Consolidate code for getting platform details into one place (#311)

Consolidate code for getting platform details into a single place

platform.cpp

@@ -0,0 +1,56 @@
+#include "platform.hpp"
+#include <cstdlib>
+#include <cstdio>
+#include <unistd.h>
+#include <sys/resource.h>
+
+#if defined(__APPLE__) || defined(__FreeBSD__)
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#include <sys/param.h>
+#include <sys/mount.h>
+#endif
+
+#include "errors.hpp"
+
+long get_num_avail_cpus() {
+	return sysconf(_SC_NPROCESSORS_ONLN);
+}
+
+long get_page_size() {
+	return sysconf(_SC_PAGESIZE);
+}
+
+size_t calc_memsize() {
+	size_t mem;
+
+#ifdef __APPLE__
+	int64_t hw_memsize;
+	size_t len = sizeof(int64_t);
+	if (sysctlbyname("hw.memsize", &hw_memsize, &len, NULL, 0) < 0) {
+		perror("sysctl hw.memsize");
+		exit(EXIT_MEMORY);
+	}
+	mem = hw_memsize;
+#else
+	long long pagesize = sysconf(_SC_PAGESIZE);
+	long long pages = sysconf(_SC_PHYS_PAGES);
+	if (pages < 0 || pagesize < 0) {
+		perror("sysconf _SC_PAGESIZE or _SC_PHYS_PAGES");
+		exit(EXIT_MEMORY);
+	}
+
+	mem = (long long) pages * pagesize;
+#endif
+
+	return mem;
+}
+
+size_t get_max_open_files() {
+	struct rlimit rl;
+	if (getrlimit(RLIMIT_NOFILE, &rl) != 0) {
+		perror("getrlimit");
+		exit(EXIT_PTHREAD);
+	}
+	return rl.rlim_cur;
+}