Redo rule match/build logic

Now the rule is fully responsible for searching, matching, and building
of prerequisites.

1 files changed, 59 insertions, 0 deletions

diff --git a/build/algorithm.txx b/build/algorithm.txx
new file mode 100644
index 0000000..9086bfe
--- /dev/null
+++ b/build/algorithm.txx
@@ -0,0 +1,59 @@
+// file      : build/algorithm.txx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
+// license   : MIT; see accompanying LICENSE file
+
+namespace build
+{
+  template <typename T>
+  T*
+  update_prerequisites (target& t, const timestamp& mt)
+  {
+    //@@ Can factor the bulk of it into a non-template code. Can
+    // either do a function template that will do dynamic_cast check
+    // or can scan the target type info myself. I think latter.
+    //
+
+    T* r (nullptr);
+    bool u (mt == timestamp_nonexistent);
+
+    for (const prerequisite& p: t.prerequisites)
+    {
+      assert (p.target != nullptr);
+      target& pt (*p.target);
+
+      target_state ts (update (pt));
+
+      if (!u)
+      {
+        // If this is an mtime-based target, then compare timestamps.
+        //
+        if (auto mpt = dynamic_cast<const mtime_target*> (&pt))
+        {
+          timestamp mp (mpt->mtime ());
+
+          // What do we do if timestamps are equal? This can happen, for
+          // example, on filesystems that don't have subsecond resolution.
+          // There is not much we can do here except detect the case where
+          // the prerequisite was updated in this run which means the
+          // target must be out of date.
+          //
+          if (mt < mp || mt == mp && ts == target_state::updated)
+            u = true;
+        }
+        else
+        {
+          // Otherwise we assume the prerequisite is newer if it was updated.
+          //
+          if (ts == target_state::updated)
+            u = true;
+        }
+      }
+
+      if (r == nullptr)
+        r = dynamic_cast<T*> (&pt);
+    }
+
+    assert (r != nullptr);
+    return u ? r : nullptr;
+  }
+}