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Diffstat (limited to 'lib/isc/include/isc/refcount.h')
| -rw-r--r-- | lib/isc/include/isc/refcount.h | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/lib/isc/include/isc/refcount.h b/lib/isc/include/isc/refcount.h new file mode 100644 index 0000000..6ab14ae --- /dev/null +++ b/lib/isc/include/isc/refcount.h @@ -0,0 +1,233 @@ +/* + * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC") + * Copyright (C) 2001, 2003 Internet Software Consortium. + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH + * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY + * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, + * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM + * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE + * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR + * PERFORMANCE OF THIS SOFTWARE. + */ + +/* $Id: refcount.h,v 1.15 2007/06/19 23:47:18 tbox Exp $ */ + +#ifndef ISC_REFCOUNT_H +#define ISC_REFCOUNT_H 1 + +#include <isc/atomic.h> +#include <isc/lang.h> +#include <isc/mutex.h> +#include <isc/platform.h> +#include <isc/types.h> +#include <isc/util.h> + +/*! \file isc/refcount.h + * \brief Implements a locked reference counter. + * + * These functions may actually be + * implemented using macros, and implementations of these macros are below. + * The isc_refcount_t type should not be accessed directly, as its contents + * depend on the implementation. + */ + +ISC_LANG_BEGINDECLS + +/* + * Function prototypes + */ + +/* + * isc_result_t + * isc_refcount_init(isc_refcount_t *ref, unsigned int n); + * + * Initialize the reference counter. There will be 'n' initial references. + * + * Requires: + * ref != NULL + */ + +/* + * void + * isc_refcount_destroy(isc_refcount_t *ref); + * + * Destroys a reference counter. + * + * Requires: + * ref != NULL + * The number of references is 0. + */ + +/* + * void + * isc_refcount_increment(isc_refcount_t *ref, unsigned int *targetp); + * isc_refcount_increment0(isc_refcount_t *ref, unsigned int *targetp); + * + * Increments the reference count, returning the new value in targetp if it's + * not NULL. The reference counter typically begins with the initial counter + * of 1, and will be destroyed once the counter reaches 0. Thus, + * isc_refcount_increment() additionally requires the previous counter be + * larger than 0 so that an error which violates the usage can be easily + * caught. isc_refcount_increment0() does not have this restriction. + * + * Requires: + * ref != NULL. + */ + +/* + * void + * isc_refcount_decrement(isc_refcount_t *ref, unsigned int *targetp); + * + * Decrements the reference count, returning the new value in targetp if it's + * not NULL. + * + * Requires: + * ref != NULL. + */ + + +/* + * Sample implementations + */ +#ifdef ISC_PLATFORM_USETHREADS +#ifdef ISC_PLATFORM_HAVEXADD + +#define ISC_REFCOUNT_HAVEATOMIC 1 + +typedef struct isc_refcount { + isc_int32_t refs; +} isc_refcount_t; + +#define isc_refcount_destroy(rp) (REQUIRE((rp)->refs == 0)) +#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) + +#define isc_refcount_increment0(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + isc_int32_t prev; \ + prev = isc_atomic_xadd(&(rp)->refs, 1); \ + if (_tmp != NULL) \ + *_tmp = prev + 1; \ + } while (0) + +#define isc_refcount_increment(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + isc_int32_t prev; \ + prev = isc_atomic_xadd(&(rp)->refs, 1); \ + REQUIRE(prev > 0); \ + if (_tmp != NULL) \ + *_tmp = prev + 1; \ + } while (0) + +#define isc_refcount_decrement(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + isc_int32_t prev; \ + prev = isc_atomic_xadd(&(rp)->refs, -1); \ + REQUIRE(prev > 0); \ + if (_tmp != NULL) \ + *_tmp = prev - 1; \ + } while (0) + +#else /* ISC_PLATFORM_HAVEXADD */ + +typedef struct isc_refcount { + int refs; + isc_mutex_t lock; +} isc_refcount_t; + +/*% Destroys a reference counter. */ +#define isc_refcount_destroy(rp) \ + do { \ + REQUIRE((rp)->refs == 0); \ + DESTROYLOCK(&(rp)->lock); \ + } while (0) + +#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) + +/*% Increments the reference count, returning the new value in targetp if it's not NULL. */ +#define isc_refcount_increment0(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + LOCK(&(rp)->lock); \ + ++((rp)->refs); \ + if (_tmp != NULL) \ + *_tmp = ((rp)->refs); \ + UNLOCK(&(rp)->lock); \ + } while (0) + +#define isc_refcount_increment(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + LOCK(&(rp)->lock); \ + REQUIRE((rp)->refs > 0); \ + ++((rp)->refs); \ + if (_tmp != NULL) \ + *_tmp = ((rp)->refs); \ + UNLOCK(&(rp)->lock); \ + } while (0) + +/*% Decrements the reference count, returning the new value in targetp if it's not NULL. */ +#define isc_refcount_decrement(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + LOCK(&(rp)->lock); \ + REQUIRE((rp)->refs > 0); \ + --((rp)->refs); \ + if (_tmp != NULL) \ + *_tmp = ((rp)->refs); \ + UNLOCK(&(rp)->lock); \ + } while (0) + +#endif /* ISC_PLATFORM_HAVEXADD */ +#else /* ISC_PLATFORM_USETHREADS */ + +typedef struct isc_refcount { + int refs; +} isc_refcount_t; + +#define isc_refcount_destroy(rp) (REQUIRE((rp)->refs == 0)) +#define isc_refcount_current(rp) ((unsigned int)((rp)->refs)) + +#define isc_refcount_increment0(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + int _n = ++(rp)->refs; \ + if (_tmp != NULL) \ + *_tmp = _n; \ + } while (0) + +#define isc_refcount_increment(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + int _n; \ + REQUIRE((rp)->refs > 0); \ + _n = ++(rp)->refs; \ + if (_tmp != NULL) \ + *_tmp = _n; \ + } while (0) + +#define isc_refcount_decrement(rp, tp) \ + do { \ + unsigned int *_tmp = (unsigned int *)(tp); \ + int _n; \ + REQUIRE((rp)->refs > 0); \ + _n = --(rp)->refs; \ + if (_tmp != NULL) \ + *_tmp = _n; \ + } while (0) + +#endif /* ISC_PLATFORM_USETHREADS */ + +isc_result_t +isc_refcount_init(isc_refcount_t *ref, unsigned int n); + +ISC_LANG_ENDDECLS + +#endif /* ISC_REFCOUNT_H */ |