refcount.h revision 290001
1/* 2 * Copyright (C) 2004-2007, 2009 Internet Systems Consortium, Inc. ("ISC") 3 * Copyright (C) 2001, 2003 Internet Software Consortium. 4 * 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. 8 * 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. 16 */ 17 18/* $Id: refcount.h,v 1.17 2009/09/29 23:48:04 tbox Exp $ */ 19 20#ifndef ISC_REFCOUNT_H 21#define ISC_REFCOUNT_H 1 22 23#include <isc/atomic.h> 24#include <isc/lang.h> 25#include <isc/mutex.h> 26#include <isc/platform.h> 27#include <isc/types.h> 28#include <isc/util.h> 29 30/*! \file isc/refcount.h 31 * \brief Implements a locked reference counter. 32 * 33 * These functions may actually be 34 * implemented using macros, and implementations of these macros are below. 35 * The isc_refcount_t type should not be accessed directly, as its contents 36 * depend on the implementation. 37 */ 38 39ISC_LANG_BEGINDECLS 40 41/* 42 * Function prototypes 43 */ 44 45/* 46 * isc_result_t 47 * isc_refcount_init(isc_refcount_t *ref, unsigned int n); 48 * 49 * Initialize the reference counter. There will be 'n' initial references. 50 * 51 * Requires: 52 * ref != NULL 53 */ 54 55/* 56 * void 57 * isc_refcount_destroy(isc_refcount_t *ref); 58 * 59 * Destroys a reference counter. 60 * 61 * Requires: 62 * ref != NULL 63 * The number of references is 0. 64 */ 65 66/* 67 * void 68 * isc_refcount_increment(isc_refcount_t *ref, unsigned int *targetp); 69 * isc_refcount_increment0(isc_refcount_t *ref, unsigned int *targetp); 70 * 71 * Increments the reference count, returning the new value in targetp if it's 72 * not NULL. The reference counter typically begins with the initial counter 73 * of 1, and will be destroyed once the counter reaches 0. Thus, 74 * isc_refcount_increment() additionally requires the previous counter be 75 * larger than 0 so that an error which violates the usage can be easily 76 * caught. isc_refcount_increment0() does not have this restriction. 77 * 78 * Requires: 79 * ref != NULL. 80 */ 81 82/* 83 * void 84 * isc_refcount_decrement(isc_refcount_t *ref, unsigned int *targetp); 85 * 86 * Decrements the reference count, returning the new value in targetp if it's 87 * not NULL. 88 * 89 * Requires: 90 * ref != NULL. 91 */ 92 93 94/* 95 * Sample implementations 96 */ 97#ifdef ISC_PLATFORM_USETHREADS 98#ifdef ISC_PLATFORM_HAVEXADD 99 100#define ISC_REFCOUNT_HAVEATOMIC 1 101 102typedef struct isc_refcount { 103 isc_int32_t refs; 104} isc_refcount_t; 105 106#define isc_refcount_destroy(rp) REQUIRE((rp)->refs == 0) 107#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) 108 109#define isc_refcount_increment0(rp, tp) \ 110 do { \ 111 unsigned int *_tmp = (unsigned int *)(tp); \ 112 isc_int32_t prev; \ 113 prev = isc_atomic_xadd(&(rp)->refs, 1); \ 114 if (_tmp != NULL) \ 115 *_tmp = prev + 1; \ 116 } while (0) 117 118#define isc_refcount_increment(rp, tp) \ 119 do { \ 120 unsigned int *_tmp = (unsigned int *)(tp); \ 121 isc_int32_t prev; \ 122 prev = isc_atomic_xadd(&(rp)->refs, 1); \ 123 REQUIRE(prev > 0); \ 124 if (_tmp != NULL) \ 125 *_tmp = prev + 1; \ 126 } while (0) 127 128#define isc_refcount_decrement(rp, tp) \ 129 do { \ 130 unsigned int *_tmp = (unsigned int *)(tp); \ 131 isc_int32_t prev; \ 132 prev = isc_atomic_xadd(&(rp)->refs, -1); \ 133 REQUIRE(prev > 0); \ 134 if (_tmp != NULL) \ 135 *_tmp = prev - 1; \ 136 } while (0) 137 138#else /* ISC_PLATFORM_HAVEXADD */ 139 140typedef struct isc_refcount { 141 int refs; 142 isc_mutex_t lock; 143} isc_refcount_t; 144 145/*% Destroys a reference counter. */ 146#define isc_refcount_destroy(rp) \ 147 do { \ 148 REQUIRE((rp)->refs == 0); \ 149 DESTROYLOCK(&(rp)->lock); \ 150 } while (0) 151 152#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) 153 154/*% Increments the reference count, returning the new value in targetp if it's not NULL. */ 155#define isc_refcount_increment0(rp, tp) \ 156 do { \ 157 unsigned int *_tmp = (unsigned int *)(tp); \ 158 LOCK(&(rp)->lock); \ 159 ++((rp)->refs); \ 160 if (_tmp != NULL) \ 161 *_tmp = ((rp)->refs); \ 162 UNLOCK(&(rp)->lock); \ 163 } while (0) 164 165#define isc_refcount_increment(rp, tp) \ 166 do { \ 167 unsigned int *_tmp = (unsigned int *)(tp); \ 168 LOCK(&(rp)->lock); \ 169 REQUIRE((rp)->refs > 0); \ 170 ++((rp)->refs); \ 171 if (_tmp != NULL) \ 172 *_tmp = ((rp)->refs); \ 173 UNLOCK(&(rp)->lock); \ 174 } while (0) 175 176/*% Decrements the reference count, returning the new value in targetp if it's not NULL. */ 177#define isc_refcount_decrement(rp, tp) \ 178 do { \ 179 unsigned int *_tmp = (unsigned int *)(tp); \ 180 LOCK(&(rp)->lock); \ 181 REQUIRE((rp)->refs > 0); \ 182 --((rp)->refs); \ 183 if (_tmp != NULL) \ 184 *_tmp = ((rp)->refs); \ 185 UNLOCK(&(rp)->lock); \ 186 } while (0) 187 188#endif /* ISC_PLATFORM_HAVEXADD */ 189#else /* ISC_PLATFORM_USETHREADS */ 190 191typedef struct isc_refcount { 192 int refs; 193} isc_refcount_t; 194 195#define isc_refcount_destroy(rp) REQUIRE((rp)->refs == 0) 196#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) 197 198#define isc_refcount_increment0(rp, tp) \ 199 do { \ 200 unsigned int *_tmp = (unsigned int *)(tp); \ 201 int _n = ++(rp)->refs; \ 202 if (_tmp != NULL) \ 203 *_tmp = _n; \ 204 } while (0) 205 206#define isc_refcount_increment(rp, tp) \ 207 do { \ 208 unsigned int *_tmp = (unsigned int *)(tp); \ 209 int _n; \ 210 REQUIRE((rp)->refs > 0); \ 211 _n = ++(rp)->refs; \ 212 if (_tmp != NULL) \ 213 *_tmp = _n; \ 214 } while (0) 215 216#define isc_refcount_decrement(rp, tp) \ 217 do { \ 218 unsigned int *_tmp = (unsigned int *)(tp); \ 219 int _n; \ 220 REQUIRE((rp)->refs > 0); \ 221 _n = --(rp)->refs; \ 222 if (_tmp != NULL) \ 223 *_tmp = _n; \ 224 } while (0) 225 226#endif /* ISC_PLATFORM_USETHREADS */ 227 228isc_result_t 229isc_refcount_init(isc_refcount_t *ref, unsigned int n); 230 231ISC_LANG_ENDDECLS 232 233#endif /* ISC_REFCOUNT_H */ 234