Add platform detection logic for SecureRandom (#676)

* Add CMake platform detection logic for SecureRandom

Now only builds secure_random_arc4random.cc if available.

Remove firebase/firestore/base/port.h. Nothing else was in that
directory.

* Add a SecureRandom implementation that uses OpenSSL

This is usable on Linux, Windows, and Android

* Properly check return from RAND_bytes

1 files changed, 35 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/util/config.h.in b/Firestore/core/src/firebase/firestore/util/config.h.in
new file mode 100644
index 0000000..e7a0c03
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/config.h.in
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_CONFIG_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_CONFIG_H_
+
+// This header defines macros for all available platform configuration values.
+// When building with CMake, it will substitute the lines marked with
+// cmakedefine with values corresponding to the local configuration.
+//
+// On Apple platforms we support building via CocoaPods without CMake. When
+// building this way we can't test the presence of features before building so
+// predefine all the platform-support feature macros to their expected values.
+
+#cmakedefine HAVE_ARC4RANDOM 1
+#if COCOAPODS
+#  define HAVE_ARC4RANDOM 1
+#endif
+
+#cmakedefine HAVE_OPENSSL_RAND_H 1
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_CONFIG_H_