1 files changed, 107 insertions, 0 deletions
diff --git a/libbuild2/rule.hxx b/libbuild2/rule.hxx
new file mode 100644
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--- /dev/null
+++ b/libbuild2/rule.hxx
@@ -0,0 +1,107 @@
+// file      : libbuild2/rule.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_RULE_HXX
+#define LIBBUILD2_RULE_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/action.hxx>
+#include <libbuild2/target.hxx>
+
+#include <libbuild2/export.hxx>
+
+namespace build2
+{
+  // Once a rule is registered (for a scope), it is treated as immutable. If
+  // you need to modify some state (e.g., counters or some such), then make
+  // sure it is MT-safe.
+  //
+  // Note: match() is only called once but may not be followed by apply().
+  //
+  class rule
+  {
+  public:
+    virtual bool
+    match (action, target&, const string& hint) const = 0;
+
+    virtual recipe
+    apply (action, target&) const = 0;
+  };
+
+  // Fallback rule that only matches if the file exists. It will also match
+  // an mtime_target provided it has a set timestamp.
+  //
+  class LIBBUILD2_SYMEXPORT file_rule: public rule
+  {
+  public:
+    virtual bool
+    match (action, target&, const string&) const override;
+
+    virtual recipe
+    apply (action, target&) const override;
+
+    file_rule () {}
+    static const file_rule instance;
+  };
+
+  class LIBBUILD2_SYMEXPORT alias_rule: public rule
+  {
+  public:
+    virtual bool
+    match (action, target&, const string&) const override;
+
+    virtual recipe
+    apply (action, target&) const override;
+
+    alias_rule () {}
+    static const alias_rule instance;
+  };
+
+  // Note that this rule ignores the dry_run flag; see mkdir() in filesystem
+  // for the rationale.
+  //
+  class LIBBUILD2_SYMEXPORT fsdir_rule: public rule
+  {
+  public:
+    virtual bool
+    match (action, target&, const string&) const override;
+
+    virtual recipe
+    apply (action, target&) const override;
+
+    static target_state
+    perform_update (action, const target&);
+
+    static target_state
+    perform_clean (action, const target&);
+
+    // Sometimes, as an optimization, we want to emulate execute_direct()
+    // of fsdir{} without the overhead of switching to the execute phase.
+    //
+    static void
+    perform_update_direct (action, const target&);
+
+    fsdir_rule () {}
+    static const fsdir_rule instance;
+  };
+
+  // Fallback rule that always matches and does nothing.
+  //
+  class LIBBUILD2_SYMEXPORT noop_rule: public rule
+  {
+  public:
+    virtual bool
+    match (action, target&, const string&) const override;
+
+    virtual recipe
+    apply (action, target&) const override;
+
+    noop_rule () {}
+    static const noop_rule instance;
+  };
+}
+
+#endif // LIBBUILD2_RULE_HXX