new type isc_quota_t, for client (and other) quotas

lib/isc/Makefile.in

@@ -47,7 +47,7 @@ OBJS =		@ISC_EXTRA_OBJS@ \
 		assertions.@O@ base64.@O@ bitstring.@O@ buffer.@O@ \
 		bufferlist.@O@ commandline.@O@ error.@O@ event.@O@ heap.@O@ \
 		lex.@O@ lfsr.@O@ lib.@O@ log.@O@ \
-		mem.@O@ mutexblock.@O@ random.@O@ \
+		mem.@O@ mutexblock.@O@ quota.@O@ random.@O@ \
 		ratelimiter.@O@ result.@O@ rwlock.@O@ \
 		serial.@O@ sockaddr.@O@ str.@O@ symtab.@O@ \
 		task.@O@ taskpool.@O@ timer.@O@ version.@O@ \
@@ -58,7 +58,7 @@ SRCS =		@ISC_EXTRA_SRCS@ \
 		assertions.c base64.c bitstring.c buffer.c \
 		bufferlist.c commandline.c error.c event.c heap.c \
 		lex.c lfsr.c lib.c log.c \
-		mem.c mutexblock.c random.c \
+		mem.c mutexblock.c quota.c random.c \
 		ratelimiter.c result.c rwlock.c \
 		serial.c sockaddr.c str.c symtab.c \
 		task.c taskpool.c timer.c version.c

lib/isc/include/isc/quota.h

+/*
+ * Copyright (C) 2000  Internet Software Consortium.
+ * 
+ * Permission to use, copy, modify, and 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM 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.
+ */
+
+#ifndef ISC_QUOTA_H
+#define ISC_QUOTA_H 1
+
+/*****
+ ***** Module Info
+ *****/
+
+/*
+ * Quota
+ *
+ * The isc_quota_t object is a simple helper object for implementing
+ * quotas on things like the number of simultaneous connections to
+ * a server.  It keeps track of the amount of quota in use, and
+ * encapsulates the locking necessary to allow multiple tasks to
+ * share a quota.
+ */
+
+/***
+ *** Imports.
+ ***/
+
+#include <isc/mutex.h>
+#include <isc/result.h>
+
+
+/*****
+ ***** Types.
+ *****/
+
+ISC_LANG_BEGINDECLS
+
+typedef struct isc_quota isc_quota_t;
+
+struct isc_quota {
+	isc_mutex_t	lock;
+	/* Locked by lock. */
+	int 		max;
+	int 		used;
+};
+
+isc_result_t
+isc_quota_init(isc_quota_t *quota, int max);
+/*
+ * Initialize a quota object. 
+ *
+ * Returns:
+ * 	ISC_R_SUCCESS
+ *	Other error	Lock creation failed.
+ */
+
+void
+isc_quota_destroy(isc_quota_t *quota);
+/*
+ * Destroy a quota object.
+ */
+
+isc_result_t
+isc_quota_reserve(isc_quota_t *quota);
+/*
+ * Attempt to reserve one unit of 'quota'.
+ *
+ * Returns:
+ * 	ISC_R_SUCCESS	Success
+ *	ISC_R_QUOTA	Quota is full
+ */
+
+void
+isc_quota_release(isc_quota_t *quota);
+/*
+ * Release one unit of quota.
+ */
+
+ISC_LANG_ENDDECLS
+
+#endif /* ISC_QUOTA_H */

lib/isc/quota.c

+/*
+ * Copyright (C) 2000  Internet Software Consortium.
+ * 
+ * Permission to use, copy, modify, and 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM 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.
+ */
+
+#include <isc/assertions.h>
+#include <isc/quota.h>
+#include <isc/util.h>
+
+isc_result_t
+isc_quota_init(isc_quota_t *quota, int max) {
+	quota->max = max;
+	quota->used = 0;
+	return (isc_mutex_init(&quota->lock));
+}
+
+void
+isc_quota_destroy(isc_quota_t *quota) {
+	quota->max = -1;
+	quota->used = -1;
+	RUNTIME_CHECK(isc_mutex_destroy(&quota->lock) == ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_quota_reserve(isc_quota_t *quota) {
+	isc_result_t result;
+	LOCK(&quota->lock);
+	if (quota->used < quota->max) {
+		quota->used++;
+		result = ISC_R_SUCCESS;
+	} else {
+		result = ISC_R_QUOTA;
+	}
+	UNLOCK(&quota->lock);
+	return (result);
+}
+
+void
+isc_quota_release(isc_quota_t *quota) {
+	LOCK(&quota->lock);
+	INSIST(quota->used > 0);
+	quota->used--;
+	UNLOCK(&quota->lock);	
+}
+
+

util/copyrights

@@ -567,6 +567,7 @@
 ./lib/isc/include/isc/netaddr.h			C	1998,1999
 ./lib/isc/include/isc/platform.h.in		C	1999
 ./lib/isc/include/isc/print.h			C	1999
+./lib/isc/include/isc/quota.h			C	2000
 ./lib/isc/include/isc/random.h			C	1999
 ./lib/isc/include/isc/ratelimiter.h		C	1999
 ./lib/isc/include/isc/rbtgen.h			C	1998,1999
@@ -607,6 +608,7 @@
 ./lib/isc/pthreads/include/isc/mutex.h		C	1998,1999
 ./lib/isc/pthreads/include/isc/once.h		C	1999
 ./lib/isc/pthreads/include/isc/thread.h		C	1998,1999
+./lib/isc/quota.c				C	2000
 ./lib/isc/random.c				C	1999
 ./lib/isc/ratelimiter.c				C	1999
 ./lib/isc/rbtgen.c				C	1998,1999