malloc.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 1,140 行 · 第 1/2 页

    return p;
}

/*
 * Allocate a page of fragments
 */

static __inline__ int
malloc_make_chunks(int bits)
{
    struct  pginfo *bp;
    void *pp;
    int i, k, l;

    /* Allocate a new bucket */
    pp = malloc_pages(malloc_pagesize);
    if (!pp)
	return 0;

    /* Find length of admin structure */
    l = offsetof(struct pginfo, bits[0]);
    l += sizeof bp->bits[0] *
	(((malloc_pagesize >> bits)+MALLOC_BITS-1) / MALLOC_BITS);

    /* Don't waste more than two chunks on this */
    if ((1<<(bits)) <= l+l) {
	bp = (struct  pginfo *)pp;
    } else {
	bp = (struct  pginfo *)imalloc(l);
	if (!bp) {
	    ifree(pp);
	    return 0;
	}
    }

    bp->size = (1<<bits);
    bp->shift = bits;
    bp->total = bp->free = malloc_pagesize >> bits;
    bp->page = pp;

    /* set all valid bits in the bitmap */
    k = bp->total;
    i = 0;

    /* Do a bunch at a time */
    for(;k-i >= MALLOC_BITS; i += MALLOC_BITS)
	bp->bits[i / MALLOC_BITS] = ~0;

    for(; i < k; i++)
        bp->bits[i/MALLOC_BITS] |= 1<<(i%MALLOC_BITS);

    if (bp == bp->page) {
	/* Mark the ones we stole for ourselves */
	for(i=0;l > 0;i++) {
	    bp->bits[i/MALLOC_BITS] &= ~(1<<(i%MALLOC_BITS));
	    bp->free--;
	    bp->total--;
	    l -= (1 << bits);
	}
    }

    /* MALLOC_LOCK */

    page_dir[ptr2index(pp)] = bp;

    bp->next = page_dir[bits];
    page_dir[bits] = bp;

    /* MALLOC_UNLOCK */

    return 1;
}

/*
 * Allocate a fragment
 */
static void *
malloc_bytes(size_t size)
{
    int i,j;
    u_int u;
    struct  pginfo *bp;
    int k;
    u_int *lp;

    /* Don't bother with anything less than this */
    if (size < malloc_minsize)
	size = malloc_minsize;

    /* Find the right bucket */
    j = 1;
    i = size-1;
    while (i >>= 1)
	j++;

    /* If it's empty, make a page more of that size chunks */
    if (!page_dir[j] && !malloc_make_chunks(j))
	return 0;

    bp = page_dir[j];

    /* Find first word of bitmap which isn't empty */
    for (lp = bp->bits; !*lp; lp++)
	;

    /* Find that bit, and tweak it */
    u = 1;
    k = 0;
    while (!(*lp & u)) {
	u += u;
	k++;
    }
    *lp ^= u;

    /* If there are no more free, remove from free-list */
    if (!--bp->free) {
	page_dir[j] = bp->next;
	bp->next = 0;
    }

    /* Adjust to the real offset of that chunk */
    k += (lp-bp->bits)*MALLOC_BITS;
    k <<= bp->shift;

    if (malloc_junk)
	memset((u_char*)bp->page + k, SOME_JUNK, bp->size);

    return (u_char *)bp->page + k;
}

/*
 * Allocate a piece of memory
 */
static void *
imalloc(size_t size)
{
    void *result;

    if (suicide)
	abort();

    if ((size + malloc_pagesize) < size)	/* Check for overflow */
	result = 0;
    else if (size <= malloc_maxsize)
	result =  malloc_bytes(size);
    else
	result =  malloc_pages(size);

    if (malloc_abort && !result)
	wrterror("allocation failed.\n");

    if (malloc_zero && result)
	memset(result, 0, size);

    return result;
}

/*
 * Change the size of an allocation.
 */
static void *
irealloc(void *ptr, size_t size)
{
    void *p;
    u_long osize, index;
    struct pginfo **mp;
    int i;

    if (suicide)
	abort();

    index = ptr2index(ptr);

    if (index < malloc_pageshift) {
	wrtwarning("junk pointer, too low to make sense.\n");
	return 0;
    }

    if (index > last_index) {
	wrtwarning("junk pointer, too high to make sense.\n");
	return 0;
    }

    mp = &page_dir[index];

    if (*mp == MALLOC_FIRST) {			/* Page allocation */

	/* Check the pointer */
	if ((u_long)ptr & malloc_pagemask) {
	    wrtwarning("modified (page-) pointer.\n");
	    return 0;
	}

	/* Find the size in bytes */
	for (osize = malloc_pagesize; *++mp == MALLOC_FOLLOW;)
	    osize += malloc_pagesize;

        if (!malloc_realloc && 			/* unless we have to, */
	  size <= osize && 			/* .. or are too small, */
	  size > (osize - malloc_pagesize)) {	/* .. or can free a page, */
	    return ptr;				/* don't do anything. */
	}

    } else if (*mp >= MALLOC_MAGIC) {		/* Chunk allocation */

	/* Check the pointer for sane values */
	if (((u_long)ptr & ((*mp)->size-1))) {
	    wrtwarning("modified (chunk-) pointer.\n");
	    return 0;
	}

	/* Find the chunk index in the page */
	i = ((u_long)ptr & malloc_pagemask) >> (*mp)->shift;

	/* Verify that it isn't a free chunk already */
        if ((*mp)->bits[i/MALLOC_BITS] & (1<<(i%MALLOC_BITS))) {
	    wrtwarning("chunk is already free.\n");
	    return 0;
	}

	osize = (*mp)->size;

	if (!malloc_realloc &&		/* Unless we have to, */
	  size < osize && 		/* ..or are too small, */
	  (size > osize/2 ||	 	/* ..or could use a smaller size, */
	  osize == malloc_minsize)) {	/* ..(if there is one) */
	    return ptr;			/* ..Don't do anything */
	}

    } else {
	wrtwarning("pointer to wrong page.\n");
	return 0;
    }

    p = imalloc(size);

    if (p) {
	/* copy the lesser of the two sizes, and free the old one */
	if (!size || !osize)
	    ;
	else if (osize < size)
	    memcpy(p, ptr, osize);
	else
	    memcpy(p, ptr, size);
	ifree(ptr);
    } 
    return p;
}

/*
 * Free a sequence of pages
 */

static __inline__ void
free_pages(void *ptr, int index, struct pginfo *info)
{
    int i;
    struct pgfree *pf, *pt=0;
    u_long l;
    void *tail;

    if (info == MALLOC_FREE) {
	wrtwarning("page is already free.\n");
	return;
    }

    if (info != MALLOC_FIRST) {
	wrtwarning("pointer to wrong page.\n");
	return;
    }

    if ((u_long)ptr & malloc_pagemask) {
	wrtwarning("modified (page-) pointer.\n");
	return;
    }

    /* Count how many pages and mark them free at the same time */
    page_dir[index] = MALLOC_FREE;
    for (i = 1; page_dir[index+i] == MALLOC_FOLLOW; i++)
	page_dir[index + i] = MALLOC_FREE;

    l = i << malloc_pageshift;

    if (malloc_junk)
	memset(ptr, SOME_JUNK, l);

    if (malloc_hint)
	madvise(ptr, l, MADV_FREE);

    tail = (char *)ptr+l;

    /* add to free-list */
    if (!px)
	px = imalloc(sizeof *pt);	/* This cannot fail... */
    px->page = ptr;
    px->end =  tail;
    px->size = l;
    if (!free_list.next) {

	/* Nothing on free list, put this at head */
	px->next = free_list.next;
	px->prev = &free_list;
	free_list.next = px;
	pf = px;
	px = 0;

    } else {

	/* Find the right spot, leave pf pointing to the modified entry. */
	tail = (char *)ptr+l;

	for(pf = free_list.next; pf->end < ptr && pf->next; pf = pf->next)
	    ; /* Race ahead here */

	if (pf->page > tail) {
	    /* Insert before entry */
	    px->next = pf;
	    px->prev = pf->prev;
	    pf->prev = px;
	    px->prev->next = px;
	    pf = px;
	    px = 0;
	} else if (pf->end == ptr ) {
	    /* Append to the previous entry */
	    pf->end = (char *)pf->end + l;
	    pf->size += l;
	    if (pf->next && pf->end == pf->next->page ) {
		/* And collapse the next too. */
		pt = pf->next;
		pf->end = pt->end;
		pf->size += pt->size;
		pf->next = pt->next;
		if (pf->next)
		    pf->next->prev = pf;
	    }
	} else if (pf->page == tail) {
	    /* Prepend to entry */
	    pf->size += l;
	    pf->page = ptr;
	} else if (!pf->next) {
	    /* Append at tail of chain */
	    px->next = 0;
	    px->prev = pf;
	    pf->next = px;
	    pf = px;
	    px = 0;
	} else {
	    wrterror("freelist is destroyed.\n");
	}
    }
    
    /* Return something to OS ? */
    if (!pf->next &&				/* If we're the last one, */
      pf->size > malloc_cache &&		/* ..and the cache is full, */
      pf->end == malloc_brk &&			/* ..and none behind us, */
      malloc_brk == sbrk(0)) {			/* ..and it's OK to do... */

	/*
	 * Keep the cache intact.  Notice that the '>' above guarantees that
	 * the pf will always have at least one page afterwards.
	 */
	pf->end = (char *)pf->page + malloc_cache;
	pf->size = malloc_cache;

	brk(pf->end);
	malloc_brk = pf->end;

	index = ptr2index(pf->end);
	last_index = index - 1;

	for(i=index;i <= last_index;)
	    page_dir[i++] = MALLOC_NOT_MINE;

	/* XXX: We could realloc/shrink the pagedir here I guess. */
    }
    if (pt)
	ifree(pt);
}

/*
 * Free a chunk, and possibly the page it's on, if the page becomes empty.
 */

static __inline__ void
free_bytes(void *ptr, int index, struct pginfo *info)
{
    int i;
    struct pginfo **mp;
    void *vp;

    /* Find the chunk number on the page */
    i = ((u_long)ptr & malloc_pagemask) >> info->shift;

    if (((u_long)ptr & (info->size-1))) {
	wrtwarning("modified (chunk-) pointer.\n");
	return;
    }

    if (info->bits[i/MALLOC_BITS] & (1<<(i%MALLOC_BITS))) {
	wrtwarning("chunk is already free.\n");
	return;
    }

    if (malloc_junk)
	memset(ptr, SOME_JUNK, info->size);

    info->bits[i/MALLOC_BITS] |= 1<<(i%MALLOC_BITS);
    info->free++;

    mp = page_dir + info->shift;

    if (info->free == 1) {

	/* Page became non-full */

	mp = page_dir + info->shift;
	/* Insert in address order */
	while (*mp && (*mp)->next && (*mp)->next->page < info->page)
	    mp = &(*mp)->next;
	info->next = *mp;
	*mp = info;
	return;
    }

    if (info->free != info->total)
	return;

    /* Find & remove this page in the queue */
    while (*mp != info) {
	mp = &((*mp)->next);
#ifdef EXTRA_SANITY
	if (!*mp)
		wrterror("(ES): Not on queue\n");
#endif /* EXTRA_SANITY */
    }
    *mp = info->next;

    /* Free the page & the info structure if need be */
    page_dir[ptr2index(info->page)] = MALLOC_FIRST;
    vp = info->page;		/* Order is important ! */
    if(vp != (void*)info) 
	ifree(info);
    ifree(vp);
}

static void
ifree(void *ptr)
{
    struct pginfo *info;
    int index;

    /* This is legal */
    if (!ptr)
	return;

    if (!malloc_started) {
	wrtwarning("malloc() has never been called.\n");
	return;
    }

    /* If we're already sinking, don't make matters any worse. */
    if (suicide)
	return;

    index = ptr2index(ptr);

    if (index < malloc_pageshift) {
	wrtwarning("junk pointer, too low to make sense.\n");
	return;
    }

    if (index > last_index) {
	wrtwarning("junk pointer, too high to make sense.\n");
	return;
    }

    info = page_dir[index];

    if (info < MALLOC_MAGIC)
        free_pages(ptr, index, info);
    else
	free_bytes(ptr, index, info);
    return;
}

/*
 * These are the public exported interface routines.
 */


void *
malloc(size_t size)
{
    register void *r;

    THREAD_LOCK();
    malloc_func = " in malloc():";
    if (malloc_active++) {
	wrtwarning("recursive call.\n");
        malloc_active--;
	return (0);
    }
    if (!malloc_started)
	malloc_init();
    if (malloc_sysv && !size)
	r = 0;
    else
	r = imalloc(size);
    UTRACE(0, size, r);
    malloc_active--;
    THREAD_UNLOCK();
    if (malloc_xmalloc && !r)
	wrterror("out of memory.\n");
    return (r);
}

void
free(void *ptr)
{
    THREAD_LOCK();
    malloc_func = " in free():";
    if (malloc_active++) {
	wrtwarning("recursive call.\n");
	malloc_active--;
	return;
    } else {
	ifree(ptr);
	UTRACE(ptr, 0, 0);
    }
    malloc_active--;
    THREAD_UNLOCK();
    return;
}

void *
realloc(void *ptr, size_t size)
{
    register void *r;

    THREAD_LOCK();
    malloc_func = " in realloc():";
    if (malloc_active++) {
	wrtwarning("recursive call.\n");
        malloc_active--;
	return (0);
    }
    if (ptr && !malloc_started) {
	wrtwarning("malloc() has never been called.\n");
	ptr = 0;
    }		
    if (!malloc_started)
	malloc_init();
    if (malloc_sysv && !size) {
	ifree(ptr);
	r = 0;
    } else if (!ptr) {
	r = imalloc(size);
    } else {
        r = irealloc(ptr, size);
    }
    UTRACE(ptr, size, r);
    malloc_active--;
    THREAD_UNLOCK();
    if (malloc_xmalloc && !r)
	wrterror("out of memory.\n");
    return (r);
}
#endif /* !OSKIT */