text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1997 - 2009, 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.
   *
   * $Id: splay.c,v 1.13 2009-06-10 02:49:43 yangtse Exp $
   ***************************************************************************/
  
  #include "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.
   */
  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. */
  struct Curl_tree *Curl_splayinsert(struct timeval i,
                                     struct Curl_tree *t,
                                     struct Curl_tree *node)
  {
    static struct timeval KEY_NOTUSED = {-1,-1}; /* key that 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;
  }
  
  #if 0
  /* Deletes 'i' from the tree if it's there (with an exact match). Returns a
     pointer to the resulting tree.
  
     Function not used in libcurl.
  */
  struct Curl_tree *Curl_splayremove(struct timeval i,
                                     struct Curl_tree *t,
                                     struct Curl_tree **removed)
  {
    struct Curl_tree *x;
  
    *removed = NULL; /* default to no removed */
  
    if(t==NULL)
      return NULL;
  
    t = Curl_splay(i,t);
    if(compare(i, t->key) == 0) {               /* found it */
  
      /* FIRST! Check if there is a list with identical sizes */
      if((x = t->same) != NULL) {
        /* 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
      return t;                         /* It wasn't there */
  }
  #endif
  
  /* 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 */
  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.
  */
  int Curl_splayremovebyaddr(struct Curl_tree *t,
                             struct Curl_tree *removenode,
                             struct Curl_tree **newroot)
  {
    static struct timeval KEY_NOTUSED = {-1,-1}; /* key that 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;
  }
  
  #ifdef DEBUGBUILD
  
  void Curl_splayprint(struct Curl_tree * t, int d, char output)
  {
    struct Curl_tree *node;
    int i;
    int count;
    if(t == NULL)
      return;
  
    Curl_splayprint(t->larger, d+1, output);
    for (i=0; i<d; i++)
      if(output)
        fprintf(stderr, "  ");
  
    if(output) {
  #ifdef TEST_SPLAY
      fprintf(stderr, "%ld[%d]", (long)t->key.tv_usec, i);
  #else
      fprintf(stderr, "%ld.%ld[%d]", (long)t->key.tv_sec, (long)t->key.tv_usec, i);
  #endif
    }
  
    for(count=0, node = t->same; node; node = node->same, count++)
      ;
  
    if(output) {
      if(count)
        fprintf(stderr, " [%d more]\n", count);
      else
        fprintf(stderr, "\n");
    }
  
    Curl_splayprint(t->smaller, d+1, output);
  }
  #endif
  
  #ifdef TEST_SPLAY
  
  /*#define TEST2 */
  #define MAX 50
  #define TEST2
  
  /* A sample use of these functions.  Start with the empty tree, insert some
     stuff into it, and then delete it */
  int main(int argc, argv_item_t argv[])
  {
    struct Curl_tree *root, *t;
    void *ptrs[MAX];
    int adds=0;
    int rc;
  
    static const long sizes[]={
      50, 60, 50, 100, 60, 200, 120, 300, 400, 200, 256, 122, 60, 120, 200, 300,
      220, 80, 90, 50, 100, 60, 200, 120, 300, 400, 200, 256, 122, 60, 120, 200,
      300, 220, 80, 90, 50, 100, 60, 200, 120, 300, 400, 200, 256, 122, 60, 120,
      200, 300, 220, 80, 90};
    int i;
    root = NULL;              /* the empty tree */
  
    for (i = 0; i < MAX; i++) {
      struct timeval key;
      ptrs[i] = t = malloc(sizeof(struct Curl_tree));
  
      key.tv_sec = 0;
  #ifdef TEST2
      key.tv_usec = sizes[i];
  #elif defined(TEST1)
      key.tv_usec = (541*i)%1023;
  #elif defined(TEST3)
      key.tv_usec = 100;
  #endif
  
      t->payload = (void *)key.tv_usec; /* for simplicity */
      if(!t) {
        puts("out of memory!");
        return 0;
      }
      root = Curl_splayinsert(key, root, t);
    }
  
  #if 0
    puts("Result:");
    Curl_splayprint(root, 0, 1);
  #endif
  
  #if 1
    for (i = 0; i < MAX; i++) {
      int rem = (i+7)%MAX;
      struct Curl_tree *r;
      printf("Tree look:\n");
      Curl_splayprint(root, 0, 1);
      printf("remove pointer %d, payload %ld\n", rem,
             (long)((struct Curl_tree *)ptrs[rem])->payload);
      rc = Curl_splayremovebyaddr(root, (struct Curl_tree *)ptrs[rem], &root);
      if(rc)
        /* failed! */
        printf("remove %d failed!\n", rem);
    }
  #endif
  
    return 0;
  }
  
  #endif /* TEST_SPLAY */
  