Replace sysctl on Mac with a syscall that is supported in all kernels

src/blockstore/implementations/inmemory/InMemoryBlockStore.cpp

@@ -2,6 +2,7 @@
 #include "InMemoryBlockStore.h"
 #include <memory>
 #include <cpp-utils/assert/assert.h>
+#include <cpp-utils/system/get_total_memory.h>
 
 using std::make_unique;
 using std::string;
@@ -53,10 +54,7 @@ uint64_t InMemoryBlockStore::numBlocks() const {
 }
 
 uint64_t InMemoryBlockStore::estimateNumFreeBytes() const {
-  //For windows, see http://stackoverflow.com/a/2513561/829568
-  long numRAMPages = sysconf(_SC_PHYS_PAGES);
-  long pageSize = sysconf(_SC_PAGE_SIZE);
-  return numRAMPages*pageSize;
+  return cpputils::system::get_total_memory();
 }
 
 }

src/blockstore/implementations/testfake/FakeBlockStore.cpp

@@ -2,6 +2,7 @@
 #include "FakeBlockStore.h"
 #include <cpp-utils/assert/assert.h>
 #include <sys/sysctl.h>
+#include <cpp-utils/system/get_total_memory.h>
 
 using std::make_shared;
 using std::string;
@@ -78,21 +79,7 @@ uint64_t FakeBlockStore::numBlocks() const {
 }
 
 uint64_t FakeBlockStore::estimateNumFreeBytes() const {
-  uint64_t mem;
-#ifdef __APPLE__
-  size_t size = sizeof(mem);
-  int result = sysctlbyname("hw.memsize", &mem, &size, nullptr, 0);
-  if (0 != result) {
-    throw std::runtime_error("sysctlbyname syscall failed");
-  }
-#elif __linux__
-  long numRAMPages = sysconf(_SC_PHYS_PAGES);
-  long pageSize = sysconf(_SC_PAGESIZE);
-  mem = numRAMPages * pageSize;
-#else
-#error Not supported on windows yet, TODO http://stackoverflow.com/a/2513561/829568
-#endif
-  return mem;
+  return cpputils::system::get_total_memory();
 }
 
 }

src/cpp-utils/system/get_total_memory.cpp

@@ -0,0 +1,23 @@
+#include "get_total_memory.h"
+
+namespace cpputils{
+    namespace system {
+        uint64_t get_total_memory() {
+            uint64_t mem;
+#ifdef __APPLE__
+            size_t size = sizeof(mem);
+  int result = sysctlbyname("hw.memsize", &mem, &size, nullptr, 0);
+  if (0 != result) {
+    throw std::runtime_error("sysctlbyname syscall failed");
+  }
+#elif __linux__
+            long numRAMPages = sysconf(_SC_PHYS_PAGES);
+            long pageSize = sysconf(_SC_PAGESIZE);
+            mem = numRAMPages * pageSize;
+#else
+#error Not supported on windows yet, TODO http://stackoverflow.com/a/2513561/829568
+#endif
+            return mem;
+        }
+    }
+}

src/cpp-utils/system/get_total_memory.h

@@ -0,0 +1,11 @@
+#pragma once
+#ifndef MESSMER_CPPUTILS_SYSTEM_GETTOTALMEMORY_H
+#define MESSMER_CPPUTILS_SYSTEM_GETTOTALMEMORY_H
+
+namespace cpputils {
+    namespace system {
+        uint64_t get_total_memory();
+    }
+}
+
+#endif