/src/haproxy/include/import/cebtree-prv.h

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/*
 * Compact Elastic Binary Trees - internal functions and types
 *
 * Copyright (C) 2014-2024 Willy Tarreau - w@1wt.eu
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/* This file MUST NOT be included by public code, it contains macros, enums
 * with short names and function definitions that may clash with user code.
 * It may only be included by the respective types' C files.
 */

/*
 * These trees are optimized for adding the minimalest overhead to the stored
 * data. This version uses the node's pointer as the key, for the purpose of
 * quickly finding its neighbours.
 *
 * A few properties :
 * - the xor between two branches of a node cannot be zero unless the two
 *   branches are duplicate keys
 * - the xor between two nodes has *at least* the split bit set, possibly more
 * - the split bit is always strictly smaller for a node than for its parent,
 *   which implies that the xor between the keys of the lowest level node is
 *   always smaller than the xor between a higher level node. Hence the xor
 *   between the branches of a regular leaf is always strictly larger than the
 *   xor of its parent node's branches if this node is different, since the
 *   leaf is associated with a higher level node which has at least one higher
 *   level branch. The first leaf doesn't validate this but is handled by the
 *   rules below.
 * - during the descent, the node corresponding to a leaf is always visited
 *   before the leaf, unless it's the first inserted, nodeless leaf.
 * - the first key is the only one without any node, and it has both its
 *   branches pointing to itself during insertion to detect it (i.e. xor==0).
 * - a leaf is always present as a node on the path from the root, except for
 *   the inserted first key which has no node, and is recognizable by its two
 *   branches pointing to itself.
 * - a consequence of the rules above is that a non-first leaf appearing below
 *   a node will necessarily have an associated node with a split bit equal to
 *   or greater than the node's split bit.
 * - another consequence is that below a node, the split bits are different for
 *   each branches since both of them are already present above the node, thus
 *   at different levels, so their respective XOR values will be different.
 * - since all nodes in a given path have a different split bit, if a leaf has
 *   the same split bit as its parent node, it is necessary its associated leaf
 *
 * When descending along the tree, it is possible to know that a search key is
 * not present, because its XOR with both of the branches is strictly higher
 * than the inter-branch XOR. The reason is simple : the inter-branch XOR will
 * have its highest bit set indicating the split bit. Since it's the bit that
 * differs between the two branches, the key cannot have it both set and
 * cleared when comparing to the branch values. So xoring the key with both
 * branches will emit a higher bit only when the key's bit differs from both
 * branches' similar bit. Thus, the following equation :
 *      (XOR(key, L) > XOR(L, R)) && (XOR(key, R) > XOR(L, R))
 * is only true when the key should be placed above that node. Since the key
 * has a higher bit which differs from the node, either it has it set and the
 * node has it clear (same for both branches), or it has it clear and the node
 * has it set for both branches. For this reason it's enough to compare the key
 * with any node when the equation above is true, to know if it ought to be
 * present on the left or on the right side. This is useful for insertion and
 * for range lookups.
 */

#ifndef _CEBTREE_PRV_H
#define _CEBTREE_PRV_H

#include <inttypes.h>
#include <string.h>
#include "cebtree.h"

/* If DEBUG is set, we'll print additional debugging info during the descent */
#ifdef DEBUG
#define CEBDBG(x, ...) fprintf(stderr, x, ##__VA_ARGS__)
#else
#define CEBDBG(x, ...) do { } while (0)
#endif

/* These macros are used by upper level files to create two variants of their
 * exported functions:
 *   - one which uses sizeof(struct ceb_node) as the key offset, for nodes with
 *     adjacent keys ; these ones are named <pfx><sfx>(root, ...)
 *   - one with an explicit key offset passed by the caller right after the
 *     root.
 * Both rely on a forced inline version with a body that immediately follows
 * the declaration, so that the declaration looks like a single decorated
 * function while 2 are built in practice. There are variants for the basic one
 * with 0, 1 and 2 extra arguments after the root. The root and the key offset
 * are always the first two arguments, and the key offset never appears in the
 * first variant, it's always replaced by sizeof(struct ceb_node) in the calls
 * to the inline version.
 */
#define CEB_FDECL2(type, pfx, sfx, type1, arg1, type2, arg2)    \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2);     \
  type pfx##sfx(type1 arg1) {         \
    return _##pfx##sfx(arg1, sizeof(struct ceb_node));  \
  }                \
  type pfx##_ofs##sfx(type1 arg1, type2 arg2) {     \
    return _##pfx##sfx(arg1, arg2);       \
  }                \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2)
  /* function body follows */

#define CEB_FDECL3(type, pfx, sfx, type1, arg1, type2, arg2, type3, arg3) \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2, type3 arg3);   \
  type pfx##sfx(type1 arg1, type3 arg3) {       \
    return _##pfx##sfx(arg1, sizeof(struct ceb_node), arg3); \
  }                \
  type pfx##_ofs##sfx(type1 arg1, type2 arg2, type3 arg3) { \
    return _##pfx##sfx(arg1, arg2, arg3);     \
  }                \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2, type3 arg3)
  /* function body follows */

#define CEB_FDECL4(type, pfx, sfx, type1, arg1, type2, arg2, type3, arg3, type4, arg4) \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2, type3 arg3, type4 arg4); \
  type pfx##sfx(type1 arg1, type3 arg3, type4 arg4) {   \
    return _##pfx##sfx(arg1, sizeof(struct ceb_node), arg3, arg4); \
  }                \
  type pfx##_ofs##sfx(type1 arg1, type2 arg2, type3 arg3, type4 arg4) { \
    return _##pfx##sfx(arg1, arg2, arg3, arg4);   \
  }                \
  static inline __attribute__((always_inline))      \
  type _##pfx##sfx(type1 arg1, type2 arg2, type3 arg3, type4 arg4)
  /* function body follows */

/* tree walk method: key, left, right */
enum ceb_walk_meth {
  CEB_WM_FST,     /* look up "first" (walk left only) */
  CEB_WM_NXT,     /* look up "next" (walk right once then left) */
  CEB_WM_PRV,     /* look up "prev" (walk left once then right) */
  CEB_WM_LST,     /* look up "last" (walk right only) */
  /* all methods from CEB_WM_KEQ and above do have a key */
  CEB_WM_KEQ,     /* look up the node equal to the key  */
  CEB_WM_KGE,     /* look up the node greater than or equal to the key */
  CEB_WM_KGT,     /* look up the node greater than the key */
  CEB_WM_KLE,     /* look up the node lower than or equal to the key */
  CEB_WM_KLT,     /* look up the node lower than the key */
  CEB_WM_KNX,     /* look up the node's key first, then find the next */
  CEB_WM_KPR,     /* look up the node's key first, then find the prev */
};

enum ceb_key_type {
  CEB_KT_ADDR,    /* the key is the node's address */
  CEB_KT_U32,     /* 32-bit unsigned word in key_u32 */
  CEB_KT_U64,     /* 64-bit unsigned word in key_u64 */
  CEB_KT_MB,      /* fixed size memory block in (key_u64,key_ptr), direct storage */
  CEB_KT_IM,      /* fixed size memory block in (key_u64,key_ptr), indirect storage */
  CEB_KT_ST,      /* NUL-terminated string in key_ptr, direct storage */
  CEB_KT_IS,      /* NUL-terminated string in key_ptr, indirect storage */
};

union ceb_key_storage {
  uint32_t u32;
  uint64_t u64;
  unsigned long ul;
  unsigned char mb[0];
  unsigned char str[0];
  unsigned char *ptr; /* for CEB_KT_IS */
};

/* returns the ceb_key_storage pointer for node <n> and offset <o> */
#define NODEK(n, o) ((union ceb_key_storage*)(((char *)(n)) + (o)))

/* Returns the xor (or common length) between the two sides <l> and <r> if both
 * are non-null, otherwise between the first non-null one and the value in the
 * associate key. As a reminder, memory blocks place their length in key_u64.
 * This is only intended for internal use, essentially for debugging.
 *
 * <kofs> contains the offset between the key and the node's base. When simply
 * adjacent, this would just be sizeof(ceb_node).
 */
__attribute__((unused))
static inline uint64_t _xor_branches(ptrdiff_t kofs, enum ceb_key_type key_type, uint32_t key_u32,
                                     uint64_t key_u64, const void *key_ptr,
                                     const struct ceb_node *l,
                                     const struct ceb_node *r)
{
  if (l && r) {
    if (key_type == CEB_KT_MB)
      return equal_bits(NODEK(l, kofs)->mb, NODEK(r, kofs)->mb, 0, key_u64 << 3);
    else if (key_type == CEB_KT_IM)
      return equal_bits(NODEK(l, kofs)->mb, NODEK(r, kofs)->ptr, 0, key_u64 << 3);
    else if (key_type == CEB_KT_ST)
      return string_equal_bits(NODEK(l, kofs)->str, NODEK(r, kofs)->str, 0);
    else if (key_type == CEB_KT_IS)
      return string_equal_bits(NODEK(l, kofs)->ptr, NODEK(r, kofs)->ptr, 0);
    else if (key_type == CEB_KT_U64)
      return NODEK(l, kofs)->u64 ^ NODEK(r, kofs)->u64;
    else if (key_type == CEB_KT_U32)
      return NODEK(l, kofs)->u32 ^ NODEK(r, kofs)->u32;
    else if (key_type == CEB_KT_ADDR)
      return ((uintptr_t)l ^ (uintptr_t)r);
    else
      return 0;
  }

  if (!l)
    l = r;

  if (key_type == CEB_KT_MB)
    return equal_bits(key_ptr, NODEK(l, kofs)->mb, 0, key_u64 << 3);
  else if (key_type == CEB_KT_IM)
    return equal_bits(key_ptr, NODEK(l, kofs)->ptr, 0, key_u64 << 3);
  else if (key_type == CEB_KT_ST)
    return string_equal_bits(key_ptr, NODEK(l, kofs)->str, 0);
  else if (key_type == CEB_KT_IS)
    return string_equal_bits(key_ptr, NODEK(l, kofs)->ptr, 0);
  else if (key_type == CEB_KT_U64)
    return key_u64 ^ NODEK(l, kofs)->u64;
  else if (key_type == CEB_KT_U32)
    return key_u32 ^ NODEK(l, kofs)->u32;
  else if (key_type == CEB_KT_ADDR)
    return ((uintptr_t)key_ptr ^ (uintptr_t)r);
  else
    return 0;
}

#ifdef DEBUG
__attribute__((unused))
static void dbg(int line,
                const char *pfx,
                enum ceb_walk_meth meth,
                ptrdiff_t kofs,
                enum ceb_key_type key_type,
                struct ceb_node * const *root,
                const struct ceb_node *p,
                uint32_t key_u32,
                uint64_t key_u64,
                const void *key_ptr,
                uint32_t px32,
                uint64_t px64,
                size_t plen)
{
  const char *meths[] = {
    [CEB_WM_FST] = "FST",
    [CEB_WM_NXT] = "NXT",
    [CEB_WM_PRV] = "PRV",
    [CEB_WM_LST] = "LST",
    [CEB_WM_KEQ] = "KEQ",
    [CEB_WM_KGE] = "KGE",
    [CEB_WM_KGT] = "KGT",
    [CEB_WM_KLE] = "KLE",
    [CEB_WM_KLT] = "KLT",
    [CEB_WM_KNX] = "KNX",
    [CEB_WM_KPR] = "KPR",
  };
  const char *ktypes[] = {
    [CEB_KT_ADDR] = "ADDR",
    [CEB_KT_U32]  = "U32",
    [CEB_KT_U64]  = "U64",
    [CEB_KT_MB]   = "MB",
    [CEB_KT_IM]   = "IM",
    [CEB_KT_ST]   = "ST",
    [CEB_KT_IS]   = "IS",
  };
  const char *kstr __attribute__((unused)) = ktypes[key_type];
  const char *mstr __attribute__((unused)) = meths[meth];
  long long nlen __attribute__((unused)) = 0;
  long long llen __attribute__((unused)) = 0;
  long long rlen __attribute__((unused)) = 0;
  long long xlen __attribute__((unused)) = 0;

  if (p)
    nlen = _xor_branches(kofs, key_type, key_u32, key_u64, key_ptr, p, NULL);

  if (p && p->b[0])
    llen = _xor_branches(kofs, key_type, key_u32, key_u64, key_ptr, p->b[0], NULL);

  if (p && p->b[1])
    rlen = _xor_branches(kofs, key_type, key_u32, key_u64, key_ptr, NULL, p->b[1]);

  if (p && p->b[0] && p->b[1])
    xlen = _xor_branches(kofs, key_type, key_u32, key_u64, key_ptr, p->b[0], p->b[1]);

  switch (key_type) {
  case CEB_KT_U32:
    CEBDBG("%04d (%8s) m=%s.%s key=%#x root=%p pxor=%#x p=%p,%#x(^%#llx) l=%p,%#x(^%#llx) r=%p,%#x(^%#llx) l^r=%#llx\n",
          line, pfx, kstr, mstr, key_u32, root, px32,
          p, p ? NODEK(p, kofs)->u32 : 0, nlen,
          p ? p->b[0] : NULL, p ? NODEK(p->b[0], kofs)->u32 : 0, llen,
          p ? p->b[1] : NULL, p ? NODEK(p->b[1], kofs)->u32 : 0, rlen,
          xlen);
    break;
  case CEB_KT_U64:
    CEBDBG("%04d (%8s) m=%s.%s key=%#llx root=%p pxor=%#llx p=%p,%#llx(^%#llx) l=%p,%#llx(^%#llx) r=%p,%#llx(^%#llx) l^r=%#llx\n",
          line, pfx, kstr, mstr, (long long)key_u64, root, (long long)px64,
          p, (long long)(p ? NODEK(p, kofs)->u64 : 0), nlen,
          p ? p->b[0] : NULL, (long long)(p ? NODEK(p->b[0], kofs)->u64 : 0), llen,
          p ? p->b[1] : NULL, (long long)(p ? NODEK(p->b[1], kofs)->u64 : 0), rlen,
          xlen);
    break;
  case CEB_KT_MB:
    CEBDBG("%04d (%8s) m=%s.%s key=%p root=%p plen=%ld p=%p,%p(^%llu) l=%p,%p(^%llu) r=%p,%p(^%llu) l^r=%llu\n",
          line, pfx, kstr, mstr, key_ptr, root, (long)plen,
          p, p ? NODEK(p, kofs)->mb : 0, nlen,
          p ? p->b[0] : NULL, p ? NODEK(p->b[0], kofs)->mb : 0, llen,
          p ? p->b[1] : NULL, p ? NODEK(p->b[1], kofs)->mb : 0, rlen,
          xlen);
    break;
  case CEB_KT_IM:
    CEBDBG("%04d (%8s) m=%s.%s key=%p root=%p plen=%ld p=%p,%p(^%llu) l=%p,%p(^%llu) r=%p,%p(^%llu) l^r=%llu\n",
          line, pfx, kstr, mstr, key_ptr, root, (long)plen,
          p, p ? NODEK(p, kofs)->ptr : 0, nlen,
          p ? p->b[0] : NULL, p ? NODEK(p->b[0], kofs)->ptr : 0, llen,
          p ? p->b[1] : NULL, p ? NODEK(p->b[1], kofs)->ptr : 0, rlen,
          xlen);
    break;
  case CEB_KT_ST:
    CEBDBG("%04d (%8s) m=%s.%s key='%s' root=%p plen=%ld p=%p,%s(^%llu) l=%p,%s(^%llu) r=%p,%s(^%llu) l^r=%llu\n",
          line, pfx, kstr, mstr, key_ptr ? (const char *)key_ptr : "", root, (long)plen,
          p, p ? (const char *)NODEK(p, kofs)->str : "-", nlen,
          p ? p->b[0] : NULL, p ? (const char *)NODEK(p->b[0], kofs)->str : "-", llen,
          p ? p->b[1] : NULL, p ? (const char *)NODEK(p->b[1], kofs)->str : "-", rlen,
          xlen);
    break;
  case CEB_KT_IS:
    CEBDBG("%04d (%8s) m=%s.%s key='%s' root=%p plen=%ld p=%p,%s(^%llu) l=%p,%s(^%llu) r=%p,%s(^%llu) l^r=%llu\n",
          line, pfx, kstr, mstr, key_ptr ? (const char *)key_ptr : "", root, (long)plen,
          p, p ? (const char *)NODEK(p, kofs)->ptr : "-", nlen,
          p ? p->b[0] : NULL, p ? (const char *)NODEK(p->b[0], kofs)->ptr : "-", llen,
          p ? p->b[1] : NULL, p ? (const char *)NODEK(p->b[1], kofs)->ptr : "-", rlen,
          xlen);
    break;
  case CEB_KT_ADDR:
    /* key type is the node's address */
    CEBDBG("%04d (%8s) m=%s.%s key=%#llx root=%p pxor=%#llx p=%p,%#llx(^%#llx) l=%p,%#llx(^%#llx) r=%p,%#llx(^%#llx) l^r=%#llx\n",
          line, pfx, kstr, mstr, (long long)(uintptr_t)key_ptr, root, (long long)px64,
          p, (long long)(uintptr_t)p, nlen,
          p ? p->b[0] : NULL, p ? (long long)(uintptr_t)p->b[0] : 0, llen,
          p ? p->b[1] : NULL, p ? (long long)(uintptr_t)p->b[1] : 0, rlen,
          xlen);
  }
}
#else
#define dbg(...) do { } while (0)
#endif

/* Generic tree descent function. It must absolutely be inlined so that the
 * compiler can eliminate the tests related to the various return pointers,
 * which must either point to a local variable in the caller, or be NULL.
 * It must not be called with an empty tree, it's the caller business to
 * deal with this special case. It returns in ret_root the location of the
 * pointer to the leaf (i.e. where we have to insert ourselves). The integer
 * pointed to by ret_nside will contain the side the leaf should occupy at
 * its own node, with the sibling being *ret_root. Note that keys for fixed-
 * size arrays are passed in key_ptr with their length in key_u64. For keyless
 * nodes whose address serves as the key, the pointer needs to be passed in
 * key_ptr, and pxor64 will be used internally.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_descend(struct ceb_node **root,
                               enum ceb_walk_meth meth,
                               ptrdiff_t kofs,
                               enum ceb_key_type key_type,
                               uint32_t key_u32,
                               uint64_t key_u64,
                               const void *key_ptr,
                               int *ret_nside,
                               struct ceb_node ***ret_root,
                               struct ceb_node **ret_lparent,
                               int *ret_lpside,
                               struct ceb_node **ret_nparent,
                               int *ret_npside,
                               struct ceb_node **ret_gparent,
                               int *ret_gpside,
                               struct ceb_node **ret_back)
{
#if !defined(__OPTIMIZE__) && __GNUC_PREREQ__(12, 0)
/* Avoid a bogus warning with gcc 12 and above: it warns about negative
 * memcmp() length in non-existing code paths at -O0, as reported here:
 *    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114622
 */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-overread"
#endif
  struct ceb_node *p;
  union ceb_key_storage *l, *r, *k;
  struct ceb_node *gparent = NULL;
  struct ceb_node *nparent = NULL;
  struct ceb_node *bnode = NULL;
  struct ceb_node *lparent;
  uint32_t pxor32 = ~0U;   // previous xor between branches
  uint64_t pxor64 = ~0ULL; // previous xor between branches
  int gpside = 0;   // side on the grand parent
  int npside = 0;   // side on the node's parent
  long lpside = 0;  // side on the leaf's parent
  long brside = 0;  // branch side when descending
  size_t llen = 0;  // left vs key matching length
  size_t rlen = 0;  // right vs key matching length
  size_t plen = 0;  // previous common len between branches
  int found = 0;    // key was found (saves an extra strcmp for arrays)

  dbg(__LINE__, "_enter__", meth, kofs, key_type, root, NULL, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);

  /* the parent will be the (possibly virtual) node so that
   * &lparent->l == root.
   */
  lparent = container_of(root, struct ceb_node, b[0]);
  gparent = nparent = lparent;

  /* for key-less descents we need to set the initial branch to take */
  switch (meth) {
  case CEB_WM_NXT:
  case CEB_WM_LST:
    brside = 1; // start right for next/last
    break;
  case CEB_WM_FST:
  case CEB_WM_PRV:
  default:
    brside = 0; // start left for first/prev
    break;
  }

  /* the previous xor is initialized to the largest possible inter-branch
   * value so that it can never match on the first test as we want to use
   * it to detect a leaf vs node. That's achieved with plen==0 for arrays
   * and pxorXX==~0 for scalars.
   */
  while (1) {
    p = *root;

    /* Tests have shown that for write-intensive workloads (many
     * insertions/deletion), prefetching for reads is counter
     * productive (-10% perf) but that prefetching only the next
     * nodes for writes when deleting can yield around 3% extra
     * boost.
     */
    if (ret_lpside) {
      /* this is a deletion, prefetch for writes */
      __builtin_prefetch(p->b[0], 1);
      __builtin_prefetch(p->b[1], 1);
    }

    /* neither pointer is tagged */
    k = NODEK(p, kofs);
    l = NODEK(p->b[0], kofs);
    r = NODEK(p->b[1], kofs);

    dbg(__LINE__, "newp", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);

    /* two equal pointers identifies the nodeless leaf. */
    if (l == r) {
      dbg(__LINE__, "l==r", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
      break;
    }

    /* In the following block, we're dealing with type-specific
     * operations which follow the same construct for each type:
     *   1) calculate the new side for key lookups (otherwise keep
     *      the current side, e.g. for first/last). Doing it early
     *      allows the CPU to more easily predict next branches and
     *      is faster by ~10%. For complex bits we keep the length
     *      of identical bits instead of xor. We can also xor lkey
     *      and rkey with key and use it everywhere later but it
     *      doesn't seem to bring anything.
     *
     *   2) calculate the xor between the two sides to figure the
     *      split bit position. If the new split bit is before the
     *      previous one, we've reached a leaf: each leaf we visit
     *      had its node part already visited. The only way to
     *      distinguish them is that the inter-branch xor of the
     *      leaf will be the node's one, and will necessarily be
     *      larger than the previous node's xor if the node is
     *      above (we've already checked for direct descendent
     *      below). Said differently, if an inter-branch xor is
     *      strictly larger than the previous one, it necessarily
     *      is the one of an upper node, so what we're seeing
     *      cannot be the node, hence it's the leaf. The case where
     *      they're equal was already dealt with by the test at the
     *      end of the loop (node points to self). For scalar keys,
     *      we directly store the last xor value in pxorXX. For
     *      arrays and strings, instead we store the previous equal
     *      length.
     *
     *   3) for lookups, check if the looked key still has a chance
     *      to be below: if it has a xor with both branches that is
     *      larger than the xor between them, it cannot be there,
     *      since it means that it differs from these branches by
     *      at least one bit that's higher than the split bit,
     *      hence not common to these branches. In such cases:
     *      - if we're just doing a lookup, the key is not found
     *        and we fail.
     *      - if we are inserting, we must stop here and we have
     *        the guarantee to be above a node.
     *      - if we're deleting, it could be the key we were
     *        looking for so we have to check for it as long as
     *        it's still possible to keep a copy of the node's
     *        parent. <found> is set int this case for expensive
     *        types.
     */

    if (key_type == CEB_KT_U32) {
      uint32_t xor32;   // left vs right branch xor
      uint32_t kl, kr;

      kl = l->u32; kr = r->u32;
      xor32 = kl ^ kr;

      if (xor32 > pxor32) { // test using 2 4 6 4
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* "found" is not used here */
        kl ^= key_u32; kr ^= key_u32;
        brside = kl >= kr;

        /* let's stop if our key is not there */

        if (kl > xor32 && kr > xor32) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) {
          if (key_u32 == k->u32) {
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
          }
        }
      }
      pxor32 = xor32;
    }
    else if (key_type == CEB_KT_U64) {
      uint64_t xor64;   // left vs right branch xor
      uint64_t kl, kr;

      kl = l->u64; kr = r->u64;
      xor64 = kl ^ kr;

      if (xor64 > pxor64) { // test using 2 4 6 4
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* "found" is not used here */
        kl ^= key_u64; kr ^= key_u64;
        brside = kl >= kr;

        /* let's stop if our key is not there */

        if (kl > xor64 && kr > xor64) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) {
          if (key_u64 == k->u64) {
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
          }
        }
      }
      pxor64 = xor64;
    }
    else if (key_type == CEB_KT_MB) {
      size_t xlen = 0; // left vs right matching length

      if (meth >= CEB_WM_KEQ) {
        /* measure identical lengths */
        llen = equal_bits(key_ptr, l->mb, 0, key_u64 << 3);
        rlen = equal_bits(key_ptr, r->mb, 0, key_u64 << 3);
        brside = llen <= rlen;
        if (llen == rlen && (uint64_t)llen == key_u64 << 3)
          found = 1;
      }

      xlen = equal_bits(l->mb, r->mb, 0, key_u64 << 3);
      if (xlen < plen) {
        /* this is a leaf. E.g. triggered using 2 4 6 4 */
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* let's stop if our key is not there */

        if (llen < xlen && rlen < xlen) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) { // delete ?
          size_t mlen = llen > rlen ? llen : rlen;

          if (mlen > xlen)
            mlen = xlen;

          if ((uint64_t)xlen / 8 == key_u64 || memcmp(key_ptr + mlen / 8, k->mb + mlen / 8, key_u64 - mlen / 8) == 0) {
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
            found = 1;
          }
        }
      }
      plen = xlen;
    }
    else if (key_type == CEB_KT_IM) {
      size_t xlen = 0; // left vs right matching length

      if (meth >= CEB_WM_KEQ) {
        /* measure identical lengths */
        llen = equal_bits(key_ptr, l->ptr, 0, key_u64 << 3);
        rlen = equal_bits(key_ptr, r->ptr, 0, key_u64 << 3);
        brside = llen <= rlen;
        if (llen == rlen && (uint64_t)llen == key_u64 << 3)
          found = 1;
      }

      xlen = equal_bits(l->ptr, r->ptr, 0, key_u64 << 3);
      if (xlen < plen) {
        /* this is a leaf. E.g. triggered using 2 4 6 4 */
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* let's stop if our key is not there */

        if (llen < xlen && rlen < xlen) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) { // delete ?
          size_t mlen = llen > rlen ? llen : rlen;

          if (mlen > xlen)
            mlen = xlen;

          if ((uint64_t)xlen / 8 == key_u64 || memcmp(key_ptr + mlen / 8, k->ptr + mlen / 8, key_u64 - mlen / 8) == 0) {
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
            found = 1;
          }
        }
      }
      plen = xlen;
    }
    else if (key_type == CEB_KT_ST) {
      size_t xlen = 0; // left vs right matching length

      if (meth >= CEB_WM_KEQ) {
        /* Note that a negative length indicates an
         * equal value with the final zero reached, but
         * it is still needed to descend to find the
         * leaf. We take that negative length for an
         * infinite one, hence the uint cast.
         */
        llen = string_equal_bits(key_ptr, l->str, 0);
        rlen = string_equal_bits(key_ptr, r->str, 0);
        brside = (size_t)llen <= (size_t)rlen;
        if ((ssize_t)llen < 0 || (ssize_t)rlen < 0)
          found = 1;
      }

      xlen = string_equal_bits(l->str, r->str, 0);
      if (xlen < plen) {
        /* this is a leaf. E.g. triggered using 2 4 6 4 */
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* let's stop if our key is not there */

        if ((unsigned)llen < (unsigned)xlen && (unsigned)rlen < (unsigned)xlen) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) { // delete ?
          size_t mlen = llen > rlen ? llen : rlen;

          if (mlen > xlen)
            mlen = xlen;

          if (strcmp(key_ptr + mlen / 8, (const void *)k->str + mlen / 8) == 0) {
            /* strcmp() still needed. E.g. 1 2 3 4 10 11 4 3 2 1 10 11 fails otherwise */
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
            found = 1;
          }
        }
      }
      plen = xlen;
    }
    else if (key_type == CEB_KT_IS) {
      size_t xlen = 0; // left vs right matching length

      if (meth >= CEB_WM_KEQ) {
        /* Note that a negative length indicates an
         * equal value with the final zero reached, but
         * it is still needed to descend to find the
         * leaf. We take that negative length for an
         * infinite one, hence the uint cast.
         */
        llen = string_equal_bits(key_ptr, l->ptr, 0);
        rlen = string_equal_bits(key_ptr, r->ptr, 0);
        brside = (size_t)llen <= (size_t)rlen;
        if ((ssize_t)llen < 0 || (ssize_t)rlen < 0)
          found = 1;
      }

      xlen = string_equal_bits(l->ptr, r->ptr, 0);
      if (xlen < plen) {
        /* this is a leaf. E.g. triggered using 2 4 6 4 */
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* let's stop if our key is not there */

        if ((unsigned)llen < (unsigned)xlen && (unsigned)rlen < (unsigned)xlen) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) { // delete ?
          size_t mlen = llen > rlen ? llen : rlen;

          if (mlen > xlen)
            mlen = xlen;

          if (strcmp(key_ptr + mlen / 8, (const void *)k->ptr + mlen / 8) == 0) {
            /* strcmp() still needed. E.g. 1 2 3 4 10 11 4 3 2 1 10 11 fails otherwise */
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
            found = 1;
          }
        }
      }
      plen = xlen;
    }
    else if (key_type == CEB_KT_ADDR) {
      uintptr_t xoraddr;   // left vs right branch xor
      uintptr_t kl, kr;

      kl = (uintptr_t)l; kr = (uintptr_t)r;
      xoraddr = kl ^ kr;

      if (xoraddr > (uintptr_t)pxor64) { // test using 2 4 6 4
        dbg(__LINE__, "xor>", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
        break;
      }

      if (meth >= CEB_WM_KEQ) {
        /* "found" is not used here */
        kl ^= (uintptr_t)key_ptr; kr ^= (uintptr_t)key_ptr;
        brside = kl >= kr;

        /* let's stop if our key is not there */

        if (kl > xoraddr && kr > xoraddr) {
          dbg(__LINE__, "mismatch", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
          break;
        }

        if (ret_npside || ret_nparent) {
          if ((uintptr_t)key_ptr == (uintptr_t)p) {
            dbg(__LINE__, "equal", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
            nparent = lparent;
            npside  = lpside;
          }
        }
      }
      pxor64 = xoraddr;
    }

    /* shift all copies by one */
    gparent = lparent;
    gpside = lpside;
    lparent = p;
    lpside = brside;
    if (brside) {
      if (meth == CEB_WM_KPR || meth == CEB_WM_KLE || meth == CEB_WM_KLT)
        bnode = p;
      root = &p->b[1];

      /* change branch for key-less walks */
      if (meth == CEB_WM_NXT)
        brside = 0;

      dbg(__LINE__, "side1", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
    }
    else {
      if (meth == CEB_WM_KNX || meth == CEB_WM_KGE || meth == CEB_WM_KGT)
        bnode = p;
      root = &p->b[0];

      /* change branch for key-less walks */
      if (meth == CEB_WM_PRV)
        brside = 1;

      dbg(__LINE__, "side0", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
    }

    if (p == *root) {
      /* loops over itself, it's a leaf */
      dbg(__LINE__, "loop", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);
      break;
    }
  }

  /* here we're on the closest node from the requested value. It may be
   * slightly lower (has a zero where we expected a one) or slightly
   * larger has a one where we expected a zero). Thus another check is
   * still deserved, depending on the matching method.
   */

  /* if we've exited on an exact match after visiting a regular node
   * (i.e. not the nodeless leaf), we'll avoid checking the string again.
   * However if it doesn't match, we must make sure to compare from
   * within the key (which can be shorter than the ones already there),
   * so we restart the check from the longest of the two lengths, which
   * guarantees these bits exist. Test with "100", "10", "1" to see where
   * this is needed.
   */
  if ((key_type == CEB_KT_ST || key_type == CEB_KT_IS) && meth >= CEB_WM_KEQ && !found)
    plen = (llen > rlen) ? llen : rlen;

  /* update the pointers needed for modifications (insert, delete) */
  if (ret_nside && meth >= CEB_WM_KEQ) {
    switch (key_type) {
    case CEB_KT_U32:
      *ret_nside = key_u32 >= k->u32;
      break;
    case CEB_KT_U64:
      *ret_nside = key_u64 >= k->u64;
      break;
    case CEB_KT_MB:
      *ret_nside = (uint64_t)plen / 8 == key_u64 || memcmp(key_ptr + plen / 8, k->mb + plen / 8, key_u64 - plen / 8) >= 0;
      break;
    case CEB_KT_IM:
      *ret_nside = (uint64_t)plen / 8 == key_u64 || memcmp(key_ptr + plen / 8, k->ptr + plen / 8, key_u64 - plen / 8) >= 0;
      break;
    case CEB_KT_ST:
      *ret_nside = found || strcmp(key_ptr + plen / 8, (const void *)k->str + plen / 8) >= 0;
      break;
    case CEB_KT_IS:
      *ret_nside = found || strcmp(key_ptr + plen / 8, (const void *)k->ptr + plen / 8) >= 0;
      break;
    case CEB_KT_ADDR:
      *ret_nside = (uintptr_t)key_ptr >= (uintptr_t)p;
      break;
    }
  }

  if (ret_root)
    *ret_root = root;

  /* info needed by delete */
  if (ret_lpside)
    *ret_lpside = lpside;

  if (ret_lparent)
    *ret_lparent = lparent;

  if (ret_npside)
    *ret_npside = npside;

  if (ret_nparent)
    *ret_nparent = nparent;

  if (ret_gpside)
    *ret_gpside = gpside;

  if (ret_gparent)
    *ret_gparent = gparent;

  if (ret_back)
    *ret_back = bnode;

  dbg(__LINE__, "_ret____", meth, kofs, key_type, root, p, key_u32, key_u64, key_ptr, pxor32, pxor64, plen);

  if (meth >= CEB_WM_KEQ) {
    /* For lookups, an equal value means an instant return. For insertions,
     * it is the same, we want to return the previously existing value so
     * that the caller can decide what to do. For deletion, we also want to
     * return the pointer that's about to be deleted.
     */
    if (key_type == CEB_KT_U32) {
      if ((meth == CEB_WM_KEQ && k->u32 == key_u32) ||
          (meth == CEB_WM_KNX && k->u32 == key_u32) ||
          (meth == CEB_WM_KPR && k->u32 == key_u32) ||
          (meth == CEB_WM_KGE && k->u32 >= key_u32) ||
          (meth == CEB_WM_KGT && k->u32 >  key_u32) ||
          (meth == CEB_WM_KLE && k->u32 <= key_u32) ||
          (meth == CEB_WM_KLT && k->u32 <  key_u32))
        return p;
    }
    else if (key_type == CEB_KT_U64) {
      if ((meth == CEB_WM_KEQ && k->u64 == key_u64) ||
          (meth == CEB_WM_KNX && k->u64 == key_u64) ||
          (meth == CEB_WM_KPR && k->u64 == key_u64) ||
          (meth == CEB_WM_KGE && k->u64 >= key_u64) ||
          (meth == CEB_WM_KGT && k->u64 >  key_u64) ||
          (meth == CEB_WM_KLE && k->u64 <= key_u64) ||
          (meth == CEB_WM_KLT && k->u64 <  key_u64))
        return p;
    }
    else if (key_type == CEB_KT_MB) {
      int diff;

      if ((uint64_t)plen / 8 == key_u64)
        diff = 0;
      else
        diff = memcmp(k->mb + plen / 8, key_ptr + plen / 8, key_u64 - plen / 8);

      if ((meth == CEB_WM_KEQ && diff == 0) ||
          (meth == CEB_WM_KNX && diff == 0) ||
          (meth == CEB_WM_KPR && diff == 0) ||
          (meth == CEB_WM_KGE && diff >= 0) ||
          (meth == CEB_WM_KGT && diff >  0) ||
          (meth == CEB_WM_KLE && diff <= 0) ||
          (meth == CEB_WM_KLT && diff <  0))
        return p;
    }
    else if (key_type == CEB_KT_IM) {
      int diff;

      if ((uint64_t)plen / 8 == key_u64)
        diff = 0;
      else
        diff = memcmp(k->ptr + plen / 8, key_ptr + plen / 8, key_u64 - plen / 8);

      if ((meth == CEB_WM_KEQ && diff == 0) ||
          (meth == CEB_WM_KNX && diff == 0) ||
          (meth == CEB_WM_KPR && diff == 0) ||
          (meth == CEB_WM_KGE && diff >= 0) ||
          (meth == CEB_WM_KGT && diff >  0) ||
          (meth == CEB_WM_KLE && diff <= 0) ||
          (meth == CEB_WM_KLT && diff <  0))
        return p;
    }
    else if (key_type == CEB_KT_ST) {
      int diff;

      if (found)
        diff = 0;
      else
        diff = strcmp((const void *)k->str + plen / 8, key_ptr + plen / 8);

      if ((meth == CEB_WM_KEQ && diff == 0) ||
          (meth == CEB_WM_KNX && diff == 0) ||
          (meth == CEB_WM_KPR && diff == 0) ||
          (meth == CEB_WM_KGE && diff >= 0) ||
          (meth == CEB_WM_KGT && diff >  0) ||
          (meth == CEB_WM_KLE && diff <= 0) ||
          (meth == CEB_WM_KLT && diff <  0))
        return p;
    }
    else if (key_type == CEB_KT_IS) {
      int diff;

      if (found)
        diff = 0;
      else
        diff = strcmp((const void *)k->ptr + plen / 8, key_ptr + plen / 8);

      if ((meth == CEB_WM_KEQ && diff == 0) ||
          (meth == CEB_WM_KNX && diff == 0) ||
          (meth == CEB_WM_KPR && diff == 0) ||
          (meth == CEB_WM_KGE && diff >= 0) ||
          (meth == CEB_WM_KGT && diff >  0) ||
          (meth == CEB_WM_KLE && diff <= 0) ||
          (meth == CEB_WM_KLT && diff <  0))
        return p;
    }
    else if (key_type == CEB_KT_ADDR) {
      if ((meth == CEB_WM_KEQ && (uintptr_t)p == (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KNX && (uintptr_t)p == (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KPR && (uintptr_t)p == (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KGE && (uintptr_t)p >= (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KGT && (uintptr_t)p >  (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KLE && (uintptr_t)p <= (uintptr_t)key_ptr) ||
          (meth == CEB_WM_KLT && (uintptr_t)p <  (uintptr_t)key_ptr))
        return p;
    }
  } else if (meth == CEB_WM_FST || meth == CEB_WM_LST) {
    return p;
  } else if (meth == CEB_WM_PRV || meth == CEB_WM_NXT) {
    return p;
  }

  /* lookups and deletes fail here */

  /* let's return NULL to indicate the key was not found. For a lookup or
   * a delete, it's a failure. For an insert, it's an invitation to the
   * caller to proceed since the element is not there.
   */
  return NULL;
#if __GNUC_PREREQ__(12, 0)
#pragma GCC diagnostic pop
#endif
}


/* Generic tree insertion function for trees with unique keys. Inserts node
 * <node> into tree <tree>, with key type <key_type> and key <key_*>.
 * Returns the inserted node or the one that already contains the same key.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_insert(struct ceb_node **root,
                              struct ceb_node *node,
                              ptrdiff_t kofs,
                              enum ceb_key_type key_type,
                              uint32_t key_u32,
                              uint64_t key_u64,
                              const void *key_ptr)
{
  struct ceb_node **parent;
  struct ceb_node *ret;
  int nside;

  if (!*root) {
    /* empty tree, insert a leaf only */
    node->b[0] = node->b[1] = node;
    *root = node;
    return node;
  }

  ret = _cebu_descend(root, CEB_WM_KEQ, kofs, key_type, key_u32, key_u64, key_ptr, &nside, &parent, NULL, NULL, NULL, NULL, NULL, NULL, NULL);

  if (!ret) {
    /* The key was not in the tree, we can insert it. Better use an
     * "if" like this because the inline function above already has
     * quite identifiable code paths. This reduces the code and
     * optimizes it a bit.
     */
    if (nside) {
      node->b[1] = node;
      node->b[0] = *parent;
    } else {
      node->b[0] = node;
      node->b[1] = *parent;
    }
    *parent = node;
    ret = node;
  }
  return ret;
}

/* Returns the first node or NULL if not found, assuming a tree made of keys of
 * type <key_type>.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_first(struct ceb_node **root,
                             ptrdiff_t kofs,
                             enum ceb_key_type key_type)
{
  if (!*root)
    return NULL;

  return _cebu_descend(root, CEB_WM_FST, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Returns the last node or NULL if not found, assuming a tree made of keys of
 * type <key_type>.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_last(struct ceb_node **root,
                            ptrdiff_t kofs,
                            enum ceb_key_type key_type)
{
  if (!*root)
    return NULL;

  return _cebu_descend(root, CEB_WM_LST, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the next
 * node after the one containing the key <key_*>. Returns NULL if not found.
 * It's up to the caller to pass the current node's key in <key_*>. The
 * approach consists in looking up that node first, recalling the last time a
 * left turn was made, and returning the first node along the right branch at
 * that fork.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_next(struct ceb_node **root,
                            ptrdiff_t kofs,
                            enum ceb_key_type key_type,
                            uint32_t key_u32,
                            uint64_t key_u64,
                            const void *key_ptr)
{
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  if (!_cebu_descend(root, CEB_WM_KNX, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart))
    return NULL;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_NXT, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the prev
 * node before the one containing the key <key_*>. Returns NULL if not found.
 * It's up to the caller to pass the current node's key in <key_*>. The
 * approach consists in looking up that node first, recalling the last time a
 * right turn was made, and returning the last node along the left branch at
 * that fork.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_prev(struct ceb_node **root,
                            ptrdiff_t kofs,
                            enum ceb_key_type key_type,
                            uint32_t key_u32,
                            uint64_t key_u64,
                            const void *key_ptr)
{
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  if (!_cebu_descend(root, CEB_WM_KPR, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart))
    return NULL;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_PRV, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * containing the key <key_*>. Returns NULL if not found.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_lookup(struct ceb_node **root,
                              ptrdiff_t kofs,
                              enum ceb_key_type key_type,
                              uint32_t key_u32,
                              uint64_t key_u64,
                              const void *key_ptr)
{
  if (!*root)
    return NULL;

  return _cebu_descend(root, CEB_WM_KEQ, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * containing the key <key_*> or the highest one that's lower than it. Returns
 * NULL if not found.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_lookup_le(struct ceb_node **root,
                                 ptrdiff_t kofs,
                                 enum ceb_key_type key_type,
                                 uint32_t key_u32,
                                 uint64_t key_u64,
                                 const void *key_ptr)
{
  struct ceb_node *ret = NULL;
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  ret = _cebu_descend(root, CEB_WM_KLE, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart);
  if (ret)
    return ret;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_PRV, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * containing the greatest key that is strictly lower than <key_*>. Returns
 * NULL if not found. It's very similar to next() except that the looked up
 * value doesn't need to exist.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_lookup_lt(struct ceb_node **root,
                                 ptrdiff_t kofs,
                                 enum ceb_key_type key_type,
                                 uint32_t key_u32,
                                 uint64_t key_u64,
                                 const void *key_ptr)
{
  struct ceb_node *ret = NULL;
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  ret = _cebu_descend(root, CEB_WM_KLT, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart);
  if (ret)
    return ret;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_PRV, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * containing the key <key_*> or the smallest one that's greater than it.
 * Returns NULL if not found.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_lookup_ge(struct ceb_node **root,
                                 ptrdiff_t kofs,
                                 enum ceb_key_type key_type,
                                 uint32_t key_u32,
                                 uint64_t key_u64,
                                 const void *key_ptr)
{
  struct ceb_node *ret = NULL;
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  ret = _cebu_descend(root, CEB_WM_KGE, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart);
  if (ret)
    return ret;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_NXT, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * containing the lowest key that is strictly greater than <key_*>. Returns
 * NULL if not found. It's very similar to prev() except that the looked up
 * value doesn't need to exist.
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_lookup_gt(struct ceb_node **root,
                                 ptrdiff_t kofs,
                                 enum ceb_key_type key_type,
                                 uint32_t key_u32,
                                 uint64_t key_u64,
                                 const void *key_ptr)
{
  struct ceb_node *ret = NULL;
  struct ceb_node *restart;

  if (!*root)
    return NULL;

  ret = _cebu_descend(root, CEB_WM_KGT, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &restart);
  if (ret)
    return ret;

  if (!restart)
    return NULL;

  return _cebu_descend(&restart, CEB_WM_NXT, kofs, key_type, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/* Searches in the tree <root> made of keys of type <key_type>, for the node
 * that contains the key <key_*>, and deletes it. If <node> is non-NULL, a
 * check is performed and the node found is deleted only if it matches. The
 * found node is returned in any case, otherwise NULL if not found. A deleted
 * node is detected since it has b[0]==NULL, which this functions also clears
 * after operation. The function is idempotent, so it's safe to attempt to
 * delete an already deleted node (NULL is returned in this case since the node
 * was not in the tree).
 */
static inline __attribute__((always_inline))
struct ceb_node *_cebu_delete(struct ceb_node **root,
                              struct ceb_node *node,
                              ptrdiff_t kofs,
                              enum ceb_key_type key_type,
                              uint32_t key_u32,
                              uint64_t key_u64,
                              const void *key_ptr)
{
  struct ceb_node *lparent, *nparent, *gparent;
  int lpside, npside, gpside;
  struct ceb_node *ret = NULL;

  if (node && !node->b[0]) {
    /* NULL on a branch means the node is not in the tree */
    return NULL;
  }

  if (!*root) {
    /* empty tree, the node cannot be there */
    goto done;
  }

  ret = _cebu_descend(root, CEB_WM_KEQ, kofs, key_type, key_u32, key_u64, key_ptr, NULL, NULL,
          &lparent, &lpside, &nparent, &npside, &gparent, &gpside, NULL);

  if (!ret) {
    /* key not found */
    goto done;
  }

  if (ret == node || !node) {
    if (&lparent->b[0] == root) {
      /* there was a single entry, this one, so we're just
       * deleting the nodeless leaf.
       */
      *root = NULL;
      goto mark_and_leave;
    }

    /* then we necessarily have a gparent */
    gparent->b[gpside] = lparent->b[!lpside];

    if (lparent == ret) {
      /* we're removing the leaf and node together, nothing
       * more to do.
       */
      goto mark_and_leave;
    }

    if (ret->b[0] == ret->b[1]) {
      /* we're removing the node-less item, the parent will
       * take this role.
       */
      lparent->b[0] = lparent->b[1] = lparent;
      goto mark_and_leave;
    }

    /* more complicated, the node was split from the leaf, we have
     * to find a spare one to switch it. The parent node is not
     * needed anymore so we can reuse it.
     */
    lparent->b[0] = ret->b[0];
    lparent->b[1] = ret->b[1];
    nparent->b[npside] = lparent;

  mark_and_leave:
    /* now mark the node as deleted */
    ret->b[0] = NULL;
  }
done:
  return ret;
}

/*
 * Functions used to dump trees in Dot format.
 */

/* dump the root and its link to the first node or leaf */
__attribute__((unused))
static void cebu_default_dump_root(ptrdiff_t kofs, enum ceb_key_type key_type, struct ceb_node *const *root, const void *ctx)
{
  const struct ceb_node *node;

  printf("  \"%lx_n\" [label=\"root\\n%lx\"]\n", (long)root, (long)root);

  node = *root;
  if (node) {
    /* under the root we've either a node or the first leaf */
    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"B\" arrowsize=0.66];\n",
           (long)root, (long)node,
           (node->b[0] == node->b[1]) ? 'l' : 'n');
  }
}

/* dump a node */
__attribute__((unused))
static void cebu_default_dump_node(ptrdiff_t kofs, enum ceb_key_type key_type, const struct ceb_node *node, int level, const void *ctx)
{
  unsigned long long int_key = 0;
  uint64_t pxor, lxor, rxor;

  switch (key_type) {
  case CEB_KT_ADDR:
    int_key = (uintptr_t)node;
    break;
  case CEB_KT_U32:
    int_key = NODEK(node, kofs)->u32;
    break;
  case CEB_KT_U64:
    int_key = NODEK(node, kofs)->u64;
    break;
  default:
    break;
  }

  /* xor of the keys of the two lower branches */
  pxor = _xor_branches(kofs, key_type, 0, 0, NULL,
           node->b[0], node->b[1]);

  /* xor of the keys of the left branch's lower branches */
  lxor = _xor_branches(kofs, key_type, 0, 0, NULL,
           (((struct ceb_node*)node->b[0])->b[0]),
           (((struct ceb_node*)node->b[0])->b[1]));

  /* xor of the keys of the right branch's lower branches */
  rxor = _xor_branches(kofs, key_type, 0, 0, NULL,
           (((struct ceb_node*)node->b[1])->b[0]),
           (((struct ceb_node*)node->b[1])->b[1]));

  switch (key_type) {
  case CEB_KT_ADDR:
  case CEB_KT_U32:
  case CEB_KT_U64:
    printf("  \"%lx_n\" [label=\"%lx\\nlev=%d bit=%d\\nkey=%llu\" fillcolor=\"lightskyblue1\"%s];\n",
           (long)node, (long)node, level, flsnz(pxor) - 1, int_key, (ctx == node) ? " color=red" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"L\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[0],
           (lxor < pxor && ((struct ceb_node*)node->b[0])->b[0] != ((struct ceb_node*)node->b[0])->b[1]) ? 'n' : 'l',
           (node == node->b[0]) ? " dir=both" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"R\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[1],
           (rxor < pxor && ((struct ceb_node*)node->b[1])->b[0] != ((struct ceb_node*)node->b[1])->b[1]) ? 'n' : 'l',
           (node == node->b[1]) ? " dir=both" : "");
    break;
  case CEB_KT_MB:
    break;
  case CEB_KT_IM:
    break;
  case CEB_KT_ST:
    printf("  \"%lx_n\" [label=\"%lx\\nlev=%d bit=%ld\\nkey=\\\"%s\\\"\" fillcolor=\"lightskyblue1\"%s];\n",
           (long)node, (long)node, level, (long)pxor, NODEK(node, kofs)->str, (ctx == node) ? " color=red" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"L\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[0],
           (lxor > pxor && ((struct ceb_node*)node->b[0])->b[0] != ((struct ceb_node*)node->b[0])->b[1]) ? 'n' : 'l',
           (node == node->b[0]) ? " dir=both" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"R\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[1],
           (rxor > pxor && ((struct ceb_node*)node->b[1])->b[0] != ((struct ceb_node*)node->b[1])->b[1]) ? 'n' : 'l',
           (node == node->b[1]) ? " dir=both" : "");
    break;
  case CEB_KT_IS:
    printf("  \"%lx_n\" [label=\"%lx\\nlev=%d bit=%ld\\nkey=\\\"%s\\\"\" fillcolor=\"lightskyblue1\"%s];\n",
           (long)node, (long)node, level, (long)pxor, NODEK(node, kofs)->ptr, (ctx == node) ? " color=red" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"L\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[0],
           (lxor > pxor && ((struct ceb_node*)node->b[0])->b[0] != ((struct ceb_node*)node->b[0])->b[1]) ? 'n' : 'l',
           (node == node->b[0]) ? " dir=both" : "");

    printf("  \"%lx_n\" -> \"%lx_%c\" [label=\"R\" arrowsize=0.66 %s];\n",
           (long)node, (long)node->b[1],
           (rxor > pxor && ((struct ceb_node*)node->b[1])->b[0] != ((struct ceb_node*)node->b[1])->b[1]) ? 'n' : 'l',
           (node == node->b[1]) ? " dir=both" : "");
    break;
  }
}

/* dump a leaf */
__attribute__((unused))
static void cebu_default_dump_leaf(ptrdiff_t kofs, enum ceb_key_type key_type, const struct ceb_node *node, int level, const void *ctx)
{
  unsigned long long int_key = 0;
  uint64_t pxor;

  switch (key_type) {
  case CEB_KT_ADDR:
    int_key = (uintptr_t)node;
    break;
  case CEB_KT_U32:
    int_key = NODEK(node, kofs)->u32;
    break;
  case CEB_KT_U64:
    int_key = NODEK(node, kofs)->u64;
    break;
  default:
    break;
  }

  /* xor of the keys of the two lower branches */
  pxor = _xor_branches(kofs, key_type, 0, 0, NULL,
           node->b[0], node->b[1]);

  switch (key_type) {
  case CEB_KT_ADDR:
  case CEB_KT_U32:
  case CEB_KT_U64:
    if (node->b[0] == node->b[1])
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d\\nkey=%llu\\n\" fillcolor=\"green\"%s];\n",
             (long)node, (long)node, level, int_key, (ctx == node) ? " color=red" : "");
    else
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d bit=%d\\nkey=%llu\\n\" fillcolor=\"yellow\"%s];\n",
             (long)node, (long)node, level, flsnz(pxor) - 1, int_key, (ctx == node) ? " color=red" : "");
    break;
  case CEB_KT_MB:
    break;
  case CEB_KT_IM:
    break;
  case CEB_KT_ST:
    if (node->b[0] == node->b[1])
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d\\nkey=\\\"%s\\\"\\n\" fillcolor=\"green\"%s];\n",
             (long)node, (long)node, level, NODEK(node, kofs)->str, (ctx == node) ? " color=red" : "");
    else
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d bit=%ld\\nkey=\\\"%s\\\"\\n\" fillcolor=\"yellow\"%s];\n",
             (long)node, (long)node, level, (long)pxor, NODEK(node, kofs)->str, (ctx == node) ? " color=red" : "");
    break;
  case CEB_KT_IS:
    if (node->b[0] == node->b[1])
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d\\nkey=\\\"%s\\\"\\n\" fillcolor=\"green\"%s];\n",
             (long)node, (long)node, level, NODEK(node, kofs)->ptr, (ctx == node) ? " color=red" : "");
    else
      printf("  \"%lx_l\" [label=\"%lx\\nlev=%d bit=%ld\\nkey=\\\"%s\\\"\\n\" fillcolor=\"yellow\"%s];\n",
             (long)node, (long)node, level, (long)pxor, NODEK(node, kofs)->ptr, (ctx == node) ? " color=red" : "");
    break;
  }
}

/* Dumps a tree through the specified callbacks, falling back to the default
 * callbacks above if left NULL.
 */
__attribute__((unused))
static const struct ceb_node *cebu_default_dump_tree(ptrdiff_t kofs, enum ceb_key_type key_type, struct ceb_node *const *root,
                                                     uint64_t pxor, const void *last, int level, const void *ctx,
                                                     void (*root_dump)(ptrdiff_t kofs, enum ceb_key_type key_type, struct ceb_node *const *root, const void *ctx),
                                                     void (*node_dump)(ptrdiff_t kofs, enum ceb_key_type key_type, const struct ceb_node *node, int level, const void *ctx),
                                                     void (*leaf_dump)(ptrdiff_t kofs, enum ceb_key_type key_type, const struct ceb_node *node, int level, const void *ctx))
{
  const struct ceb_node *node = *root;
  uint64_t xor;

  if (!node) /* empty tree */
    return node;

  if (!root_dump)
    root_dump = cebu_default_dump_root;

  if (!node_dump)
    node_dump = cebu_default_dump_node;

  if (!leaf_dump)
    leaf_dump = cebu_default_dump_leaf;

  if (!level) {
    /* dump the first arrow */
    root_dump(kofs, key_type, root, ctx);
  }

  /* regular nodes, all branches are canonical */

  if (node->b[0] == node->b[1]) {
    /* first inserted leaf */
    leaf_dump(kofs, key_type, node, level, ctx);
    return node;
  }

  xor = _xor_branches(kofs, key_type, 0, 0, NULL,
          node->b[0], node->b[1]);

  switch (key_type) {
  case CEB_KT_ADDR:
  case CEB_KT_U32:
  case CEB_KT_U64:
    if (pxor && xor >= pxor) {
      /* that's a leaf for a scalar type */
      leaf_dump(kofs, key_type, node, level, ctx);
      return node;
    }
    break;
  default:
    if (pxor && xor <= pxor) {
      /* that's a leaf for a non-scalar type */
      leaf_dump(kofs, key_type, node, level, ctx);
      return node;
    }
    break;
  }

  /* that's a regular node */
  node_dump(kofs, key_type, node, level, ctx);

  last = cebu_default_dump_tree(kofs, key_type, &node->b[0], xor, last, level + 1, ctx, root_dump, node_dump, leaf_dump);
  return cebu_default_dump_tree(kofs, key_type, &node->b[1], xor, last, level + 1, ctx, root_dump, node_dump, leaf_dump);
}


#endif /* _CEBTREE_PRV_H */

Coverage Report

Created: 2025-08-28 06:25