucketprice[bucket] = 0;
	    if (((char*)nextf[bucket]) - M_OVERHEAD == last_op) {
		last_op = NULL;		/* Disable optimization */
	    }
	    nextf[bucket] = nextf[bucket]->ov_next;
#ifdef DEBUGGING_MSTATS
	    nmalloc[bucket]--;
	    start_slack -= M_OVERHEAD;
#endif 
	    add_to_chain(ret, (BUCKET_SIZE(bucket) +
			       POW2_OPTIMIZE_SURPLUS(bucket)), 
			 size);
	    return ret;
	}
	bucket++;
    }
    return NULL;
}

static union overhead *
getpages(int needed, int *nblksp, int bucket)
{
    /* Need to do (possibly expensive) system call. Try to
       optimize it for rare calling. */
    MEM_SIZE require = needed - sbrked_remains;
    char *cp;
    union overhead *ovp;
    int slack = 0;

    if (sbrk_good > 0) {
	if (!last_sbrk_top && require < FIRST_SBRK) 
	    require = FIRST_SBRK;
	else if (require < MIN_SBRK) require = MIN_SBRK;

	if (require < goodsbrk * MIN_SBRK_FRAC / 100)
	    require = goodsbrk * MIN_SBRK_FRAC / 100;
	require = ((require - 1 + MIN_SBRK) / MIN_SBRK) * MIN_SBRK;
    } else {
	require = needed;
	last_sbrk_top = 0;
	sbrked_remains = 0;
    }

    DEBUG_m(PerlIO_printf(Perl_debug_log, 
			  "sbrk(%ld) for %ld-byte-long arena\n",
			  (long)require, (long) needed));
    cp = (char *)sbrk(require);
#ifdef DEBUGGING_MSTATS
    sbrks++;
#endif 
    if (cp == last_sbrk_top) {
	/* Common case, anything is fine. */
	sbrk_good++;
	ovp = (union overhead *) (cp - sbrked_remains);
	sbrked_remains = require - (needed - sbrked_remains);
    } else if (cp == (char *)-1) { /* no more room! */
	ovp = (union overhead *)emergency_sbrk(needed);
	if (ovp == (union overhead *)-1)
	    return 0;
	return ovp;
    } else {			/* Non-continuous or first sbrk(). */
	long add = sbrked_remains;
	char *newcp;

	if (sbrked_remains) {	/* Put rest into chain, we
				   cannot use it right now. */
	    add_to_chain((void*)(last_sbrk_top - sbrked_remains),
			 sbrked_remains, 0);
	}

	/* Second, check alignment. */
	slack = 0;

#ifndef atarist /* on the atari we dont have to worry about this */
#  ifndef I286 	/* The sbrk(0) call on the I286 always returns the next segment */

	/* CHUNK_SHIFT is 1 for PACK_MALLOC, 0 otherwise. */
	if ((UV)cp & (0x7FF >> CHUNK_SHIFT)) { /* Not aligned. */
	    slack = (0x800 >> CHUNK_SHIFT)
		- ((UV)cp & (0x7FF >> CHUNK_SHIFT));
	    add += slack;
	}
#  endif
#endif /* atarist */
		
	if (add) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "sbrk(%ld) to fix non-continuous/off-page sbrk:\n\t%ld for alignement,\t%ld were assumed to come from the tail of the previous sbrk\n",
				  (long)add, (long) slack,
				  (long) sbrked_remains));
	    newcp = (char *)sbrk(add);
#if defined(DEBUGGING_MSTATS)
	    sbrks++;
	    sbrk_slack += add;
#endif
	    if (newcp != cp + require) {
		/* Too bad: even rounding sbrk() is not continuous.*/
		DEBUG_m(PerlIO_printf(Perl_debug_log, 
				      "failed to fix bad sbrk()\n"));
#ifdef PACK_MALLOC
		if (slack) {
		    MUTEX_UNLOCK(&malloc_mutex);
		    croak("%s", "panic: Off-page sbrk");
		}
#endif
		if (sbrked_remains) {
		    /* Try again. */
#if defined(DEBUGGING_MSTATS)
		    sbrk_slack += require;
#endif
		    require = needed;
		    DEBUG_m(PerlIO_printf(Perl_debug_log, 
					  "straight sbrk(%ld)\n",
					  (long)require));
		    cp = (char *)sbrk(require);
#ifdef DEBUGGING_MSTATS
		    sbrks++;
#endif 
		    if (cp == (char *)-1)
			return 0;
		}
		sbrk_good = -1;	/* Disable optimization!
				   Continue with not-aligned... */
	    } else {
		cp += slack;
		require += sbrked_remains;
	    }
	}

	if (last_sbrk_top) {
	    sbrk_good -= SBRK_FAILURE_PRICE;
	}

	ovp = (union overhead *) cp;
	/*
	 * Round up to minimum allocation size boundary
	 * and deduct from block count to reflect.
	 */

#ifndef I286	/* Again, this should always be ok on an 80286 */
	if ((UV)ovp & 7) {
	    ovp = (union overhead *)(((UV)ovp + 8) & ~7);
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "fixing sbrk(): %d bytes off machine alignement\n",
				  (int)((UV)ovp & 7)));
	    (*nblksp)--;
# if defined(DEBUGGING_MSTATS)
	    /* This is only approx. if TWO_POT_OPTIMIZE: */
	    sbrk_slack += (1 << bucket);
# endif
	}
#endif
	sbrked_remains = require - needed;
    }
    last_sbrk_top = cp + require;
    last_op = (char*) cp;
#ifdef DEBUGGING_MSTATS
    goodsbrk += require;
#endif	
    return ovp;
}

static int
getpages_adjacent(int require)
{	    
    if (require <= sbrked_remains) {
	sbrked_remains -= require;
    } else {
	char *cp;

	require -= sbrked_remains;
	/* We do not try to optimize sbrks here, we go for place. */
	cp = (char*) sbrk(require);
#ifdef DEBUGGING_MSTATS
	sbrks++;
	goodsbrk += require;
#endif 
	if (cp == last_sbrk_top) {
	    sbrked_remains = 0;
	    last_sbrk_top = cp + require;
	} else {
	    /* Report the failure: */
	    if (sbrked_remains)
		add_to_chain((void*)(last_sbrk_top - sbrked_remains),
			     sbrked_remains, 0);
	    add_to_chain((void*)cp, require, 0);
	    sbrk_good -= SBRK_FAILURE_PRICE;
	    sbrked_remains = 0;
	    last_sbrk_top = 0;
	    last_op = 0;
	    return 0;
	}
    }
	    
    return 1;
}

/*
 * Allocate more memory to the indicated bucket.
 */
static void
morecore(register int bucket)
{
  	register union overhead *ovp;
  	register int rnu;       /* 2^rnu bytes will be requested */
  	int nblks;		/* become nblks blocks of the desired size */
	register MEM_SIZE siz, needed;

  	if (nextf[bucket])
  		return;
	if (bucket == sizeof(MEM_SIZE)*8*BUCKETS_PER_POW2) {
	    MUTEX_UNLOCK(&malloc_mutex);
	    croak("%s", "Out of memory during ridiculously large request");
	}
	if (bucket > max_bucket)
	    max_bucket = bucket;

  	rnu = ( (bucket <= (LOG_OF_MIN_ARENA << BUCKET_POW2_SHIFT)) 
		? LOG_OF_MIN_ARENA 
		: (bucket >> BUCKET_POW2_SHIFT) );
	/* This may be overwritten later: */
  	nblks = 1 << (rnu - (bucket >> BUCKET_POW2_SHIFT)); /* how many blocks to get */
	needed = ((MEM_SIZE)1 << rnu) + POW2_OPTIMIZE_SURPLUS(bucket);
	if (nextf[rnu << BUCKET_POW2_SHIFT]) { /* 2048b bucket. */
	    ovp = nextf[rnu << BUCKET_POW2_SHIFT] - 1 + CHUNK_SHIFT;
	    nextf[rnu << BUCKET_POW2_SHIFT]
		= nextf[rnu << BUCKET_POW2_SHIFT]->ov_next;
#ifdef DEBUGGING_MSTATS
	    nmalloc[rnu << BUCKET_POW2_SHIFT]--;
	    start_slack -= M_OVERHEAD;
#endif 
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from %ld arena\n",
				  (long) needed, (long) rnu << BUCKET_POW2_SHIFT));
	} else if (chunk_chain 
		   && (ovp = (union overhead*) get_from_chain(needed))) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from chain\n",
				  (long) needed));
	} else if ( (ovp = (union overhead*)
		     get_from_bigger_buckets((rnu << BUCKET_POW2_SHIFT) + 1,
					     needed)) ) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from bigger buckets\n",
				  (long) needed));
	} else if (needed <= sbrked_remains) {
	    ovp = (union overhead *)(last_sbrk_top - sbrked_remains);
	    sbrked_remains -= needed;
	    last_op = (char*)ovp;
	} else 
	    ovp = getpages(needed, &nblks, bucket);

	if (!ovp)
	    return;

	/*
	 * Add new memory allocated to that on
	 * free list for this hash bucket.
	 */
  	siz = BUCKET_SIZE(bucket);
#ifdef PACK_MALLOC
	*(u_char*)ovp = bucket;	/* Fill index. */
	if (bucket <= MAX_PACKED) {
	    ovp = (union overhead *) ((char*)ovp + BLK_SHIFT(bucket));
	    nblks = N_BLKS(bucket);
#  ifdef DEBUGGING_MSTATS
	    start_slack += BLK_SHIFT(bucket);
#  endif
	} else if (bucket < LOG_OF_MIN_ARENA * BUCKETS_PER_POW2) {
	    ovp = (union overhead *) ((char*)ovp + BLK_SHIFT(bucket));
	    siz -= sizeof(union overhead);
	} else ovp++;		/* One chunk per block. */
#endif /* PACK_MALLOC */
  	nextf[bucket] = ovp;
#ifdef DEBUGGING_MSTATS
	nmalloc[bucket] += nblks;
	if (bucket > MAX_PACKED) {
	    start_slack += M_OVERHEAD * nblks;
	}
#endif 
  	while (--nblks > 0) {
		ovp->ov_next = (union overhead *)((caddr_t)ovp + siz);
		ovp = (union overhead *)((caddr_t)ovp + siz);
  	}
	/* Not all sbrks return zeroed memory.*/
	ovp->ov_next = (union overhead *)NULL;
#ifdef PACK_MALLOC
	if (bucket == 7*BUCKETS_PER_POW2) { /* Special case, explanation is above. */
	    union overhead *n_op = nextf[7*BUCKETS_PER_POW2]->ov_next;
	    nextf[7*BUCKETS_PER_POW2] = 
		(union overhead *)((caddr_t)nextf[7*BUCKETS_PER_POW2] 
				   - sizeof(union overhead));
	    nextf[7*BUCKETS_PER_POW2]->ov_next = n_op;
	}
#endif /* !PACK_MALLOC */
}

Free_t
free(void *mp)
{   
  	register MEM_SIZE size;
	register union overhead *ovp;
	char *cp = (char*)mp;
#ifdef PACK_MALLOC
	u_char bucket;
#endif 

	DEBUG_m(PerlIO_printf(Perl_debug_log, 
			      "0x%lx: (%05lu) free\n",
			      (unsigned long)cp, (unsigned long)(an++)));

	if (cp == NULL)
		return;
	ovp = (union overhead *)((caddr_t)cp 
				- sizeof (union overhead) * CHUNK_SHIFT);
#ifdef PACK_MALLOC
	bucket = OV_INDEX(ovp);
#endif 
#ifdef IGNORE_SMALL_BAD_FREE
	if ((bucket >= FIRST_BUCKET_WITH_CHECK) 
	    && (OV_MAGIC(ovp, bucket) != MAGIC))
#else
	if (OV_MAGIC(ovp, bucket) != MAGIC)
#endif 
	    {
		static int bad_free_warn = -1;
		if (bad_free_warn == -1) {
		    char *pbf = PerlEnv_getenv("PERL_BADFREE");
		    bad_free_warn = (pbf) ? atoi(pbf) : 1;
		}
		if (!bad_free_warn)
		    return;
#ifdef RCHECK
		warn("%s free() ignored",
		    ovp->ov_rmagic == RMAGIC - 1 ? "Duplicate" : "Bad");
#else
		warn("%s", "Bad free() ignored");
#endif
		return;				/* sanity */
	    }
	MUTEX_LOCK(&malloc_mutex);
#ifdef RCHECK
  	ASSERT(ovp->ov_rmagic == RMAGIC, "chunk's head overwrite");
	if (OV_INDEX(ovp) <= MAX_SHORT_BUCKET) {
	    int i;
	    MEM_SIZE nbytes = ovp->ov_size + 1;

	    if ((i = nbytes & 3)) {
		i = 4 - i;
		while (i--) {
		    ASSERT(*((char *)((caddr_t)ovp + nbytes - RSLOP + i))
			   == RMAGIC_C, "chunk's tail overwrite");
		}
	    }
	    nbytes = (nbytes + 3) &~ 3; 
	    ASSERT(*(u_int *)((caddr_t)ovp + nbytes - RSLOP) == RMAGIC, "chunk's tail overwrite");	    
	}
	ovp->ov_rmagic = RMAGIC - 1;
#endif
  	ASSERT(OV_INDEX(ovp) < NBUCKETS, "chunk's head overwrite");
  	size = OV_INDEX(ovp);
	ovp->ov_next = nextf[size];
  	nextf[size] = ovp;
	MUTEX_UNLOCK(&malloc_mutex);
}

/*
 * When a program attempts "storage compaction" as mentioned in the
 * old malloc man page, it realloc's an already freed block.  Usually
 * this is the last block it freed; occasionally it might be farther
 * back.  We have to search all the free lists for the block in order
 * to determine its bucket: 1st we make one pass thru the lists
 * checking only the first block in each; if that fails we search
 * ``reall_srchlen'' blocks in each list for a match (the variable
 * is extern so the caller can modify it).  If that fails we just copy
 * however many bytes was given to realloc() and hope it's not huge.
 */
int reall_srchlen = 4;	/* 4 should be plenty, -1 =>'s whole list */

Malloc_t
realloc(void *mp, size_t nbytes)
{   
  	register MEM_SIZE onb;
	union overhead *ovp;
  	char *res;
	int prev_bucket;
	register int bucket;
	int was_alloced = 0, incr;
	char *cp = (char*)mp;

#if defined(DEBUGGING) || !defined(PERL_CORE)
	MEM_SIZE size = nbytes;

	if ((long)nbytes < 0)
		croak("%s", "panic: realloc");
#endif

	BARK_64K_LIMIT("Reallocation",nbytes,size);
	if (!cp)
		return malloc(nbytes);

	MUTEX_LOCK(&malloc_mutex);
	ovp = (union overhead *)((caddr_t)cp 
				- sizeof (union overhead) * CHUNK_SHIFT);
	bucket = OV_INDEX(ovp);
#ifdef IGNORE_SMALL_BAD_FREE
	if ((bucket < FIRST_BUCKET_WITH_CHECK) 
	    || (OV_MAGIC(ovp, bucket) == MAGIC))
#else
	if (OV_MAGIC(ovp, bucket) == MAGIC) 
#endif 
	{
		was_alloced = 1;
	} else {
		/*
		 * Already free, doing "compaction".
		 *
		 * Search for the old block of memory on the
		 * free list.  First, check the most common
		 * case (last element free'd), then (this failing)
		 * the last ``reall_srchlen'' items free'd.
		 * If all lookups fail, then assume the size of
		 * the memory block being realloc'd is the
		 * smallest possible.
		 */
		if ((bucket = findbucket(ovp, 1)) < 0 &&
		    (bucket = findbucket(ovp, reall_srchlen)) < 0)
			bucket = 0;
	}
	onb = BUCKET_SIZE_REAL(bucket);
	/* 
	 *  avoid the copy if same size block.
	 *  We are not agressive with boundary cases. Note that it might
	 *  (for a small number of cases) give false negative if
	 *  both new size and old one are in the bucket for
	 *  FIRST_BIG_POW2, but the new one is near the lower end.
	 *
	 *  We do not try to go to 1.5 times smaller bucket so far.
	 */
	if (nbytes > onb) incr = 1;
	else {
#ifdef DO_NOT_TRY_HARDER_WHEN_SHRINKING
	    if ( /* This is a little bit pessimal if PACK_MALLOC: */
		nbytes > ( (onb >> 1) - M_OVERHEAD )
#  ifdef TWO_POT_OPTIMIZE
		|| (bucket == FIRST_BIG_POW2 && nbytes >= LAST_SMALL_BOUND )
#  endif	
		)
#else  /* !DO_NOT_TRY_HARDER_WHEN_SHRINKING */
		prev_bucket = ( (bucket > MAX_PACKED + 1) 
				? bucket - BUCKETS_PER_POW2
				: bucket - 1);
	     if (nbytes > BUCKET_SIZE_REAL(prev_bucket))
#endif /* !DO_NOT_TRY_HARDER_WHEN_SHRINKING */
		 incr = 0;
	     else incr = -1;
	}
	if (!was_alloced
#ifdef STRESS_REALLOC
	    || 1 /* always do it the hard way */
#endif
	    ) goto hard_way;
	else if (incr == 0) {
	  inplace_label:
#ifdef RCHECK
		/*
		 * Record new allocated size of block and
		 * bound space with magic numbers.
		 */
		if (OV_INDEX(ovp) <= MAX_SHORT_BUCKET) {
		       int i, nb = ovp->ov_size + 1;

		       if ((i = nb & 3)) {
			   i = 4 - i;
			   while (i--) {
			       ASSERT(*((char *)((caddr_t)ovp + nb - RSLOP + i)) == RMAGIC_C, "chunk's tail overwrite");
			   }
		       }
		       nb = (nb + 3) &~ 3; 
		       ASSERT(*(u_int *)((caddr_t)ovp + nb - RSLOP) == RMAGIC, "chunk's tail overwrite");
			/*
			 * Convert amount of memory requested into
			 * closest block size stored in hash buckets
			 * which satisfies request.  Account for
			 * space used per block for accounting.
			 */
			nbytes += M_OVERHEAD;
			ovp->ov_size = nbytes - 1;
			if ((i = nbytes & 3)) {
			    i = 4 - i;
			    while (i--)
				*((char *)((caddr_t)ovp + nbytes - RSLOP + i))
				    = RMAGIC_C;
			}
			nbytes = (nbytes + 3) &~ 3; 
			*((u_int *)((caddr_t)ovp + nbytes - RSLOP)) = RMAGIC;
		}
#endif
		res = cp;
		MUTEX_UNLOCK(&malloc_mutex);
	} else if (incr == 1 && (cp - M_OVERHEAD == last_op) 
		   && (onb > (1 << LOG_OF_MIN_ARENA))) {
	    MEM_SIZE require, newarena = nbytes, pow;
	    int shiftr;

	    POW2_OPTIMIZE_ADJUST(newarena);
	    newarena = newarena + M_OVERHEAD;
	    /* newarena = (newarena + 3) &~ 3; */
	    shiftr = (newarena - 1) >> LOG_OF_MIN_ARENA;
	    pow = LOG_OF_MIN_ARENA + 1;
	    /* apart from this loop, this is O(1) */
	    while (shiftr >>= 1)
  		pow++;
	    newarena = (1 << pow) + POW2_OPTIMIZE_SURPLUS(pow * BUCKETS_PER_POW2);
	    require = newarena - onb - M_OVERHEAD;
	    
	    if (getpages_adjacent(require)) {
#ifdef DEBUGGING_MSTATS
		nmalloc[bucket]--;
		nmalloc[pow * BUCKETS_PER_POW2]++;
#endif 	    
		*(cp - M_OVERHEAD) = pow * BUCKETS_PER_POW2; /* Fill index. */
		goto inplace_label;
	    } else
		goto hard_way;
	} else {
	  hard_way:
	    MUTEX_UNLOCK(&malloc_mutex);
	    if ((res = (char*)malloc(nbytes)) == NULL)
		return (NULL);
	    if (cp != res)			/* common optimization */
		Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
	    if (was_alloced)
		free(cp);
	}

	DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%lu: (%05lu) rfree\n",
			      (unsigned long)res,(unsigned long)(an++)));
	DEBUG_m(PerlIO_printf(Perl_debug_log, 
			      "0x%lx: (%05lu) realloc %ld bytes\n",
			      (unsigned long)res,(unsigned long)(an++),
			      (long)size));
  	return ((Malloc_t)res);
}

/*
 * Search ``srchlen'' elements of each free list for a block whose
 * header starts at ``freep''.  If srchlen is -1 search the whole list.
 * Return bucket number, or -1 if not found.
 */
static int
findbucket(union overhead *freep, int srchlen)
{
	register union overhead *p;
	register int i, j;

	for (i = 0; i < NBUCKETS; i++) {
		j = 0;
		for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
			if (p == freep)
				return (i);
			j++;
		}
	}
	return (-1);
}

Malloc_t
calloc(register size_t elements, register size_t size)
{
    long sz = elements * size;
    Malloc_t p = malloc(sz);

    if (p) {
	memset((void*)p, 0, sz);
    }
    return p;
}

MEM_SIZE
malloced_size(void *p)
{
    int bucket = OV_INDEX((union overhead *)p);

    return BUCKET_SIZE_REAL(bucket);
}

#ifdef DEBUGGING_MSTATS

#  ifdef BUCKETS_ROOT2
#    define MIN_EVEN_REPORT 6
#  else
#    define MIN_EVEN_REPORT MIN_BUCKET
#  endif 
/*
 * mstats - print out statistics about malloc
 * 
 * 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.
 */
void
dump_mstats(char *s)
{
  	register int i, j;
  	register union overhead *p;
  	int topbucket=0, topbucket_ev=0, topbucket_odd=0, totfree=0, total=0;
	u_int nfree[NBUCKETS];
	int total_chain = 0;
	struct chunk_chain_s* nextchain = chunk_chain;

  	for (i = MIN_BUCKET ; i < NBUCKETS; i++) {
  		for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
  			;
		nfree[i] = j;
  		totfree += nfree[i] * BUCKET_SIZE_REAL(i);
  		total += nmalloc[i] * BUCKET_SIZE_REAL(i);
		if (nmalloc[i]) {
		    i % 2 ? (topbucket_odd = i) : (topbucket_ev = i);
		    topbucket = i;
		}
  	}
  	if (s)
	    PerlIO_printf(PerlIO_stderr(),
			  "Memory allocation statistics %s (buckets %ld(%ld)..%ld(%ld)\n",
			  s, 
			  (long)BUCKET_SIZE_REAL(MIN_BUCKET), 
			  (long)BUCKET_SIZE(MIN_BUCKET),
			  (long)BUCKET_SIZE_REAL(topbucket), (long)BUCKET_SIZE(topbucket));
  	PerlIO_printf(PerlIO_stderr(), "%8d free:", totfree);
  	for (i = MIN_EVEN_REPORT; i <= topbucket; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(PerlIO_stderr(), 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5d" 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3d" : " %d")),
			      nfree[i]);
  	}
#ifdef BUCKETS_ROOT2
	PerlIO_printf(PerlIO_stderr(), "\n\t   ");
  	for (i = MIN_BUCKET + 1; i <= topbucket_odd; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(PerlIO_stderr(), 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5d" 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3d" : " %d")),
			      nfree[i]);
  	}
#endif 
  	PerlIO_printf(PerlIO_stderr(), "\n%8d used:", total - totfree);
  	for (i = MIN_EVEN_REPORT; i <= topbucket; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(PerlIO_stderr(), 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5d" 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3d" : " %d")), 
			      nmalloc[i] - nfree[i]);
  	}
#ifdef BUCKETS_ROOT2
	PerlIO_printf(PerlIO_stderr(), "\n\t   ");
  	for (i = MIN_BUCKET + 1; i <= topbucket_odd; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(PerlIO_stderr(), 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5d" 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3d" : " %d")),
			      nmalloc[i] - nfree[i]);
  	}
#endif 
	while (nextchain) {
	    total_chain += nextchain->size;
	    nextchain = nextchain->next;
	}
	PerlIO_printf(PerlIO_stderr(), "\nTotal sbrk(): %d/%d:%d. Odd ends: pad+heads+chain+tail: %d+%d+%d+%d.\n",
		      goodsbrk + sbrk_slack, sbrks, sbrk_good, sbrk_slack,
		      start_slack, total_chain, sbrked_remains);
}
#else
void
dump_mstats(char *s)
{
}
#endif
#endif /* lint */


#ifdef USE_PERL_SBRK

#   ifdef NeXT
#      define PERL_SBRK_VIA_MALLOC
#   endif

#   ifdef PERL_SBRK_VIA_MALLOC
#      if defined(HIDEMYMALLOC) || defined(EMBEDMYMALLOC)
#         undef malloc
#      else
#         include "Error: -DPERL_SBRK_VIA_MALLOC needs -D(HIDE|EMBED)MYMALLOC"
#      endif

/* it may seem schizophrenic to use perl's malloc and let it call system */
/* malloc, the reason for that is only the 3.2 version of the OS that had */
/* frequent core dumps within nxzonefreenolock. This sbrk routine put an */
/* end to the cores */

#      define SYSTEM_ALLOC(a) malloc(a)

#   endif  /* PERL_SBRK_VIA_MALLOC */

static IV Perl_sbrk_oldchunk;
static long Perl_sbrk_oldsize;

#   define PERLSBRK_32_K (1<<15)
#   define PERLSBRK_64_K (1<<16)

Malloc_t
Perl_sbrk(size)
int size;
{
    IV got;
    int small, reqsize;

    if (!size) return 0;
#ifdef PERL_CORE
    reqsize = size; /* just for the DEBUG_m statement */
#endif
#ifdef PACK_MALLOC
    size = (size + 0x7ff) & ~0x7ff;
#endif
    if (size <= Perl_sbrk_oldsize) {
	got = Perl_sbrk_oldchunk;
	Perl_sbrk_oldchunk += size;
	Perl_sbrk_oldsize -= size;
    } else {
      if (size >= PERLSBRK_32_K) {
	small = 0;
      } else {
	size = PERLSBRK_64_K;
	small = 1;
      }
      got = (IV)SYSTEM_ALLOC(size);
#ifdef PACK_MALLOC
      got = (got + 0x7ff) & ~0x7ff;
#endif
      if (small) {
	/* Chunk is small, register the rest for future allocs. */
	Perl_sbrk_oldchunk = got + reqsize;
	Perl_sbrk_oldsize = size - reqsize;
      }
    }

    DEBUG_m(PerlIO_printf(Perl_debug_log, "sbrk malloc size %ld (reqsize %ld), left size %ld, give addr 0x%lx\n",
		    size, reqsize, Perl_sbrk_oldsize, got));

    return (void *)got;
}

#endif /* ! defined USE_PERL_SBRK */