Move SysctlUtil from eden to edencommon

Summary:
To support better telemetry and logging in watchman we want to use Eden's components. Lets migrate and detangle the needed pieces.

This change moves SysctlUtil from eden to edencommon.

Reviewed By: genevievehelsel

Differential Revision: D54471684

fbshipit-source-id: df6d0716dfe371d8c7fc1fe80079649b85b50e6b

eden/common/utils/SysctlUtil.cpp

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "eden/common/utils/SysctlUtil.h"
+
+#ifdef __APPLE__
+
+#include <sys/sysctl.h> // @manual
+#include <sys/types.h>
+
+#include <folly/Exception.h>
+
+std::string getSysCtlByName(const char* name, size_t size) {
+  if (size == 0) {
+    return std::string{};
+  }
+  std::string buffer(size, 0);
+  size_t returnedSize = size - 1;
+  auto ret = sysctlbyname(name, &buffer[0], &returnedSize, nullptr, 0);
+  if (ret != 0) {
+    folly::throwSystemError("failed to retrieve sysctl ", name);
+  }
+  buffer.resize(returnedSize);
+  return buffer;
+}
+#endif

eden/common/utils/SysctlUtil.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <string>
+
+#ifdef __APPLE__
+// Fetches the value of a sysctl by name.
+// The result is assumed to be a string.
+std::string getSysCtlByName(const char* name, size_t size);
+#endif