Consolidate HwFinder (#23)

- Move the `popen` function check instead of relying on the `CpuCoreCounter`'s `proc_open` check.
- Refactor `HwFinder::find()` for better readability
- Handle potential `fgets` `false` value returned

src/HwFinder.php

@@ -15,6 +15,7 @@
 
 use function fgets;
 use function filter_var;
+use function function_exists;
 use function is_int;
 use function is_resource;
 use function pclose;
@@ -35,17 +36,23 @@ final class HwFinder implements CpuCoreFinder
      */
     public function find(): ?int
     {
-        $process = popen('sysctl -n hw.ncpu', 'rb');
+        if (!function_exists('popen')) {
+            return null;
+        }
 
-        if (is_resource($process)) {
-            // *nix (Linux, BSD and Mac)
-            $cores = self::countCpuCores(fgets($process));
-            pclose($process);
+        // -n to show only the variable value
+        $process = popen('sysctl -n hw.ncpu', 'rb');
 
-            return $cores;
+        if (!is_resource($process)) {
+            return null;
         }
 
-        return null;
+        $processResult = fgets($process);
+        pclose($process);
+
+        return false === $processResult
+            ? null
+            : self::countCpuCores($processResult);
     }
 
     /**