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diff --git a/lib/skiplist.c b/lib/skiplist.c
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+/*
+ * Copyright 1990 William Pugh
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * Permission to include in quagga provide on March 31, 2016
+ */
+
+/*
+ * Skip List implementation based on code from William Pugh.
+ * ftp://ftp.cs.umd.edu/pub/skipLists/
+ *
+ * Skip Lists are a probabilistic alternative to balanced trees, as
+ * described in the June 1990 issue of CACM and were invented by
+ * William Pugh in 1987.
+ *
+ * This file contains source code to implement a dictionary using
+ * skip lists and a test driver to test the routines.
+ *
+ * A couple of comments about this implementation:
+ * The routine randomLevel has been hard-coded to generate random
+ * levels using p=0.25. It can be easily changed.
+ *
+ * The insertion routine has been implemented so as to use the
+ * dirty hack described in the CACM paper: if a random level is
+ * generated that is more than the current maximum level, the
+ * current maximum level plus one is used instead.
+ *
+ * Levels start at zero and go up to MaxLevel (which is equal to
+ * (MaxNumberOfLevels-1).
+ *
+ * The run-time flag SKIPLIST_FLAG_ALLOW_DUPLICATES determines whether or
+ * not duplicates are allowed for a given list. If set, duplicates are
+ * allowed and act in a FIFO manner. If not set, an insertion of a value
+ * already in the list updates the previously existing binding.
+ *
+ * BitsInRandom is defined to be the number of bits returned by a call to
+ * random(). For most all machines with 32-bit integers, this is 31 bits
+ * as currently set.
+ */
+
+
+#include <zebra.h>
+
+#include "memory.h"
+#include "log.h"
+#include "vty.h"
+#include "skiplist.h"
+#include "lib_errors.h"
+#include "network.h"
+
+DEFINE_MTYPE_STATIC(LIB, SKIP_LIST, "Skip List");
+DEFINE_MTYPE_STATIC(LIB, SKIP_LIST_NODE, "Skip Node");
+DEFINE_MTYPE_STATIC(LIB, SKIP_LIST_STATS, "Skiplist Counters");
+
+#define BitsInRandom 31
+
+#define MaxNumberOfLevels 16
+#define MaxLevel (MaxNumberOfLevels-1)
+#define newNodeOfLevel(l) \
+ XCALLOC(MTYPE_SKIP_LIST_NODE, \
+ sizeof(struct skiplistnode) \
+ + (l) * sizeof(struct skiplistnode *))
+
+/* XXX must match type of (struct skiplist).level_stats */
+#define newStatsOfLevel(l) \
+ XCALLOC(MTYPE_SKIP_LIST_STATS, ((l) + 1) * sizeof(int))
+
+static int randomsLeft;
+static int randomBits;
+
+#ifdef SKIPLIST_DEBUG
+#define CHECKLAST(sl) \
+ do { \
+ if ((sl)->header->forward[0] && !(sl)->last) \
+ assert(0); \
+ if (!(sl)->header->forward[0] && (sl)->last) \
+ assert(0); \
+ } while (0)
+#else
+#define CHECKLAST(sl)
+#endif
+
+
+static int randomLevel(void)
+{
+ register int level = 0;
+ register int b;
+
+ do {
+ if (randomsLeft <= 0) {
+ randomBits = frr_weak_random();
+ randomsLeft = BitsInRandom / 2;
+ }
+ b = randomBits & 3;
+ randomBits >>= 2;
+ --randomsLeft;
+
+ if (!b) {
+ level++;
+ if (level >= MaxLevel)
+ return MaxLevel;
+ }
+ } while (!b);
+
+ return level;
+}
+
+static int default_cmp(const void *key1, const void *key2)
+{
+ if (key1 < key2)
+ return -1;
+ if (key1 > key2)
+ return 1;
+ return 0;
+}
+
+unsigned int skiplist_count(struct skiplist *l)
+{
+ return l->count;
+}
+
+struct skiplist *skiplist_new(int flags,
+ int (*cmp)(const void *key1, const void *key2),
+ void (*del)(void *val))
+{
+ struct skiplist *new;
+
+ new = XCALLOC(MTYPE_SKIP_LIST, sizeof(struct skiplist));
+ assert(new);
+
+ new->level = 0;
+ new->count = 0;
+ new->header = newNodeOfLevel(MaxNumberOfLevels);
+ new->level_stats = newStatsOfLevel(MaxNumberOfLevels);
+
+ new->flags = flags;
+ if (cmp)
+ new->cmp = cmp;
+ else
+ new->cmp = default_cmp;
+
+ if (del)
+ new->del = del;
+
+ return new;
+}
+
+void skiplist_free(struct skiplist *l)
+{
+ register struct skiplistnode *p, *q;
+
+ p = l->header;
+
+ do {
+ q = p->forward[0];
+ if (l->del && p != l->header)
+ (*l->del)(p->value);
+ XFREE(MTYPE_SKIP_LIST_NODE, p);
+ p = q;
+ } while (p);
+
+ XFREE(MTYPE_SKIP_LIST_STATS, l->level_stats);
+ XFREE(MTYPE_SKIP_LIST, l);
+}
+
+
+int skiplist_insert(register struct skiplist *l, register void *key,
+ register void *value)
+{
+ register int k;
+ struct skiplistnode *update[MaxNumberOfLevels];
+ register struct skiplistnode *p, *q;
+
+ CHECKLAST(l);
+
+#ifdef SKIPLIST_DEBUG
+ /* DEBUG */
+ if (!key) {
+ flog_err(EC_LIB_DEVELOPMENT, "%s: key is 0, value is %p",
+ __func__, value);
+ }
+#endif
+
+ p = l->header;
+ k = l->level;
+ do {
+ while (q = p->forward[k], q && (*l->cmp)(q->key, key) < 0)
+ p = q;
+ update[k] = p;
+ } while (--k >= 0);
+
+ if (!(l->flags & SKIPLIST_FLAG_ALLOW_DUPLICATES) && q
+ && ((*l->cmp)(q->key, key) == 0)) {
+
+ return -1;
+ }
+
+ k = randomLevel();
+ assert(k >= 0);
+ if (k > l->level) {
+ k = ++l->level;
+ update[k] = l->header;
+ }
+
+ q = newNodeOfLevel(k);
+ q->key = key;
+ q->value = value;
+#ifdef SKIPLIST_0TIMER_DEBUG
+ q->flags = SKIPLIST_NODE_FLAG_INSERTED; /* debug */
+#endif
+
+ ++(l->level_stats[k]);
+#ifdef SKIPLIST_DEBUG
+ zlog_debug("%s: incremented level_stats @%p:%d, now %d", __func__, l, k,
+ l->level_stats[k]);
+#endif
+
+ do {
+ p = update[k];
+ q->forward[k] = p->forward[k];
+ p->forward[k] = q;
+ } while (--k >= 0);
+
+ /*
+ * If this is the last item in the list, update the "last" pointer
+ */
+ if (!q->forward[0]) {
+ l->last = q;
+ }
+
+ ++(l->count);
+
+ CHECKLAST(l);
+
+ return 0;
+}
+
+int skiplist_delete(register struct skiplist *l, register void *key,
+ register void *value) /* used only if duplicates allowed */
+{
+ register int k, m;
+ struct skiplistnode *update[MaxNumberOfLevels];
+ register struct skiplistnode *p, *q;
+
+ CHECKLAST(l);
+
+ /* to make debugging easier */
+ for (k = 0; k < MaxNumberOfLevels; ++k)
+ update[k] = NULL;
+
+ p = l->header;
+ k = m = l->level;
+ do {
+ while (q = p->forward[k], q && (*l->cmp)(q->key, key) < 0)
+ p = q;
+ update[k] = p;
+ } while (--k >= 0);
+
+ if (l->flags & SKIPLIST_FLAG_ALLOW_DUPLICATES) {
+ while (q && ((*l->cmp)(q->key, key) == 0)
+ && (q->value != value)) {
+ int i;
+ for (i = 0; i <= l->level; ++i) {
+ if (update[i]->forward[i] == q)
+ update[i] = q;
+ }
+ q = q->forward[0];
+ }
+ }
+
+ if (q && (*l->cmp)(q->key, key) == 0) {
+ if (!(l->flags & SKIPLIST_FLAG_ALLOW_DUPLICATES)
+ || (q->value == value)) {
+
+/*
+ * found node to delete
+ */
+#ifdef SKIPLIST_0TIMER_DEBUG
+ q->flags &= ~SKIPLIST_NODE_FLAG_INSERTED;
+#endif
+ /*
+ * If we are deleting the last element of the list,
+ * update the list's "last" pointer.
+ */
+ if (l->last == q) {
+ if (update[0] == l->header)
+ l->last = NULL;
+ else
+ l->last = update[0];
+ }
+
+ for (k = 0; k <= m && (p = update[k])->forward[k] == q;
+ k++) {
+ p->forward[k] = q->forward[k];
+ }
+ --(l->level_stats[k - 1]);
+#ifdef SKIPLIST_DEBUG
+ zlog_debug("%s: decremented level_stats @%p:%d, now %d",
+ __func__, l, k - 1, l->level_stats[k - 1]);
+#endif
+ if (l->del)
+ (*l->del)(q->value);
+ XFREE(MTYPE_SKIP_LIST_NODE, q);
+ while (l->header->forward[m] == NULL && m > 0)
+ m--;
+ l->level = m;
+ CHECKLAST(l);
+ --(l->count);
+ return 0;
+ }
+ }
+
+ CHECKLAST(l);
+ return -1;
+}
+
+/*
+ * Obtain first value matching "key". Unless SKIPLIST_FLAG_ALLOW_DUPLICATES
+ * is set, this will also be the only value matching "key".
+ *
+ * Also set a cursor for use with skiplist_next_value.
+ */
+int skiplist_first_value(register struct skiplist *l, /* in */
+ register const void *key, /* in */
+ void **valuePointer, /* out */
+ void **cursor) /* out */
+{
+ register int k;
+ register struct skiplistnode *p, *q;
+
+ p = l->header;
+ k = l->level;
+
+ do {
+ while (q = p->forward[k], q && (*l->cmp)(q->key, key) < 0)
+ p = q;
+
+ } while (--k >= 0);
+
+ if (!q || (*l->cmp)(q->key, key))
+ return -1;
+
+ if (valuePointer)
+ *valuePointer = q->value;
+
+ if (cursor)
+ *cursor = q;
+
+ return 0;
+}
+
+int skiplist_search(register struct skiplist *l, register void *key,
+ void **valuePointer)
+{
+ return skiplist_first_value(l, key, valuePointer, NULL);
+}
+
+
+/*
+ * Caller supplies key and value of an existing item in the list.
+ * Function returns the value of the next list item that has the
+ * same key (useful when SKIPLIST_FLAG_ALLOW_DUPLICATES is set).
+ *
+ * Returns 0 on success. If the caller-supplied key and value
+ * do not correspond to a list element, or if they specify the
+ * last element with the given key, -1 is returned.
+ */
+int skiplist_next_value(register struct skiplist *l, /* in */
+ register const void *key, /* in */
+ void **valuePointer, /* in/out */
+ void **cursor) /* in/out */
+{
+ register int k;
+ register struct skiplistnode *p, *q;
+
+ CHECKLAST(l);
+
+ if (!(l->flags & SKIPLIST_FLAG_ALLOW_DUPLICATES)) {
+ return -1;
+ }
+
+ if (!cursor || !*cursor) {
+ p = l->header;
+ k = l->level;
+
+ /*
+ * Find matching key
+ */
+ do {
+ while (q = p->forward[k],
+ q && (*l->cmp)(q->key, key) < 0)
+ p = q;
+ } while (--k >= 0);
+
+ /*
+ * Find matching value
+ */
+ while (q && ((*l->cmp)(q->key, key) == 0)
+ && (q->value != *valuePointer)) {
+ q = q->forward[0];
+ }
+
+ if (!q || ((*l->cmp)(q->key, key) != 0)
+ || (q->value != *valuePointer)) {
+ /*
+ * No matching value
+ */
+ CHECKLAST(l);
+ return -1;
+ }
+ } else {
+ q = (struct skiplistnode *)*cursor;
+ }
+
+ /*
+ * Advance cursor
+ */
+ q = q->forward[0];
+
+ /*
+ * If we reached end-of-list or if the key is no longer the same,
+ * then return error
+ */
+ if (!q || ((*l->cmp)(q->key, key) != 0))
+ return -1;
+
+ *valuePointer = q->value;
+ if (cursor)
+ *cursor = q;
+ CHECKLAST(l);
+ return 0;
+}
+
+int skiplist_first(register struct skiplist *l, void **keyPointer,
+ void **valuePointer)
+{
+ register struct skiplistnode *p;
+
+ CHECKLAST(l);
+ p = l->header->forward[0];
+ if (!p)
+ return -1;
+
+ if (keyPointer)
+ *keyPointer = p->key;
+
+ if (valuePointer)
+ *valuePointer = p->value;
+
+ CHECKLAST(l);
+
+ return 0;
+}
+
+int skiplist_last(register struct skiplist *l, void **keyPointer,
+ void **valuePointer)
+{
+ CHECKLAST(l);
+ if (l->last) {
+ if (keyPointer)
+ *keyPointer = l->last->key;
+ if (valuePointer)
+ *valuePointer = l->last->value;
+ return 0;
+ }
+ return -1;
+}
+
+/*
+ * true = empty
+ */
+int skiplist_empty(register struct skiplist *l)
+{
+ CHECKLAST(l);
+ if (l->last)
+ return 0;
+ return 1;
+}
+
+/*
+ * Use this to walk the list. Caller sets *cursor to NULL to obtain
+ * first element. Return value of 0 indicates valid cursor/element
+ * returned, otherwise NULL cursor arg or EOL.
+ */
+int skiplist_next(register struct skiplist *l, /* in */
+ void **keyPointer, /* out */
+ void **valuePointer, /* out */
+ void **cursor) /* in/out */
+{
+ struct skiplistnode *p;
+
+ if (!cursor)
+ return -1;
+
+ CHECKLAST(l);
+
+ if (!*cursor) {
+ p = l->header->forward[0];
+ } else {
+ p = *cursor;
+ p = p->forward[0];
+ }
+ *cursor = p;
+
+ if (!p)
+ return -1;
+
+ if (keyPointer)
+ *keyPointer = p->key;
+
+ if (valuePointer)
+ *valuePointer = p->value;
+
+ CHECKLAST(l);
+
+ return 0;
+}
+
+int skiplist_delete_first(register struct skiplist *l)
+{
+ register int k;
+ register struct skiplistnode *p, *q;
+ int nodelevel = 0;
+
+ CHECKLAST(l);
+
+ p = l->header;
+ q = l->header->forward[0];
+
+ if (!q)
+ return -1;
+
+ for (k = l->level; k >= 0; --k) {
+ if (p->forward[k] == q) {
+ p->forward[k] = q->forward[k];
+ if ((k == l->level) && (p->forward[k] == NULL)
+ && (l->level > 0))
+ --(l->level);
+ if (!nodelevel)
+ nodelevel = k;
+ }
+ }
+
+#ifdef SKIPLIST_0TIMER_DEBUG
+ q->flags &= ~SKIPLIST_NODE_FLAG_INSERTED;
+#endif
+ /*
+ * If we are deleting the last element of the list,
+ * update the list's "last" pointer.
+ */
+ if (l->last == q) {
+ l->last = NULL;
+ }
+
+ --(l->level_stats[nodelevel]);
+#ifdef SKIPLIST_DEBUG
+ zlog_debug("%s: decremented level_stats @%p:%d, now %d", __func__, l,
+ nodelevel, l->level_stats[nodelevel]);
+#endif
+
+ if (l->del)
+ (*l->del)(q->value);
+
+ XFREE(MTYPE_SKIP_LIST_NODE, q);
+
+ CHECKLAST(l);
+
+ --(l->count);
+
+ return 0;
+}
+
+void skiplist_debug(struct vty *vty, struct skiplist *l)
+{
+ int i;
+
+ if (!l)
+ return;
+
+ vty_out(vty, "Skiplist %p has max level %d\n", l, l->level);
+ for (i = l->level; i >= 0; --i)
+ vty_out(vty, " @%d: %d\n", i, l->level_stats[i]);
+}
+
+static void *scramble(int i)
+{
+ uintptr_t result;
+
+ result = (unsigned)(i & 0xff) << 24;
+ result |= (unsigned)i >> 8;
+
+ return (void *)result;
+}
+
+#define sampleSize 65536
+void skiplist_test(struct vty *vty)
+{
+ struct skiplist *l;
+ register int i, k;
+ void *keys[sampleSize];
+ void *v = NULL;
+
+ zlog_debug("%s: entry", __func__);
+
+ l = skiplist_new(SKIPLIST_FLAG_ALLOW_DUPLICATES, NULL, NULL);
+
+ zlog_debug("%s: skiplist_new returned %p", __func__, l);
+
+ for (i = 0; i < 4; i++) {
+
+ for (k = 0; k < sampleSize; k++) {
+ if (!(k % 1000)) {
+ zlog_debug("%s: (%d:%d)", __func__, i, k);
+ }
+ // keys[k] = (void *)random();
+ keys[k] = scramble(k);
+ if (skiplist_insert(l, keys[k], keys[k]))
+ zlog_debug("error in insert #%d,#%d", i, k);
+ }
+
+ zlog_debug("%s: inserts done", __func__);
+
+ for (k = 0; k < sampleSize; k++) {
+
+ if (!(k % 1000))
+ zlog_debug("[%d:%d]", i, k);
+ if (skiplist_search(l, keys[k], &v))
+ zlog_debug("error in search #%d,#%d", i, k);
+
+ if (v != keys[k])
+ zlog_debug("search returned wrong value");
+ }
+
+
+ for (k = 0; k < sampleSize; k++) {
+
+ if (!(k % 1000))
+ zlog_debug("<%d:%d>", i, k);
+ if (skiplist_delete(l, keys[k], keys[k]))
+ zlog_debug("error in delete");
+ keys[k] = scramble(k ^ 0xf0f0f0f0);
+ if (skiplist_insert(l, keys[k], keys[k]))
+ zlog_debug("error in insert #%d,#%d", i, k);
+ }
+
+ for (k = 0; k < sampleSize; k++) {
+
+ if (!(k % 1000))
+ zlog_debug("{%d:%d}", i, k);
+ if (skiplist_delete_first(l))
+ zlog_debug("error in delete_first");
+ }
+ }
+
+ skiplist_free(l);
+}
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