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https://gitlab.torproject.org/tpo/core/tor.git
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Enhance pqueue so we can remove items from the middle.
This changes the pqueue API by requiring an additional int in every structure that we store in a pqueue to hold the index of that structure within the heap.
This commit is contained in:
Nick Mathewson
parent
d086c9a7f7
commit
c210db0d41
@ -605,6 +605,38 @@ smartlist_uniq_strings(smartlist_t *sl)
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/* Heap-based priority queue implementation for O(lg N) insert and remove.
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* Recall that the heap property is that, for every index I, h[I] <
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* H[LEFT_CHILD[I]] and h[I] < H[RIGHT_CHILD[I]].
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*
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* For us to remove items other than the topmost item, each item must store
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* its own index within the heap. When calling the pqueue functions, tell
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* them about the offset of the field that stores the index within the item.
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*
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* Example:
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*
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* typedef struct timer_t {
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* struct timeval tv;
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* int heap_index;
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* } timer_t;
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*
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* static int compare(const void *p1, const void *p2) {
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* const timer_t *t1 = p1, *t2 = p2;
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* if (t1->tv.tv_sec < t2->tv.tv_sec) {
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* return -1;
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* } else if (t1->tv.tv_sec > t2->tv.tv_sec) {
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* return 1;
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* } else {
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* return t1->tv.tv_usec - t2->tv_usec;
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* }
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* }
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*
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* void timer_heap_insert(smartlist_t *heap, timer_t *timer) {
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* smartlist_pqueue_add(heap, compare, STRUCT_OFFSET(timer_t, heap_index),
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* timer);
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* }
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*
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* void timer_heap_pop(smartlist_t *heap) {
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* return smartlist_pqueue_pop(heap, compare,
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* STRUCT_OFFSET(timer_t, heap_index));
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* }
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*/
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/* For a 1-indexed array, we would use LEFT_CHILD[x] = 2*x and RIGHT_CHILD[x]
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@ -616,12 +648,22 @@ smartlist_uniq_strings(smartlist_t *sl)
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#define RIGHT_CHILD(i) ( 2*(i) + 2 )
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#define PARENT(i) ( ((i)-1) / 2 )
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#define IDXP(p) ((int*)STRUCT_VAR_P(p, idx_field_offset))
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#define UPDATE_IDX(i) do { \
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void *updated = sl->list[i]; \
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*IDXP(updated) = i; \
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} while (0)
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#define IDX_OF_ITEM(p) (*IDXP(p))
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/** Helper. <b>sl</b> may have at most one violation of the heap property:
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* the item at <b>idx</b> may be greater than one or both of its children.
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* Restore the heap property. */
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static INLINE void
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smartlist_heapify(smartlist_t *sl,
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int (*compare)(const void *a, const void *b),
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int idx_field_offset,
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int idx)
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{
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while (1) {
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@ -644,21 +686,28 @@ smartlist_heapify(smartlist_t *sl,
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void *tmp = sl->list[idx];
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sl->list[idx] = sl->list[best_idx];
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sl->list[best_idx] = tmp;
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UPDATE_IDX(idx);
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UPDATE_IDX(best_idx);
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idx = best_idx;
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}
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}
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}
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/** Insert <b>item</b> into the heap stored in <b>sl</b>, where order
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* is determined by <b>compare</b>. */
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/** Insert <b>item</b> into the heap stored in <b>sl</b>, where order is
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* determined by <b>compare</b> and the offset of the item in the heap is
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* stored in an int-typed field at position <b>idx_field_offset</b> within
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* item.
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*/
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void
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smartlist_pqueue_add(smartlist_t *sl,
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int (*compare)(const void *a, const void *b),
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int idx_field_offset,
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void *item)
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{
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int idx;
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smartlist_add(sl,item);
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UPDATE_IDX(sl->num_used-1);
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for (idx = sl->num_used - 1; idx; ) {
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int parent = PARENT(idx);
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@ -666,6 +715,8 @@ smartlist_pqueue_add(smartlist_t *sl,
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void *tmp = sl->list[parent];
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sl->list[parent] = sl->list[idx];
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sl->list[idx] = tmp;
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UPDATE_IDX(parent);
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UPDATE_IDX(idx);
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idx = parent;
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} else {
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return;
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@ -674,32 +725,63 @@ smartlist_pqueue_add(smartlist_t *sl,
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}
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/** Remove and return the top-priority item from the heap stored in <b>sl</b>,
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* where order is determined by <b>compare</b>. <b>sl</b> must not be
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* empty. */
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* where order is determined by <b>compare</b> and the item's position in is
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* stored at position <b>idx_field_offset</b> within the item. <b>sl</b> must
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* not be empty. */
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void *
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smartlist_pqueue_pop(smartlist_t *sl,
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int (*compare)(const void *a, const void *b))
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int (*compare)(const void *a, const void *b),
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int idx_field_offset)
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{
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void *top;
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tor_assert(sl->num_used);
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top = sl->list[0];
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*IDXP(top)=-1;
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if (--sl->num_used) {
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sl->list[0] = sl->list[sl->num_used];
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smartlist_heapify(sl, compare, 0);
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UPDATE_IDX(0);
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smartlist_heapify(sl, compare, idx_field_offset, 0);
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}
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return top;
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}
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/** Remove the item <b>item</b> from the heap stored in <b>sl</b>,
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* where order is determined by <b>compare</b> and the item's position in is
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* stored at position <b>idx_field_offset</b> within the item. <b>sl</b> must
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* not be empty. */
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void
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smartlist_pqueue_remove(smartlist_t *sl,
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int (*compare)(const void *a, const void *b),
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int idx_field_offset,
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void *item)
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{
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int idx = IDX_OF_ITEM(item);
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tor_assert(idx >= 0);
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tor_assert(sl->list[idx] == item);
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--sl->num_used;
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*IDXP(item) = -1;
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if (idx == sl->num_used) {
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return;
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} else {
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sl->list[idx] = sl->list[sl->num_used];
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UPDATE_IDX(idx);
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smartlist_heapify(sl, compare, idx_field_offset, idx);
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}
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}
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/** Assert that the heap property is correctly maintained by the heap stored
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* in <b>sl</b>, where order is determined by <b>compare</b>. */
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void
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smartlist_pqueue_assert_ok(smartlist_t *sl,
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int (*compare)(const void *a, const void *b))
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int (*compare)(const void *a, const void *b),
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int idx_field_offset)
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{
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int i;
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for (i = sl->num_used - 1; i > 0; --i) {
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for (i = sl->num_used - 1; i >= 0; --i) {
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if (i>0)
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tor_assert(compare(sl->list[PARENT(i)], sl->list[i]) <= 0);
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tor_assert(IDX_OF_ITEM(sl->list[i]) == i);
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}
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}
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@ -118,11 +118,18 @@ int smartlist_bsearch_idx(const smartlist_t *sl, const void *key,
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void smartlist_pqueue_add(smartlist_t *sl,
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int (*compare)(const void *a, const void *b),
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int idx_field_offset,
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void *item);
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void *smartlist_pqueue_pop(smartlist_t *sl,
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int (*compare)(const void *a, const void *b));
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int (*compare)(const void *a, const void *b),
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int idx_field_offset);
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void smartlist_pqueue_remove(smartlist_t *sl,
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int (*compare)(const void *a, const void *b),
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int idx_field_offset,
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void *item);
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void smartlist_pqueue_assert_ok(smartlist_t *sl,
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int (*compare)(const void *a, const void *b));
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int (*compare)(const void *a, const void *b),
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int idx_field_offset);
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#define SPLIT_SKIP_SPACE 0x01
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#define SPLIT_IGNORE_BLANK 0x02
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10
src/or/dns.c
10
src/or/dns.c
@ -128,6 +128,8 @@ typedef struct cached_resolve_t {
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uint32_t ttl; /**< What TTL did the nameserver tell us? */
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/** Connections that want to know when we get an answer for this resolve. */
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pending_connection_t *pending_connections;
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/** Position of this element in the heap*/
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int minheap_idx;
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} cached_resolve_t;
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static void purge_expired_resolves(time_t now);
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@ -344,6 +346,7 @@ set_expiry(cached_resolve_t *resolve, time_t expires)
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resolve->expire = expires;
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smartlist_pqueue_add(cached_resolve_pqueue,
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_compare_cached_resolves_by_expiry,
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STRUCT_OFFSET(cached_resolve_t, minheap_idx),
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resolve);
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}
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@ -389,7 +392,8 @@ purge_expired_resolves(time_t now)
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if (resolve->expire > now)
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break;
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smartlist_pqueue_pop(cached_resolve_pqueue,
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_compare_cached_resolves_by_expiry);
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_compare_cached_resolves_by_expiry,
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STRUCT_OFFSET(cached_resolve_t, minheap_idx));
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if (resolve->state == CACHE_STATE_PENDING) {
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log_debug(LD_EXIT,
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@ -751,6 +755,7 @@ dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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resolve = tor_malloc_zero(sizeof(cached_resolve_t));
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resolve->magic = CACHED_RESOLVE_MAGIC;
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resolve->state = CACHE_STATE_PENDING;
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resolve->minheap_idx = -1;
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resolve->is_reverse = is_reverse;
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strlcpy(resolve->address, exitconn->_base.address, sizeof(resolve->address));
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@ -1734,7 +1739,8 @@ _assert_cache_ok(void)
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return;
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smartlist_pqueue_assert_ok(cached_resolve_pqueue,
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_compare_cached_resolves_by_expiry);
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_compare_cached_resolves_by_expiry,
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STRUCT_OFFSET(cached_resolve_t, minheap_idx));
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SMARTLIST_FOREACH(cached_resolve_pqueue, cached_resolve_t *, res,
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{
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@ -515,11 +515,17 @@ test_container_digestset(void)
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smartlist_free(included);
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}
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/** Helper: return a tristate based on comparing two strings. */
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typedef struct pq_entry_t {
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const char *val;
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int idx;
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} pq_entry_t;
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/** Helper: return a tristate based on comparing two pq_entry_t values. */
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static int
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_compare_strings_for_pqueue(const void *s1, const void *s2)
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_compare_strings_for_pqueue(const void *p1, const void *p2)
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{
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return strcmp((const char*)s1, (const char*)s2);
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const pq_entry_t *e1=p1, *e2=p2;
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return strcmp(e1->val, e2->val);
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}
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/** Run unit tests for heap-based priority queue functions. */
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@ -528,50 +534,90 @@ test_container_pqueue(void)
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{
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smartlist_t *sl = smartlist_create();
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int (*cmp)(const void *, const void*);
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#define OK() smartlist_pqueue_assert_ok(sl, cmp)
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const int offset = STRUCT_OFFSET(pq_entry_t, idx);
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#define ENTRY(s) pq_entry_t s = { #s, -1 }
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ENTRY(cows);
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ENTRY(zebras);
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ENTRY(fish);
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ENTRY(frogs);
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ENTRY(apples);
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ENTRY(squid);
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ENTRY(daschunds);
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ENTRY(eggplants);
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ENTRY(weissbier);
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ENTRY(lobsters);
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ENTRY(roquefort);
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ENTRY(chinchillas);
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ENTRY(fireflies);
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#define OK() smartlist_pqueue_assert_ok(sl, cmp, offset)
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cmp = _compare_strings_for_pqueue;
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smartlist_pqueue_add(sl, cmp, (char*)"cows");
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smartlist_pqueue_add(sl, cmp, (char*)"zebras");
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smartlist_pqueue_add(sl, cmp, (char*)"fish");
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smartlist_pqueue_add(sl, cmp, (char*)"frogs");
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smartlist_pqueue_add(sl, cmp, (char*)"apples");
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smartlist_pqueue_add(sl, cmp, (char*)"squid");
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smartlist_pqueue_add(sl, cmp, (char*)"daschunds");
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smartlist_pqueue_add(sl, cmp, (char*)"eggplants");
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smartlist_pqueue_add(sl, cmp, (char*)"weissbier");
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smartlist_pqueue_add(sl, cmp, (char*)"lobsters");
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smartlist_pqueue_add(sl, cmp, (char*)"roquefort");
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smartlist_pqueue_add(sl, cmp, offset, &cows);
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smartlist_pqueue_add(sl, cmp, offset, &zebras);
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smartlist_pqueue_add(sl, cmp, offset, &fish);
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smartlist_pqueue_add(sl, cmp, offset, &frogs);
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smartlist_pqueue_add(sl, cmp, offset, &apples);
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smartlist_pqueue_add(sl, cmp, offset, &squid);
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smartlist_pqueue_add(sl, cmp, offset, &daschunds);
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smartlist_pqueue_add(sl, cmp, offset, &eggplants);
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smartlist_pqueue_add(sl, cmp, offset, &weissbier);
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smartlist_pqueue_add(sl, cmp, offset, &lobsters);
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smartlist_pqueue_add(sl, cmp, offset, &roquefort);
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OK();
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test_eq(smartlist_len(sl), 11);
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test_streq(smartlist_get(sl, 0), "apples");
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test_streq(smartlist_pqueue_pop(sl, cmp), "apples");
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test_eq_ptr(smartlist_get(sl, 0), &apples);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &apples);
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test_eq(smartlist_len(sl), 10);
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OK();
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test_streq(smartlist_pqueue_pop(sl, cmp), "cows");
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test_streq(smartlist_pqueue_pop(sl, cmp), "daschunds");
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smartlist_pqueue_add(sl, cmp, (char*)"chinchillas");
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &cows);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &daschunds);
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smartlist_pqueue_add(sl, cmp, offset, &chinchillas);
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OK();
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smartlist_pqueue_add(sl, cmp, (char*)"fireflies");
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smartlist_pqueue_add(sl, cmp, offset, &fireflies);
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OK();
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test_streq(smartlist_pqueue_pop(sl, cmp), "chinchillas");
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test_streq(smartlist_pqueue_pop(sl, cmp), "eggplants");
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test_streq(smartlist_pqueue_pop(sl, cmp), "fireflies");
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &chinchillas);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &eggplants);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &fireflies);
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OK();
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test_streq(smartlist_pqueue_pop(sl, cmp), "fish");
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test_streq(smartlist_pqueue_pop(sl, cmp), "frogs");
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test_streq(smartlist_pqueue_pop(sl, cmp), "lobsters");
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test_streq(smartlist_pqueue_pop(sl, cmp), "roquefort");
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &fish);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &frogs);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &lobsters);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &roquefort);
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OK();
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test_eq(smartlist_len(sl), 3);
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test_streq(smartlist_pqueue_pop(sl, cmp), "squid");
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test_streq(smartlist_pqueue_pop(sl, cmp), "weissbier");
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test_streq(smartlist_pqueue_pop(sl, cmp), "zebras");
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &squid);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &weissbier);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &zebras);
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test_eq(smartlist_len(sl), 0);
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OK();
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/* Now test remove. */
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smartlist_pqueue_add(sl, cmp, offset, &cows);
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smartlist_pqueue_add(sl, cmp, offset, &fish);
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smartlist_pqueue_add(sl, cmp, offset, &frogs);
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smartlist_pqueue_add(sl, cmp, offset, &apples);
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smartlist_pqueue_add(sl, cmp, offset, &squid);
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smartlist_pqueue_add(sl, cmp, offset, &zebras);
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test_eq(smartlist_len(sl), 6);
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OK();
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smartlist_pqueue_remove(sl, cmp, offset, &zebras);
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test_eq(smartlist_len(sl), 5);
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OK();
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smartlist_pqueue_remove(sl, cmp, offset, &cows);
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test_eq(smartlist_len(sl), 4);
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OK();
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smartlist_pqueue_remove(sl, cmp, offset, &apples);
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test_eq(smartlist_len(sl), 3);
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OK();
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &fish);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &frogs);
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test_eq_ptr(smartlist_pqueue_pop(sl, cmp, offset), &squid);
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test_eq(smartlist_len(sl), 0);
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OK();
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#undef OK
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done:
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