A few VCD trace changes

interface/vsrtl_interface.h

@@ -712,14 +712,15 @@ class SimDesign : public SimComponent {
   long long getCycleCount() const { return m_cycleCount; }
 
   /**
-   * @brief vcdDump
-   * @param enabled; enables dumping of all ports to a vcd file. For each port
-   * in the circuit, we connect an additional slot which will queue a notice to
-   * this top-level Design that the variable change is to be written to the VCD
-   * file.
+   * @brief vcdTrace
+   * @param enabled; enables dumping of all ports to a vcd file. For each
+   * port in the circuit, we connect an additional slot which will queue a
+   * notice to this top-level Design that the variable change is to be
+   * written to the VCD file.
    */
-  void vcdDump(bool enabled) {
+  void vcdTrace(bool enabled, const std::string &filename = "") {
     m_dumpVcdFiles = enabled;
+    m_vcdFileName = filename.empty() ? getName() + ".vcd" : filename;
     std::map<SimComponent *, std::vector<SimComponent *>> componentGraph;
     getComponentGraph(componentGraph);
     for (const auto &compIt : componentGraph) {
@@ -745,7 +746,7 @@ class SimDesign : public SimComponent {
    * wherein they reside.
    */
   void resetVcdFile() {
-    m_vcdFile = std::make_unique<VCDFile>(getName() + ".vcd");
+    m_vcdFile = std::make_unique<VCDFile>(m_vcdFileName);
     {
       auto def1 = m_vcdFile->writeHeader();
       auto def2 = m_vcdFile->scopeDef("TOP");
@@ -819,6 +820,7 @@ class SimDesign : public SimComponent {
   std::set<const SimPort *> m_vcdVarChangeQueue;
   std::string m_vcdClkId;
   bool m_dumpVcdFiles = false;
+  std::string m_vcdFileName;
 
 #ifndef NDEBUG
   long long m_cycleCountPre = 0;

interface/vsrtl_vcdfile.cpp

@@ -23,16 +23,18 @@ std::string binStr(T val, unsigned width) {
   return s;
 }
 
-VCDFile::VCDFile(const std::string &filename) {
-  m_file.open(filename, std::ios_base::trunc);
+VCDFile::VCDFile(const std::string &filename) { m_filename = filename; }
+
+void VCDFile::ensureOpen() {
+  if (m_file.is_open())
+    return;
+  m_file.open(m_filename, std::ios_base::trunc);
 }
 
 VCDFile::~VCDFile() { m_file.close(); }
 
 void VCDFile::writeLine(const std::string &line) {
-  if (!m_file.is_open()) {
-    throw std::runtime_error("Tried to write to file, but file was not open");
-  }
+  ensureOpen();
   const std::string indent = std::string(m_scopeLevel * 4, ' ');
   m_file << indent << line + "\n";
 };

interface/vsrtl_vcdfile.h

@@ -36,12 +36,15 @@ class VCDFile {
   }
 
 private:
+  // Ensures that the file is opened and ready for writing.
+  void ensureOpen();
   std::string genId();
   void writeLine(const std::string &line);
   std::ofstream m_file;
   std::map<std::string, unsigned> m_varWidths;
   std::map<std::string, uint64_t> m_dumpVars;
 
+  std::string m_filename;
   unsigned m_varCntr = 0;
   unsigned m_scopeLevel = 0;
 };