Quelle assoc_array_priv.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Private definitions for the generic associative array implementation.
*
* See Documentation/core-api/assoc_array.rst for information.
*
* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/

#ifndef _LINUX_ASSOC_ARRAY_PRIV_H
#define _LINUX_ASSOC_ARRAY_PRIV_H

#ifdef CONFIG_ASSOCIATIVE_ARRAY

#include <linux/assoc_array.h>

#define ASSOC_ARRAY_FAN_OUT  16 /* Number of slots per node */
#define ASSOC_ARRAY_FAN_MASK  (ASSOC_ARRAY_FAN_OUT - 1)
#define ASSOC_ARRAY_LEVEL_STEP  (ilog2(ASSOC_ARRAY_FAN_OUT))
#define ASSOC_ARRAY_LEVEL_STEP_MASK (ASSOC_ARRAY_LEVEL_STEP - 1)
#define ASSOC_ARRAY_KEY_CHUNK_MASK (ASSOC_ARRAY_KEY_CHUNK_SIZE - 1)
#define ASSOC_ARRAY_KEY_CHUNK_SHIFT (ilog2(BITS_PER_LONG))

/*
* Undefined type representing a pointer with type information in the bottom
* two bits.
*/
struct assoc_array_ptr;

/*
* An N-way node in the tree.
*
* Each slot contains one of four things:
*
* (1) Nothing (NULL).
*
* (2) A leaf object (pointer types 0).
*
* (3) A next-level node (pointer type 1, subtype 0).
*
* (4) A shortcut (pointer type 1, subtype 1).
*
* The tree is optimised for search-by-ID, but permits reasonable iteration
* also.
*
* The tree is navigated by constructing an index key consisting of an array of
* segments, where each segment is ilog2(ASSOC_ARRAY_FAN_OUT) bits in size.
*
* The segments correspond to levels of the tree (the first segment is used at
* level 0, the second at level 1, etc.).
*/
struct assoc_array_node {
struct assoc_array_ptr *back_pointer;
u8   parent_slot;
struct assoc_array_ptr *slots[ASSOC_ARRAY_FAN_OUT];
unsigned long  nr_leaves_on_branch;
};

/*
* A shortcut through the index space out to where a collection of nodes/leaves
* with the same IDs live.
*/
struct assoc_array_shortcut {
struct assoc_array_ptr *back_pointer;
int   parent_slot;
int   skip_to_level;
struct assoc_array_ptr *next_node;
unsigned long  index_key[];
};

/*
* Preallocation cache.
*/
struct assoc_array_edit {
struct rcu_head   rcu;
struct assoc_array  *array;
const struct assoc_array_ops *ops;
const struct assoc_array_ops *ops_for_excised_subtree;
struct assoc_array_ptr  *leaf;
struct assoc_array_ptr  **leaf_p;
struct assoc_array_ptr  *dead_leaf;
struct assoc_array_ptr  *new_meta[3];
struct assoc_array_ptr  *excised_meta[1];
struct assoc_array_ptr  *excised_subtree;
struct assoc_array_ptr  **set_backpointers[ASSOC_ARRAY_FAN_OUT];
struct assoc_array_ptr  *set_backpointers_to;
struct assoc_array_node  *adjust_count_on;
long    adjust_count_by;
struct {
  struct assoc_array_ptr **ptr;
  struct assoc_array_ptr *to;
} set[2];
struct {
  u8   *p;
  u8   to;
} set_parent_slot[1];
u8    segment_cache[ASSOC_ARRAY_FAN_OUT + 1];
};

/*
* Internal tree member pointers are marked in the bottom one or two bits to
* indicate what type they are so that we don't have to look behind every
* pointer to see what it points to.
*
* We provide functions to test type annotations and to create and translate
* the annotated pointers.
*/
#define ASSOC_ARRAY_PTR_TYPE_MASK 0x1UL
#define ASSOC_ARRAY_PTR_LEAF_TYPE 0x0UL /* Points to leaf (or nowhere) */
#define ASSOC_ARRAY_PTR_META_TYPE 0x1UL /* Points to node or shortcut */
#define ASSOC_ARRAY_PTR_SUBTYPE_MASK 0x2UL
#define ASSOC_ARRAY_PTR_NODE_SUBTYPE 0x0UL
#define ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE 0x2UL

static inline bool assoc_array_ptr_is_meta(const struct assoc_array_ptr *x)
{
return (unsigned long)x & ASSOC_ARRAY_PTR_TYPE_MASK;
}
static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
{
return !assoc_array_ptr_is_meta(x);
}
static inline bool assoc_array_ptr_is_shortcut(const struct assoc_array_ptr *x)
{
return (unsigned long)x & ASSOC_ARRAY_PTR_SUBTYPE_MASK;
}
static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
{
return !assoc_array_ptr_is_shortcut(x);
}

static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
{
return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
}

static inline
unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
{
return (unsigned long)x &
  ~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
}
static inline
struct assoc_array_node *assoc_array_ptr_to_node(const struct assoc_array_ptr *x)
{
return (struct assoc_array_node *)__assoc_array_ptr_to_meta(x);
}
static inline
struct assoc_array_shortcut *assoc_array_ptr_to_shortcut(const struct assoc_array_ptr *x)
{
return (struct assoc_array_shortcut *)__assoc_array_ptr_to_meta(x);
}

static inline
struct assoc_array_ptr *__assoc_array_x_to_ptr(const void *p, unsigned long t)
{
return (struct assoc_array_ptr *)((unsigned long)p | t);
}
static inline
struct assoc_array_ptr *assoc_array_leaf_to_ptr(const void *p)
{
return __assoc_array_x_to_ptr(p, ASSOC_ARRAY_PTR_LEAF_TYPE);
}
static inline
struct assoc_array_ptr *assoc_array_node_to_ptr(const struct assoc_array_node *p)
{
return __assoc_array_x_to_ptr(
  p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_NODE_SUBTYPE);
}
static inline
struct assoc_array_ptr *assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut *p)
{
return __assoc_array_x_to_ptr(
  p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE);
}

#endif /* CONFIG_ASSOCIATIVE_ARRAY */
#endif /* _LINUX_ASSOC_ARRAY_PRIV_H */

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