+ { /* This works on linux-gnu, solaris2 and cygwin. */
+ double pages = sysconf (_SC_AVPHYS_PAGES);
+ double pagesize = sysconf (_SC_PAGESIZE);
+ if (0 <= pages && 0 <= pagesize)
+ return pages * pagesize;
+ }
+#endif
+
+#if HAVE_PSTAT_GETSTATIC && HAVE_PSTAT_GETDYNAMIC
+ { /* This works on hpux11. */
+ struct pst_static pss;
+ struct pst_dynamic psd;
+ if (0 <= pstat_getstatic (&pss, sizeof pss, 1, 0)
+ && 0 <= pstat_getdynamic (&psd, sizeof psd, 1, 0))
+ {
+ double pages = psd.psd_free;
+ double pagesize = pss.page_size;
+ if (0 <= pages && 0 <= pagesize)
+ return pages * pagesize;
+ }
+ }
+#endif
+
+#if HAVE_SYSMP && defined MP_SAGET && defined MPSA_RMINFO && defined _SC_PAGESIZE
+ { /* This works on irix6. */
+ struct rminfo realmem;
+ if (sysmp (MP_SAGET, MPSA_RMINFO, &realmem, sizeof realmem) == 0)
+ {
+ double pagesize = sysconf (_SC_PAGESIZE);
+ double pages = realmem.availrmem;
+ if (0 <= pages && 0 <= pagesize)
+ return pages * pagesize;
+ }
+ }
+#endif
+
+#if HAVE_TABLE && defined TBL_VMSTATS
+ { /* This works on Tru64 UNIX V4/5. */
+ struct tbl_vmstats vmstats;
+
+ if (table (TBL_VMSTATS, 0, &vmstats, 1, sizeof (vmstats)) == 1)
+ {
+ double pages = vmstats.free_count;
+ double pagesize = vmstats.pagesize;
+
+ if (0 <= pages && 0 <= pagesize)
+ return pages * pagesize;
+ }
+ }
+#endif
+
+#if HAVE_SYSCTL && defined HW_USERMEM
+ { /* This works on *bsd and darwin. */
+ unsigned int usermem;
+ size_t len = sizeof usermem;
+ static int mib[2] = { CTL_HW, HW_USERMEM };
+
+ if (sysctl (mib, ARRAY_SIZE (mib), &usermem, &len, NULL, 0) == 0
+ && len == sizeof (usermem))
+ return (double) usermem;
+ }
+#endif
+
+#if defined _WIN32
+ { /* this works on windows */
+ PFN_MS_EX pfnex;
+ HMODULE h = GetModuleHandle ("kernel32.dll");
+
+ if (!h)
+ return 0.0;
+
+ /* Use GlobalMemoryStatusEx if available. */
+ if ((pfnex = (PFN_MS_EX) GetProcAddress (h, "GlobalMemoryStatusEx")))
+ {
+ lMEMORYSTATUSEX lms_ex;
+ lms_ex.dwLength = sizeof lms_ex;
+ if (!pfnex (&lms_ex))
+ return 0.0;
+ return (double) lms_ex.ullAvailPhys;
+ }
+
+ /* Fall back to GlobalMemoryStatus which is always available.
+ but returns wrong results for physical memory > 4GB */
+ else
+ {
+ MEMORYSTATUS ms;
+ GlobalMemoryStatus (&ms);
+ return (double) ms.dwAvailPhys;
+ }
+ }