job/queue: add default constructor

job/queue.cpp

@@ -16,12 +16,43 @@
 
 #include "queue.hpp"
 
+#include "../parse.hpp"
 #include "../raii.hpp"
 
 using util::job::queue;
 
 
 ///////////////////////////////////////////////////////////////////////////////
+static unsigned
+default_parallelism (void)
+{
+    if (auto var = getenv ("JOB_THREADS")) {
+        return util::parse<unsigned> (var);
+    }
+
+    return std::thread::hardware_concurrency ();
+}
+
+
+//-----------------------------------------------------------------------------
+static unsigned
+default_depth (void)
+{
+    if (auto var = getenv ("JOB_DEPTH")) {
+        return util::parse<unsigned> (var);
+    }
+
+    return 1024;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+queue::queue ():
+    queue (default_parallelism (), default_depth ())
+{ ; }
+
+
+//-----------------------------------------------------------------------------
 queue::queue (unsigned thread_count, unsigned pool_size):
     m_tasks {
         {}, util::pool<task> {pool_size}, {}, {}

job/queue.hpp

@@ -41,10 +41,7 @@
 namespace util::job {
     class queue {
     public:
-        queue ():
-            queue (std::thread::hardware_concurrency (), 1024)
-        { ; }
-
+        queue ();
         queue (unsigned thread_count, unsigned pool_size);
         ~queue ();