/src/haproxy/include/import/ebmbtree.h

Source
/*
 * Elastic Binary Trees - macros and structures for Multi-Byte data nodes.
 * Version 6.0.6
 * (C) 2002-2011 - Willy Tarreau <w@1wt.eu>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, version 2.1
 * exclusively.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef _EBMBTREE_H
#define _EBMBTREE_H

#include <string.h>
#include "ebtree.h"

/* Return the structure of type <type> whose member <member> points to <ptr> */
#define ebmb_entry(ptr, type, member) container_of(ptr, type, member)

/*
 * Exported functions and macros.
 * Many of them are always inlined because they are extremely small, and
 * are generally called at most once or twice in a program.
 */

/* Return leftmost node in the tree, or NULL if none */
static forceinline struct ebmb_node *ebmb_first(struct eb_root *root)
{
  return ebmb_entry(eb_first(root), struct ebmb_node, node);
}

/* Return rightmost node in the tree, or NULL if none */
static forceinline struct ebmb_node *ebmb_last(struct eb_root *root)
{
  return ebmb_entry(eb_last(root), struct ebmb_node, node);
}

/* Return next node in the tree, or NULL if none */
static forceinline struct ebmb_node *ebmb_next(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_next(&ebmb->node), struct ebmb_node, node);
}

/* Return previous node in the tree, or NULL if none */
static forceinline struct ebmb_node *ebmb_prev(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_prev(&ebmb->node), struct ebmb_node, node);
}

/* Return next leaf node within a duplicate sub-tree, or NULL if none. */
static inline struct ebmb_node *ebmb_next_dup(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_next_dup(&ebmb->node), struct ebmb_node, node);
}

/* Return previous leaf node within a duplicate sub-tree, or NULL if none. */
static inline struct ebmb_node *ebmb_prev_dup(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_prev_dup(&ebmb->node), struct ebmb_node, node);
}

/* Return next node in the tree, skipping duplicates, or NULL if none */
static forceinline struct ebmb_node *ebmb_next_unique(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_next_unique(&ebmb->node), struct ebmb_node, node);
}

/* Return previous node in the tree, skipping duplicates, or NULL if none */
static forceinline struct ebmb_node *ebmb_prev_unique(struct ebmb_node *ebmb)
{
  return ebmb_entry(eb_prev_unique(&ebmb->node), struct ebmb_node, node);
}

/* Delete node from the tree if it was linked in. Mark the node unused. Note
 * that this function relies on a non-inlined generic function: eb_delete.
 */
static forceinline void ebmb_delete(struct ebmb_node *ebmb)
{
  eb_delete(&ebmb->node);
}

/* The following functions are not inlined by default. They are declared
 * in ebmbtree.c, which simply relies on their inline version.
 */
struct ebmb_node *ebmb_lookup(struct eb_root *root, const void *x, unsigned int len);
struct ebmb_node *ebmb_insert(struct eb_root *root, struct ebmb_node *new, unsigned int len);
struct ebmb_node *ebmb_lookup_longest(struct eb_root *root, const void *x);
struct ebmb_node *ebmb_lookup_prefix(struct eb_root *root, const void *x, unsigned int pfx);
struct ebmb_node *ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int len);

/* start from a valid leaf and find the next matching prefix that's either a
 * duplicate, or immediately shorter than the node's current one and still
 * matches it. The purpose is to permit a caller that is not satisfied with a
 * result provided by ebmb_lookup_longest() to evaluate the next matching
 * entry. Given that shorter keys are necessarily attached to nodes located
 * above the current one, it's sufficient to restart from the current leaf and
 * go up until we find a shorter prefix, or a non-matching one.
 */
static inline struct ebmb_node *ebmb_lookup_shorter(struct ebmb_node *start)
{
  eb_troot_t *t = start->node.leaf_p;
  struct ebmb_node *node;

  /* first, check for duplicates */
  node = ebmb_next_dup(start);
  if (node)
    return node;

  while (1) {
    if (eb_gettag(t) == EB_LEFT) {
      /* Walking up from left branch. We must ensure that we never
       * walk beyond root.
       */
      if (unlikely(eb_clrtag((eb_untag(t, EB_LEFT))->b[EB_RGHT]) == NULL))
        return NULL;
      node = container_of(eb_root_to_node(eb_untag(t, EB_LEFT)), struct ebmb_node, node);
    } else {
      /* Walking up from right branch, so we cannot be below
       * root. However, if we end up on a node with an even
       * and positive bit, this is a cover node, which mandates
       * that the left branch only contains cover values, so we
       * must descend it.
       */
      node = container_of(eb_root_to_node(eb_untag(t, EB_RGHT)), struct ebmb_node, node);
      if (node->node.bit > 0 && !(node->node.bit & 1))
        return ebmb_entry(eb_walk_down(t, EB_LEFT), struct ebmb_node, node);
    }

    /* Note that <t> cannot be NULL at this stage */
    t = node->node.node_p;

    /* this is a node attached to a deeper (and possibly different)
     * leaf, not interesting for us.
     */
    if (node->node.pfx >= start->node.pfx)
      continue;

    if (check_bits(start->key, node->key, 0, node->node.pfx) == 0)
      break;
  }
  return node;
}

/* The following functions are less likely to be used directly, because their
 * code is larger. The non-inlined version is preferred.
 */

/* Delete node from the tree if it was linked in. Mark the node unused. */
static forceinline void __ebmb_delete(struct ebmb_node *ebmb)
{
  __eb_delete(&ebmb->node);
}

/* Find the first occurrence of a key of a least <len> bytes matching <x> in the
 * tree <root>. The caller is responsible for ensuring that <len> will not exceed
 * the common parts between the tree's keys and <x>. In case of multiple matches,
 * the leftmost node is returned. This means that this function can be used to
 * lookup string keys by prefix if all keys in the tree are zero-terminated. If
 * no match is found, NULL is returned. Returns first node if <len> is zero.
 */
static forceinline struct ebmb_node *__ebmb_lookup(struct eb_root *root, const void *x, unsigned int len)
{
  struct ebmb_node *node;
  eb_troot_t *troot;
  int pos, side;
  int node_bit;

  troot = root->b[EB_LEFT];
  if (unlikely(troot == NULL))
    goto ret_null;

  if (unlikely(len == 0))
    goto walk_down;

  pos = 0;
  while (1) {
    void *b0, *b1;
    unsigned char k, b;

    if (eb_gettag(troot) == EB_LEAF) {
      node = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      if (eb_memcmp(node->key + pos, x, len) != 0)
        goto ret_null;
      else
        goto ret_node;
    }
    node = container_of(eb_untag(troot, EB_NODE),
            struct ebmb_node, node.branches);

    node_bit = node->node.bit;
    if (node_bit < 0) {
      /* We have a dup tree now. Either it's for the same
       * value, and we walk down left, or it's a different
       * one and we don't have our key.
       */
      if (eb_memcmp(node->key + pos, x, len) != 0)
        goto ret_null;
      else
        goto walk_left;
    }

    /* OK, normal data node, let's walk down. We check if all full
     * bytes are equal, and we start from the last one we did not
     * completely check. We stop as soon as we reach the last byte,
     * because we must decide to go left/right or abort.
     */
    node_bit = ~node_bit + (pos << 3) + 8; // = (pos<<3) + (7 - node_bit)
    if (node_bit < 0) {
      /* This surprising construction gives better performance
       * because gcc does not try to reorder the loop. Tested to
       * be fine with 2.95 to 4.2.
       */
      while (1) {
        if (node->key[pos++] ^ *(unsigned char*)(x++))
          goto ret_null;  /* more than one full byte is different */
        if (--len == 0)
          goto walk_left; /* return first node if all bytes matched */
        node_bit += 8;
        if (node_bit >= 0)
          break;
      }
    }

    /* here we know that only the last byte differs, so node_bit < 8.
     * We have 2 possibilities :
     *   - more than the last bit differs => return NULL
     *   - walk down on side = (x[pos] >> node_bit) & 1
     */
    b = *(unsigned char *)x;
    side = 1 << node_bit;

    eb_prefetch(node->node.branches.b[0], 0);
    eb_prefetch(node->node.branches.b[1], 0);

    k = node->key[pos];
    b0 = node->node.branches.b[0];
    b1 = node->node.branches.b[1];
    troot = (b & side) ? b1 : b0;

    if ((k ^ b) & -(side << 1))
      goto ret_null;
  }
 walk_left:
  troot = node->node.branches.b[EB_LEFT];
 walk_down:
  while (eb_gettag(troot) != EB_LEAF)
    troot = (eb_untag(troot, EB_NODE))->b[EB_LEFT];
  node = container_of(eb_untag(troot, EB_LEAF),
          struct ebmb_node, node.branches);
 ret_node:
  return node;
 ret_null:
  return NULL;
}

/* Insert ebmb_node <new> into subtree starting at node root <root>.
 * Only new->key needs be set with the key. The ebmb_node is returned.
 * If root->b[EB_RGHT]==1, the tree may only contain unique keys. The
 * len is specified in bytes. It is absolutely mandatory that this length
 * is the same for all keys in the tree. This function cannot be used to
 * insert strings.
 */
static forceinline struct ebmb_node *
__ebmb_insert(struct eb_root *root, struct ebmb_node *new, unsigned int len)
{
  struct ebmb_node *old;
  unsigned int side;
  eb_troot_t *troot, **up_ptr;
  eb_troot_t *root_right;
  int diff;
  int bit;
  eb_troot_t *new_left, *new_rght;
  eb_troot_t *new_leaf;
  int old_node_bit;

  side = EB_LEFT;
  troot = root->b[EB_LEFT];
  root_right = root->b[EB_RGHT];
  if (unlikely(troot == NULL)) {
    /* Tree is empty, insert the leaf part below the left branch */
    root->b[EB_LEFT] = eb_dotag(&new->node.branches, EB_LEAF);
    new->node.leaf_p = eb_dotag(root, EB_LEFT);
    new->node.node_p = NULL; /* node part unused */
    return new;
  }

  /* The tree descent is fairly easy :
   *  - first, check if we have reached a leaf node
   *  - second, check if we have gone too far
   *  - third, reiterate
   * Everywhere, we use <new> for the node node we are inserting, <root>
   * for the node we attach it to, and <old> for the node we are
   * displacing below <new>. <troot> will always point to the future node
   * (tagged with its type). <side> carries the side the node <new> is
   * attached to below its parent, which is also where previous node
   * was attached.
   */

  bit = 0;
  while (1) {
    if (unlikely(eb_gettag(troot) == EB_LEAF)) {
      /* insert above a leaf */
      old = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      new->node.node_p = old->node.leaf_p;
      up_ptr = &old->node.leaf_p;
      goto check_bit_and_break;
    }

    /* OK we're walking down this link */
    old = container_of(eb_untag(troot, EB_NODE),
           struct ebmb_node, node.branches);
    old_node_bit = old->node.bit;

    if (unlikely(old->node.bit < 0)) {
      /* We're above a duplicate tree, so we must compare the whole value */
      new->node.node_p = old->node.node_p;
      up_ptr = &old->node.node_p;
    check_bit_and_break:
      bit = equal_bits(new->key, old->key, bit, len << 3);
      break;
    }

    /* Stop going down when we don't have common bits anymore. We
     * also stop in front of a duplicates tree because it means we
     * have to insert above. Note: we can compare more bits than
     * the current node's because as long as they are identical, we
     * know we descend along the correct side.
     */

    bit = equal_bits(new->key, old->key, bit, old_node_bit);
    if (unlikely(bit < old_node_bit)) {
      /* The tree did not contain the key, so we insert <new> before the
       * node <old>, and set ->bit to designate the lowest bit position in
       * <new> which applies to ->branches.b[].
       */
      new->node.node_p = old->node.node_p;
      up_ptr = &old->node.node_p;
      break;
    }
    /* we don't want to skip bits for further comparisons, so we must limit <bit>.
     * However, since we're going down around <old_node_bit>, we know it will be
     * properly matched, so we can skip this bit.
     */
    bit = old_node_bit + 1;

    /* walk down */
    root = &old->node.branches;
    side = old_node_bit & 7;
    side ^= 7;
    side = (new->key[old_node_bit >> 3] >> side) & 1;
    troot = root->b[side];
  }

  new_left = eb_dotag(&new->node.branches, EB_LEFT);
  new_rght = eb_dotag(&new->node.branches, EB_RGHT);
  new_leaf = eb_dotag(&new->node.branches, EB_LEAF);

  new->node.bit = bit;

  /* Note: we can compare more bits than the current node's because as
   * long as they are identical, we know we descend along the correct
   * side. However we don't want to start to compare past the end.
   */
  diff = 0;
  if (((unsigned)bit >> 3) < len)
    diff = cmp_bits(new->key, old->key, bit);

  if (diff == 0) {
    new->node.bit = -1; /* mark as new dup tree, just in case */

    if (likely(eb_gettag(root_right))) {
      /* we refuse to duplicate this key if the tree is
       * tagged as containing only unique keys.
       */
      return old;
    }

    if (eb_gettag(troot) != EB_LEAF) {
      /* there was already a dup tree below */
      struct eb_node *ret;
      ret = eb_insert_dup(&old->node, &new->node);
      return container_of(ret, struct ebmb_node, node);
    }
    /* otherwise fall through */
  }

  if (diff >= 0) {
    new->node.branches.b[EB_LEFT] = troot;
    new->node.branches.b[EB_RGHT] = new_leaf;
    new->node.leaf_p = new_rght;
    *up_ptr = new_left;
  }
  else {
    new->node.branches.b[EB_LEFT] = new_leaf;
    new->node.branches.b[EB_RGHT] = troot;
    new->node.leaf_p = new_left;
    *up_ptr = new_rght;
  }

  /* Ok, now we are inserting <new> between <root> and <old>. <old>'s
   * parent is already set to <new>, and the <root>'s branch is still in
   * <side>. Update the root's leaf till we have it. Note that we can also
   * find the side by checking the side of new->node.node_p.
   */

  root->b[side] = eb_dotag(&new->node.branches, EB_NODE);
  return new;
}


/* Find the first occurrence of the longest prefix matching a key <x> in the
 * tree <root>. It's the caller's responsibility to ensure that key <x> is at
 * least as long as the keys in the tree. Note that this can be ensured by
 * having a byte at the end of <x> which cannot be part of any prefix, typically
 * the trailing zero for a string. If none can be found, return NULL.
 */
static forceinline struct ebmb_node *__ebmb_lookup_longest(struct eb_root *root, const void *x)
{
  struct ebmb_node *node;
  eb_troot_t *troot, *cover;
  int pos, side;
  int node_bit;

  troot = root->b[EB_LEFT];
  if (unlikely(troot == NULL))
    return NULL;

  cover = NULL;
  pos = 0;
  while (1) {
    if ((eb_gettag(troot) == EB_LEAF)) {
      node = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      if (check_bits(x - pos, node->key, pos, node->node.pfx))
        goto not_found;

      return node;
    }
    node = container_of(eb_untag(troot, EB_NODE),
            struct ebmb_node, node.branches);

    node_bit = node->node.bit;
    if (node_bit < 0) {
      /* We have a dup tree now. Either it's for the same
       * value, and we walk down left, or it's a different
       * one and we don't have our key.
       */
      if (check_bits(x - pos, node->key, pos, node->node.pfx))
        goto not_found;

      troot = node->node.branches.b[EB_LEFT];
      while (eb_gettag(troot) != EB_LEAF)
        troot = (eb_untag(troot, EB_NODE))->b[EB_LEFT];
      node = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      return node;
    }

    node_bit >>= 1; /* strip cover bit */
    node_bit = ~node_bit + (pos << 3) + 8; // = (pos<<3) + (7 - node_bit)
    if (node_bit < 0) {
      /* This uncommon construction gives better performance
       * because gcc does not try to reorder the loop. Tested to
       * be fine with 2.95 to 4.2.
       */
      while (1) {
        x++; pos++;
        if (node->key[pos-1] ^ *(unsigned char*)(x-1))
          goto not_found; /* more than one full byte is different */
        node_bit += 8;
        if (node_bit >= 0)
          break;
      }
    }

    /* here we know that only the last byte differs, so 0 <= node_bit <= 7.
     * We have 2 possibilities :
     *   - more than the last bit differs => data does not match
     *   - walk down on side = (x[pos] >> node_bit) & 1
     */
    side = *(unsigned char *)x >> node_bit;
    if (((node->key[pos] >> node_bit) ^ side) > 1)
      goto not_found;

    if (!(node->node.bit & 1)) {
      /* This is a cover node, let's keep a reference to it
       * for later. The covering subtree is on the left, and
       * the covered subtree is on the right, so we have to
       * walk down right.
       */
      cover = node->node.branches.b[EB_LEFT];
      troot = node->node.branches.b[EB_RGHT];
      continue;
    }
    side &= 1;
    troot = node->node.branches.b[side];
  }

 not_found:
  /* Walk down last cover tree if it exists. It does not matter if cover is NULL */
  return ebmb_entry(eb_walk_down(cover, EB_LEFT), struct ebmb_node, node);
}


/* Find the first occurrence of a prefix matching a key <x> of <pfx> BITS in the
 * tree <root>. It's the caller's responsibility to ensure that key <x> is at
 * least as long as the keys in the tree. Note that this can be ensured by
 * having a byte at the end of <x> which cannot be part of any prefix, typically
 * the trailing zero for a string. If none can be found, return NULL.
 */
static forceinline struct ebmb_node *__ebmb_lookup_prefix(struct eb_root *root, const void *x, unsigned int pfx)
{
  struct ebmb_node *node;
  eb_troot_t *troot;
  int pos, side;
  int node_bit;

  troot = root->b[EB_LEFT];
  if (unlikely(troot == NULL))
    return NULL;

  pos = 0;
  while (1) {
    if ((eb_gettag(troot) == EB_LEAF)) {
      node = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      if (node->node.pfx != pfx)
        return NULL;
      if (check_bits(x - pos, node->key, pos, node->node.pfx))
        return NULL;
      return node;
    }
    node = container_of(eb_untag(troot, EB_NODE),
            struct ebmb_node, node.branches);

    node_bit = node->node.bit;
    if (node_bit < 0) {
      /* We have a dup tree now. Either it's for the same
       * value, and we walk down left, or it's a different
       * one and we don't have our key.
       */
      if (node->node.pfx != pfx)
        return NULL;
      if (check_bits(x - pos, node->key, pos, node->node.pfx))
        return NULL;

      troot = node->node.branches.b[EB_LEFT];
      while (eb_gettag(troot) != EB_LEAF)
        troot = (eb_untag(troot, EB_NODE))->b[EB_LEFT];
      node = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      return node;
    }

    node_bit >>= 1; /* strip cover bit */
    node_bit = ~node_bit + (pos << 3) + 8; // = (pos<<3) + (7 - node_bit)
    if (node_bit < 0) {
      /* This uncommon construction gives better performance
       * because gcc does not try to reorder the loop. Tested to
       * be fine with 2.95 to 4.2.
       */
      while (1) {
        x++; pos++;
        if (node->key[pos-1] ^ *(unsigned char*)(x-1))
          return NULL; /* more than one full byte is different */
        node_bit += 8;
        if (node_bit >= 0)
          break;
      }
    }

    /* here we know that only the last byte differs, so 0 <= node_bit <= 7.
     * We have 2 possibilities :
     *   - more than the last bit differs => data does not match
     *   - walk down on side = (x[pos] >> node_bit) & 1
     */
    side = *(unsigned char *)x >> node_bit;
    if (((node->key[pos] >> node_bit) ^ side) > 1)
      return NULL;

    if (!(node->node.bit & 1)) {
      /* This is a cover node, it may be the entry we're
       * looking for. We already know that it matches all the
       * bits, let's compare prefixes and descend the cover
       * subtree if they match.
       */
      if ((unsigned short)node->node.bit >> 1 == pfx)
        troot = node->node.branches.b[EB_LEFT];
      else
        troot = node->node.branches.b[EB_RGHT];
      continue;
    }
    side &= 1;
    troot = node->node.branches.b[side];
  }
}


/* Insert ebmb_node <new> into a prefix subtree starting at node root <root>.
 * Only new->key and new->pfx need be set with the key and its prefix length.
 * Note that bits between <pfx> and <len> are theoretically ignored and should be
 * zero, as it is not certain yet that they will always be ignored everywhere
 * (eg in bit compare functions).
 * The ebmb_node is returned.
 * If root->b[EB_RGHT]==1, the tree may only contain unique keys. The
 * len is specified in bytes.
 */
static forceinline struct ebmb_node *
__ebmb_insert_prefix(struct eb_root *root, struct ebmb_node *new, unsigned int len)
{
  struct ebmb_node *old;
  unsigned int side;
  eb_troot_t *troot, **up_ptr;
  eb_troot_t *root_right;
  int diff;
  int bit;
  eb_troot_t *new_left, *new_rght;
  eb_troot_t *new_leaf;
  int old_node_bit;
  unsigned int npfx = new->node.pfx;
  unsigned int npfx1 = npfx << 1;
  const unsigned char *nkey = new->key;

  side = EB_LEFT;
  troot = root->b[EB_LEFT];
  root_right = root->b[EB_RGHT];
  if (unlikely(troot == NULL)) {
    /* Tree is empty, insert the leaf part below the left branch */
    root->b[EB_LEFT] = eb_dotag(&new->node.branches, EB_LEAF);
    new->node.leaf_p = eb_dotag(root, EB_LEFT);
    new->node.node_p = NULL; /* node part unused */
    return new;
  }

  len <<= 3;
  if (len > npfx)
    len = npfx;

  /* The tree descent is fairly easy :
   *  - first, check if we have reached a leaf node
   *  - second, check if we have gone too far
   *  - third, reiterate
   * Everywhere, we use <new> for the node node we are inserting, <root>
   * for the node we attach it to, and <old> for the node we are
   * displacing below <new>. <troot> will always point to the future node
   * (tagged with its type). <side> carries the side the node <new> is
   * attached to below its parent, which is also where previous node
   * was attached.
   */

  bit = 0;
  while (1) {
    if (unlikely(eb_gettag(troot) == EB_LEAF)) {
      /* Insert above a leaf. Note that this leaf could very
       * well be part of a cover node.
       */
      old = container_of(eb_untag(troot, EB_LEAF),
              struct ebmb_node, node.branches);
      new->node.node_p = old->node.leaf_p;
      up_ptr = &old->node.leaf_p;
      goto check_bit_and_break;
    }

    /* OK we're walking down this link */
    old = container_of(eb_untag(troot, EB_NODE),
           struct ebmb_node, node.branches);
    old_node_bit = old->node.bit;
    /* Note that old_node_bit can be :
     *   < 0    : dup tree
     *   = 2N   : cover node for N bits
     *   = 2N+1 : normal node at N bits
     */

    if (unlikely(old_node_bit < 0)) {
      /* We're above a duplicate tree, so we must compare the whole value */
      new->node.node_p = old->node.node_p;
      up_ptr = &old->node.node_p;
    check_bit_and_break:
      /* No need to compare everything if the leaves are shorter than the new one. */
      if (len > old->node.pfx)
        len = old->node.pfx;
      bit = equal_bits(nkey, old->key, bit, len);
      break;
    }

    /* WARNING: for the two blocks below, <bit> is counted in half-bits */

    bit = equal_bits(nkey, old->key, bit, old_node_bit >> 1);
    bit = (bit << 1) + 1; // assume comparisons with normal nodes

    /* we must always check that our prefix is larger than the nodes
     * we visit, otherwise we have to stop going down. The following
     * test is able to stop before both normal and cover nodes.
     */
    if (bit >= npfx1 && npfx1 < old_node_bit) {
      /* insert cover node here on the left */
      new->node.node_p = old->node.node_p;
      up_ptr = &old->node.node_p;
      new->node.bit = npfx1;
      diff = -1;
      goto insert_above;
    }

    if (unlikely(bit < old_node_bit)) {
      /* The tree did not contain the key, so we insert <new> before the
       * node <old>, and set ->bit to designate the lowest bit position in
       * <new> which applies to ->branches.b[]. We know that the bit is not
       * greater than the prefix length thanks to the test above.
       */
      new->node.node_p = old->node.node_p;
      up_ptr = &old->node.node_p;
      new->node.bit = bit;
      diff = cmp_bits(nkey, old->key, bit >> 1);
      goto insert_above;
    }

    if (!(old_node_bit & 1)) {
      /* if we encounter a cover node with our exact prefix length, it's
       * necessarily the same value, so we insert there as a duplicate on
       * the left. For that, we go down on the left and the leaf detection
       * code will finish the job.
       */
      if (npfx1 == old_node_bit) {
        root = &old->node.branches;
        side = EB_LEFT;
        troot = root->b[side];
        continue;
      }

      /* cover nodes are always walked through on the right */
      side = EB_RGHT;
      bit = old_node_bit >> 1; /* recheck that bit */
      root = &old->node.branches;
      troot = root->b[side];
      continue;
    }

    /* we don't want to skip bits for further comparisons, so we must limit <bit>.
     * However, since we're going down around <old_node_bit>, we know it will be
     * properly matched, so we can skip this bit.
     */
    old_node_bit >>= 1;
    bit = old_node_bit + 1;

    /* walk down */
    root = &old->node.branches;
    side = old_node_bit & 7;
    side ^= 7;
    side = (nkey[old_node_bit >> 3] >> side) & 1;
    troot = root->b[side];
  }

  /* Right here, we have 4 possibilities :
   * - the tree does not contain any leaf matching the
   *   key, and we have new->key < old->key. We insert
   *   new above old, on the left ;
   *
   * - the tree does not contain any leaf matching the
   *   key, and we have new->key > old->key. We insert
   *   new above old, on the right ;
   *
   * - the tree does contain the key with the same prefix
   *   length. We add the new key next to it as a first
   *   duplicate (since it was alone).
   *
   * The last two cases can easily be partially merged.
   *
   * - the tree contains a leaf matching the key, we have
   *   to insert above it as a cover node. The leaf with
   *   the shortest prefix becomes the left subtree and
   *   the leaf with the longest prefix becomes the right
   *   one. The cover node gets the min of both prefixes
   *   as its new bit.
   */

  /* first we want to ensure that we compare the correct bit, which means
   * the largest common to both nodes.
   */
  if (bit > npfx)
    bit = npfx;
  if (bit > old->node.pfx)
    bit = old->node.pfx;

  new->node.bit = (bit << 1) + 1; /* assume normal node by default */

  /* if one prefix is included in the second one, we don't compare bits
   * because they won't necessarily match, we just proceed with a cover
   * node insertion.
   */
  diff = 0;
  if (bit < old->node.pfx && bit < npfx)
    diff = cmp_bits(nkey, old->key, bit);

  if (diff == 0) {
    /* Both keys match. Either it's a duplicate entry or we have to
     * put the shortest prefix left and the largest one right below
     * a new cover node. By default, diff==0 means we'll be inserted
     * on the right.
     */
    new->node.bit--; /* anticipate cover node insertion */
    if (npfx == old->node.pfx) {
      new->node.bit = -1; /* mark as new dup tree, just in case */

      if (unlikely(eb_gettag(root_right))) {
        /* we refuse to duplicate this key if the tree is
         * tagged as containing only unique keys.
         */
        return old;
      }

      if (eb_gettag(troot) != EB_LEAF) {
        /* there was already a dup tree below */
        struct eb_node *ret;
        ret = eb_insert_dup(&old->node, &new->node);
        return container_of(ret, struct ebmb_node, node);
      }
      /* otherwise fall through to insert first duplicate */
    }
    /* otherwise we just rely on the tests below to select the right side */
    else if (npfx < old->node.pfx)
      diff = -1; /* force insertion to left side */
  }

 insert_above:
  new_left = eb_dotag(&new->node.branches, EB_LEFT);
  new_rght = eb_dotag(&new->node.branches, EB_RGHT);
  new_leaf = eb_dotag(&new->node.branches, EB_LEAF);

  if (diff >= 0) {
    new->node.branches.b[EB_LEFT] = troot;
    new->node.branches.b[EB_RGHT] = new_leaf;
    new->node.leaf_p = new_rght;
    *up_ptr = new_left;
  }
  else {
    new->node.branches.b[EB_LEFT] = new_leaf;
    new->node.branches.b[EB_RGHT] = troot;
    new->node.leaf_p = new_left;
    *up_ptr = new_rght;
  }

  root->b[side] = eb_dotag(&new->node.branches, EB_NODE);
  return new;
}



#endif /* _EBMBTREE_H */


Coverage Report

Created: 2026-04-03 06:23