Add experimental --pipe-filter to filter all Verilog input.

src/V3File.h

@@ -71,6 +71,23 @@ public:
     static void createMakeDir();
 };
 
+//============================================================================
+// V3InFilter: Read a input file, possibly filtering it, and caching contents
+
+class V3InFilterImp;
+
+class V3InFilter {
+    V3InFilterImp* m_impp;
+public:
+    // METHODS
+    // Read file contents and return it.  Return true on success.   
+    bool readWholefile(const string& filename, string& out);
+
+    // CONSTRUCTORS
+    V3InFilter(const string& command);
+    ~V3InFilter();
+};
+
 //============================================================================
 // V3OutFormatter: A class for automatic indentation of C++ or Verilog code.