24def7bb92
Refactor searching and inserting into hashtabs to pave the way for converting hashtab_search() and hashtab_insert() to inline functions in the next patch. This will avoid indirect calls and allow the compiler to better optimize individual callers, leading to a significant performance improvement. In order to avoid the indirect calls, the key hashing and comparison callbacks need to be extracted from the hashtab struct and passed directly to hashtab_search()/_insert() by the callers so that the callback address is always known at compile time. The kernel's rhashtable library (<linux/rhashtable*.h>) does the same thing. This of course makes the hashtab functions slightly easier to misuse by passing a wrong callback set, but unfortunately there is no better way to implement a hash table that is both generic and efficient in C. This patch tries to somewhat mitigate this by only calling the hashtab functions in the same file where the corresponding callbacks are defined (wrapping them into more specialized functions as needed). Note that this patch doesn't bring any benefit without also moving the definitions of hashtab_search() and -_insert() to the header file, which is done in a follow-up patch for easier review of the hashtab.c changes in this patch. Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com> Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
90 lines
2.4 KiB
C
90 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* A hash table (hashtab) maintains associations between
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* key values and datum values. The type of the key values
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* and the type of the datum values is arbitrary. The
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* functions for hash computation and key comparison are
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* provided by the creator of the table.
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*
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* Author : Stephen Smalley, <sds@tycho.nsa.gov>
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*/
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#ifndef _SS_HASHTAB_H_
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#define _SS_HASHTAB_H_
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#define HASHTAB_MAX_NODES 0xffffffff
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struct hashtab_key_params {
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u32 (*hash)(const void *key); /* hash function */
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int (*cmp)(const void *key1, const void *key2);
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/* key comparison function */
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};
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struct hashtab_node {
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void *key;
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void *datum;
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struct hashtab_node *next;
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};
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struct hashtab {
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struct hashtab_node **htable; /* hash table */
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u32 size; /* number of slots in hash table */
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u32 nel; /* number of elements in hash table */
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};
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struct hashtab_info {
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u32 slots_used;
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u32 max_chain_len;
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};
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/*
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* Initializes a new hash table with the specified characteristics.
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*
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* Returns -ENOMEM if insufficient space is available or 0 otherwise.
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*/
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int hashtab_init(struct hashtab *h, u32 nel_hint);
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/*
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* Inserts the specified (key, datum) pair into the specified hash table.
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*
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* Returns -ENOMEM on memory allocation error,
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* -EEXIST if there is already an entry with the same key,
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* -EINVAL for general errors or
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0 otherwise.
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*/
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int hashtab_insert(struct hashtab *h, void *k, void *d,
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struct hashtab_key_params key_params);
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/*
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* Searches for the entry with the specified key in the hash table.
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*
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* Returns NULL if no entry has the specified key or
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* the datum of the entry otherwise.
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*/
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void *hashtab_search(struct hashtab *h, const void *k,
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struct hashtab_key_params key_params);
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/*
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* Destroys the specified hash table.
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*/
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void hashtab_destroy(struct hashtab *h);
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/*
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* Applies the specified apply function to (key,datum,args)
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* for each entry in the specified hash table.
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*
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* The order in which the function is applied to the entries
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* is dependent upon the internal structure of the hash table.
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*
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* If apply returns a non-zero status, then hashtab_map will cease
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* iterating through the hash table and will propagate the error
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* return to its caller.
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*/
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int hashtab_map(struct hashtab *h,
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int (*apply)(void *k, void *d, void *args),
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void *args);
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/* Fill info with some hash table statistics */
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void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
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#endif /* _SS_HASHTAB_H */
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