diff --git a/server/mpm/event/config.m4 b/server/mpm/event/config.m4
index c891c75..351f1ac 100644
--- a/server/mpm/event/config.m4
+++ b/server/mpm/event/config.m4
@@ -7,8 +7,6 @@ elif test $have_threaded_sig_graceful != yes; then
AC_MSG_RESULT(no - SIG_GRACEFUL cannot be used with a threaded MPM)
elif test $ac_cv_have_threadsafe_pollset != yes; then
AC_MSG_RESULT(no - APR_POLLSET_THREADSAFE is not supported)
-elif test $apr_has_skiplist != yes; then
- AC_MSG_RESULT(no - APR skiplist is not available, need APR 1.5.x or later)
else
AC_MSG_RESULT(yes)
APACHE_MPM_SUPPORTED(event, yes, yes)
diff --git a/server/mpm/event/config3.m4 b/server/mpm/event/config3.m4
index 8aa1631..fa9b8af 100644
--- a/server/mpm/event/config3.m4
+++ b/server/mpm/event/config3.m4
@@ -2,6 +2,6 @@ dnl ## XXX - Need a more thorough check of the proper flags to use
APACHE_SUBST(MOD_MPM_EVENT_LDADD)
-APACHE_MPM_MODULE(event, $enable_mpm_event, event.lo fdqueue.lo,[
+APACHE_MPM_MODULE(event, $enable_mpm_event, event.lo fdqueue.lo apr_skiplist.lo,[
AC_CHECK_FUNCS(pthread_kill)
], , [\$(MOD_MPM_EVENT_LDADD)])
diff --git a/server/mpm/event/apr_skiplist.c b/server/mpm/event/apr_skiplist.c
new file mode 100644
index 0000000..effcf60
--- /dev/null
+++ b/server/mpm/event/apr_skiplist.c
@@ -0,0 +1,650 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Modified to use APR and APR pools.
+ * TODO: Is malloc() better? Will long running skiplists grow too much?
+ * Keep the skiplist_alloc() and skiplist_free() until we know
+ * Yeah, if using pools it means some bogus cycles for checks
+ * (and an useless function call for skiplist_free) which we
+ * can removed if/when needed.
+ */
+
+#include "apr_skiplist.h"
+
+struct apr_skiplist {
+ apr_skiplist_compare compare;
+ apr_skiplist_compare comparek;
+ int height;
+ int preheight;
+ int size;
+ apr_skiplistnode *top;
+ apr_skiplistnode *bottom;
+ /* These two are needed for appending */
+ apr_skiplistnode *topend;
+ apr_skiplistnode *bottomend;
+ apr_skiplist *index;
+ apr_array_header_t *memlist;
+ apr_pool_t *pool;
+};
+
+struct apr_skiplistnode {
+ void *data;
+ apr_skiplistnode *next;
+ apr_skiplistnode *prev;
+ apr_skiplistnode *down;
+ apr_skiplistnode *up;
+ apr_skiplistnode *previndex;
+ apr_skiplistnode *nextindex;
+ apr_skiplist *sl;
+};
+
+#ifndef MIN
+#define MIN(a,b) ((a<b)?(a):(b))
+#endif
+
+static int get_b_rand(void)
+{
+ static int ph = 32; /* More bits than we will ever use */
+ static apr_uint32_t randseq;
+ if (ph > 31) { /* Num bits in return of rand() */
+ ph = 0;
+ randseq = (apr_uint32_t) rand();
+ }
+ ph++;
+ return ((randseq & (1 << (ph - 1))) >> (ph - 1));
+}
+
+typedef struct {
+ size_t size;
+ apr_array_header_t *list;
+} memlist_t;
+
+typedef struct {
+ void *ptr;
+ char inuse;
+} chunk_t;
+
+APR_DECLARE(void *) apr_skiplist_alloc(apr_skiplist *sl, size_t size)
+{
+ if (sl->pool) {
+ void *ptr;
+ int found_size = 0;
+ int i;
+ chunk_t *newchunk;
+ memlist_t *memlist = (memlist_t *)sl->memlist->elts;
+ for (i = 0; i < sl->memlist->nelts; i++) {
+ if (memlist->size == size) {
+ int j;
+ chunk_t *chunk = (chunk_t *)memlist->list->elts;
+ found_size = 1;
+ for (j = 0; j < memlist->list->nelts; j++) {
+ if (!chunk->inuse) {
+ chunk->inuse = 1;
+ return chunk->ptr;
+ }
+ chunk++;
+ }
+ break; /* no free of this size; punt */
+ }
+ memlist++;
+ }
+ /* no free chunks */
+ ptr = apr_pcalloc(sl->pool, size);
+ if (!ptr) {
+ return ptr;
+ }
+ /*
+ * is this a new sized chunk? If so, we need to create a new
+ * array of them. Otherwise, re-use what we already have.
+ */
+ if (!found_size) {
+ memlist = apr_array_push(sl->memlist);
+ memlist->size = size;
+ memlist->list = apr_array_make(sl->pool, 20, sizeof(chunk_t));
+ }
+ newchunk = apr_array_push(memlist->list);
+ newchunk->ptr = ptr;
+ newchunk->inuse = 1;
+ return ptr;
+ }
+ else {
+ return calloc(1, size);
+ }
+}
+
+APR_DECLARE(void) apr_skiplist_free(apr_skiplist *sl, void *mem)
+{
+ if (!sl->pool) {
+ free(mem);
+ }
+ else {
+ int i;
+ memlist_t *memlist = (memlist_t *)sl->memlist->elts;
+ for (i = 0; i < sl->memlist->nelts; i++) {
+ int j;
+ chunk_t *chunk = (chunk_t *)memlist->list->elts;
+ for (j = 0; j < memlist->list->nelts; j++) {
+ if (chunk->ptr == mem) {
+ chunk->inuse = 0;
+ return;
+ }
+ chunk++;
+ }
+ memlist++;
+ }
+ }
+}
+
+static apr_status_t skiplisti_init(apr_skiplist **s, apr_pool_t *p)
+{
+ apr_skiplist *sl;
+ if (p) {
+ sl = apr_pcalloc(p, sizeof(apr_skiplist));
+ sl->memlist = apr_array_make(p, 20, sizeof(memlist_t));
+ }
+ else {
+ sl = calloc(1, sizeof(apr_skiplist));
+ }
+#if 0
+ sl->compare = (apr_skiplist_compare) NULL;
+ sl->comparek = (apr_skiplist_compare) NULL;
+ sl->height = 0;
+ sl->preheight = 0;
+ sl->size = 0;
+ sl->top = NULL;
+ sl->bottom = NULL;
+ sl->index = NULL;
+#endif
+ sl->pool = p;
+ *s = sl;
+ return APR_SUCCESS;
+}
+
+static int indexing_comp(void *a, void *b)
+{
+ void *ac = (void *) (((apr_skiplist *) a)->compare);
+ void *bc = (void *) (((apr_skiplist *) b)->compare);
+ return ((ac < bc) ? -1 : ((ac > bc) ? 1 : 0));
+}
+
+static int indexing_compk(void *ac, void *b)
+{
+ void *bc = (void *) (((apr_skiplist *) b)->compare);
+ return ((ac < bc) ? -1 : ((ac > bc) ? 1 : 0));
+}
+
+APR_DECLARE(apr_status_t) apr_skiplist_init(apr_skiplist **s, apr_pool_t *p)
+{
+ apr_skiplist *sl;
+ skiplisti_init(s, p);
+ sl = *s;
+ skiplisti_init(&(sl->index), p);
+ apr_skiplist_set_compare(sl->index, indexing_comp, indexing_compk);
+ return APR_SUCCESS;
+}
+
+APR_DECLARE(void) apr_skiplist_set_compare(apr_skiplist *sl,
+ apr_skiplist_compare comp,
+ apr_skiplist_compare compk)
+{
+ if (sl->compare && sl->comparek) {
+ apr_skiplist_add_index(sl, comp, compk);
+ }
+ else {
+ sl->compare = comp;
+ sl->comparek = compk;
+ }
+}
+
+APR_DECLARE(void) apr_skiplist_add_index(apr_skiplist *sl,
+ apr_skiplist_compare comp,
+ apr_skiplist_compare compk)
+{
+ apr_skiplistnode *m;
+ apr_skiplist *ni;
+ int icount = 0;
+ apr_skiplist_find(sl->index, (void *)comp, &m);
+ if (m) {
+ return; /* Index already there! */
+ }
+ skiplisti_init(&ni, sl->pool);
+ apr_skiplist_set_compare(ni, comp, compk);
+ /* Build the new index... This can be expensive! */
+ m = apr_skiplist_insert(sl->index, ni);
+ while (m->prev) {
+ m = m->prev;
+ icount++;
+ }
+ for (m = apr_skiplist_getlist(sl); m; apr_skiplist_next(sl, &m)) {
+ int j = icount - 1;
+ apr_skiplistnode *nsln;
+ nsln = apr_skiplist_insert(ni, m->data);
+ /* skip from main index down list */
+ while (j > 0) {
+ m = m->nextindex;
+ j--;
+ }
+ /* insert this node in the indexlist after m */
+ nsln->nextindex = m->nextindex;
+ if (m->nextindex) {
+ m->nextindex->previndex = nsln;
+ }
+ nsln->previndex = m;
+ m->nextindex = nsln;
+ }
+}
+
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_getlist(apr_skiplist *sl)
+{
+ if (!sl->bottom) {
+ return NULL;
+ }
+ return sl->bottom->next;
+}
+
+APR_DECLARE(void *) apr_skiplist_find(apr_skiplist *sl, void *data, apr_skiplistnode **iter)
+{
+ void *ret;
+ apr_skiplistnode *aiter;
+ if (!sl->compare) {
+ return 0;
+ }
+ if (iter) {
+ ret = apr_skiplist_find_compare(sl, data, iter, sl->compare);
+ }
+ else {
+ ret = apr_skiplist_find_compare(sl, data, &aiter, sl->compare);
+ }
+ return ret;
+}
+
+static int skiplisti_find_compare(apr_skiplist *sl, void *data,
+ apr_skiplistnode **ret,
+ apr_skiplist_compare comp)
+{
+ apr_skiplistnode *m = NULL;
+ int count = 0;
+ m = sl->top;
+ while (m) {
+ int compared;
+ compared = (m->next) ? comp(data, m->next->data) : -1;
+ if (compared == 0) {
+ m = m->next;
+ while (m->down) {
+ m = m->down;
+ }
+ *ret = m;
+ return count;
+ }
+ if ((m->next == NULL) || (compared < 0)) {
+ m = m->down;
+ count++;
+ }
+ else {
+ m = m->next;
+ count++;
+ }
+ }
+ *ret = NULL;
+ return count;
+}
+
+APR_DECLARE(void *) apr_skiplist_find_compare(apr_skiplist *sli, void *data,
+ apr_skiplistnode **iter,
+ apr_skiplist_compare comp)
+{
+ apr_skiplistnode *m = NULL;
+ apr_skiplist *sl;
+ if (comp == sli->compare || !sli->index) {
+ sl = sli;
+ }
+ else {
+ apr_skiplist_find(sli->index, (void *)comp, &m);
+ sl = (apr_skiplist *) m->data;
+ }
+ skiplisti_find_compare(sl, data, iter, sl->comparek);
+ return (iter && *iter) ? ((*iter)->data) : NULL;
+}
+
+
+APR_DECLARE(void *) apr_skiplist_next(apr_skiplist *sl, apr_skiplistnode **iter)
+{
+ if (!*iter) {
+ return NULL;
+ }
+ *iter = (*iter)->next;
+ return (*iter) ? ((*iter)->data) : NULL;
+}
+
+APR_DECLARE(void *) apr_skiplist_previous(apr_skiplist *sl, apr_skiplistnode **iter)
+{
+ if (!*iter) {
+ return NULL;
+ }
+ *iter = (*iter)->prev;
+ return (*iter) ? ((*iter)->data) : NULL;
+}
+
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert(apr_skiplist *sl, void *data)
+{
+ if (!sl->compare) {
+ return 0;
+ }
+ return apr_skiplist_insert_compare(sl, data, sl->compare);
+}
+
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert_compare(apr_skiplist *sl, void *data,
+ apr_skiplist_compare comp)
+{
+ apr_skiplistnode *m, *p, *tmp, *ret = NULL, **stack;
+ int nh = 1, ch, stacki;
+ if (!sl->top) {
+ sl->height = 1;
+ sl->topend = sl->bottomend = sl->top = sl->bottom =
+ (apr_skiplistnode *)apr_skiplist_alloc(sl, sizeof(apr_skiplistnode));
+#if 0
+ sl->top->next = (apr_skiplistnode *)NULL;
+ sl->top->data = (apr_skiplistnode *)NULL;
+ sl->top->prev = (apr_skiplistnode *)NULL;
+ sl->top->up = (apr_skiplistnode *)NULL;
+ sl->top->down = (apr_skiplistnode *)NULL;
+ sl->top->nextindex = (apr_skiplistnode *)NULL;
+ sl->top->previndex = (apr_skiplistnode *)NULL;
+#endif
+ sl->top->sl = sl;
+ }
+ if (sl->preheight) {
+ while (nh < sl->preheight && get_b_rand()) {
+ nh++;
+ }
+ }
+ else {
+ while (nh <= sl->height && get_b_rand()) {
+ nh++;
+ }
+ }
+ /* Now we have the new height at which we wish to insert our new node */
+ /*
+ * Let us make sure that our tree is a least that tall (grow if
+ * necessary)
+ */
+ for (; sl->height < nh; sl->height++) {
+ sl->top->up =
+ (apr_skiplistnode *)apr_skiplist_alloc(sl, sizeof(apr_skiplistnode));
+ sl->top->up->down = sl->top;
+ sl->top = sl->topend = sl->top->up;
+#if 0
+ sl->top->prev = sl->top->next = sl->top->nextindex =
+ sl->top->previndex = sl->top->up = NULL;
+ sl->top->data = NULL;
+#endif
+ sl->top->sl = sl;
+ }
+ ch = sl->height;
+ /* Find the node (or node after which we would insert) */
+ /* Keep a stack to pop back through for insertion */
+ /* malloc() is OK since we free the temp stack */
+ m = sl->top;
+ stack = (apr_skiplistnode **)malloc(sizeof(apr_skiplistnode *) * (nh));
+ stacki = 0;
+ while (m) {
+ int compared = -1;
+ if (m->next) {
+ compared = comp(data, m->next->data);
+ }
+ if (compared == 0) {
+ free(stack); /* OK. was malloc'ed */
+ return 0;
+ }
+ if ((m->next == NULL) || (compared < 0)) {
+ if (ch <= nh) {
+ /* push on stack */
+ stack[stacki++] = m;
+ }
+ m = m->down;
+ ch--;
+ }
+ else {
+ m = m->next;
+ }
+ }
+ /* Pop the stack and insert nodes */
+ p = NULL;
+ for (; stacki > 0; stacki--) {
+ m = stack[stacki - 1];
+ tmp = (apr_skiplistnode *)apr_skiplist_alloc(sl, sizeof(apr_skiplistnode));
+ tmp->next = m->next;
+ if (m->next) {
+ m->next->prev = tmp;
+ }
+ tmp->prev = m;
+ tmp->up = NULL;
+ tmp->nextindex = tmp->previndex = NULL;
+ tmp->down = p;
+ if (p) {
+ p->up = tmp;
+ }
+ tmp->data = data;
+ tmp->sl = sl;
+ m->next = tmp;
+ /* This sets ret to the bottom-most node we are inserting */
+ if (!p) {
+ ret = tmp;
+ sl->size++; /* this seems to go here got each element to be counted */
+ }
+ p = tmp;
+ }
+ free(stack); /* OK. was malloc'ed */
+ if (sl->index != NULL) {
+ /*
+ * this is a external insertion, we must insert into each index as
+ * well
+ */
+ apr_skiplistnode *ni, *li;
+ li = ret;
+ for (p = apr_skiplist_getlist(sl->index); p; apr_skiplist_next(sl->index, &p)) {
+ ni = apr_skiplist_insert((apr_skiplist *) p->data, ret->data);
+ li->nextindex = ni;
+ ni->previndex = li;
+ li = ni;
+ }
+ }
+ else {
+ /* sl->size++; */
+ }
+ sl->size++;
+ return ret;
+}
+
+APR_DECLARE(int) apr_skiplist_remove(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree)
+{
+ if (!sl->compare) {
+ return 0;
+ }
+ return apr_skiplist_remove_compare(sl, data, myfree, sl->comparek);
+}
+
+#if 0
+void skiplist_print_struct(apr_skiplist * sl, char *prefix)
+{
+ apr_skiplistnode *p, *q;
+ fprintf(stderr, "Skiplist Structure (height: %d)\n", sl->height);
+ p = sl->bottom;
+ while (p) {
+ q = p;
+ fprintf(stderr, prefix);
+ while (q) {
+ fprintf(stderr, "%p ", q->data);
+ q = q->up;
+ }
+ fprintf(stderr, "\n");
+ p = p->next;
+ }
+}
+#endif
+
+static int skiplisti_remove(apr_skiplist *sl, apr_skiplistnode *m, apr_skiplist_freefunc myfree)
+{
+ apr_skiplistnode *p;
+ if (!m) {
+ return 0;
+ }
+ if (m->nextindex) {
+ skiplisti_remove(m->nextindex->sl, m->nextindex, NULL);
+ }
+ while (m->up) {
+ m = m->up;
+ }
+ while (m) {
+ p = m;
+ p->prev->next = p->next;/* take me out of the list */
+ if (p->next) {
+ p->next->prev = p->prev; /* take me out of the list */
+ }
+ m = m->down;
+ /* This only frees the actual data in the bottom one */
+ if (!m && myfree && p->data) {
+ myfree(p->data);
+ }
+ apr_skiplist_free(sl, p);
+ }
+ sl->size--;
+ while (sl->top && sl->top->next == NULL) {
+ /* While the row is empty and we are not on the bottom row */
+ p = sl->top;
+ sl->top = sl->top->down;/* Move top down one */
+ if (sl->top) {
+ sl->top->up = NULL; /* Make it think its the top */
+ }
+ apr_skiplist_free(sl, p);
+ sl->height--;
+ }
+ if (!sl->top) {
+ sl->bottom = NULL;
+ }
+ return sl->height; /* return 1; ?? */
+}
+
+APR_DECLARE(int) apr_skiplist_remove_compare(apr_skiplist *sli,
+ void *data,
+ apr_skiplist_freefunc myfree, apr_skiplist_compare comp)
+{
+ apr_skiplistnode *m;
+ apr_skiplist *sl;
+ if (comp == sli->comparek || !sli->index) {
+ sl = sli;
+ }
+ else {
+ apr_skiplist_find(sli->index, (void *)comp, &m);
+ sl = (apr_skiplist *) m->data;
+ }
+ skiplisti_find_compare(sl, data, &m, comp);
+ if (!m) {
+ return 0;
+ }
+ while (m->previndex) {
+ m = m->previndex;
+ }
+ return skiplisti_remove(sl, m, myfree);
+}
+
+APR_DECLARE(void) apr_skiplist_remove_all(apr_skiplist *sl, apr_skiplist_freefunc myfree)
+{
+ /*
+ * This must remove even the place holder nodes (bottom though top)
+ * because we specify in the API that one can free the Skiplist after
+ * making this call without memory leaks
+ */
+ apr_skiplistnode *m, *p, *u;
+ m = sl->bottom;
+ while (m) {
+ p = m->next;
+ if (p && myfree && p->data)
+ myfree(p->data);
+ while (m) {
+ u = m->up;
+ apr_skiplist_free(sl, p);
+ m = u;
+ }
+ m = p;
+ }
+ sl->top = sl->bottom = NULL;
+ sl->height = 0;
+ sl->size = 0;
+}
+
+APR_DECLARE(void *) apr_skiplist_pop(apr_skiplist *a, apr_skiplist_freefunc myfree)
+{
+ apr_skiplistnode *sln;
+ void *data = NULL;
+ sln = apr_skiplist_getlist(a);
+ if (sln) {
+ data = sln->data;
+ skiplisti_remove(a, sln, myfree);
+ }
+ return data;
+}
+
+APR_DECLARE(void *) apr_skiplist_peek(apr_skiplist *a)
+{
+ apr_skiplistnode *sln;
+ sln = apr_skiplist_getlist(a);
+ if (sln) {
+ return sln->data;
+ }
+ return NULL;
+}
+
+static void skiplisti_destroy(void *vsl)
+{
+ apr_skiplist_destroy((apr_skiplist *) vsl, NULL);
+ apr_skiplist_free((apr_skiplist *) vsl, vsl);
+}
+
+APR_DECLARE(void) apr_skiplist_destroy(apr_skiplist *sl, apr_skiplist_freefunc myfree)
+{
+ while (apr_skiplist_pop(sl->index, skiplisti_destroy) != NULL)
+ ;
+ apr_skiplist_remove_all(sl, myfree);
+}
+
+APR_DECLARE(apr_skiplist *) apr_skiplist_merge(apr_skiplist *sl1, apr_skiplist *sl2)
+{
+ /* Check integrity! */
+ apr_skiplist temp;
+ struct apr_skiplistnode *b2;
+ if (sl1->bottomend == NULL || sl1->bottomend->prev == NULL) {
+ apr_skiplist_remove_all(sl1, NULL);
+ temp = *sl1;
+ *sl1 = *sl2;
+ *sl2 = temp;
+ /* swap them so that sl2 can be freed normally upon return. */
+ return sl1;
+ }
+ if(sl2->bottom == NULL || sl2->bottom->next == NULL) {
+ apr_skiplist_remove_all(sl2, NULL);
+ return sl1;
+ }
+ /* This is what makes it brute force... Just insert :/ */
+ b2 = apr_skiplist_getlist(sl2);
+ while (b2) {
+ apr_skiplist_insert(sl1, b2->data);
+ apr_skiplist_next(sl2, &b2);
+ }
+ apr_skiplist_remove_all(sl2, NULL);
+ return sl1;
+}
diff --git a/server/mpm/event/apr_skiplist.h b/server/mpm/event/apr_skiplist.h
new file mode 100644
index 0000000..bc17efd
--- /dev/null
+++ b/server/mpm/event/apr_skiplist.h
@@ -0,0 +1,259 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef APR_SKIPLIST_H
+#define APR_SKIPLIST_H
+/**
+ * @file apr_skiplist.h
+ * @brief APR skip list implementation
+ */
+
+#include "apr.h"
+#include "apr_portable.h"
+#include <stdlib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/**
+ * @defgroup apr_skiplist Skip list implementation
+ * Refer to http://en.wikipedia.org/wiki/Skip_list for information
+ * about the purpose of and ideas behind skip lists.
+ * @ingroup APR
+ * @{
+ */
+
+/**
+ * apr_skiplist_compare is the function type that must be implemented
+ * per object type that is used in a skip list for comparisons to maintain
+ * order
+ * */
+typedef int (*apr_skiplist_compare) (void *, void *);
+
+/**
+ * apr_skiplist_freefunc is the function type that must be implemented
+ * to handle elements as they are removed from a skip list.
+ */
+typedef void (*apr_skiplist_freefunc) (void *);
+
+/** Opaque structure used to represent the skip list */
+struct apr_skiplist;
+/** Opaque structure used to represent the skip list */
+typedef struct apr_skiplist apr_skiplist;
+
+/**
+ * Opaque structure used to represent abstract nodes in the skip list
+ * (an abstraction above the raw elements which are collected in the
+ * skip list).
+ */
+struct apr_skiplistnode;
+/** Opaque structure */
+typedef struct apr_skiplistnode apr_skiplistnode;
+
+/**
+ * Allocate memory using the same mechanism as the skip list.
+ * @param sl The skip list
+ * @param size The amount to allocate
+ * @remark If a pool was provided to apr_skiplist_init(), memory will
+ * be allocated from the pool or from a free list maintained with
+ * the skip list. Otherwise, memory will be allocated using the
+ * C standard library heap functions.
+ */
+APR_DECLARE(void *) apr_skiplist_alloc(apr_skiplist *sl, size_t size);
+
+/**
+ * Free memory using the same mechanism as the skip list.
+ * @param sl The skip list
+ * @param mem The object to free
+ * @remark If a pool was provided to apr_skiplist_init(), memory will
+ * be added to a free list maintained with the skip list and be available
+ * to operations on the skip list or to other calls to apr_skiplist_alloc().
+ * Otherwise, memory will be freed using the C standard library heap
+ * functions.
+ */
+APR_DECLARE(void) apr_skiplist_free(apr_skiplist *sl, void *mem);
+
+/**
+ * Allocate a new skip list
+ * @param sl The pointer in which to return the newly created skip list
+ * @param p The pool from which to allocate the skip list (optional).
+ * @remark Unlike most APR functions, a pool is optional. If no pool
+ * is provided, the C standard library heap functions will be used instead.
+ */
+APR_DECLARE(apr_status_t) apr_skiplist_init(apr_skiplist **sl, apr_pool_t *p);
+
+/**
+ * Set the comparison functions to be used for searching the skip list.
+ * @param sl The skip list
+ * @param XXX1 FIXME
+ * @param XXX2 FIXME
+ *
+ * @remark If existing comparison functions are being replaced, the index
+ * will be replaced during this call. That is a potentially expensive
+ * operation.
+ */
+APR_DECLARE(void) apr_skiplist_set_compare(apr_skiplist *sl, apr_skiplist_compare XXX1,
+ apr_skiplist_compare XXX2);
+
+/**
+ * Set the indexing functions to the specified comparison functions and
+ * rebuild the index.
+ * @param sl The skip list
+ * @param XXX1 FIXME
+ * @param XXX2 FIXME
+ *
+ * @remark If an index already exists, it will not be replaced and the
+ * comparison functions will not be changed.
+ */
+APR_DECLARE(void) apr_skiplist_add_index(apr_skiplist *sl, apr_skiplist_compare XXX1,
+ apr_skiplist_compare XXX2);
+
+/**
+ * Return the list maintained by the skip list abstraction.
+ * @param sl The skip list
+ */
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_getlist(apr_skiplist *sl);
+
+/**
+ * Return the next matching element in the skip list using the specified
+ * comparison function.
+ * @param sl The skip list
+ * @param data The value to search for
+ * @param iter A pointer to the returned skip list node representing the element
+ * found
+ * @param func The comparison function to use
+ */
+APR_DECLARE(void *) apr_skiplist_find_compare(apr_skiplist *sl,
+ void *data,
+ apr_skiplistnode **iter,
+ apr_skiplist_compare func);
+
+/**
+ * Return the next matching element in the skip list using the current comparison
+ * function.
+ * @param sl The skip list
+ * @param data The value to search for
+ * @param iter A pointer to the returned skip list node representing the element
+ * found
+ */
+APR_DECLARE(void *) apr_skiplist_find(apr_skiplist *sl, void *data, apr_skiplistnode **iter);
+
+/**
+ * Return the next element in the skip list.
+ * @param sl The skip list
+ * @param iter On entry, a pointer to the skip list node to start with; on return,
+ * a pointer to the skip list node representing the element returned
+ * @remark If iter points to a NULL value on entry, NULL will be returned.
+ */
+APR_DECLARE(void *) apr_skiplist_next(apr_skiplist *sl, apr_skiplistnode **iter);
+
+/**
+ * Return the previous element in the skip list.
+ * @param sl The skip list
+ * @param iter On entry, a pointer to the skip list node to start with; on return,
+ * a pointer to the skip list node representing the element returned
+ * @remark If iter points to a NULL value on entry, NULL will be returned.
+ */
+APR_DECLARE(void *) apr_skiplist_previous(apr_skiplist *sl, apr_skiplistnode **iter);
+
+/**
+ * Insert an element into the skip list using the specified comparison function.
+ * @param sl The skip list
+ * @param data The element to insert
+ * @param comp The comparison function to use for placement into the skip list
+ */
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert_compare(apr_skiplist *sl,
+ void *data, apr_skiplist_compare comp);
+
+/**
+ * Insert an element into the skip list using the existing comparison function.
+ * @param sl The skip list
+ * @param data The element to insert
+ * @remark If no comparison function has been set for the skip list, the element
+ * will not be inserted and NULL will be returned.
+ */
+APR_DECLARE(apr_skiplistnode *) apr_skiplist_insert(apr_skiplist* sl, void *data);
+
+/**
+ * Remove an element from the skip list using the specified comparison function for
+ * locating the element.
+ * @param sl The skip list
+ * @param data The element to remove
+ * @param myfree A function to be called for each removed element
+ * @param comp The comparison function to use for placement into the skip list
+ * @remark If the element is not found, 0 will be returned. Otherwise, the heightXXX
+ * will be returned.
+ */
+APR_DECLARE(int) apr_skiplist_remove_compare(apr_skiplist *sl, void *data,
+ apr_skiplist_freefunc myfree, apr_skiplist_compare comp);
+
+/**
+ * Remove an element from the skip list using the existing comparison function for
+ * locating the element.
+ * @param sl The skip list
+ * @param data The element to remove
+ * @param myfree A function to be called for each removed element
+ * @remark If the element is not found, 0 will be returned. Otherwise, the heightXXX
+ * will be returned.
+ * @remark If no comparison function has been set for the skip list, the element
+ * will not be removed and 0 will be returned.
+ */
+APR_DECLARE(int) apr_skiplist_remove(apr_skiplist *sl, void *data, apr_skiplist_freefunc myfree);
+
+/**
+ * Remove all elements from the skip list.
+ * @param sl The skip list
+ * @param myfree A function to be called for each removed element
+ */
+APR_DECLARE(void) apr_skiplist_remove_all(apr_skiplist *sl, apr_skiplist_freefunc myfree);
+
+/**
+ * Remove each element from the skip list.
+ * @param sl The skip list
+ * @param myfree A function to be called for each removed element
+ */
+APR_DECLARE(void) apr_skiplist_destroy(apr_skiplist *sl, apr_skiplist_freefunc myfree);
+
+/**
+ * Return the first element in the skip list, leaving the element in the skip list.
+ * @param sl The skip list
+ * @param myfree A function to be called for the removed element
+ * @remark NULL will be returned if there are no elements
+ */
+APR_DECLARE(void *) apr_skiplist_pop(apr_skiplist *sl, apr_skiplist_freefunc myfree);
+
+/**
+ * Return the first element in the skip list, leaving the element in the skip list.
+ * @param sl The skip list
+ * @remark NULL will be returned if there are no elements
+ */
+APR_DECLARE(void *) apr_skiplist_peek(apr_skiplist *sl);
+
+/**
+ * Merge two skip lists. XXX SEMANTICS
+ * @param sl1 One of two skip lists to be merged
+ * @param sl2 The other of two skip lists to be merged
+ */
+APR_DECLARE(apr_skiplist *) apr_skiplist_merge(apr_skiplist *sl1, apr_skiplist *sl2);
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ! APR_SKIPLIST_H */