Annotation of embedaddon/curl/lib/splay.c, revision 1.1
1.1 ! misho 1: /***************************************************************************
! 2: * _ _ ____ _
! 3: * Project ___| | | | _ \| |
! 4: * / __| | | | |_) | |
! 5: * | (__| |_| | _ <| |___
! 6: * \___|\___/|_| \_\_____|
! 7: *
! 8: * Copyright (C) 1997 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
! 9: *
! 10: * This software is licensed as described in the file COPYING, which
! 11: * you should have received as part of this distribution. The terms
! 12: * are also available at https://curl.haxx.se/docs/copyright.html.
! 13: *
! 14: * You may opt to use, copy, modify, merge, publish, distribute and/or sell
! 15: * copies of the Software, and permit persons to whom the Software is
! 16: * furnished to do so, under the terms of the COPYING file.
! 17: *
! 18: * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
! 19: * KIND, either express or implied.
! 20: *
! 21: ***************************************************************************/
! 22:
! 23: #include "curl_setup.h"
! 24:
! 25: #include "splay.h"
! 26:
! 27: /*
! 28: * This macro compares two node keys i and j and returns:
! 29: *
! 30: * negative value: when i is smaller than j
! 31: * zero : when i is equal to j
! 32: * positive when : when i is larger than j
! 33: */
! 34: #define compare(i,j) Curl_splaycomparekeys((i),(j))
! 35:
! 36: /*
! 37: * Splay using the key i (which may or may not be in the tree.) The starting
! 38: * root is t.
! 39: */
! 40: struct Curl_tree *Curl_splay(struct curltime i,
! 41: struct Curl_tree *t)
! 42: {
! 43: struct Curl_tree N, *l, *r, *y;
! 44:
! 45: if(t == NULL)
! 46: return t;
! 47: N.smaller = N.larger = NULL;
! 48: l = r = &N;
! 49:
! 50: for(;;) {
! 51: long comp = compare(i, t->key);
! 52: if(comp < 0) {
! 53: if(t->smaller == NULL)
! 54: break;
! 55: if(compare(i, t->smaller->key) < 0) {
! 56: y = t->smaller; /* rotate smaller */
! 57: t->smaller = y->larger;
! 58: y->larger = t;
! 59: t = y;
! 60: if(t->smaller == NULL)
! 61: break;
! 62: }
! 63: r->smaller = t; /* link smaller */
! 64: r = t;
! 65: t = t->smaller;
! 66: }
! 67: else if(comp > 0) {
! 68: if(t->larger == NULL)
! 69: break;
! 70: if(compare(i, t->larger->key) > 0) {
! 71: y = t->larger; /* rotate larger */
! 72: t->larger = y->smaller;
! 73: y->smaller = t;
! 74: t = y;
! 75: if(t->larger == NULL)
! 76: break;
! 77: }
! 78: l->larger = t; /* link larger */
! 79: l = t;
! 80: t = t->larger;
! 81: }
! 82: else
! 83: break;
! 84: }
! 85:
! 86: l->larger = t->smaller; /* assemble */
! 87: r->smaller = t->larger;
! 88: t->smaller = N.larger;
! 89: t->larger = N.smaller;
! 90:
! 91: return t;
! 92: }
! 93:
! 94: /* Insert key i into the tree t. Return a pointer to the resulting tree or
! 95: * NULL if something went wrong.
! 96: *
! 97: * @unittest: 1309
! 98: */
! 99: struct Curl_tree *Curl_splayinsert(struct curltime i,
! 100: struct Curl_tree *t,
! 101: struct Curl_tree *node)
! 102: {
! 103: static const struct curltime KEY_NOTUSED = {
! 104: (time_t)-1, (unsigned int)-1
! 105: }; /* will *NEVER* appear */
! 106:
! 107: if(node == NULL)
! 108: return t;
! 109:
! 110: if(t != NULL) {
! 111: t = Curl_splay(i, t);
! 112: if(compare(i, t->key) == 0) {
! 113: /* There already exists a node in the tree with the very same key. Build
! 114: a doubly-linked circular list of nodes. We add the new 'node' struct
! 115: to the end of this list. */
! 116:
! 117: node->key = KEY_NOTUSED; /* we set the key in the sub node to NOTUSED
! 118: to quickly identify this node as a subnode */
! 119: node->samen = t;
! 120: node->samep = t->samep;
! 121: t->samep->samen = node;
! 122: t->samep = node;
! 123:
! 124: return t; /* the root node always stays the same */
! 125: }
! 126: }
! 127:
! 128: if(t == NULL) {
! 129: node->smaller = node->larger = NULL;
! 130: }
! 131: else if(compare(i, t->key) < 0) {
! 132: node->smaller = t->smaller;
! 133: node->larger = t;
! 134: t->smaller = NULL;
! 135:
! 136: }
! 137: else {
! 138: node->larger = t->larger;
! 139: node->smaller = t;
! 140: t->larger = NULL;
! 141: }
! 142: node->key = i;
! 143:
! 144: /* no identical nodes (yet), we are the only one in the list of nodes */
! 145: node->samen = node;
! 146: node->samep = node;
! 147: return node;
! 148: }
! 149:
! 150: /* Finds and deletes the best-fit node from the tree. Return a pointer to the
! 151: resulting tree. best-fit means the smallest node if it is not larger than
! 152: the key */
! 153: struct Curl_tree *Curl_splaygetbest(struct curltime i,
! 154: struct Curl_tree *t,
! 155: struct Curl_tree **removed)
! 156: {
! 157: static struct curltime tv_zero = {0, 0};
! 158: struct Curl_tree *x;
! 159:
! 160: if(!t) {
! 161: *removed = NULL; /* none removed since there was no root */
! 162: return NULL;
! 163: }
! 164:
! 165: /* find smallest */
! 166: t = Curl_splay(tv_zero, t);
! 167: if(compare(i, t->key) < 0) {
! 168: /* even the smallest is too big */
! 169: *removed = NULL;
! 170: return t;
! 171: }
! 172:
! 173: /* FIRST! Check if there is a list with identical keys */
! 174: x = t->samen;
! 175: if(x != t) {
! 176: /* there is, pick one from the list */
! 177:
! 178: /* 'x' is the new root node */
! 179:
! 180: x->key = t->key;
! 181: x->larger = t->larger;
! 182: x->smaller = t->smaller;
! 183: x->samep = t->samep;
! 184: t->samep->samen = x;
! 185:
! 186: *removed = t;
! 187: return x; /* new root */
! 188: }
! 189:
! 190: /* we splayed the tree to the smallest element, there is no smaller */
! 191: x = t->larger;
! 192: *removed = t;
! 193:
! 194: return x;
! 195: }
! 196:
! 197:
! 198: /* Deletes the very node we point out from the tree if it's there. Stores a
! 199: * pointer to the new resulting tree in 'newroot'.
! 200: *
! 201: * Returns zero on success and non-zero on errors!
! 202: * When returning error, it does not touch the 'newroot' pointer.
! 203: *
! 204: * NOTE: when the last node of the tree is removed, there's no tree left so
! 205: * 'newroot' will be made to point to NULL.
! 206: *
! 207: * @unittest: 1309
! 208: */
! 209: int Curl_splayremovebyaddr(struct Curl_tree *t,
! 210: struct Curl_tree *removenode,
! 211: struct Curl_tree **newroot)
! 212: {
! 213: static const struct curltime KEY_NOTUSED = {
! 214: (time_t)-1, (unsigned int)-1
! 215: }; /* will *NEVER* appear */
! 216: struct Curl_tree *x;
! 217:
! 218: if(!t || !removenode)
! 219: return 1;
! 220:
! 221: if(compare(KEY_NOTUSED, removenode->key) == 0) {
! 222: /* Key set to NOTUSED means it is a subnode within a 'same' linked list
! 223: and thus we can unlink it easily. */
! 224: if(removenode->samen == removenode)
! 225: /* A non-subnode should never be set to KEY_NOTUSED */
! 226: return 3;
! 227:
! 228: removenode->samep->samen = removenode->samen;
! 229: removenode->samen->samep = removenode->samep;
! 230:
! 231: /* Ensures that double-remove gets caught. */
! 232: removenode->samen = removenode;
! 233:
! 234: *newroot = t; /* return the same root */
! 235: return 0;
! 236: }
! 237:
! 238: t = Curl_splay(removenode->key, t);
! 239:
! 240: /* First make sure that we got the same root node as the one we want
! 241: to remove, as otherwise we might be trying to remove a node that
! 242: isn't actually in the tree.
! 243:
! 244: We cannot just compare the keys here as a double remove in quick
! 245: succession of a node with key != KEY_NOTUSED && same != NULL
! 246: could return the same key but a different node. */
! 247: if(t != removenode)
! 248: return 2;
! 249:
! 250: /* Check if there is a list with identical sizes, as then we're trying to
! 251: remove the root node of a list of nodes with identical keys. */
! 252: x = t->samen;
! 253: if(x != t) {
! 254: /* 'x' is the new root node, we just make it use the root node's
! 255: smaller/larger links */
! 256:
! 257: x->key = t->key;
! 258: x->larger = t->larger;
! 259: x->smaller = t->smaller;
! 260: x->samep = t->samep;
! 261: t->samep->samen = x;
! 262: }
! 263: else {
! 264: /* Remove the root node */
! 265: if(t->smaller == NULL)
! 266: x = t->larger;
! 267: else {
! 268: x = Curl_splay(removenode->key, t->smaller);
! 269: x->larger = t->larger;
! 270: }
! 271: }
! 272:
! 273: *newroot = x; /* store new root pointer */
! 274:
! 275: return 0;
! 276: }
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