GEMini Atari/GEMini_Atari_CD-ROM_Walnut_Creek_December_1993.iso/files/mint/mntlib24/malloc.c

C/C++ Source or Header | 1993-08-03 | 4.9 KB | 211 lines

/* from the TOS GCC library */
/* malloc, free, realloc: dynamic memory allocation */
/* ERS: added mlalloc, relalloc, etc. for 16 bit compilers. Changed
   argument of malloc, etc.,  to size_t (per ANSI draft). */
/* 5/2/92 sb -- modified for Heat-n-Serve C to accomodate its 16-bit size_t */
/* 5/5/92 sb -- split off realloc() & calloc() to reduce library drag */

#include <compiler.h>
#include <stddef.h>    /* for size_t */
#include <stdlib.h>
#include <memory.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include "lib.h"

extern long _stksize;
void *_malloc __PROTO((unsigned long));

/* minimum chunk to ask OS for */
static size_t MINHUNK =    4096L;    /* default */
static size_t MAXHUNK = 32*1024L; /* max. default */

    /* CAUTION: use _mallocChunkSize() to tailor to your environment,
            do not make the default too large, as the compiler
            gets screwed on a 1M machine otherwise (stack/heap clash)
     */

/* linked list of free blocks struct defined in lib.h */

struct mem_chunk _mchunk_free_list = { VAL_FREE, NULL, 0L };

/* flag to control zero'ing of malloc'ed chunks */
static int _ZeroMallocs = 0;

__EXTERN void _bzero __PROTO((void *, unsigned long));

#ifdef __GNUC__
asm(".stabs \"_malloc\",5,0,0,__malloc"); /* dept of clean tricks */
#endif

void * _malloc(n)
unsigned long n;
{
  struct mem_chunk *p, *q;
  long sz;
  extern void *_heapbase;
  extern short _split_mem;

/* add a mem_chunk to required size and round up */
  n = n + sizeof(struct mem_chunk);
  n = (7 + n) & ~7;
/* look for first block big enough in free list */
  p = &_mchunk_free_list;
  q = _mchunk_free_list.next;

  while ((q != NULL) && (q->size < n))
    {
    p = q;
    q = q->next;
    }

/* if not enough memory, get more from the system */
  if (q == NULL)
    {
    if (((!_split_mem) && (_heapbase != NULL)) || (n > MINHUNK))
        sz = n;
    else {
        sz = MINHUNK;
        if (MINHUNK < MAXHUNK)
            MINHUNK *= 2;
    }
    q = (struct mem_chunk * )_sbrk(sz);

    if (((long)q) == -1)         /* can't alloc any more? */
        return(NULL);

    /* Note: q may be below the highest allocated chunk */
    p = &_mchunk_free_list;
    while (p->next != NULL && q > p->next)
      p = p->next;
    q->size = sz;
    q->next = p->next;
    q->valid = VAL_FREE;
    p->next = q;
    }

  if (q->size > n + sizeof(struct mem_chunk))
    {                /* split, leave part of free list */
    q->size -= n;
    q = (struct mem_chunk * )(((long) q) + q->size);
    q->size = n;
    q->valid = VAL_ALLOC;
    }
    else
    {                /* just unlink it */
    p->next = q->next;
    q->valid = VAL_ALLOC;
    }

  q->next = NULL;
  q++;    /* hand back ptr to after chunk desc */
  if(_ZeroMallocs != 0)
      _bzero((void *)q, (long)(n - sizeof(struct mem_chunk)));

  return((void * )q);
}

void free(param)
    void *param;
{
  struct mem_chunk *o, *p, *q, *s;
  struct mem_chunk *r = (struct mem_chunk *) param;
  extern void *_heapbase;
  extern short _split_mem;

/* free(NULL) should do nothing */
  if (r == 0)
     return;

/* move back to uncover the mem_chunk */
  r--;            /* there it is! */

  if (r->valid != VAL_ALLOC)
    return;

  r->valid = VAL_FREE;

/* stick it into free list, preserving ascending address order */
  o = NULL;
  p = &_mchunk_free_list;
  q = _mchunk_free_list.next;
  while (q != NULL && q < r)
    {
    o = p;
    p = q;
    q = q->next;
    }

/* merge after if possible */
  s = (struct mem_chunk * )(((long) r) + r->size);
  if (q != NULL && s >= q)
    {
    assert(s == q);
    r->size += q->size;
    q = q->next;
    s->size = 0;
    s->next = NULL;
    }
  r->next = q;

/* merge before if possible, otherwise link it in */
  s = (struct mem_chunk * )(((long) p) + p->size);
  if (s >= r && p != &_mchunk_free_list)
    /* remember: r may be below &_mchunk_free_list in memory */
    {
    assert(s == r);
    p->size += r->size;
    p->next = r->next;
    r->size = 0;
    r->next = NULL;
    s = (struct mem_chunk * )(((long) p) + p->size);
    if ((!_split_mem) && _heapbase != NULL &&
        s >= (struct mem_chunk *) _heapbase &&
        s < (struct mem_chunk *) ((char *)_heapbase + _stksize)) {
      assert(s == (struct mem_chunk *) _heapbase);
      _heapbase = (void *) p;
      _stksize += p->size;
      o->next = p->next;    /* o is always != NULL here */
    }
    }
    else
        {
      s = (struct mem_chunk * )(((long) r) + r->size);
      if ((!_split_mem) && _heapbase != NULL &&
          s >= (struct mem_chunk *) _heapbase &&
          s < (struct mem_chunk *) ((char *)_heapbase + _stksize)) {
        assert(s == (struct mem_chunk *) _heapbase);
        _heapbase = (void *) r;
        _stksize += r->size;
        p->next = r->next;
      } else p->next = r;
    }
}

/*
 * Set zero block after malloc flag
 */
void _malloczero(yes)
int yes;
{
    _ZeroMallocs = yes;
}

/*
 * tune chunk size
 */
void _mallocChunkSize (siz)
size_t siz;
{
    MAXHUNK = MINHUNK = siz;
}

#ifndef __GNUC__
void * malloc(n)
size_t n;
{
  return _malloc((unsigned long) n);
}
#endif