diff options
Diffstat (limited to 'libcurl/src/lib/splay.c')
| -rw-r--r-- | libcurl/src/lib/splay.c | 288 |
1 files changed, 288 insertions, 0 deletions
diff --git a/libcurl/src/lib/splay.c b/libcurl/src/lib/splay.c new file mode 100644 index 0000000..6f8227e --- /dev/null +++ b/libcurl/src/lib/splay.c @@ -0,0 +1,288 @@ +/***************************************************************************
+ * _ _ ____ _
+ * Project ___| | | | _ \| |
+ * / __| | | | |_) | |
+ * | (__| |_| | _ <| |___
+ * \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1997 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#include "splay.h"
+
+/*
+ * This macro compares two node keys i and j and returns:
+ *
+ * negative value: when i is smaller than j
+ * zero : when i is equal to j
+ * positive when : when i is larger than j
+ */
+#define compare(i,j) Curl_splaycomparekeys((i),(j))
+
+/*
+ * Splay using the key i (which may or may not be in the tree.) The starting
+ * root is t.
+ */
+CURL_STATIC struct Curl_tree *Curl_splay(struct timeval i,
+ struct Curl_tree *t)
+{
+ struct Curl_tree N, *l, *r, *y;
+ long comp;
+
+ if(t == NULL)
+ return t;
+ N.smaller = N.larger = NULL;
+ l = r = &N;
+
+ for(;;) {
+ comp = compare(i, t->key);
+ if(comp < 0) {
+ if(t->smaller == NULL)
+ break;
+ if(compare(i, t->smaller->key) < 0) {
+ y = t->smaller; /* rotate smaller */
+ t->smaller = y->larger;
+ y->larger = t;
+ t = y;
+ if(t->smaller == NULL)
+ break;
+ }
+ r->smaller = t; /* link smaller */
+ r = t;
+ t = t->smaller;
+ }
+ else if(comp > 0) {
+ if(t->larger == NULL)
+ break;
+ if(compare(i, t->larger->key) > 0) {
+ y = t->larger; /* rotate larger */
+ t->larger = y->smaller;
+ y->smaller = t;
+ t = y;
+ if(t->larger == NULL)
+ break;
+ }
+ l->larger = t; /* link larger */
+ l = t;
+ t = t->larger;
+ }
+ else
+ break;
+ }
+
+ l->larger = t->smaller; /* assemble */
+ r->smaller = t->larger;
+ t->smaller = N.larger;
+ t->larger = N.smaller;
+
+ return t;
+}
+
+/* Insert key i into the tree t. Return a pointer to the resulting tree or
+ * NULL if something went wrong.
+ *
+ * @unittest: 1309
+ */
+CURL_STATIC struct Curl_tree *Curl_splayinsert(struct timeval i,
+ struct Curl_tree *t,
+ struct Curl_tree *node)
+{
+ static const struct timeval KEY_NOTUSED = {-1, -1}; /* will *NEVER* appear */
+
+ if(node == NULL)
+ return t;
+
+ if(t != NULL) {
+ t = Curl_splay(i, t);
+ if(compare(i, t->key)==0) {
+ /* There already exists a node in the tree with the very same key. Build
+ a linked list of nodes. We make the new 'node' struct the new master
+ node and make the previous node the first one in the 'same' list. */
+
+ node->same = t;
+ node->key = i;
+ node->smaller = t->smaller;
+ node->larger = t->larger;
+
+ t->smaller = node; /* in the sub node for this same key, we use the
+ smaller pointer to point back to the master
+ node */
+
+ t->key = KEY_NOTUSED; /* and we set the key in the sub node to NOTUSED
+ to quickly identify this node as a subnode */
+
+ return node; /* new root node */
+ }
+ }
+
+ if(t == NULL) {
+ node->smaller = node->larger = NULL;
+ }
+ else if(compare(i, t->key) < 0) {
+ node->smaller = t->smaller;
+ node->larger = t;
+ t->smaller = NULL;
+
+ }
+ else {
+ node->larger = t->larger;
+ node->smaller = t;
+ t->larger = NULL;
+ }
+ node->key = i;
+
+ node->same = NULL; /* no identical node (yet) */
+ return node;
+}
+
+/* Finds and deletes the best-fit node from the tree. Return a pointer to the
+ resulting tree. best-fit means the node with the given or lower key */
+CURL_STATIC struct Curl_tree *Curl_splaygetbest(struct timeval i,
+ struct Curl_tree *t,
+ struct Curl_tree **removed)
+{
+ struct Curl_tree *x;
+
+ if(!t) {
+ *removed = NULL; /* none removed since there was no root */
+ return NULL;
+ }
+
+ t = Curl_splay(i, t);
+ if(compare(i, t->key) < 0) {
+ /* too big node, try the smaller chain */
+ if(t->smaller)
+ t=Curl_splay(t->smaller->key, t);
+ else {
+ /* fail */
+ *removed = NULL;
+ return t;
+ }
+ }
+
+ if(compare(i, t->key) >= 0) { /* found it */
+ /* FIRST! Check if there is a list with identical keys */
+ x = t->same;
+ if(x) {
+ /* there is, pick one from the list */
+
+ /* 'x' is the new root node */
+
+ x->key = t->key;
+ x->larger = t->larger;
+ x->smaller = t->smaller;
+
+ *removed = t;
+ return x; /* new root */
+ }
+
+ if(t->smaller == NULL) {
+ x = t->larger;
+ }
+ else {
+ x = Curl_splay(i, t->smaller);
+ x->larger = t->larger;
+ }
+ *removed = t;
+
+ return x;
+ }
+ else {
+ *removed = NULL; /* no match */
+ return t; /* It wasn't there */
+ }
+}
+
+
+/* Deletes the very node we point out from the tree if it's there. Stores a
+ * pointer to the new resulting tree in 'newroot'.
+ *
+ * Returns zero on success and non-zero on errors! TODO: document error codes.
+ * When returning error, it does not touch the 'newroot' pointer.
+ *
+ * NOTE: when the last node of the tree is removed, there's no tree left so
+ * 'newroot' will be made to point to NULL.
+ *
+ * @unittest: 1309
+ */
+CURL_STATIC int Curl_splayremovebyaddr(struct Curl_tree *t,
+ struct Curl_tree *removenode,
+ struct Curl_tree **newroot)
+{
+ static const struct timeval KEY_NOTUSED = {-1, -1}; /* will *NEVER* appear */
+ struct Curl_tree *x;
+
+ if(!t || !removenode)
+ return 1;
+
+ if(compare(KEY_NOTUSED, removenode->key) == 0) {
+ /* Key set to NOTUSED means it is a subnode within a 'same' linked list
+ and thus we can unlink it easily. The 'smaller' link of a subnode
+ links to the parent node. */
+ if(removenode->smaller == NULL)
+ return 3;
+
+ removenode->smaller->same = removenode->same;
+ if(removenode->same)
+ removenode->same->smaller = removenode->smaller;
+
+ /* Ensures that double-remove gets caught. */
+ removenode->smaller = NULL;
+
+ /* voila, we're done! */
+ *newroot = t; /* return the same root */
+ return 0;
+ }
+
+ t = Curl_splay(removenode->key, t);
+
+ /* First make sure that we got the same root node as the one we want
+ to remove, as otherwise we might be trying to remove a node that
+ isn't actually in the tree.
+
+ We cannot just compare the keys here as a double remove in quick
+ succession of a node with key != KEY_NOTUSED && same != NULL
+ could return the same key but a different node. */
+ if(t != removenode)
+ return 2;
+
+ /* Check if there is a list with identical sizes, as then we're trying to
+ remove the root node of a list of nodes with identical keys. */
+ x = t->same;
+ if(x) {
+ /* 'x' is the new root node, we just make it use the root node's
+ smaller/larger links */
+
+ x->key = t->key;
+ x->larger = t->larger;
+ x->smaller = t->smaller;
+ }
+ else {
+ /* Remove the root node */
+ if(t->smaller == NULL)
+ x = t->larger;
+ else {
+ x = Curl_splay(removenode->key, t->smaller);
+ x->larger = t->larger;
+ }
+ }
+
+ *newroot = x; /* store new root pointer */
+
+ return 0;
+}
+
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