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src/speedy_slot.c  view on Meta::CPAN

void speedy_slot_insert(slotnum_t slotnum, slotnum_t *head, slotnum_t *tail) {
    SLOT(slotnum).next_slot = *head;
    SLOT(slotnum).prev_slot = 0;
    if (*head)
	SLOT(*head).prev_slot = slotnum;
    *head = slotnum;
    if (tail && !*tail)
	*tail = slotnum;
}

void speedy_slot_append(slotnum_t slotnum, slotnum_t *head, slotnum_t *tail) {
    SLOT(slotnum).prev_slot = *tail;
    SLOT(slotnum).next_slot = 0;
    if (*tail)
	SLOT(*tail).next_slot = slotnum;
    *tail = slotnum;
    if (!*head)
	*head = slotnum;
}

#ifdef SPEEDY_BACKEND
void speedy_slot_insert_sorted(
    slotnum_t slotnum, slotnum_t *head, slotnum_t *tail,
    int (*compar)(slotnum_t, slotnum_t)
)
{
    slotnum_t *next_ptr;
    for (next_ptr = head; *next_ptr; next_ptr = &(SLOT(*next_ptr).next_slot)) {
	if (compar(slotnum, *next_ptr) <= 0) {
	    SLOT(slotnum).next_slot = *next_ptr;
	    SLOT(slotnum).prev_slot = SLOT(*next_ptr).prev_slot;
	    SLOT(*next_ptr).prev_slot = slotnum;
	    *next_ptr = slotnum;
	    return;
	}
    }
    speedy_slot_append(slotnum, head, tail);
}
#endif

/* Allocate a slot */
slotnum_t speedy_slot_alloc(void) {
    slotnum_t slotnum;

    /* Try to get a slot from the beginning of the free list */
    if ((slotnum = FILE_HEAD.slot_free)) {

	/* Got it - remove it from the free list */
	FILE_HEAD.slot_free = SLOT(slotnum).next_slot;

    } else {
	/* Allocate a new slot */
	slotnum = FILE_HEAD.slots_alloced + 1;

	/* Abort if too many slots */
	if (slotnum >= MAX_SLOTS)
	    DIE_QUIET("Out of slots");

	/* Check here if the file is large enough to hold this slot.
	 * The speedy_file code is supposed to allocate enough extra
	 * slots (MIN_SLOTS_FREE) when the file is locked to satisfy
	 * all slot_alloc's until the file is unlocked.  But if the
	 * code starts allocating too many slots for whatever reason,
	 * that will not work, and we'll drop off the end of the file.
	 * In that case, either fix the code or bump MIN_SLOTS_FREE
         */
	if (sizeof(file_head_t)+slotnum*sizeof(slot_t) > speedy_file_size()) {
	    speedy_util_die(
		"File too small for another slot while allocating slotnum %d. File size=%d. Try increasing MIN_SLOTS_FREE.",
		slotnum, speedy_file_size()
	    );
	}

	/* Successfully got a slot, so bump the count in the header */
	FILE_HEAD.slots_alloced++;
    }
    speedy_bzero(FILE_SLOTS + (slotnum-1), sizeof(slot_t));
    return slotnum;
}

/* Free a slot */
void speedy_slot_free(slotnum_t slotnum) {
    if (slotnum) {
	/* See if this is a previously freed slot */
	if (SLOT(slotnum).prev_slot == slotnum)
	    DIE_QUIET("Freeing free slot %d", slotnum);

	/* Mark this slot free by pointing prev to itself */
	SLOT(slotnum).prev_slot = slotnum;

	/* Put at beginning of free list */
	SLOT(slotnum).next_slot = FILE_HEAD.slot_free;
	FILE_HEAD.slot_free = slotnum;
    }
    else
	DIE_QUIET("Attempted free of slotnum 0");
}

slotnum_t speedy_slot_check(slotnum_t slotnum) {
    if (BAD_SLOTNUM(slotnum)) {
	DIE_QUIET("slotnum %d out of range, only %d alloced",
	    slotnum, FILE_HEAD.slots_alloced
	);
    }
    return slotnum;
}