2 * Copyright (C) 2004-2007, 2009, 2011, 2012 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1996-2001 Internet Software Consortium.
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
11 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
15 * PERFORMANCE OF THIS SOFTWARE.
21 #define ISC_SYMTAB_H 1
27 /*! \file isc/symtab.h
28 * \brief Provides a simple memory-based symbol table.
30 * Keys are C strings, and key comparisons are case-insensitive. A type may
31 * be specified when looking up, defining, or undefining. A type value of
32 * 0 means "match any type"; any other value will only match the given
35 * It's possible that a client will attempt to define a <key, type, value>
36 * tuple when a tuple with the given key and type already exists in the table.
37 * What to do in this case is specified by the client. Possible policies are:
39 *\li #isc_symexists_reject Disallow the define, returning #ISC_R_EXISTS
40 *\li #isc_symexists_replace Replace the old value with the new. The
41 * undefine action (if provided) will be called
42 * with the old <key, type, value> tuple.
43 *\li #isc_symexists_add Add the new tuple, leaving the old tuple in
44 * the table. Subsequent lookups will retrieve
45 * the most-recently-defined tuple.
47 * A lookup of a key using type 0 will return the most-recently defined
48 * symbol with that key. An undefine of a key using type 0 will undefine the
49 * most-recently defined symbol with that key. Trying to define a key with
52 * The symbol table library does not make a copy the key field, so the
53 * caller must ensure that any key it passes to isc_symtab_define() will not
54 * change until it calls isc_symtab_undefine() or isc_symtab_destroy().
56 * A user-specified action will be called (if provided) when a symbol is
57 * undefined. It can be used to free memory associated with keys and/or
60 * A symbol table is implemented as a hash table of lists; the size of the
61 * hash table is set by the 'size' parameter to isc_symtbl_create(). When
62 * the number of entries in the symbol table reaches three quarters of this
63 * value, the hash table is reallocated with size doubled, in order to
64 * optimize lookup performance. This has a negative effect on insertion
65 * performance, which can be mitigated by sizing the table appropriately
69 * The callers of this module must ensure any required synchronization.
72 * No anticipated impact.
78 * No anticipated impact.
89 #include <isc/types.h>
94 /*% Symbol table value. */
95 typedef union isc_symvalue {
97 const void * as_cpointer;
99 unsigned int as_uinteger;
102 typedef void (*isc_symtabaction_t)(char *key, unsigned int type,
103 isc_symvalue_t value, void *userarg);
104 /*% Symbol table exists. */
106 isc_symexists_reject = 0, /*%< Disallow the define */
107 isc_symexists_replace = 1, /*%< Replace the old value with the new */
108 isc_symexists_add = 2 /*%< Add the new tuple */
113 /*% Create a symbol table. */
115 isc_symtab_create(isc_mem_t *mctx, unsigned int size,
116 isc_symtabaction_t undefine_action, void *undefine_arg,
117 isc_boolean_t case_sensitive, isc_symtab_t **symtabp);
119 /*% Destroy a symbol table. */
121 isc_symtab_destroy(isc_symtab_t **symtabp);
123 /*% Lookup a symbol table. */
125 isc_symtab_lookup(isc_symtab_t *symtab, const char *key, unsigned int type,
126 isc_symvalue_t *value);
128 /*% Define a symbol table. */
130 isc_symtab_define(isc_symtab_t *symtab, const char *key, unsigned int type,
131 isc_symvalue_t value, isc_symexists_t exists_policy);
133 /*% Undefine a symbol table. */
135 isc_symtab_undefine(isc_symtab_t *symtab, const char *key, unsigned int type);
139 #endif /* ISC_SYMTAB_H */