add isc_random_t, and all the isc_random_*() function to use it. Right now it is

a pretty empty type, but it would be good to flesh it out so each random state
will be separated from one another.  Right now they all just lock
around rand(), which isn't perfect, but good enough for what I need
today.

lib/isc/random.c

@@ -0,0 +1,97 @@
+/*
+ * Wrapper around the ANSI rand() function.
+ */
+#include <config.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <isc/assertions.h>
+#include <isc/mutex.h>
+#include <isc/once.h>
+#include <isc/random.h>
+
+#include "util.h"
+
+static isc_once_t once = ISC_ONCE_INIT;
+static isc_mutex_t rand_lock;
+
+static void
+initialize_rand(void)
+{
+	RUNTIME_CHECK(isc_mutex_init(&rand_lock) == ISC_R_SUCCESS);
+}
+
+static void
+initialize(void)
+{
+	RUNTIME_CHECK(isc_once_do(&once, initialize_rand) == ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_random_init(isc_random_t *r)
+{
+	REQUIRE(r != NULL);
+
+	r->magic = ISC_RANDOM_MAGIC;
+#if 0
+	return (isc_mutex_init(&r->lock));
+#else
+	return (ISC_R_SUCCESS);
+#endif
+}
+
+isc_result_t
+isc_random_invalidate(isc_random_t *r)
+{
+	isc_result_t result;
+
+	REQUIRE(ISC_RANDOM_VALID(r));
+
+#if 0
+	result = isc_mutex_destroy(&r->lock);
+#else
+	result = ISC_R_SUCCESS;
+#endif
+
+	memset(r, 0, sizeof(isc_random_t));
+
+	return (result);
+}
+
+void
+isc_random_seed(isc_random_t *r, isc_uint32_t seed)
+{
+	REQUIRE(ISC_RANDOM_VALID(r));
+
+	initialize();
+
+#if 0
+	LOCK(&r->lock);
+#endif
+	LOCK(&rand_lock);
+	srand(seed);
+	UNLOCK(&rand_lock);
+#if 0
+	UNLOCK(&r->lock);
+#endif
+}
+
+void
+isc_random_get(isc_random_t *r, isc_uint32_t *val)
+{
+	REQUIRE(ISC_RANDOM_VALID(r));
+	REQUIRE(val != NULL);
+
+	initialize();
+
+#if 0
+	LOCK(&r->lock);
+#endif
+	LOCK(&rand_lock);
+	*val = rand();
+	UNLOCK(&rand_lock);
+#if 0
+	UNLOCK(&r->lock);
+#endif
+}