Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/libnest2d/include/libnest2d/parallel.hpp

@@ -0,0 +1,63 @@
+#ifndef LIBNEST2D_PARALLEL_HPP
+#define LIBNEST2D_PARALLEL_HPP
+
+#include <iterator>
+#include <functional>
+#include <future>
+
+#ifdef LIBNEST2D_THREADING_tbb
+#include <tbb/parallel_for.h>
+#endif
+
+#ifdef LIBNEST2D_THREADING_omp
+#include <omp.h>
+#endif
+
+namespace libnest2d { namespace __parallel {
+    
+template<class It> 
+using TIteratorValue = typename std::iterator_traits<It>::value_type;
+
+template<class Iterator>
+inline void enumerate(
+        Iterator from, Iterator to,
+        std::function<void(TIteratorValue<Iterator>, size_t)> fn,
+        std::launch policy = std::launch::deferred | std::launch::async)
+{
+    using TN = size_t;
+    auto iN = to-from;
+    TN N = iN < 0? 0 : TN(iN);
+
+#ifdef LIBNEST2D_THREADING_tbb
+    if((policy & std::launch::async) == std::launch::async) {
+        tbb::parallel_for<TN>(0, N, [from, fn] (TN n) { fn(*(from + n), n); } );
+    } else {
+        for(TN n = 0; n < N; n++) fn(*(from + n), n);
+    }
+#endif
+
+#ifdef LIBNEST2D_THREADING_omp
+    if((policy & std::launch::async) == std::launch::async) {
+        #pragma omp parallel for
+        for(int n = 0; n < int(N); n++) fn(*(from + n), TN(n));
+    }
+    else {
+        for(TN n = 0; n < N; n++) fn(*(from + n), n);
+    }
+#endif
+
+#ifdef LIBNEST2D_THREADING_std
+    std::vector<std::future<void>> rets(N);
+
+    auto it = from;
+    for(TN b = 0; b < N; b++) {
+        rets[b] = std::async(policy, fn, *it++, unsigned(b));
+    }
+
+    for(TN fi = 0; fi < N; ++fi) rets[fi].wait();
+#endif
+}
+
+}}
+
+#endif //LIBNEST2D_PARALLEL_HPP