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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>
54 lines
1.1 KiB
C
54 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Implementation of the symbol table type.
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*
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* Author : Stephen Smalley, <sds@tycho.nsa.gov>
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*/
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include "symtab.h"
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static unsigned int symhash(const void *key)
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{
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const char *p, *keyp;
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unsigned int size;
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unsigned int val;
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val = 0;
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keyp = key;
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size = strlen(keyp);
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for (p = keyp; (p - keyp) < size; p++)
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val = (val << 4 | (val >> (8*sizeof(unsigned int)-4))) ^ (*p);
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return val;
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}
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static int symcmp(const void *key1, const void *key2)
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{
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const char *keyp1, *keyp2;
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keyp1 = key1;
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keyp2 = key2;
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return strcmp(keyp1, keyp2);
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}
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static const struct hashtab_key_params symtab_key_params = {
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.hash = symhash,
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.cmp = symcmp,
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};
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int symtab_init(struct symtab *s, unsigned int size)
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{
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s->nprim = 0;
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return hashtab_init(&s->table, size);
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}
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int symtab_insert(struct symtab *s, char *name, void *datum)
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{
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return hashtab_insert(&s->table, name, datum, symtab_key_params);
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}
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void *symtab_search(struct symtab *s, const char *name)
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{
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return hashtab_search(&s->table, name, symtab_key_params);
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}
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