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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef ISC_SYMTAB_H
#define ISC_SYMTAB_H 1
/*****
***** Module Info
*****/
/*! \file isc/symtab.h
* \brief Provides a simple memory-based symbol table.
*
* Keys are C strings, and key comparisons are case-insensitive. A type may
* be specified when looking up, defining, or undefining. A type value of
* 0 means "match any type"; any other value will only match the given
* type.
*
* It's possible that a client will attempt to define a <key, type, value>
* tuple when a tuple with the given key and type already exists in the table.
* What to do in this case is specified by the client. Possible policies are:
*
*\li #isc_symexists_reject Disallow the define, returning #ISC_R_EXISTS
*\li #isc_symexists_replace Replace the old value with the new. The
* undefine action (if provided) will be called
* with the old <key, type, value> tuple.
*\li #isc_symexists_add Add the new tuple, leaving the old tuple in
* the table. Subsequent lookups will retrieve
* the most-recently-defined tuple.
*
* A lookup of a key using type 0 will return the most-recently defined
* symbol with that key. An undefine of a key using type 0 will undefine the
* most-recently defined symbol with that key. Trying to define a key with
* type 0 is illegal.
*
* The symbol table library does not make a copy the key field, so the
* caller must ensure that any key it passes to isc_symtab_define() will not
* change until it calls isc_symtab_undefine() or isc_symtab_destroy().
*
* A user-specified action will be called (if provided) when a symbol is
* undefined. It can be used to free memory associated with keys and/or
* values.
*
* A symbol table is implemented as a hash table of lists; the size of the
* hash table is set by the 'size' parameter to isc_symtbl_create(). When
* the number of entries in the symbol table reaches three quarters of this
* value, the hash table is reallocated with size doubled, in order to
* optimize lookup performance. This has a negative effect on insertion
* performance, which can be mitigated by sizing the table appropriately
* when creating it.
*
* \li MP:
* The callers of this module must ensure any required synchronization.
*
* \li Reliability:
* No anticipated impact.
*
* \li Resources:
* TBS
*
* \li Security:
* No anticipated impact.
*
* \li Standards:
* None.
*/
/***
*** Imports.
***/
#include <stdbool.h>
#include <isc/lang.h>
#include <isc/types.h>
/*
*** Symbol Tables.
***/
/*% Symbol table value. */
typedef union isc_symvalue {
void * as_pointer;
const void * as_cpointer;
int as_integer;
unsigned int as_uinteger;
} isc_symvalue_t;
typedef void (*isc_symtabaction_t)(char *key, unsigned int type,
isc_symvalue_t value, void *userarg);
/*% Symbol table exists. */
typedef enum {
isc_symexists_reject = 0, /*%< Disallow the define */
isc_symexists_replace = 1, /*%< Replace the old value with the new */
isc_symexists_add = 2 /*%< Add the new tuple */
} isc_symexists_t;
ISC_LANG_BEGINDECLS
/*% Create a symbol table. */
isc_result_t
isc_symtab_create(isc_mem_t *mctx, unsigned int size,
isc_symtabaction_t undefine_action, void *undefine_arg,
bool case_sensitive, isc_symtab_t **symtabp);
/*% Destroy a symbol table. */
void
isc_symtab_destroy(isc_symtab_t **symtabp);
/*% Lookup a symbol table. */
isc_result_t
isc_symtab_lookup(isc_symtab_t *symtab, const char *key, unsigned int type,
isc_symvalue_t *value);
/*% Define a symbol table. */
isc_result_t
isc_symtab_define(isc_symtab_t *symtab, const char *key, unsigned int type,
isc_symvalue_t value, isc_symexists_t exists_policy);
/*% Undefine a symbol table. */
isc_result_t
isc_symtab_undefine(isc_symtab_t *symtab, const char *key, unsigned int type);
/*% Return the number of items in a symbol table. */
unsigned int
isc_symtab_count(isc_symtab_t *symtab);
ISC_LANG_ENDDECLS
#endif /* ISC_SYMTAB_H */
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