Imported Upstream version 4.8.0.309

Former-commit-id: 5f9c6ae75f295e057a7d2971f3a6df4656fa8850

external/boringssl/crypto/refcount_c11.c

@@ -0,0 +1,67 @@
+/* Copyright (c) 2015, Google Inc.
+ *
+ * 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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 "internal.h"
+
+
+#if defined(OPENSSL_C11_ATOMIC)
+
+#include <assert.h>
+#include <stdalign.h>
+#include <stdatomic.h>
+#include <stdlib.h>
+
+#include <openssl/type_check.h>
+
+
+/* See comment above the typedef of CRYPTO_refcount_t about these tests. */
+static_assert(alignof(CRYPTO_refcount_t) == alignof(_Atomic CRYPTO_refcount_t),
+              "_Atomic alters the needed alignment of a reference count");
+static_assert(sizeof(CRYPTO_refcount_t) == sizeof(_Atomic CRYPTO_refcount_t),
+              "_Atomic alters the size of a reference count");
+
+static_assert((CRYPTO_refcount_t)-1 == CRYPTO_REFCOUNT_MAX,
+              "CRYPTO_REFCOUNT_MAX is incorrect");
+
+void CRYPTO_refcount_inc(CRYPTO_refcount_t *in_count) {
+  _Atomic CRYPTO_refcount_t *count = (_Atomic CRYPTO_refcount_t *) in_count;
+  uint32_t expected = atomic_load(count);
+
+  while (expected != CRYPTO_REFCOUNT_MAX) {
+    uint32_t new_value = expected + 1;
+    if (atomic_compare_exchange_weak(count, &expected, new_value)) {
+      break;
+    }
+  }
+}
+
+int CRYPTO_refcount_dec_and_test_zero(CRYPTO_refcount_t *in_count) {
+  _Atomic CRYPTO_refcount_t *count = (_Atomic CRYPTO_refcount_t *)in_count;
+  uint32_t expected = atomic_load(count);
+
+  for (;;) {
+    if (expected == 0) {
+      abort();
+    } else if (expected == CRYPTO_REFCOUNT_MAX) {
+      return 0;
+    } else {
+      const uint32_t new_value = expected - 1;
+      if (atomic_compare_exchange_weak(count, &expected, new_value)) {
+        return new_value == 0;
+      }
+    }
+  }
+}
+
+#endif  /* OPENSSL_C11_ATOMIC */