Merge pull request #2431 from kubo39/cpu_count

Add CPU_COUNT
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Author: dlang-bot

changelog/cpu_count.dd

@@ -0,0 +1,3 @@
+Added `core.sys.linux.sched.CPU_COUNT`.
+
+Added `core.sys.linux.sched.CPU_COUNT`, which returns the number of CPUs in set.

src/core/sys/linux/sched.d

@@ -14,6 +14,7 @@
 
 module core.sys.linux.sched;
 
+import core.bitop : popcnt;
 import core.sys.posix.sched;
 import core.sys.posix.config;
 import core.sys.posix.sys.types;
@@ -63,6 +64,14 @@ private // helpers
             return (cpusetp.__bits[__CPUELT(cpu)] & __CPUMASK(cpu)) != 0;
         return false;
     }
+
+    int __CPU_COUNT_S(size_t setsize, cpu_set_t* cpusetp) pure
+    {
+        int s = 0;
+        foreach (i; cpusetp.__bits[0 .. (setsize / cpu_mask.sizeof)])
+            s += popcnt(i);
+        return s;
+    }
 }
 
 /// Type for array elements in 'cpu_set_t'.
@@ -86,6 +95,11 @@ bool CPU_ISSET(size_t cpu, cpu_set_t* cpusetp) pure
     return __CPU_ISSET_S(cpu, cpu_set_t.sizeof, cpusetp);
 }
 
+int CPU_COUNT(cpu_set_t* cpusetp) pure
+{
+    return __CPU_COUNT_S(cpu_set_t.sizeof, cpusetp);
+}
+
 /* Functions */
 int sched_setaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask);
 int sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask);